Merge github.com:grpc/grpc into y12kdm3

Conflicts:
	src/core/security/google_default_credentials.c
	test/core/security/verify_jwt.c

150 files changed, 4145 insertions, 1352 deletions

diff --git a/src/core/channel/client_channel.c b/src/core/channel/client_channel.c
index 2ee260b799..6c2e6b38a8 100644
--- a/src/core/channel/client_channel.c
+++ b/src/core/channel/client_channel.c
@@ -401,6 +401,7 @@ static void perform_transport_stream_op(grpc_call_element *elem,
             calld->state = CALL_WAITING_FOR_CONFIG;
             add_to_lb_policy_wait_queue_locked_state_config(elem);
             if (!chand->started_resolving && chand->resolver != NULL) {
+              GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
               chand->started_resolving = 1;
               grpc_resolver_next(chand->resolver,
                                  &chand->incoming_configuration,
@@ -526,6 +527,7 @@ static void cc_on_config_changed(void *arg, int iomgr_success) {
   }
 
   if (old_lb_policy != NULL) {
+    grpc_lb_policy_shutdown(old_lb_policy);
     GRPC_LB_POLICY_UNREF(old_lb_policy, "channel");
   }
 
@@ -701,11 +703,11 @@ void grpc_client_channel_set_resolver(grpc_channel_stack *channel_stack,
   gpr_mu_lock(&chand->mu_config);
   GPR_ASSERT(!chand->resolver);
   chand->resolver = resolver;
-  GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
   GRPC_RESOLVER_REF(resolver, "channel");
   if (chand->waiting_for_config_closures != NULL ||
       chand->exit_idle_when_lb_policy_arrives) {
     chand->started_resolving = 1;
+    GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
     grpc_resolver_next(resolver, &chand->incoming_configuration,
                        &chand->on_config_changed);
   }
@@ -724,6 +726,7 @@ grpc_connectivity_state grpc_client_channel_check_connectivity_state(
     } else {
       chand->exit_idle_when_lb_policy_arrives = 1;
       if (!chand->started_resolving && chand->resolver != NULL) {
+        GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
         chand->started_resolving = 1;
         grpc_resolver_next(chand->resolver, &chand->incoming_configuration,
                            &chand->on_config_changed);
diff --git a/src/core/channel/compress_filter.c b/src/core/channel/compress_filter.c
index 9fc8589fbb..8963c13b0f 100644
--- a/src/core/channel/compress_filter.c
+++ b/src/core/channel/compress_filter.c
@@ -204,7 +204,7 @@ static void process_send_ops(grpc_call_element *elem,
           }
           grpc_metadata_batch_add_tail(
               &(sop->data.metadata), &calld->compression_algorithm_storage,
-              grpc_mdelem_ref(channeld->mdelem_compression_algorithms
+              GRPC_MDELEM_REF(channeld->mdelem_compression_algorithms
                                   [calld->compression_algorithm]));
           calld->written_initial_metadata = 1; /* GPR_TRUE */
         }
@@ -295,7 +295,7 @@ static void init_channel_elem(grpc_channel_element *elem, grpc_channel *master,
     channeld->mdelem_compression_algorithms[algo_idx] =
         grpc_mdelem_from_metadata_strings(
             mdctx,
-            grpc_mdstr_ref(channeld->mdstr_outgoing_compression_algorithm_key),
+            GRPC_MDSTR_REF(channeld->mdstr_outgoing_compression_algorithm_key),
             grpc_mdstr_from_string(mdctx, algorithm_name, 0));
   }
 
@@ -307,11 +307,11 @@ static void destroy_channel_elem(grpc_channel_element *elem) {
   channel_data *channeld = elem->channel_data;
   grpc_compression_algorithm algo_idx;
 
-  grpc_mdstr_unref(channeld->mdstr_request_compression_algorithm_key);
-  grpc_mdstr_unref(channeld->mdstr_outgoing_compression_algorithm_key);
+  GRPC_MDSTR_UNREF(channeld->mdstr_request_compression_algorithm_key);
+  GRPC_MDSTR_UNREF(channeld->mdstr_outgoing_compression_algorithm_key);
   for (algo_idx = 0; algo_idx < GRPC_COMPRESS_ALGORITHMS_COUNT;
        ++algo_idx) {
-    grpc_mdelem_unref(channeld->mdelem_compression_algorithms[algo_idx]);
+    GRPC_MDELEM_UNREF(channeld->mdelem_compression_algorithms[algo_idx]);
   }
 }
 
diff --git a/src/core/httpcli/httpcli.c b/src/core/httpcli/httpcli.c
index 65997d5f44..9012070e8e 100644
--- a/src/core/httpcli/httpcli.c
+++ b/src/core/httpcli/httpcli.c
@@ -40,9 +40,7 @@
 #include "src/core/iomgr/resolve_address.h"
 #include "src/core/iomgr/tcp_client.h"
 #include "src/core/httpcli/format_request.h"
-#include "src/core/httpcli/httpcli_security_connector.h"
 #include "src/core/httpcli/parser.h"
-#include "src/core/security/secure_transport_setup.h"
 #include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -57,7 +55,7 @@ typedef struct {
   char *host;
   gpr_timespec deadline;
   int have_read_byte;
-  int use_ssl;
+  const grpc_httpcli_handshaker *handshaker;
   grpc_httpcli_response_cb on_response;
   void *user_data;
   grpc_httpcli_context *context;
@@ -68,6 +66,16 @@ typedef struct {
 static grpc_httpcli_get_override g_get_override = NULL;
 static grpc_httpcli_post_override g_post_override = NULL;
 
+static void plaintext_handshake(void *arg, grpc_endpoint *endpoint,
+                                const char *host,
+                                void (*on_done)(void *arg,
+                                                grpc_endpoint *endpoint)) {
+  on_done(arg, endpoint);
+}
+
+const grpc_httpcli_handshaker grpc_httpcli_plaintext = {"http",
+                                                        plaintext_handshake};
+
 void grpc_httpcli_context_init(grpc_httpcli_context *context) {
   grpc_pollset_set_init(&context->pollset_set);
 }
@@ -163,18 +171,16 @@ static void start_write(internal_request *req) {
   }
 }
 
-static void on_secure_transport_setup_done(void *rp,
-                                           grpc_security_status status,
-                                           grpc_endpoint *wrapped_endpoint,
-                                           grpc_endpoint *secure_endpoint) {
-  internal_request *req = rp;
-  if (status != GRPC_SECURITY_OK) {
-    gpr_log(GPR_ERROR, "Secure transport setup failed with error %d.", status);
-    finish(req, 0);
-  } else {
-    req->ep = secure_endpoint;
-    start_write(req);
+static void on_handshake_done(void *arg, grpc_endpoint *ep) {
+  internal_request *req = arg;
+
+  if (!ep) {
+    next_address(req);
+    return;
   }
+
+  req->ep = ep;
+  start_write(req);
 }
 
 static void on_connected(void *arg, grpc_endpoint *tcp) {
@@ -184,25 +190,7 @@ static void on_connected(void *arg, grpc_endpoint *tcp) {
     next_address(req);
     return;
   }
-  req->ep = tcp;
-  if (req->use_ssl) {
-    grpc_channel_security_connector *sc = NULL;
-    const unsigned char *pem_root_certs = NULL;
-    size_t pem_root_certs_size = grpc_get_default_ssl_roots(&pem_root_certs);
-    if (pem_root_certs == NULL || pem_root_certs_size == 0) {
-      gpr_log(GPR_ERROR, "Could not get default pem root certs.");
-      finish(req, 0);
-      return;
-    }
-    GPR_ASSERT(grpc_httpcli_ssl_channel_security_connector_create(
-                   pem_root_certs, pem_root_certs_size, req->host, &sc) ==
-               GRPC_SECURITY_OK);
-    grpc_setup_secure_transport(&sc->base, tcp, on_secure_transport_setup_done,
-                                req);
-    GRPC_SECURITY_CONNECTOR_UNREF(&sc->base, "httpcli");
-  } else {
-    start_write(req);
-  }
+  req->handshaker->handshake(req, tcp, req->host, on_handshake_done);
 }
 
 static void next_address(internal_request *req) {
@@ -245,18 +233,17 @@ void grpc_httpcli_get(grpc_httpcli_context *context, grpc_pollset *pollset,
   req->on_response = on_response;
   req->user_data = user_data;
   req->deadline = deadline;
-  req->use_ssl = request->use_ssl;
+  req->handshaker =
+      request->handshaker ? request->handshaker : &grpc_httpcli_plaintext;
   req->context = context;
   req->pollset = pollset;
   gpr_asprintf(&name, "HTTP:GET:%s:%s", request->host, request->path);
   grpc_iomgr_register_object(&req->iomgr_obj, name);
   gpr_free(name);
-  if (req->use_ssl) {
-    req->host = gpr_strdup(request->host);
-  }
+  req->host = gpr_strdup(request->host);
 
   grpc_pollset_set_add_pollset(&req->context->pollset_set, req->pollset);
-  grpc_resolve_address(request->host, req->use_ssl ? "https" : "http",
+  grpc_resolve_address(request->host, req->handshaker->default_port,
                        on_resolved, req);
 }
 
@@ -279,18 +266,17 @@ void grpc_httpcli_post(grpc_httpcli_context *context, grpc_pollset *pollset,
   req->on_response = on_response;
   req->user_data = user_data;
   req->deadline = deadline;
-  req->use_ssl = request->use_ssl;
+  req->handshaker =
+      request->handshaker ? request->handshaker : &grpc_httpcli_plaintext;
   req->context = context;
   req->pollset = pollset;
   gpr_asprintf(&name, "HTTP:GET:%s:%s", request->host, request->path);
   grpc_iomgr_register_object(&req->iomgr_obj, name);
   gpr_free(name);
-  if (req->use_ssl) {
-    req->host = gpr_strdup(request->host);
-  }
+  req->host = gpr_strdup(request->host);
 
   grpc_pollset_set_add_pollset(&req->context->pollset_set, req->pollset);
-  grpc_resolve_address(request->host, req->use_ssl ? "https" : "http",
+  grpc_resolve_address(request->host, req->handshaker->default_port,
                        on_resolved, req);
 }
 
diff --git a/src/core/httpcli/httpcli.h b/src/core/httpcli/httpcli.h
index ab98178f8a..c45966714c 100644
--- a/src/core/httpcli/httpcli.h
+++ b/src/core/httpcli/httpcli.h
@@ -38,6 +38,7 @@
 
 #include <grpc/support/time.h>
 
+#include "src/core/iomgr/endpoint.h"
 #include "src/core/iomgr/pollset_set.h"
 
 /* User agent this library reports */
@@ -58,6 +59,15 @@ typedef struct grpc_httpcli_context {
   grpc_pollset_set pollset_set;
 } grpc_httpcli_context;
 
+typedef struct {
+  const char *default_port;
+  void (*handshake)(void *arg, grpc_endpoint *endpoint, const char *host,
+                    void (*on_done)(void *arg, grpc_endpoint *endpoint));
+} grpc_httpcli_handshaker;
+
+extern const grpc_httpcli_handshaker grpc_httpcli_plaintext;
+extern const grpc_httpcli_handshaker grpc_httpcli_ssl;
+
 /* A request */
 typedef struct grpc_httpcli_request {
   /* The host name to connect to */
@@ -69,8 +79,8 @@ typedef struct grpc_httpcli_request {
        Host, Connection, User-Agent */
   size_t hdr_count;
   grpc_httpcli_header *hdrs;
-  /* whether to use ssl for the request */
-  int use_ssl;
+  /* handshaker to use ssl for the request */
+  const grpc_httpcli_handshaker *handshaker;
 } grpc_httpcli_request;
 
 /* A response */
diff --git a/src/core/httpcli/httpcli_security_connector.c b/src/core/httpcli/httpcli_security_connector.c
index ce0d3d5a70..7887f9d530 100644
--- a/src/core/httpcli/httpcli_security_connector.c
+++ b/src/core/httpcli/httpcli_security_connector.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/httpcli/httpcli_security_connector.h"
+#include "src/core/httpcli/httpcli.h"
 
 #include <string.h>
 
@@ -96,7 +96,7 @@ static grpc_security_status httpcli_ssl_check_peer(grpc_security_connector *sc,
 static grpc_security_connector_vtable httpcli_ssl_vtable = {
     httpcli_ssl_destroy, httpcli_ssl_create_handshaker, httpcli_ssl_check_peer};
 
-grpc_security_status grpc_httpcli_ssl_channel_security_connector_create(
+static grpc_security_status httpcli_ssl_channel_security_connector_create(
     const unsigned char *pem_root_certs, size_t pem_root_certs_size,
     const char *secure_peer_name, grpc_channel_security_connector **sc) {
   tsi_result result = TSI_OK;
@@ -130,3 +130,48 @@ grpc_security_status grpc_httpcli_ssl_channel_security_connector_create(
   *sc = &c->base;
   return GRPC_SECURITY_OK;
 }
+
+/* handshaker */
+
+typedef struct {
+  void (*func)(void *arg, grpc_endpoint *endpoint);
+  void *arg;
+} on_done_closure;
+
+static void on_secure_transport_setup_done(void *rp,
+                                           grpc_security_status status,
+                                           grpc_endpoint *wrapped_endpoint,
+                                           grpc_endpoint *secure_endpoint) {
+  on_done_closure *c = rp;
+  if (status != GRPC_SECURITY_OK) {
+    gpr_log(GPR_ERROR, "Secure transport setup failed with error %d.", status);
+    c->func(c->arg, NULL);
+  } else {
+    c->func(c->arg, secure_endpoint);
+  }
+  gpr_free(c);
+}
+
+static void ssl_handshake(void *arg, grpc_endpoint *tcp, const char *host,
+                          void (*on_done)(void *arg, grpc_endpoint *endpoint)) {
+  grpc_channel_security_connector *sc = NULL;
+  const unsigned char *pem_root_certs = NULL;
+  on_done_closure *c = gpr_malloc(sizeof(*c));
+  size_t pem_root_certs_size = grpc_get_default_ssl_roots(&pem_root_certs);
+  if (pem_root_certs == NULL || pem_root_certs_size == 0) {
+    gpr_log(GPR_ERROR, "Could not get default pem root certs.");
+    on_done(arg, NULL);
+    gpr_free(c);
+    return;
+  }
+  c->func = on_done;
+  c->arg = arg;
+  GPR_ASSERT(httpcli_ssl_channel_security_connector_create(
+                 pem_root_certs, pem_root_certs_size, host, &sc) ==
+             GRPC_SECURITY_OK);
+  grpc_setup_secure_transport(&sc->base, tcp, on_secure_transport_setup_done,
+                              c);
+  GRPC_SECURITY_CONNECTOR_UNREF(&sc->base, "httpcli");
+}
+
+const grpc_httpcli_handshaker grpc_httpcli_ssl = {"https", ssl_handshake};
diff --git a/src/core/security/client_auth_filter.c b/src/core/security/client_auth_filter.c
index e86b5430b2..0e699874bc 100644
--- a/src/core/security/client_auth_filter.c
+++ b/src/core/security/client_auth_filter.c
@@ -77,10 +77,9 @@ typedef struct {
 
 static void bubble_up_error(grpc_call_element *elem, const char *error_msg) {
   call_data *calld = elem->call_data;
-  channel_data *chand = elem->channel_data;
-  grpc_transport_stream_op_add_cancellation(
-      &calld->op, GRPC_STATUS_UNAUTHENTICATED,
-      grpc_mdstr_from_string(chand->md_ctx, error_msg, 0));
+  gpr_log(GPR_ERROR, "Client side authentication failure: %s", error_msg);
+  grpc_transport_stream_op_add_cancellation(&calld->op,
+                                            GRPC_STATUS_UNAUTHENTICATED);
   grpc_call_next_op(elem, &calld->op);
 }
 
diff --git a/src/core/security/credentials.c b/src/core/security/credentials.c
index 15268cefbe..6421ce673d 100644
--- a/src/core/security/credentials.c
+++ b/src/core/security/credentials.c
@@ -149,6 +149,12 @@ grpc_security_status grpc_server_credentials_create_security_connector(
   return creds->vtable->create_security_connector(creds, sc);
 }
 
+void grpc_server_credentials_set_auth_metadata_processor(
+    grpc_server_credentials *creds, grpc_auth_metadata_processor processor) {
+  if (creds == NULL) return;
+  creds->processor = processor;
+}
+
 /* -- Ssl credentials. -- */
 
 static void ssl_destroy(grpc_credentials *creds) {
@@ -679,7 +685,7 @@ static void service_account_fetch_oauth2(
   request.path = GRPC_GOOGLE_OAUTH2_SERVICE_TOKEN_PATH;
   request.hdr_count = 1;
   request.hdrs = &header;
-  request.use_ssl = 1;
+  request.handshaker = &grpc_httpcli_ssl;
   grpc_httpcli_post(httpcli_context, pollset, &request, body, strlen(body),
                     deadline, response_cb, metadata_req);
   gpr_free(body);
@@ -738,7 +744,7 @@ static void refresh_token_fetch_oauth2(
   request.path = GRPC_GOOGLE_OAUTH2_SERVICE_TOKEN_PATH;
   request.hdr_count = 1;
   request.hdrs = &header;
-  request.use_ssl = 1;
+  request.handshaker = &grpc_httpcli_ssl;
   grpc_httpcli_post(httpcli_context, pollset, &request, body, strlen(body),
                     deadline, response_cb, metadata_req);
   gpr_free(body);
@@ -765,19 +771,19 @@ grpc_credentials *grpc_refresh_token_credentials_create(
       grpc_auth_refresh_token_create_from_string(json_refresh_token));
 }
 
-/* -- Fake Oauth2 credentials. -- */
+/* -- Metadata-only credentials. -- */
 
-static void fake_oauth2_destroy(grpc_credentials *creds) {
-  grpc_fake_oauth2_credentials *c = (grpc_fake_oauth2_credentials *)creds;
-  grpc_credentials_md_store_unref(c->access_token_md);
+static void md_only_test_destroy(grpc_credentials *creds) {
+  grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)creds;
+  grpc_credentials_md_store_unref(c->md_store);
   gpr_free(c);
 }
 
-static int fake_oauth2_has_request_metadata(const grpc_credentials *creds) {
+static int md_only_test_has_request_metadata(const grpc_credentials *creds) {
   return 1;
 }
 
-static int fake_oauth2_has_request_metadata_only(
+static int md_only_test_has_request_metadata_only(
     const grpc_credentials *creds) {
   return 1;
 }
@@ -785,19 +791,19 @@ static int fake_oauth2_has_request_metadata_only(
 void on_simulated_token_fetch_done(void *user_data, int success) {
   grpc_credentials_metadata_request *r =
       (grpc_credentials_metadata_request *)user_data;
-  grpc_fake_oauth2_credentials *c = (grpc_fake_oauth2_credentials *)r->creds;
+  grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)r->creds;
   GPR_ASSERT(success);
-  r->cb(r->user_data, c->access_token_md->entries,
-        c->access_token_md->num_entries, GRPC_CREDENTIALS_OK);
+  r->cb(r->user_data, c->md_store->entries,
+        c->md_store->num_entries, GRPC_CREDENTIALS_OK);
   grpc_credentials_metadata_request_destroy(r);
 }
 
-static void fake_oauth2_get_request_metadata(grpc_credentials *creds,
+static void md_only_test_get_request_metadata(grpc_credentials *creds,
                                              grpc_pollset *pollset,
                                              const char *service_url,
                                              grpc_credentials_metadata_cb cb,
                                              void *user_data) {
-  grpc_fake_oauth2_credentials *c = (grpc_fake_oauth2_credentials *)creds;
+  grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)creds;
 
   if (c->is_async) {
     grpc_credentials_metadata_request *cb_arg =
@@ -806,26 +812,26 @@ static void fake_oauth2_get_request_metadata(grpc_credentials *creds,
                             on_simulated_token_fetch_done, cb_arg);
     grpc_iomgr_add_callback(cb_arg->on_simulated_token_fetch_done_closure);
   } else {
-    cb(user_data, c->access_token_md->entries, 1, GRPC_CREDENTIALS_OK);
+    cb(user_data, c->md_store->entries, 1, GRPC_CREDENTIALS_OK);
   }
 }
 
-static grpc_credentials_vtable fake_oauth2_vtable = {
-    fake_oauth2_destroy, fake_oauth2_has_request_metadata,
-    fake_oauth2_has_request_metadata_only, fake_oauth2_get_request_metadata,
+static grpc_credentials_vtable md_only_test_vtable = {
+    md_only_test_destroy, md_only_test_has_request_metadata,
+    md_only_test_has_request_metadata_only, md_only_test_get_request_metadata,
     NULL};
 
-grpc_credentials *grpc_fake_oauth2_credentials_create(
-    const char *token_md_value, int is_async) {
-  grpc_fake_oauth2_credentials *c =
-      gpr_malloc(sizeof(grpc_fake_oauth2_credentials));
-  memset(c, 0, sizeof(grpc_fake_oauth2_credentials));
+grpc_credentials *grpc_md_only_test_credentials_create(const char *md_key,
+                                                       const char *md_value,
+                                                       int is_async) {
+  grpc_md_only_test_credentials *c =
+      gpr_malloc(sizeof(grpc_md_only_test_credentials));
+  memset(c, 0, sizeof(grpc_md_only_test_credentials));
   c->base.type = GRPC_CREDENTIALS_TYPE_OAUTH2;
-  c->base.vtable = &fake_oauth2_vtable;
+  c->base.vtable = &md_only_test_vtable;
   gpr_ref_init(&c->base.refcount, 1);
-  c->access_token_md = grpc_credentials_md_store_create(1);
-  grpc_credentials_md_store_add_cstrings(
-      c->access_token_md, GRPC_AUTHORIZATION_METADATA_KEY, token_md_value);
+  c->md_store = grpc_credentials_md_store_create(1);
+  grpc_credentials_md_store_add_cstrings(c->md_store, md_key, md_value);
   c->is_async = is_async;
   return &c->base;
 }
diff --git a/src/core/security/credentials.h b/src/core/security/credentials.h
index 8d40da47c1..04736525dc 100644
--- a/src/core/security/credentials.h
+++ b/src/core/security/credentials.h
@@ -190,9 +190,10 @@ grpc_oauth2_token_fetcher_credentials_parse_server_response(
     grpc_credentials_md_store **token_md, gpr_timespec *token_lifetime);
 void grpc_flush_cached_google_default_credentials(void);
 
-/* Simulates an oauth2 token fetch with the specified value for testing. */
-grpc_credentials *grpc_fake_oauth2_credentials_create(
-    const char *token_md_value, int is_async);
+/* Metadata-only credentials with the specified key and value where
+   asynchronicity can be simulated for testing. */
+grpc_credentials *grpc_md_only_test_credentials_create(
+    const char *md_key, const char *md_value, int is_async);
 
 /* Private constructor for jwt credentials from an already parsed json key.
    Takes ownership of the key. */
@@ -216,6 +217,7 @@ typedef struct {
 struct grpc_server_credentials {
   const grpc_server_credentials_vtable *vtable;
   const char *type;
+  grpc_auth_metadata_processor processor;
 };
 
 grpc_security_status grpc_server_credentials_create_security_connector(
@@ -297,13 +299,13 @@ typedef struct {
   grpc_credentials_md_store *access_token_md;
 } grpc_access_token_credentials;
 
-/* -- Fake Oauth2 credentials. -- */
+/* --  Metadata-only Test credentials. -- */
 
 typedef struct {
   grpc_credentials base;
-  grpc_credentials_md_store *access_token_md;
+  grpc_credentials_md_store *md_store;
   int is_async;
-} grpc_fake_oauth2_credentials;
+} grpc_md_only_test_credentials;
 
 /* -- IAM credentials. -- */
 
diff --git a/src/core/security/google_default_credentials.c b/src/core/security/google_default_credentials.c
index cf12a8e0fa..347b0da643 100644
--- a/src/core/security/google_default_credentials.c
+++ b/src/core/security/google_default_credentials.c
@@ -84,6 +84,8 @@ static void on_compute_engine_detection_http_response(
   gpr_mu_unlock(GRPC_POLLSET_MU(&detector->pollset));
 }
 
+static void destroy_pollset(void *p) { grpc_pollset_destroy(p); }
+
 static int is_stack_running_on_compute_engine(void) {
   compute_engine_detector detector;
   grpc_httpcli_request request;
@@ -114,12 +116,12 @@ static int is_stack_running_on_compute_engine(void) {
   while (!detector.is_done) {
     grpc_pollset_worker worker;
     grpc_pollset_work(&detector.pollset, &worker, gpr_now(GPR_CLOCK_MONOTONIC),
-                      gpr_inf_future(GPR_CLOCK_REALTIME));
+                      gpr_inf_future(GPR_CLOCK_MONOTONIC));
   }
   gpr_mu_unlock(GRPC_POLLSET_MU(&detector.pollset));
 
   grpc_httpcli_context_destroy(&context);
-  grpc_pollset_destroy(&detector.pollset);
+  grpc_pollset_shutdown(&detector.pollset, destroy_pollset, &detector.pollset);
 
   return detector.success;
 }
diff --git a/src/core/security/jwt_verifier.c b/src/core/security/jwt_verifier.c
index 1276693da7..38ad134a6a 100644
--- a/src/core/security/jwt_verifier.c
+++ b/src/core/security/jwt_verifier.c
@@ -628,7 +628,7 @@ static void on_openid_config_retrieved(void *user_data,
     goto error;
   }
   jwks_uri += 8;
-  req.use_ssl = 1;
+  req.handshaker = &grpc_httpcli_ssl;
   req.host = gpr_strdup(jwks_uri);
   req.path = strchr(jwks_uri, '/');
   if (req.path == NULL) {
@@ -685,7 +685,7 @@ static void retrieve_key_and_verify(verifier_cb_ctx *ctx) {
   const char *iss;
   grpc_httpcli_request req;
   memset(&req, 0, sizeof(grpc_httpcli_request));
-  req.use_ssl = 1;
+  req.handshaker = &grpc_httpcli_ssl;
 
   GPR_ASSERT(ctx != NULL && ctx->header != NULL && ctx->claims != NULL);
   iss = ctx->claims->iss;
diff --git a/src/core/security/security_connector.c b/src/core/security/security_connector.c
index 726b4c1e12..a354536dcd 100644
--- a/src/core/security/security_connector.c
+++ b/src/core/security/security_connector.c
@@ -263,9 +263,9 @@ static grpc_security_status fake_check_peer(grpc_security_connector *sc,
     goto end;
   }
   GRPC_AUTH_CONTEXT_UNREF(sc->auth_context, "connector");
-  sc->auth_context = grpc_auth_context_create(NULL, 1);
-  sc->auth_context->properties[0] = grpc_auth_property_init_from_cstring(
-      GRPC_TRANSPORT_SECURITY_TYPE_PROPERTY_NAME,
+  sc->auth_context = grpc_auth_context_create(NULL);
+  grpc_auth_context_add_cstring_property(
+      sc->auth_context, GRPC_TRANSPORT_SECURITY_TYPE_PROPERTY_NAME,
       GRPC_FAKE_TRANSPORT_SECURITY_TYPE);
 
 end:
@@ -409,31 +409,35 @@ static int ssl_host_matches_name(const tsi_peer *peer, const char *peer_name) {
 grpc_auth_context *tsi_ssl_peer_to_auth_context(const tsi_peer *peer) {
   size_t i;
   grpc_auth_context *ctx = NULL;
+  const char *peer_identity_property_name = NULL;
 
   /* The caller has checked the certificate type property. */
   GPR_ASSERT(peer->property_count >= 1);
-  ctx = grpc_auth_context_create(NULL, peer->property_count);
-  ctx->properties[0] = grpc_auth_property_init_from_cstring(
-      GRPC_TRANSPORT_SECURITY_TYPE_PROPERTY_NAME,
+  ctx = grpc_auth_context_create(NULL);
+  grpc_auth_context_add_cstring_property(
+      ctx, GRPC_TRANSPORT_SECURITY_TYPE_PROPERTY_NAME,
       GRPC_SSL_TRANSPORT_SECURITY_TYPE);
-  ctx->property_count = 1;
   for (i = 0; i < peer->property_count; i++) {
     const tsi_peer_property *prop = &peer->properties[i];
     if (prop->name == NULL) continue;
     if (strcmp(prop->name, TSI_X509_SUBJECT_COMMON_NAME_PEER_PROPERTY) == 0) {
       /* If there is no subject alt name, have the CN as the identity. */
-      if (ctx->peer_identity_property_name == NULL) {
-        ctx->peer_identity_property_name = GRPC_X509_CN_PROPERTY_NAME;
+      if (peer_identity_property_name == NULL) {
+        peer_identity_property_name = GRPC_X509_CN_PROPERTY_NAME;
       }
-      ctx->properties[ctx->property_count++] = grpc_auth_property_init(
-          GRPC_X509_CN_PROPERTY_NAME, prop->value.data, prop->value.length);
+      grpc_auth_context_add_property(ctx, GRPC_X509_CN_PROPERTY_NAME,
+                                     prop->value.data, prop->value.length);
     } else if (strcmp(prop->name,
                       TSI_X509_SUBJECT_ALTERNATIVE_NAME_PEER_PROPERTY) == 0) {
-      ctx->peer_identity_property_name = GRPC_X509_SAN_PROPERTY_NAME;
-      ctx->properties[ctx->property_count++] = grpc_auth_property_init(
-          GRPC_X509_SAN_PROPERTY_NAME, prop->value.data, prop->value.length);
+      peer_identity_property_name = GRPC_X509_SAN_PROPERTY_NAME;
+      grpc_auth_context_add_property(ctx, GRPC_X509_SAN_PROPERTY_NAME,
+                                     prop->value.data, prop->value.length);
     }
   }
+  if (peer_identity_property_name != NULL) {
+    GPR_ASSERT(grpc_auth_context_set_peer_identity_property_name(
+                   ctx, peer_identity_property_name) == 1);
+  }
   return ctx;
 }
 
diff --git a/src/core/security/security_context.c b/src/core/security/security_context.c
index 8ce7876bd8..1ef0fc9255 100644
--- a/src/core/security/security_context.c
+++ b/src/core/security/security_context.c
@@ -42,6 +42,19 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 
+/* --- grpc_process_auth_metadata_func --- */
+
+static grpc_auth_metadata_processor server_processor = {NULL, NULL};
+
+grpc_auth_metadata_processor grpc_server_get_auth_metadata_processor(void) {
+  return server_processor;
+}
+
+void grpc_server_register_auth_metadata_processor(
+    grpc_auth_metadata_processor processor) {
+  server_processor = processor;
+}
+
 /* --- grpc_call --- */
 
 grpc_call_error grpc_call_set_credentials(grpc_call *call,
@@ -120,15 +133,15 @@ void grpc_server_security_context_destroy(void *ctx) {
 
 static grpc_auth_property_iterator empty_iterator = {NULL, 0, NULL};
 
-grpc_auth_context *grpc_auth_context_create(grpc_auth_context *chained,
-                                            size_t property_count) {
+grpc_auth_context *grpc_auth_context_create(grpc_auth_context *chained) {
   grpc_auth_context *ctx = gpr_malloc(sizeof(grpc_auth_context));
   memset(ctx, 0, sizeof(grpc_auth_context));
-  ctx->properties = gpr_malloc(property_count * sizeof(grpc_auth_property));
-  memset(ctx->properties, 0, property_count * sizeof(grpc_auth_property));
-  ctx->property_count = property_count;
   gpr_ref_init(&ctx->refcount, 1);
-  if (chained != NULL) ctx->chained = GRPC_AUTH_CONTEXT_REF(chained, "chained");
+  if (chained != NULL) {
+    ctx->chained = GRPC_AUTH_CONTEXT_REF(chained, "chained");
+    ctx->peer_identity_property_name =
+        ctx->chained->peer_identity_property_name;
+  }
   return ctx;
 }
 
@@ -162,11 +175,11 @@ void grpc_auth_context_unref(grpc_auth_context *ctx) {
   if (gpr_unref(&ctx->refcount)) {
     size_t i;
     GRPC_AUTH_CONTEXT_UNREF(ctx->chained, "chained");
-    if (ctx->properties != NULL) {
-      for (i = 0; i < ctx->property_count; i++) {
-        grpc_auth_property_reset(&ctx->properties[i]);
+    if (ctx->properties.array != NULL) {
+      for (i = 0; i < ctx->properties.count; i++) {
+        grpc_auth_property_reset(&ctx->properties.array[i]);
       }
-      gpr_free(ctx->properties);
+      gpr_free(ctx->properties.array);
     }
     gpr_free(ctx);
   }
@@ -177,6 +190,20 @@ const char *grpc_auth_context_peer_identity_property_name(
   return ctx->peer_identity_property_name;
 }
 
+int grpc_auth_context_set_peer_identity_property_name(grpc_auth_context *ctx,
+                                                      const char *name) {
+  grpc_auth_property_iterator it =
+      grpc_auth_context_find_properties_by_name(ctx, name);
+  const grpc_auth_property *prop = grpc_auth_property_iterator_next(&it);
+  if (prop == NULL) {
+    gpr_log(GPR_ERROR, "Property name %s not found in auth context.",
+            name != NULL ? name : "NULL");
+    return 0;
+  }
+  ctx->peer_identity_property_name = prop->name;
+  return 1;
+}
+
 int grpc_auth_context_peer_is_authenticated(
     const grpc_auth_context *ctx) {
   return ctx->peer_identity_property_name == NULL ? 0 : 1;
@@ -193,16 +220,16 @@ grpc_auth_property_iterator grpc_auth_context_property_iterator(
 const grpc_auth_property *grpc_auth_property_iterator_next(
     grpc_auth_property_iterator *it) {
   if (it == NULL || it->ctx == NULL) return NULL;
-  while (it->index == it->ctx->property_count) {
+  while (it->index == it->ctx->properties.count) {
     if (it->ctx->chained == NULL) return NULL;
     it->ctx = it->ctx->chained;
     it->index = 0;
   }
   if (it->name == NULL) {
-    return &it->ctx->properties[it->index++];
+    return &it->ctx->properties.array[it->index++];
   } else {
-    while (it->index < it->ctx->property_count) {
-      const grpc_auth_property *prop = &it->ctx->properties[it->index++];
+    while (it->index < it->ctx->properties.count) {
+      const grpc_auth_property *prop = &it->ctx->properties.array[it->index++];
       GPR_ASSERT(prop->name != NULL);
       if (strcmp(it->name, prop->name) == 0) {
         return prop;
@@ -229,24 +256,37 @@ grpc_auth_property_iterator grpc_auth_context_peer_identity(
       ctx, ctx->peer_identity_property_name);
 }
 
-grpc_auth_property grpc_auth_property_init_from_cstring(const char *name,
-                                                        const char *value) {
-  grpc_auth_property prop;
-  prop.name = gpr_strdup(name);
-  prop.value = gpr_strdup(value);
-  prop.value_length = strlen(value);
-  return prop;
+static void ensure_auth_context_capacity(grpc_auth_context *ctx) {
+  if (ctx->properties.count == ctx->properties.capacity) {
+    ctx->properties.capacity =
+        GPR_MAX(ctx->properties.capacity + 8, ctx->properties.capacity * 2);
+    ctx->properties.array =
+        gpr_realloc(ctx->properties.array,
+                    ctx->properties.capacity * sizeof(grpc_auth_property));
+  }
 }
 
-grpc_auth_property grpc_auth_property_init(const char *name, const char *value,
-                                           size_t value_length) {
-  grpc_auth_property prop;
-  prop.name = gpr_strdup(name);
-  prop.value = gpr_malloc(value_length + 1);
-  memcpy(prop.value, value, value_length);
-  prop.value[value_length] = '\0';
-  prop.value_length = value_length;
-  return prop;
+void grpc_auth_context_add_property(grpc_auth_context *ctx, const char *name,
+                                    const char *value, size_t value_length) {
+  grpc_auth_property *prop;
+  ensure_auth_context_capacity(ctx);
+  prop = &ctx->properties.array[ctx->properties.count++];
+  prop->name = gpr_strdup(name);
+  prop->value = gpr_malloc(value_length + 1);
+  memcpy(prop->value, value, value_length);
+  prop->value[value_length] = '\0';
+  prop->value_length = value_length;
+}
+
+void grpc_auth_context_add_cstring_property(grpc_auth_context *ctx,
+                                            const char *name,
+                                            const char *value) {
+  grpc_auth_property *prop;
+  ensure_auth_context_capacity(ctx);
+  prop = &ctx->properties.array[ctx->properties.count++];
+  prop->name = gpr_strdup(name);
+  prop->value = gpr_strdup(value);
+  prop->value_length = strlen(value);
 }
 
 void grpc_auth_property_reset(grpc_auth_property *property) {
@@ -255,3 +295,35 @@ void grpc_auth_property_reset(grpc_auth_property *property) {
   memset(property, 0, sizeof(grpc_auth_property));
 }
 
+grpc_arg grpc_auth_metadata_processor_to_arg(grpc_auth_metadata_processor *p) {
+  grpc_arg arg;
+  memset(&arg, 0, sizeof(grpc_arg));
+  arg.type = GRPC_ARG_POINTER;
+  arg.key = GRPC_AUTH_METADATA_PROCESSOR_ARG;
+  arg.value.pointer.p = p;
+  return arg;
+}
+
+grpc_auth_metadata_processor *grpc_auth_metadata_processor_from_arg(
+    const grpc_arg *arg) {
+  if (strcmp(arg->key, GRPC_AUTH_METADATA_PROCESSOR_ARG) != 0) return NULL;
+  if (arg->type != GRPC_ARG_POINTER) {
+    gpr_log(GPR_ERROR, "Invalid type %d for arg %s", arg->type,
+            GRPC_AUTH_METADATA_PROCESSOR_ARG);
+    return NULL;
+  }
+  return arg->value.pointer.p;
+}
+
+grpc_auth_metadata_processor *grpc_find_auth_metadata_processor_in_args(
+    const grpc_channel_args *args) {
+  size_t i;
+  if (args == NULL) return NULL;
+  for (i = 0; i < args->num_args; i++) {
+    grpc_auth_metadata_processor *p =
+        grpc_auth_metadata_processor_from_arg(&args->args[i]);
+    if (p != NULL) return p;
+  }
+  return NULL;
+}
+
diff --git a/src/core/security/security_context.h b/src/core/security/security_context.h
index 76a45910bb..7fcd438cf6 100644
--- a/src/core/security/security_context.h
+++ b/src/core/security/security_context.h
@@ -34,29 +34,31 @@
 #ifndef GRPC_INTERNAL_CORE_SECURITY_SECURITY_CONTEXT_H
 #define GRPC_INTERNAL_CORE_SECURITY_SECURITY_CONTEXT_H
 
+#include "src/core/iomgr/pollset.h"
 #include "src/core/security/credentials.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* --- grpc_auth_context ---
 
    High level authentication context object. Can optionally be chained. */
 
 /* Property names are always NULL terminated. */
 
+typedef struct {
+  grpc_auth_property *array;
+  size_t count;
+  size_t capacity;
+} grpc_auth_property_array;
+
 struct grpc_auth_context {
   struct grpc_auth_context *chained;
-  grpc_auth_property *properties;
-  size_t property_count;
+  grpc_auth_property_array properties;
   gpr_refcount refcount;
   const char *peer_identity_property_name;
+  grpc_pollset *pollset;
 };
 
-/* Constructor. */
-grpc_auth_context *grpc_auth_context_create(grpc_auth_context *chained,
-                                            size_t property_count);
+/* Creation. */
+grpc_auth_context *grpc_auth_context_create(grpc_auth_context *chained);
 
 /* Refcounting. */
 #ifdef GRPC_AUTH_CONTEXT_REFCOUNT_DEBUG
@@ -76,12 +78,6 @@ grpc_auth_context *grpc_auth_context_ref(grpc_auth_context *policy);
 void grpc_auth_context_unref(grpc_auth_context *policy);
 #endif
 
-grpc_auth_property grpc_auth_property_init_from_cstring(const char *name,
-                                                        const char *value);
-
-grpc_auth_property grpc_auth_property_init(const char *name, const char *value,
-                                           size_t value_length);
-
 void grpc_auth_property_reset(grpc_auth_property *property);
 
 /* --- grpc_client_security_context ---
@@ -107,9 +103,14 @@ typedef struct {
 grpc_server_security_context *grpc_server_security_context_create(void);
 void grpc_server_security_context_destroy(void *ctx);
 
-#ifdef __cplusplus
-}
-#endif
+/* --- Auth metadata processing. --- */
+#define GRPC_AUTH_METADATA_PROCESSOR_ARG "grpc.auth_metadata_processor"
+
+grpc_arg grpc_auth_metadata_processor_to_arg(grpc_auth_metadata_processor *p);
+grpc_auth_metadata_processor *grpc_auth_metadata_processor_from_arg(
+    const grpc_arg *arg);
+grpc_auth_metadata_processor *grpc_find_auth_metadata_processor_in_args(
+    const grpc_channel_args *args);
 
 #endif  /* GRPC_INTERNAL_CORE_SECURITY_SECURITY_CONTEXT_H */
 
diff --git a/src/core/security/server_auth_filter.c b/src/core/security/server_auth_filter.c
index 69789c2f0d..2fc689caec 100644
--- a/src/core/security/server_auth_filter.c
+++ b/src/core/security/server_auth_filter.c
@@ -31,20 +31,140 @@
  *
  */
 
+#include <string.h>
+
 #include "src/core/security/auth_filters.h"
 #include "src/core/security/security_connector.h"
 #include "src/core/security/security_context.h"
 
+#include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 
 typedef struct call_data {
-  int unused; /* C89 requires at least one struct element */
+  gpr_uint8 got_client_metadata;
+  grpc_stream_op_buffer *recv_ops;
+  /* Closure to call when finished with the auth_on_recv hook. */
+  grpc_iomgr_closure *on_done_recv;
+  /* Receive closures are chained: we inject this closure as the on_done_recv
+     up-call on transport_op, and remember to call our on_done_recv member after
+     handling it. */
+  grpc_iomgr_closure auth_on_recv;
+  grpc_transport_stream_op transport_op;
+  const grpc_metadata *consumed_md;
+  size_t num_consumed_md;
+  grpc_stream_op *md_op;
+  grpc_auth_context *auth_context;
 } call_data;
 
 typedef struct channel_data {
   grpc_security_connector *security_connector;
+  grpc_auth_metadata_processor processor;
+  grpc_mdctx *mdctx;
 } channel_data;
 
+static grpc_metadata_array metadata_batch_to_md_array(
+    const grpc_metadata_batch *batch) {
+  grpc_linked_mdelem *l;
+  grpc_metadata_array result;
+  grpc_metadata_array_init(&result);
+  for (l = batch->list.head; l != NULL; l = l->next) {
+    grpc_metadata *usr_md = NULL;
+    grpc_mdelem *md = l->md;
+    grpc_mdstr *key = md->key;
+    grpc_mdstr *value = md->value;
+    if (result.count == result.capacity) {
+      result.capacity = GPR_MAX(result.capacity + 8, result.capacity * 2);
+      result.metadata =
+          gpr_realloc(result.metadata, result.capacity * sizeof(grpc_metadata));
+    }
+    usr_md = &result.metadata[result.count++];
+    usr_md->key = grpc_mdstr_as_c_string(key);
+    usr_md->value = grpc_mdstr_as_c_string(value);
+    usr_md->value_length = GPR_SLICE_LENGTH(value->slice);
+  }
+  return result;
+}
+
+static grpc_mdelem *remove_consumed_md(void *user_data, grpc_mdelem *md) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+  size_t i;
+  for (i = 0; i < calld->num_consumed_md; i++) {
+    /* Maybe we could do a pointer comparison but we do not have any guarantee
+       that the metadata processor used the same pointers for consumed_md in the
+       callback. */
+    if (memcmp(GPR_SLICE_START_PTR(md->key->slice), calld->consumed_md[i].key,
+               GPR_SLICE_LENGTH(md->key->slice)) == 0 &&
+        memcmp(GPR_SLICE_START_PTR(md->value->slice),
+               calld->consumed_md[i].value,
+               GPR_SLICE_LENGTH(md->value->slice)) == 0) {
+      return NULL; /* Delete. */
+    }
+  }
+  return md;
+}
+
+static void on_md_processing_done(void *user_data,
+                                  const grpc_metadata *consumed_md,
+                                  size_t num_consumed_md, int success) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+
+  if (success) {
+    calld->consumed_md = consumed_md;
+    calld->num_consumed_md = num_consumed_md;
+    grpc_metadata_batch_filter(&calld->md_op->data.metadata, remove_consumed_md,
+                               elem);
+    calld->on_done_recv->cb(calld->on_done_recv->cb_arg, success);
+  } else {
+    gpr_slice message = gpr_slice_from_copied_string(
+        "Authentication metadata processing failed.");
+    grpc_sopb_reset(calld->recv_ops);
+    grpc_transport_stream_op_add_close(&calld->transport_op,
+                                       GRPC_STATUS_UNAUTHENTICATED, &message);
+    grpc_call_next_op(elem, &calld->transport_op);
+  }
+}
+
+static void auth_on_recv(void *user_data, int success) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+  channel_data *chand = elem->channel_data;
+  if (success) {
+    size_t i;
+    size_t nops = calld->recv_ops->nops;
+    grpc_stream_op *ops = calld->recv_ops->ops;
+    for (i = 0; i < nops; i++) {
+      grpc_metadata_array md_array;
+      grpc_stream_op *op = &ops[i];
+      if (op->type != GRPC_OP_METADATA || calld->got_client_metadata) continue;
+      calld->got_client_metadata = 1;
+      if (chand->processor.process == NULL) continue;
+      calld->md_op = op;
+      md_array = metadata_batch_to_md_array(&op->data.metadata);
+      chand->processor.process(chand->processor.state, calld->auth_context,
+                               md_array.metadata, md_array.count,
+                               on_md_processing_done, elem);
+      grpc_metadata_array_destroy(&md_array);
+      return;
+    }
+  }
+  calld->on_done_recv->cb(calld->on_done_recv->cb_arg, success);
+}
+
+static void set_recv_ops_md_callbacks(grpc_call_element *elem,
+                                      grpc_transport_stream_op *op) {
+  call_data *calld = elem->call_data;
+
+  if (op->recv_ops && !calld->got_client_metadata) {
+    /* substitute our callback for the higher callback */
+    calld->recv_ops = op->recv_ops;
+    calld->on_done_recv = op->on_done_recv;
+    op->on_done_recv = &calld->auth_on_recv;
+    calld->transport_op = *op;
+  }
+}
+
 /* Called either:
      - in response to an API call (or similar) from above, to send something
      - a network event (or similar) from below, to receive something
@@ -52,9 +172,7 @@ typedef struct channel_data {
    that is being sent or received. */
 static void auth_start_transport_op(grpc_call_element *elem,
                                     grpc_transport_stream_op *op) {
-  /* TODO(jboeuf): Get the metadata and get a new context from it. */
-
-  /* pass control down the stack */
+  set_recv_ops_md_callbacks(elem, op);
   grpc_call_next_op(elem, op);
 }
 
@@ -68,7 +186,8 @@ static void init_call_elem(grpc_call_element *elem,
   grpc_server_security_context *server_ctx = NULL;
 
   /* initialize members */
-  calld->unused = 0;
+  memset(calld, 0, sizeof(*calld));
+  grpc_iomgr_closure_init(&calld->auth_on_recv, auth_on_recv, elem);
 
   GPR_ASSERT(initial_op && initial_op->context != NULL &&
              initial_op->context[GRPC_CONTEXT_SECURITY].value == NULL);
@@ -80,21 +199,29 @@ static void init_call_elem(grpc_call_element *elem,
         initial_op->context[GRPC_CONTEXT_SECURITY].value);
   }
   server_ctx = grpc_server_security_context_create();
-  server_ctx->auth_context = GRPC_AUTH_CONTEXT_REF(
-      chand->security_connector->auth_context, "server_security_context");
+  server_ctx->auth_context =
+      grpc_auth_context_create(chand->security_connector->auth_context);
+  server_ctx->auth_context->pollset = initial_op->bind_pollset;
   initial_op->context[GRPC_CONTEXT_SECURITY].value = server_ctx;
   initial_op->context[GRPC_CONTEXT_SECURITY].destroy =
       grpc_server_security_context_destroy;
+  calld->auth_context = server_ctx->auth_context;
+
+  /* Set the metadata callbacks. */
+  set_recv_ops_md_callbacks(elem, initial_op);
 }
 
 /* Destructor for call_data */
-static void destroy_call_elem(grpc_call_element *elem) {}
+static void destroy_call_elem(grpc_call_element *elem) {
+}
 
 /* Constructor for channel_data */
 static void init_channel_elem(grpc_channel_element *elem, grpc_channel *master,
                               const grpc_channel_args *args, grpc_mdctx *mdctx,
                               int is_first, int is_last) {
   grpc_security_connector *sc = grpc_find_security_connector_in_args(args);
+  grpc_auth_metadata_processor *processor =
+      grpc_find_auth_metadata_processor_in_args(args);
   /* grab pointers to our data from the channel element */
   channel_data *chand = elem->channel_data;
 
@@ -104,11 +231,14 @@ static void init_channel_elem(grpc_channel_element *elem, grpc_channel *master,
   GPR_ASSERT(!is_first);
   GPR_ASSERT(!is_last);
   GPR_ASSERT(sc != NULL);
+  GPR_ASSERT(processor != NULL);
 
   /* initialize members */
   GPR_ASSERT(!sc->is_client_side);
   chand->security_connector =
       GRPC_SECURITY_CONNECTOR_REF(sc, "server_auth_filter");
+  chand->mdctx = mdctx;
+  chand->processor = *processor;
 }
 
 /* Destructor for channel data */
diff --git a/src/core/security/server_secure_chttp2.c b/src/core/security/server_secure_chttp2.c
index 3717b8989f..8d9d036d80 100644
--- a/src/core/security/server_secure_chttp2.c
+++ b/src/core/security/server_secure_chttp2.c
@@ -43,6 +43,7 @@
 #include "src/core/security/auth_filters.h"
 #include "src/core/security/credentials.h"
 #include "src/core/security/security_connector.h"
+#include "src/core/security/security_context.h"
 #include "src/core/security/secure_transport_setup.h"
 #include "src/core/surface/server.h"
 #include "src/core/transport/chttp2_transport.h"
@@ -60,6 +61,7 @@ typedef struct grpc_server_secure_state {
   grpc_server *server;
   grpc_tcp_server *tcp;
   grpc_security_connector *sc;
+  grpc_auth_metadata_processor processor;
   tcp_endpoint_list *handshaking_tcp_endpoints;
   int is_shutdown;
   gpr_mu mu;
@@ -86,9 +88,13 @@ static void setup_transport(void *statep, grpc_transport *transport,
   static grpc_channel_filter const *extra_filters[] = {
       &grpc_server_auth_filter, &grpc_http_server_filter};
   grpc_server_secure_state *state = statep;
-  grpc_arg connector_arg = grpc_security_connector_to_arg(state->sc);
-  grpc_channel_args *args_copy = grpc_channel_args_copy_and_add(
-      grpc_server_get_channel_args(state->server), &connector_arg, 1);
+  grpc_channel_args *args_copy;
+  grpc_arg args_to_add[2];
+  args_to_add[0] = grpc_security_connector_to_arg(state->sc);
+  args_to_add[1] = grpc_auth_metadata_processor_to_arg(&state->processor);
+  args_copy = grpc_channel_args_copy_and_add(
+      grpc_server_get_channel_args(state->server), args_to_add,
+      GPR_ARRAY_SIZE(args_to_add));
   grpc_server_setup_transport(state->server, transport, extra_filters,
                               GPR_ARRAY_SIZE(extra_filters), mdctx, args_copy);
   grpc_channel_args_destroy(args_copy);
@@ -252,9 +258,11 @@ int grpc_server_add_secure_http2_port(grpc_server *server, const char *addr,
   grpc_resolved_addresses_destroy(resolved);
 
   state = gpr_malloc(sizeof(*state));
+  memset(state, 0, sizeof(*state));
   state->server = server;
   state->tcp = tcp;
   state->sc = sc;
+  state->processor = creds->processor;
   state->handshaking_tcp_endpoints = NULL;
   state->is_shutdown = 0;
   gpr_mu_init(&state->mu);
diff --git a/src/core/surface/call.c b/src/core/surface/call.c
index d3e66e9c4c..5839d3ac2e 100644
--- a/src/core/surface/call.c
+++ b/src/core/surface/call.c
@@ -456,20 +456,6 @@ void grpc_call_internal_ref(grpc_call *c) {
 static void destroy_call(void *call, int ignored_success) {
   size_t i;
   grpc_call *c = call;
-  grpc_call *parent = c->parent;
-  if (parent) {
-    gpr_mu_lock(&parent->mu);
-    if (call == parent->first_child) {
-      parent->first_child = c->sibling_next;
-      if (c == parent->first_child) {
-        parent->first_child = NULL;
-      }
-      c->sibling_prev->sibling_next = c->sibling_next;
-      c->sibling_next->sibling_prev = c->sibling_prev;
-    }
-    gpr_mu_unlock(&parent->mu);
-    GRPC_CALL_INTERNAL_UNREF(parent, "child", 1);
-  }
   grpc_call_stack_destroy(CALL_STACK_FROM_CALL(c));
   GRPC_CHANNEL_INTERNAL_UNREF(c->channel, "call");
   gpr_mu_destroy(&c->mu);
@@ -1257,6 +1243,22 @@ grpc_call_error grpc_call_start_ioreq_and_call_back(
 
 void grpc_call_destroy(grpc_call *c) {
   int cancel;
+  grpc_call *parent = c->parent;
+
+  if (parent) {
+    gpr_mu_lock(&parent->mu);
+    if (c == parent->first_child) {
+      parent->first_child = c->sibling_next;
+      if (c == parent->first_child) {
+        parent->first_child = NULL;
+      }
+      c->sibling_prev->sibling_next = c->sibling_next;
+      c->sibling_next->sibling_prev = c->sibling_prev;
+    }
+    gpr_mu_unlock(&parent->mu);
+    GRPC_CALL_INTERNAL_UNREF(parent, "child", 1);
+  }
+
   lock(c);
   GPR_ASSERT(!c->destroy_called);
   c->destroy_called = 1;
@@ -1537,6 +1539,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
         /* Flag validation: currently allow no flags */
         if (op->flags != 0) return GRPC_CALL_ERROR_INVALID_FLAGS;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_SEND_INITIAL_METADATA;
         req->data.send_metadata.count = op->data.send_initial_metadata.count;
         req->data.send_metadata.metadata =
@@ -1551,6 +1554,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
           return GRPC_CALL_ERROR_INVALID_MESSAGE;
         }
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_SEND_MESSAGE;
         req->data.send_message = op->data.send_message;
         req->flags = op->flags;
@@ -1562,6 +1566,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
           return GRPC_CALL_ERROR_NOT_ON_SERVER;
         }
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_SEND_CLOSE;
         req->flags = op->flags;
         break;
@@ -1572,6 +1577,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
           return GRPC_CALL_ERROR_NOT_ON_CLIENT;
         }
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_SEND_TRAILING_METADATA;
         req->flags = op->flags;
         req->data.send_metadata.count =
@@ -1579,6 +1585,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
         req->data.send_metadata.metadata =
             op->data.send_status_from_server.trailing_metadata;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_SEND_STATUS;
         req->data.send_status.code = op->data.send_status_from_server.status;
         req->data.send_status.details =
@@ -1588,6 +1595,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
                       op->data.send_status_from_server.status_details, 0)
                 : NULL;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_SEND_CLOSE;
         break;
       case GRPC_OP_RECV_INITIAL_METADATA:
@@ -1597,6 +1605,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
           return GRPC_CALL_ERROR_NOT_ON_SERVER;
         }
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_INITIAL_METADATA;
         req->data.recv_metadata = op->data.recv_initial_metadata;
         req->data.recv_metadata->count = 0;
@@ -1606,6 +1615,7 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
         /* Flag validation: currently allow no flags */
         if (op->flags != 0) return GRPC_CALL_ERROR_INVALID_FLAGS;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_MESSAGE;
         req->data.recv_message = op->data.recv_message;
         req->flags = op->flags;
@@ -1617,22 +1627,26 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
           return GRPC_CALL_ERROR_NOT_ON_SERVER;
         }
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_STATUS;
         req->flags = op->flags;
         req->data.recv_status.set_value = set_status_value_directly;
         req->data.recv_status.user_data = op->data.recv_status_on_client.status;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_STATUS_DETAILS;
         req->data.recv_status_details.details =
             op->data.recv_status_on_client.status_details;
         req->data.recv_status_details.details_capacity =
             op->data.recv_status_on_client.status_details_capacity;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_TRAILING_METADATA;
         req->data.recv_metadata =
             op->data.recv_status_on_client.trailing_metadata;
         req->data.recv_metadata->count = 0;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_CLOSE;
         finish_func = finish_batch_with_close;
         break;
@@ -1640,12 +1654,14 @@ grpc_call_error grpc_call_start_batch(grpc_call *call, const grpc_op *ops,
         /* Flag validation: currently allow no flags */
         if (op->flags != 0) return GRPC_CALL_ERROR_INVALID_FLAGS;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_STATUS;
         req->flags = op->flags;
         req->data.recv_status.set_value = set_cancelled_value;
         req->data.recv_status.user_data =
             op->data.recv_close_on_server.cancelled;
         req = &reqs[out++];
+	if (out > GRPC_IOREQ_OP_COUNT) return GRPC_CALL_ERROR_BATCH_TOO_BIG;
         req->op = GRPC_IOREQ_RECV_CLOSE;
         finish_func = finish_batch_with_close;
         break;
diff --git a/src/core/surface/secure_channel_create.c b/src/core/surface/secure_channel_create.c
index 1f89353025..c3150250b8 100644
--- a/src/core/surface/secure_channel_create.c
+++ b/src/core/surface/secure_channel_create.c
@@ -88,8 +88,8 @@ static void on_secure_transport_setup_done(void *arg,
         c->args.channel_args, secure_endpoint, c->args.metadata_context, 1);
     grpc_chttp2_transport_start_reading(c->result->transport, NULL, 0);
     c->result->filters = gpr_malloc(sizeof(grpc_channel_filter *) * 2);
-    c->result->filters[0] = &grpc_client_auth_filter;
-    c->result->filters[1] = &grpc_http_client_filter;
+    c->result->filters[0] = &grpc_http_client_filter;
+    c->result->filters[1] = &grpc_client_auth_filter;
     c->result->num_filters = 2;
   }
   notify = c->notify;
diff --git a/src/core/surface/version.c b/src/core/surface/version.c
index 4f5d648371..d7aaba3868 100644
--- a/src/core/surface/version.c
+++ b/src/core/surface/version.c
@@ -37,5 +37,5 @@
 #include <grpc/grpc.h>
 
 const char *grpc_version_string(void) {
-	return "0.10.0.0";
+	return "0.10.1.0";
 }
diff --git a/src/core/transport/chttp2/internal.h b/src/core/transport/chttp2/internal.h
index cb428f8e3c..42cf0ecd5b 100644
--- a/src/core/transport/chttp2/internal.h
+++ b/src/core/transport/chttp2/internal.h
@@ -388,6 +388,8 @@ typedef struct {
   gpr_uint8 in_stream_map;
   /** bitmask of GRPC_CHTTP2_WRITING_xxx above */
   gpr_uint8 writing_now;
+  /** has anything been written to this stream? */
+  gpr_uint8 written_anything;
 
   /** stream state already published to the upper layer */
   grpc_stream_state published_state;
diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index 6ba144faa4..a9f91b64d5 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -107,6 +107,11 @@ static void cancel_from_api(grpc_chttp2_transport_global *transport_global,
                             grpc_chttp2_stream_global *stream_global,
                             grpc_status_code status);
 
+static void close_from_api(grpc_chttp2_transport_global *transport_global,
+                           grpc_chttp2_stream_global *stream_global,
+                           grpc_status_code status,
+                           gpr_slice *optional_message);
+
 /** Add endpoint from this transport to pollset */
 static void add_to_pollset_locked(grpc_chttp2_transport *t,
                                   grpc_pollset *pollset);
@@ -602,10 +607,16 @@ static void perform_stream_op_locked(
     cancel_from_api(transport_global, stream_global, op->cancel_with_status);
   }
 
+  if (op->close_with_status != GRPC_STATUS_OK) {
+    close_from_api(transport_global, stream_global, op->close_with_status,
+                   op->optional_close_message);
+  }
+
   if (op->send_ops) {
     GPR_ASSERT(stream_global->outgoing_sopb == NULL);
     stream_global->send_done_closure = op->on_done_send;
     if (!stream_global->cancelled) {
+      stream_global->written_anything = 1;
       stream_global->outgoing_sopb = op->send_ops;
       if (op->is_last_send &&
           stream_global->write_state == GRPC_WRITE_STATE_OPEN) {
@@ -900,6 +911,108 @@ static void cancel_from_api(grpc_chttp2_transport_global *transport_global,
                                                 stream_global);
 }
 
+static void close_from_api(grpc_chttp2_transport_global *transport_global,
+                           grpc_chttp2_stream_global *stream_global,
+                           grpc_status_code status,
+                           gpr_slice *optional_message) {
+  gpr_slice hdr;
+  gpr_slice status_hdr;
+  gpr_slice message_pfx;
+  gpr_uint8 *p;
+  gpr_uint32 len = 0;
+
+  GPR_ASSERT(status >= 0 && (int)status < 100);
+
+  stream_global->cancelled = 1;
+  stream_global->cancelled_status = status;
+  GPR_ASSERT(stream_global->id != 0);
+  GPR_ASSERT(!stream_global->written_anything);
+
+  /* Hand roll a header block.
+     This is unnecessarily ugly - at some point we should find a more elegant
+     solution.
+     It's complicated by the fact that our send machinery would be dead by the
+     time we got around to sending this, so instead we ignore HPACK compression
+     and just write the uncompressed bytes onto the wire. */
+  status_hdr = gpr_slice_malloc(15 + (status >= 10));
+  p = GPR_SLICE_START_PTR(status_hdr);
+  *p++ = 0x40; /* literal header */
+  *p++ = 11;   /* len(grpc-status) */
+  *p++ = 'g';
+  *p++ = 'r';
+  *p++ = 'p';
+  *p++ = 'c';
+  *p++ = '-';
+  *p++ = 's';
+  *p++ = 't';
+  *p++ = 'a';
+  *p++ = 't';
+  *p++ = 'u';
+  *p++ = 's';
+  if (status < 10) {
+    *p++ = 1;
+    *p++ = '0' + status;
+  } else {
+    *p++ = 2;
+    *p++ = '0' + (status / 10);
+    *p++ = '0' + (status % 10);
+  }
+  GPR_ASSERT(p == GPR_SLICE_END_PTR(status_hdr));
+  len += GPR_SLICE_LENGTH(status_hdr);
+
+  if (optional_message) {
+    GPR_ASSERT(GPR_SLICE_LENGTH(*optional_message) < 127);
+    message_pfx = gpr_slice_malloc(15);
+    p = GPR_SLICE_START_PTR(message_pfx);
+    *p++ = 0x40;
+    *p++ = 12; /* len(grpc-message) */
+    *p++ = 'g';
+    *p++ = 'r';
+    *p++ = 'p';
+    *p++ = 'c';
+    *p++ = '-';
+    *p++ = 'm';
+    *p++ = 'e';
+    *p++ = 's';
+    *p++ = 's';
+    *p++ = 'a';
+    *p++ = 'g';
+    *p++ = 'e';
+    *p++ = GPR_SLICE_LENGTH(*optional_message);
+    GPR_ASSERT(p == GPR_SLICE_END_PTR(message_pfx));
+    len += GPR_SLICE_LENGTH(message_pfx);
+    len += GPR_SLICE_LENGTH(*optional_message);
+  }
+
+  hdr = gpr_slice_malloc(9);
+  p = GPR_SLICE_START_PTR(hdr);
+  *p++ = len >> 16;
+  *p++ = len >> 8;
+  *p++ = len;
+  *p++ = GRPC_CHTTP2_FRAME_HEADER;
+  *p++ = GRPC_CHTTP2_DATA_FLAG_END_STREAM | GRPC_CHTTP2_DATA_FLAG_END_HEADERS;
+  *p++ = stream_global->id >> 24;
+  *p++ = stream_global->id >> 16;
+  *p++ = stream_global->id >> 8;
+  *p++ = stream_global->id;
+  GPR_ASSERT(p == GPR_SLICE_END_PTR(hdr));
+
+  gpr_slice_buffer_add(&transport_global->qbuf, hdr);
+  gpr_slice_buffer_add(&transport_global->qbuf, status_hdr);
+  if (optional_message) {
+    gpr_slice_buffer_add(&transport_global->qbuf, message_pfx);
+    gpr_slice_buffer_add(&transport_global->qbuf,
+                         gpr_slice_ref(*optional_message));
+  }
+
+  gpr_slice_buffer_add(
+      &transport_global->qbuf,
+      grpc_chttp2_rst_stream_create(stream_global->id, GRPC_CHTTP2_NO_ERROR));
+
+  grpc_chttp2_list_add_read_write_state_changed(transport_global,
+                                                stream_global);
+}
+
 static void cancel_stream_cb(grpc_chttp2_transport_global *transport_global,
                              void *user_data,
                              grpc_chttp2_stream_global *stream_global) {
diff --git a/src/core/transport/metadata.c b/src/core/transport/metadata.c
index 967fd4898c..44d32b6cb2 100644
--- a/src/core/transport/metadata.c
+++ b/src/core/transport/metadata.c
@@ -135,7 +135,9 @@ static void unlock(grpc_mdctx *ctx) {
   if (ctx->refs == 0) {
     /* uncomment if you're having trouble diagnosing an mdelem leak to make
        things clearer (slows down destruction a lot, however) */
+#ifdef GRPC_METADATA_REFCOUNT_DEBUG
     gc_mdtab(ctx);
+#endif
     if (ctx->mdtab_count && ctx->mdtab_count == ctx->mdtab_free) {
       discard_metadata(ctx);
     }
diff --git a/src/core/transport/stream_op.h b/src/core/transport/stream_op.h
index f27ef1b66b..227320cf2a 100644
--- a/src/core/transport/stream_op.h
+++ b/src/core/transport/stream_op.h
@@ -108,7 +108,7 @@ void grpc_metadata_batch_move(grpc_metadata_batch *dst,
                               grpc_metadata_batch *src);
 
 /** Add \a storage to the beginning of \a batch. storage->md is
-    assumed to be valid. 
+    assumed to be valid.
     \a storage is owned by the caller and must survive for the
     lifetime of batch. This usually means it should be around
     for the lifetime of the call. */
diff --git a/src/core/transport/transport.c b/src/core/transport/transport.c
index 69c00b6a4f..c0d92cf93f 100644
--- a/src/core/transport/transport.c
+++ b/src/core/transport/transport.c
@@ -32,6 +32,8 @@
  */
 
 #include "src/core/transport/transport.h"
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
 #include "src/core/transport/transport_impl.h"
 
 size_t grpc_transport_stream_size(grpc_transport *transport) {
@@ -83,12 +85,54 @@ void grpc_transport_stream_op_finish_with_failure(
 }
 
 void grpc_transport_stream_op_add_cancellation(grpc_transport_stream_op *op,
-                                               grpc_status_code status,
-                                               grpc_mdstr *message) {
+                                               grpc_status_code status) {
+  GPR_ASSERT(status != GRPC_STATUS_OK);
   if (op->cancel_with_status == GRPC_STATUS_OK) {
     op->cancel_with_status = status;
   }
-  if (message) {
-    GRPC_MDSTR_UNREF(message);
+  if (op->close_with_status != GRPC_STATUS_OK) {
+    op->close_with_status = GRPC_STATUS_OK;
+    if (op->optional_close_message != NULL) {
+      gpr_slice_unref(*op->optional_close_message);
+      op->optional_close_message = NULL;
+    }
   }
 }
+
+typedef struct {
+  gpr_slice message;
+  grpc_iomgr_closure *then_call;
+  grpc_iomgr_closure closure;
+} close_message_data;
+
+static void free_message(void *p, int iomgr_success) {
+  close_message_data *cmd = p;
+  gpr_slice_unref(cmd->message);
+  if (cmd->then_call != NULL) {
+    cmd->then_call->cb(cmd->then_call->cb_arg, iomgr_success);
+  }
+  gpr_free(cmd);
+}
+
+void grpc_transport_stream_op_add_close(grpc_transport_stream_op *op,
+                                        grpc_status_code status,
+                                        gpr_slice *optional_message) {
+  close_message_data *cmd;
+  GPR_ASSERT(status != GRPC_STATUS_OK);
+  if (op->cancel_with_status != GRPC_STATUS_OK ||
+      op->close_with_status != GRPC_STATUS_OK) {
+    if (optional_message) {
+      gpr_slice_unref(*optional_message);
+    }
+    return;
+  }
+  if (optional_message) {
+    cmd = gpr_malloc(sizeof(*cmd));
+    cmd->message = *optional_message;
+    cmd->then_call = op->on_consumed;
+    grpc_iomgr_closure_init(&cmd->closure, free_message, cmd);
+    op->on_consumed = &cmd->closure;
+    op->optional_close_message = &cmd->message;
+  }
+  op->close_with_status = status;
+}
diff --git a/src/core/transport/transport.h b/src/core/transport/transport.h
index 7efcfcf970..92c1f38c5e 100644
--- a/src/core/transport/transport.h
+++ b/src/core/transport/transport.h
@@ -80,8 +80,14 @@ typedef struct grpc_transport_stream_op {
 
   grpc_pollset *bind_pollset;
 
+  /** If != GRPC_STATUS_OK, cancel this stream */
   grpc_status_code cancel_with_status;
 
+  /** If != GRPC_STATUS_OK, send grpc-status, grpc-message, and close this
+      stream for both reading and writing */
+  grpc_status_code close_with_status;
+  gpr_slice *optional_close_message;
+
   /* Indexes correspond to grpc_context_index enum values */
   grpc_call_context_element *context;
 } grpc_transport_stream_op;
@@ -148,8 +154,11 @@ void grpc_transport_destroy_stream(grpc_transport *transport,
 void grpc_transport_stream_op_finish_with_failure(grpc_transport_stream_op *op);
 
 void grpc_transport_stream_op_add_cancellation(grpc_transport_stream_op *op,
-                                               grpc_status_code status,
-                                               grpc_mdstr *message);
+                                               grpc_status_code status);
+
+void grpc_transport_stream_op_add_close(grpc_transport_stream_op *op,
+                                        grpc_status_code status,
+                                        gpr_slice *optional_message);
 
 char *grpc_transport_stream_op_string(grpc_transport_stream_op *op);
 
diff --git a/src/core/tsi/transport_security_interface.h b/src/core/tsi/transport_security_interface.h
index 936b0c25b0..e27e6b9fc9 100644
--- a/src/core/tsi/transport_security_interface.h
+++ b/src/core/tsi/transport_security_interface.h
@@ -158,6 +158,8 @@ tsi_result tsi_frame_protector_protect_flush(
      value is expected to be at most max_protected_frame_size minus overhead
      which means that max_protected_frame_size is a safe bet. The output value
      is the number of bytes actually written.
+     If *unprotected_bytes_size is unchanged, there may be more data remaining
+     to unprotect, and the caller should call this function again.
 
    - This method returns TSI_OK in case of success. Success includes cases where
      there is not enough data to output a frame in which case
diff --git a/src/cpp/client/channel.cc b/src/cpp/client/channel.cc
index 5f54e7fcc1..af7366eb01 100644
--- a/src/cpp/client/channel.cc
+++ b/src/cpp/client/channel.cc
@@ -48,6 +48,7 @@
 #include <grpc++/impl/call.h>
 #include <grpc++/impl/rpc_method.h>
 #include <grpc++/status.h>
+#include <grpc++/time.h>
 
 namespace grpc {
 
@@ -95,4 +96,43 @@ void* Channel::RegisterMethod(const char* method) {
                                     host_.empty() ? NULL : host_.c_str());
 }
 
+grpc_connectivity_state Channel::GetState(bool try_to_connect) {
+  return grpc_channel_check_connectivity_state(c_channel_, try_to_connect);
+}
+
+namespace {
+class TagSaver GRPC_FINAL : public CompletionQueueTag {
+ public:
+  explicit TagSaver(void* tag) : tag_(tag) {}
+  ~TagSaver() GRPC_OVERRIDE {}
+  bool FinalizeResult(void** tag, bool* status) GRPC_OVERRIDE {
+    *tag = tag_;
+    delete this;
+    return true;
+  }
+ private:
+  void* tag_;
+};
+
+}  // namespace
+
+void Channel::NotifyOnStateChangeImpl(grpc_connectivity_state last_observed,
+                                      gpr_timespec deadline,
+                                      CompletionQueue* cq, void* tag) {
+  TagSaver* tag_saver = new TagSaver(tag);
+  grpc_channel_watch_connectivity_state(c_channel_, last_observed, deadline,
+                                        cq->cq(), tag_saver);
+}
+
+bool Channel::WaitForStateChangeImpl(grpc_connectivity_state last_observed,
+                                     gpr_timespec deadline) {
+  CompletionQueue cq;
+  bool ok = false;
+  void* tag = NULL;
+  NotifyOnStateChangeImpl(last_observed, deadline, &cq, NULL);
+  cq.Next(&tag, &ok);
+  GPR_ASSERT(tag == NULL);
+  return ok;
+}
+
 }  // namespace grpc
diff --git a/src/cpp/client/channel.h b/src/cpp/client/channel.h
index 8660146856..cb8e8d98d2 100644
--- a/src/cpp/client/channel.h
+++ b/src/cpp/client/channel.h
@@ -56,13 +56,22 @@ class Channel GRPC_FINAL : public GrpcLibrary, public ChannelInterface {
   Channel(const grpc::string& host, grpc_channel* c_channel);
   ~Channel() GRPC_OVERRIDE;
 
-  virtual void* RegisterMethod(const char* method) GRPC_OVERRIDE;
-  virtual Call CreateCall(const RpcMethod& method, ClientContext* context,
+  void* RegisterMethod(const char* method) GRPC_OVERRIDE;
+  Call CreateCall(const RpcMethod& method, ClientContext* context,
                           CompletionQueue* cq) GRPC_OVERRIDE;
-  virtual void PerformOpsOnCall(CallOpSetInterface* ops,
+  void PerformOpsOnCall(CallOpSetInterface* ops,
                                 Call* call) GRPC_OVERRIDE;
 
+  grpc_connectivity_state GetState(bool try_to_connect) GRPC_OVERRIDE;
+
  private:
+  void NotifyOnStateChangeImpl(grpc_connectivity_state last_observed,
+                               gpr_timespec deadline, CompletionQueue* cq,
+                               void* tag) GRPC_OVERRIDE;
+
+  bool WaitForStateChangeImpl(grpc_connectivity_state last_observed,
+                              gpr_timespec deadline) GRPC_OVERRIDE;
+
   const grpc::string host_;
   grpc_channel* const c_channel_;  // owned
 };
diff --git a/src/cpp/client/secure_credentials.cc b/src/cpp/client/secure_credentials.cc
index 2d6114e06b..6cd6b77fcf 100644
--- a/src/cpp/client/secure_credentials.cc
+++ b/src/cpp/client/secure_credentials.cc
@@ -34,6 +34,7 @@
 #include <grpc/support/log.h>
 
 #include <grpc++/channel_arguments.h>
+#include <grpc++/impl/grpc_library.h>
 #include "src/cpp/client/channel.h"
 #include "src/cpp/client/secure_credentials.h"
 
@@ -61,12 +62,14 @@ std::shared_ptr<Credentials> WrapCredentials(grpc_credentials* creds) {
 }  // namespace
 
 std::shared_ptr<Credentials> GoogleDefaultCredentials() {
+  GrpcLibrary init;  // To call grpc_init().
   return WrapCredentials(grpc_google_default_credentials_create());
 }
 
 // Builds SSL Credentials given SSL specific options
 std::shared_ptr<Credentials> SslCredentials(
     const SslCredentialsOptions& options) {
+  GrpcLibrary init;  // To call grpc_init().
   grpc_ssl_pem_key_cert_pair pem_key_cert_pair = {
       options.pem_private_key.c_str(), options.pem_cert_chain.c_str()};
 
@@ -78,6 +81,7 @@ std::shared_ptr<Credentials> SslCredentials(
 
 // Builds credentials for use when running in GCE
 std::shared_ptr<Credentials> ComputeEngineCredentials() {
+  GrpcLibrary init;  // To call grpc_init().
   return WrapCredentials(grpc_compute_engine_credentials_create());
 }
 
@@ -85,6 +89,7 @@ std::shared_ptr<Credentials> ComputeEngineCredentials() {
 std::shared_ptr<Credentials> ServiceAccountCredentials(
     const grpc::string& json_key, const grpc::string& scope,
     long token_lifetime_seconds) {
+  GrpcLibrary init;  // To call grpc_init().
   if (token_lifetime_seconds <= 0) {
     gpr_log(GPR_ERROR,
             "Trying to create ServiceAccountCredentials "
@@ -100,6 +105,7 @@ std::shared_ptr<Credentials> ServiceAccountCredentials(
 // Builds JWT credentials.
 std::shared_ptr<Credentials> ServiceAccountJWTAccessCredentials(
     const grpc::string& json_key, long token_lifetime_seconds) {
+  GrpcLibrary init;  // To call grpc_init().
   if (token_lifetime_seconds <= 0) {
     gpr_log(GPR_ERROR,
             "Trying to create JWTCredentials with non-positive lifetime");
@@ -114,6 +120,7 @@ std::shared_ptr<Credentials> ServiceAccountJWTAccessCredentials(
 // Builds refresh token credentials.
 std::shared_ptr<Credentials> RefreshTokenCredentials(
     const grpc::string& json_refresh_token) {
+  GrpcLibrary init;  // To call grpc_init().
   return WrapCredentials(
       grpc_refresh_token_credentials_create(json_refresh_token.c_str()));
 }
@@ -121,6 +128,7 @@ std::shared_ptr<Credentials> RefreshTokenCredentials(
 // Builds access token credentials.
 std::shared_ptr<Credentials> AccessTokenCredentials(
     const grpc::string& access_token) {
+  GrpcLibrary init;  // To call grpc_init().
   return WrapCredentials(
       grpc_access_token_credentials_create(access_token.c_str()));
 }
@@ -129,6 +137,7 @@ std::shared_ptr<Credentials> AccessTokenCredentials(
 std::shared_ptr<Credentials> IAMCredentials(
     const grpc::string& authorization_token,
     const grpc::string& authority_selector) {
+  GrpcLibrary init;  // To call grpc_init().
   return WrapCredentials(grpc_iam_credentials_create(
       authorization_token.c_str(), authority_selector.c_str()));
 }
diff --git a/src/cpp/common/auth_property_iterator.cc b/src/cpp/common/auth_property_iterator.cc
index e706c6c921..ba88983515 100644
--- a/src/cpp/common/auth_property_iterator.cc
+++ b/src/cpp/common/auth_property_iterator.cc
@@ -31,7 +31,7 @@
  *
  */
 
-#include <grpc++/auth_property_iterator.h>
+#include <grpc++/auth_context.h>
 
 #include <grpc/grpc_security.h>
 
diff --git a/src/csharp/Grpc.Auth/GoogleCredential.cs b/src/csharp/Grpc.Auth/GoogleCredential.cs
deleted file mode 100644
index 9936cf583c..0000000000
--- a/src/csharp/Grpc.Auth/GoogleCredential.cs
+++ /dev/null
@@ -1,125 +0,0 @@
-#region Copyright notice and license
-
-// Copyright 2015, Google Inc.
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#endregion
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Security.Cryptography;
-using System.Threading;
-using System.Threading.Tasks;
-
-using Google.Apis.Auth.OAuth2;
-using Google.Apis.Auth.OAuth2.Responses;
-using Newtonsoft.Json.Linq;
-using Org.BouncyCastle.Crypto.Parameters;
-using Org.BouncyCastle.Security;
-
-namespace Grpc.Auth
-{
-    // TODO(jtattermusch): Remove this class once possible.
-    /// <summary>
-    /// A temporary placeholder for Google credential from 
-    /// Google Auth library for .NET. It emulates the usage pattern 
-    /// for Usable auth.
-    /// </summary>
-    public class GoogleCredential
-    {
-        private const string GoogleApplicationCredentialsEnvName = "GOOGLE_APPLICATION_CREDENTIALS";
-        private const string ClientEmailFieldName = "client_email";
-        private const string PrivateKeyFieldName = "private_key";
-
-        private ServiceCredential credential;
-
-        private GoogleCredential(ServiceCredential credential)
-        {
-            this.credential = credential;
-        }
-
-        public static GoogleCredential GetApplicationDefault()
-        {
-            return new GoogleCredential(null);  
-        }
-
-        public bool IsCreateScopedRequired
-        {
-            get
-            {
-                return true;
-            }
-        }
-
-        public GoogleCredential CreateScoped(IEnumerable<string> scopes)
-        {
-            var credsPath = Environment.GetEnvironmentVariable(GoogleApplicationCredentialsEnvName);
-            if (credsPath == null)
-            {
-                // Default to ComputeCredentials if path to JSON key is not set.
-                // ComputeCredential is not scoped actually, but for our use case it's
-                // fine to treat is as such.
-                return new GoogleCredential(new ComputeCredential(new ComputeCredential.Initializer()));
-            }
-
-            JObject jsonCredentialParameters = JObject.Parse(File.ReadAllText(credsPath));
-            string clientEmail = jsonCredentialParameters.GetValue(ClientEmailFieldName).Value<string>();
-            string privateKeyString = jsonCredentialParameters.GetValue(PrivateKeyFieldName).Value<string>();
-
-            var serviceCredential = new ServiceAccountCredential(
-                new ServiceAccountCredential.Initializer(clientEmail)
-                {
-                    Scopes = scopes,
-                }.FromPrivateKey(privateKeyString));
-            return new GoogleCredential(serviceCredential);
-        }
-
-        public Task<bool> RequestAccessTokenAsync(CancellationToken taskCancellationToken)
-        {
-            return credential.RequestAccessTokenAsync(taskCancellationToken);
-        }
-
-        public TokenResponse Token
-        {
-            get
-            {
-                return credential.Token;
-            }
-        }
-
-        internal ServiceCredential InternalCredential
-        {
-            get
-            {
-                return credential;
-            }
-        }
-    }
-}
diff --git a/src/csharp/Grpc.Auth/Grpc.Auth.csproj b/src/csharp/Grpc.Auth/Grpc.Auth.csproj
index 8e5036832d..930a34b0c3 100644
--- a/src/csharp/Grpc.Auth/Grpc.Auth.csproj
+++ b/src/csharp/Grpc.Auth/Grpc.Auth.csproj
@@ -11,7 +11,7 @@
     <AssemblyName>Grpc.Auth</AssemblyName>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <DocumentationFile>bin\$(Configuration)\Grpc.Auth.Xml</DocumentationFile>
-    <NuGetPackageImportStamp>9b408026</NuGetPackageImportStamp>
+    <NuGetPackageImportStamp>4f8487a9</NuGetPackageImportStamp>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -41,28 +41,32 @@
     <AssemblyOriginatorKeyFile>C:\keys\Grpc.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="BouncyCastle.Crypto">
+    <Reference Include="BouncyCastle.Crypto, Version=1.7.4137.9688, Culture=neutral, PublicKeyToken=a4292a325f69b123, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
       <HintPath>..\packages\BouncyCastle.1.7.0\lib\Net40-Client\BouncyCastle.Crypto.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Auth, Version=1.9.2.27817, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+    <Reference Include="Google.Apis.Auth, Version=1.9.3.19379, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Google.Apis.Auth.1.9.2\lib\net40\Google.Apis.Auth.dll</HintPath>
+      <HintPath>..\packages\Google.Apis.Auth.1.9.3\lib\net40\Google.Apis.Auth.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Auth.PlatformServices, Version=1.9.2.27820, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+    <Reference Include="Google.Apis.Auth.PlatformServices, Version=1.9.3.19383, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Google.Apis.Auth.1.9.2\lib\net40\Google.Apis.Auth.PlatformServices.dll</HintPath>
+      <HintPath>..\packages\Google.Apis.Auth.1.9.3\lib\net40\Google.Apis.Auth.PlatformServices.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Core, Version=1.9.2.27816, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+    <Reference Include="Google.Apis.Core, Version=1.9.3.19379, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Google.Apis.Core.1.9.2\lib\portable-net40+sl50+win+wpa81+wp80\Google.Apis.Core.dll</HintPath>
+      <HintPath>..\packages\Google.Apis.Core.1.9.3\lib\portable-net40+sl50+win+wpa81+wp80\Google.Apis.Core.dll</HintPath>
     </Reference>
-    <Reference Include="Microsoft.Threading.Tasks">
+    <Reference Include="Microsoft.Threading.Tasks, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
       <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.dll</HintPath>
     </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions">
+    <Reference Include="Microsoft.Threading.Tasks.Extensions, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
       <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.dll</HintPath>
     </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions.Desktop">
+    <Reference Include="Microsoft.Threading.Tasks.Extensions.Desktop, Version=1.0.168.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
       <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.Desktop.dll</HintPath>
     </Reference>
     <Reference Include="Newtonsoft.Json, Version=7.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
@@ -87,7 +91,6 @@
       <Link>Version.cs</Link>
     </Compile>
     <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="GoogleCredential.cs" />
     <Compile Include="OAuth2Interceptors.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
diff --git a/src/csharp/Grpc.Auth/OAuth2Interceptors.cs b/src/csharp/Grpc.Auth/OAuth2Interceptors.cs
index cc9d2c175f..d628a83246 100644
--- a/src/csharp/Grpc.Auth/OAuth2Interceptors.cs
+++ b/src/csharp/Grpc.Auth/OAuth2Interceptors.cs
@@ -54,7 +54,7 @@ namespace Grpc.Auth
         /// </summary>
         public static MetadataInterceptorDelegate FromCredential(GoogleCredential googleCredential)
         {
-            var interceptor = new OAuth2Interceptor(googleCredential.InternalCredential, SystemClock.Default);
+            var interceptor = new OAuth2Interceptor(googleCredential, SystemClock.Default);
             return new MetadataInterceptorDelegate(interceptor.InterceptHeaders);
         }
 
@@ -66,7 +66,7 @@ namespace Grpc.Auth
         public static MetadataInterceptorDelegate FromAccessToken(string oauth2Token)
         {
             Preconditions.CheckNotNull(oauth2Token);
-            return new MetadataInterceptorDelegate((metadata) =>
+            return new MetadataInterceptorDelegate((authUri, metadata) =>
             {
                 metadata.Add(OAuth2Interceptor.CreateBearerTokenHeader(oauth2Token));
             });
@@ -80,10 +80,10 @@ namespace Grpc.Auth
             private const string AuthorizationHeader = "Authorization";
             private const string Schema = "Bearer";
 
-            private ServiceCredential credential;
+            private ITokenAccess credential;
             private IClock clock;
 
-            public OAuth2Interceptor(ServiceCredential credential, IClock clock)
+            public OAuth2Interceptor(ITokenAccess credential, IClock clock)
             {
                 this.credential = credential;
                 this.clock = clock;
@@ -94,23 +94,15 @@ namespace Grpc.Auth
             /// </summary>
             /// <param name="cancellationToken"></param>
             /// <returns></returns>
-            public string GetAccessToken(CancellationToken cancellationToken)
+            public string GetAccessToken(string authUri, CancellationToken cancellationToken)
             {
-                if (credential.Token == null || credential.Token.IsExpired(clock))
-                {
-                    // TODO(jtattermusch): Parallel requests will spawn multiple requests to refresh the token once the token expires.
-                    // TODO(jtattermusch): Rethink synchronous wait to obtain the result.
-                    if (!credential.RequestAccessTokenAsync(cancellationToken).Result)
-                    {
-                        throw new InvalidOperationException("The access token has expired but we can't refresh it");
-                    }
-                }
-                return credential.Token.AccessToken;
+                // TODO(jtattermusch): Rethink synchronous wait to obtain the result.
+                return credential.GetAccessTokenForRequestAsync(authUri, cancellationToken: cancellationToken).GetAwaiter().GetResult();
             }
 
-            public void InterceptHeaders(Metadata metadata)
+            public void InterceptHeaders(string authUri, Metadata metadata)
             {
-                var accessToken = GetAccessToken(CancellationToken.None);
+                var accessToken = GetAccessToken(authUri, CancellationToken.None);
                 metadata.Add(CreateBearerTokenHeader(accessToken));
             }
 
diff --git a/src/csharp/Grpc.Auth/app.config b/src/csharp/Grpc.Auth/app.config
index 0a82bb4f16..84d7534d65 100644
--- a/src/csharp/Grpc.Auth/app.config
+++ b/src/csharp/Grpc.Auth/app.config
@@ -10,6 +10,10 @@
         <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
         <bindingRedirect oldVersion="0.0.0.0-4.2.28.0" newVersion="4.0.0.0" />
       </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="Google.Apis.Core" publicKeyToken="4b01fa6e34db77ab" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-1.9.2.38523" newVersion="1.9.2.38523" />
+      </dependentAssembly>
     </assemblyBinding>
   </runtime>
 </configuration>
\ No newline at end of file
diff --git a/src/csharp/Grpc.Auth/packages.config b/src/csharp/Grpc.Auth/packages.config
index 29be953bf3..7a02c95db9 100644
--- a/src/csharp/Grpc.Auth/packages.config
+++ b/src/csharp/Grpc.Auth/packages.config
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
   <package id="BouncyCastle" version="1.7.0" targetFramework="net45" />
-  <package id="Google.Apis.Auth" version="1.9.2" targetFramework="net45" />
-  <package id="Google.Apis.Core" version="1.9.2" targetFramework="net45" />
+  <package id="Google.Apis.Auth" version="1.9.3" targetFramework="net45" />
+  <package id="Google.Apis.Core" version="1.9.3" targetFramework="net45" />
   <package id="Microsoft.Bcl" version="1.1.10" targetFramework="net45" />
   <package id="Microsoft.Bcl.Async" version="1.0.168" targetFramework="net45" />
   <package id="Microsoft.Bcl.Build" version="1.0.21" targetFramework="net45" />
diff --git a/src/csharp/Grpc.Core.Tests/ChannelOptionsTest.cs b/src/csharp/Grpc.Core.Tests/ChannelOptionsTest.cs
index df09857efe..52be77c846 100644
--- a/src/csharp/Grpc.Core.Tests/ChannelOptionsTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ChannelOptionsTest.cs
@@ -67,9 +67,9 @@ namespace Grpc.Core.Internal.Tests
         [Test]
         public void ConstructorPreconditions()
         {
-            Assert.Throws(typeof(NullReferenceException), () => { new ChannelOption(null, "abc"); });
-            Assert.Throws(typeof(NullReferenceException), () => { new ChannelOption(null, 1); });
-            Assert.Throws(typeof(NullReferenceException), () => { new ChannelOption("abc", null); });
+            Assert.Throws(typeof(ArgumentNullException), () => { new ChannelOption(null, "abc"); });
+            Assert.Throws(typeof(ArgumentNullException), () => { new ChannelOption(null, 1); });
+            Assert.Throws(typeof(ArgumentNullException), () => { new ChannelOption("abc", null); });
         }
 
         [Test]
diff --git a/src/csharp/Grpc.Core.Tests/ChannelTest.cs b/src/csharp/Grpc.Core.Tests/ChannelTest.cs
index 60b45176e5..2787572924 100644
--- a/src/csharp/Grpc.Core.Tests/ChannelTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ChannelTest.cs
@@ -50,7 +50,7 @@ namespace Grpc.Core.Tests
         [Test]
         public void Constructor_RejectsInvalidParams()
         {
-            Assert.Throws(typeof(NullReferenceException), () => new Channel(null, Credentials.Insecure));
+            Assert.Throws(typeof(ArgumentNullException), () => new Channel(null, Credentials.Insecure));
         }
 
         [Test]
@@ -72,11 +72,11 @@ namespace Grpc.Core.Tests
         }
 
         [Test]
-        public void Target()
+        public void ResolvedTarget()
         {
             using (var channel = new Channel("127.0.0.1", Credentials.Insecure))
             {
-                Assert.IsTrue(channel.Target.Contains("127.0.0.1"));
+                Assert.IsTrue(channel.ResolvedTarget.Contains("127.0.0.1"));
             }
         }
 
diff --git a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
index 64ea21800f..e49fdb5268 100644
--- a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
@@ -46,47 +46,18 @@ namespace Grpc.Core.Tests
     public class ClientServerTest
     {
         const string Host = "127.0.0.1";
-        const string ServiceName = "tests.Test";
-
-        static readonly Method<string, string> EchoMethod = new Method<string, string>(
-            MethodType.Unary,
-            ServiceName,
-            "Echo",
-            Marshallers.StringMarshaller,
-            Marshallers.StringMarshaller);
-
-        static readonly Method<string, string> ConcatAndEchoMethod = new Method<string, string>(
-            MethodType.ClientStreaming,
-            ServiceName,
-            "ConcatAndEcho",
-            Marshallers.StringMarshaller,
-            Marshallers.StringMarshaller);
-
-        static readonly Method<string, string> NonexistentMethod = new Method<string, string>(
-            MethodType.Unary,
-            ServiceName,
-            "NonexistentMethod",
-            Marshallers.StringMarshaller,
-            Marshallers.StringMarshaller);
-
-        static readonly ServerServiceDefinition ServiceDefinition = ServerServiceDefinition.CreateBuilder(ServiceName)
-            .AddMethod(EchoMethod, EchoHandler)
-            .AddMethod(ConcatAndEchoMethod, ConcatAndEchoHandler)
-            .Build();
 
+        MockServiceHelper helper;
         Server server;
         Channel channel;
 
         [SetUp]
         public void Init()
         {
-            server = new Server
-            {
-                Services = { ServiceDefinition },
-                Ports = { { Host, ServerPort.PickUnused, ServerCredentials.Insecure } }
-            };
+            helper = new MockServiceHelper(Host);
+            server = helper.GetServer();
             server.Start();
-            channel = new Channel(Host, server.Ports.Single().BoundPort, Credentials.Insecure);
+            channel = helper.GetChannel();
         }
 
         [TearDown]
@@ -103,123 +74,127 @@ namespace Grpc.Core.Tests
         }
 
         [Test]
-        public void UnaryCall()
+        public async Task UnaryCall()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            Assert.AreEqual("ABC", Calls.BlockingUnaryCall(callDetails, "ABC"));
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                return request;
+            });
+
+            Assert.AreEqual("ABC", Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "ABC"));
+
+            Assert.AreEqual("ABC", await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "ABC"));
         }
 
         [Test]
         public void UnaryCall_ServerHandlerThrows()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            try
+            helper.UnaryHandler = new UnaryServerMethod<string, string>((request, context) =>
             {
-                Calls.BlockingUnaryCall(callDetails, "THROW");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                Assert.AreEqual(StatusCode.Unknown, e.Status.StatusCode); 
-            }
+                throw new Exception("This was thrown on purpose by a test");
+            });
+                
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unknown, ex.Status.StatusCode); 
+
+            var ex2 = Assert.Throws<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unknown, ex2.Status.StatusCode);
         }
 
         [Test]
         public void UnaryCall_ServerHandlerThrowsRpcException()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            try
-            {
-                Calls.BlockingUnaryCall(callDetails, "THROW_UNAUTHENTICATED");
-                Assert.Fail();
-            }
-            catch (RpcException e)
+            helper.UnaryHandler = new UnaryServerMethod<string, string>((request, context) =>
             {
-                Assert.AreEqual(StatusCode.Unauthenticated, e.Status.StatusCode);
-            }
+                throw new RpcException(new Status(StatusCode.Unauthenticated, ""));
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
+
+            var ex2 = Assert.Throws<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
         }
 
         [Test]
         public void UnaryCall_ServerHandlerSetsStatus()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            try
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
             {
-                Calls.BlockingUnaryCall(callDetails, "SET_UNAUTHENTICATED");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                Assert.AreEqual(StatusCode.Unauthenticated, e.Status.StatusCode); 
-            }
-        }
+                context.Status = new Status(StatusCode.Unauthenticated, "");
+                return "";
+            });
 
-        [Test]
-        public async Task AsyncUnaryCall()
-        {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            var result = await Calls.AsyncUnaryCall(callDetails, "ABC");
-            Assert.AreEqual("ABC", result);
-        }
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
 
-        [Test]
-        public async Task AsyncUnaryCall_ServerHandlerThrows()
-        {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            try
-            {
-                await Calls.AsyncUnaryCall(callDetails, "THROW");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                Assert.AreEqual(StatusCode.Unknown, e.Status.StatusCode);
-            }
+            var ex2 = Assert.Throws<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
         }
 
         [Test]
         public async Task ClientStreamingCall()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, ConcatAndEchoMethod, new CallOptions());
-            var call = Calls.AsyncClientStreamingCall(callDetails);
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                string result = "";
+                await requestStream.ForEachAsync(async (request) =>
+                {
+                    result += request;
+                });
+                await Task.Delay(100);
+                return result;
+            });
 
-            await call.RequestStream.WriteAll(new string[] { "A", "B", "C" });
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall());
+            await call.RequestStream.WriteAllAsync(new string[] { "A", "B", "C" });
             Assert.AreEqual("ABC", await call.ResponseAsync);
         }
 
         [Test]
         public async Task ClientStreamingCall_CancelAfterBegin()
         {
+            var barrier = new TaskCompletionSource<object>();
+
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                barrier.SetResult(null);
+                await requestStream.ToListAsync();
+                return "";
+            });
+
             var cts = new CancellationTokenSource();
-            var callDetails = new CallInvocationDetails<string, string>(channel, ConcatAndEchoMethod, new CallOptions(cancellationToken: cts.Token));
-            var call = Calls.AsyncClientStreamingCall(callDetails);
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(cancellationToken: cts.Token)));
 
-            // TODO(jtattermusch): we need this to ensure call has been initiated once we cancel it.
-            await Task.Delay(1000);
+            await barrier.Task;  // make sure the handler has started.
             cts.Cancel();
 
-            try
-            {
-                await call.ResponseAsync;
-            }
-            catch (RpcException e)
-            {
-                Assert.AreEqual(StatusCode.Cancelled, e.Status.StatusCode);
-            }
+            var ex = Assert.Throws<RpcException>(async () => await call.ResponseAsync);
+            Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
         }
 
         [Test]
-        public void AsyncUnaryCall_EchoMetadata()
+        public async Task AsyncUnaryCall_EchoMetadata()
         {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                foreach (Metadata.Entry metadataEntry in context.RequestHeaders)
+                {
+                    if (metadataEntry.Key != "user-agent")
+                    {
+                        context.ResponseTrailers.Add(metadataEntry);
+                    }
+                }
+                return "";
+            });
+
             var headers = new Metadata
             {
-                new Metadata.Entry("ascii-header", "abcdefg"),
-                new Metadata.Entry("binary-header-bin", new byte[] { 1, 2, 3, 0, 0xff }),
+                { "ascii-header", "abcdefg" },
+                { "binary-header-bin", new byte[] { 1, 2, 3, 0, 0xff } }
             };
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions(headers: headers));
-            var call = Calls.AsyncUnaryCall(callDetails, "ABC");
-
-            Assert.AreEqual("ABC", call.ResponseAsync.Result);
+            var call = Calls.AsyncUnaryCall(helper.CreateUnaryCall(new CallOptions(headers: headers)), "ABC");
+            await call;
 
             Assert.AreEqual(StatusCode.OK, call.GetStatus().StatusCode);
 
@@ -236,15 +211,18 @@ namespace Grpc.Core.Tests
         public void UnaryCall_DisposedChannel()
         {
             channel.Dispose();
-
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            Assert.Throws(typeof(ObjectDisposedException), () => Calls.BlockingUnaryCall(callDetails, "ABC"));
+            Assert.Throws(typeof(ObjectDisposedException), () => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "ABC"));
         }
 
         [Test]
         public void UnaryCallPerformance()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                return request;
+            });
+
+            var callDetails = helper.CreateUnaryCall();
             BenchmarkUtil.RunBenchmark(100, 100,
                                        () => { Calls.BlockingUnaryCall(callDetails, "ABC"); });
         }
@@ -252,44 +230,57 @@ namespace Grpc.Core.Tests
         [Test]
         public void UnknownMethodHandler()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, NonexistentMethod, new CallOptions());
-            try
-            {
-                Calls.BlockingUnaryCall(callDetails, "ABC");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                Assert.AreEqual(StatusCode.Unimplemented, e.Status.StatusCode);
-            }
+            var nonexistentMethod = new Method<string, string>(
+                MethodType.Unary,
+                MockServiceHelper.ServiceName,
+                "NonExistentMethod",
+                Marshallers.StringMarshaller,
+                Marshallers.StringMarshaller);
+
+            var callDetails = new CallInvocationDetails<string, string>(channel, nonexistentMethod, new CallOptions());
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(callDetails, "abc"));
+            Assert.AreEqual(StatusCode.Unimplemented, ex.Status.StatusCode);
         }
 
         [Test]
         public void UserAgentStringPresent()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            string userAgent = Calls.BlockingUnaryCall(callDetails, "RETURN-USER-AGENT");
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                return context.RequestHeaders.Where(entry => entry.Key == "user-agent").Single().Value;
+            });
+
+            string userAgent = Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc");
             Assert.IsTrue(userAgent.StartsWith("grpc-csharp/"));
         }
 
         [Test]
         public void PeerInfoPresent()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            string peer = Calls.BlockingUnaryCall(callDetails, "RETURN-PEER");
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                return context.Peer;
+            });
+
+            string peer = Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc");
             Assert.IsTrue(peer.Contains(Host));
         }
 
         [Test]
         public async Task Channel_WaitForStateChangedAsync()
         {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                return request;
+            });
+
             Assert.Throws(typeof(TaskCanceledException), 
                 async () => await channel.WaitForStateChangedAsync(channel.State, DateTime.UtcNow.AddMilliseconds(10)));
 
             var stateChangedTask = channel.WaitForStateChangedAsync(channel.State);
 
-            var callDetails = new CallInvocationDetails<string, string>(channel, EchoMethod, new CallOptions());
-            await Calls.AsyncUnaryCall(callDetails, "abc");
+            await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc");
 
             await stateChangedTask;
             Assert.AreEqual(ChannelState.Ready, channel.State);
@@ -300,62 +291,9 @@ namespace Grpc.Core.Tests
         {
             await channel.ConnectAsync();
             Assert.AreEqual(ChannelState.Ready, channel.State);
+
             await channel.ConnectAsync(DateTime.UtcNow.AddMilliseconds(1000));
             Assert.AreEqual(ChannelState.Ready, channel.State);
         }
-
-        private static async Task<string> EchoHandler(string request, ServerCallContext context)
-        {
-            foreach (Metadata.Entry metadataEntry in context.RequestHeaders)
-            {
-                if (metadataEntry.Key != "user-agent")
-                {
-                    context.ResponseTrailers.Add(metadataEntry);
-                }
-            }
-
-            if (request == "RETURN-USER-AGENT")
-            {
-                return context.RequestHeaders.Where(entry => entry.Key == "user-agent").Single().Value;
-            }
-
-            if (request == "RETURN-PEER")
-            {
-                return context.Peer;
-            }
-
-            if (request == "THROW")
-            {
-                throw new Exception("This was thrown on purpose by a test");
-            }
-
-            if (request == "THROW_UNAUTHENTICATED")
-            {
-                throw new RpcException(new Status(StatusCode.Unauthenticated, ""));
-            }
-
-            if (request == "SET_UNAUTHENTICATED")
-            {
-                context.Status = new Status(StatusCode.Unauthenticated, "");
-            }
-
-            return request;
-        }
-
-        private static async Task<string> ConcatAndEchoHandler(IAsyncStreamReader<string> requestStream, ServerCallContext context)
-        {
-            string result = "";
-            await requestStream.ForEach(async (request) =>
-            {
-                if (request == "THROW")
-                {
-                    throw new Exception("This was thrown on purpose by a test");
-                }
-                result += request;
-            });
-            // simulate processing takes some time.
-            await Task.Delay(250);
-            return result;
-        }
     }
 }
diff --git a/src/csharp/Grpc.Core.Tests/CompressionTest.cs b/src/csharp/Grpc.Core.Tests/CompressionTest.cs
new file mode 100644
index 0000000000..9547683f60
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/CompressionTest.cs
@@ -0,0 +1,128 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    public class CompressionTest
+    {
+        MockServiceHelper helper;
+        Server server;
+        Channel channel;
+
+        [SetUp]
+        public void Init()
+        {
+            helper = new MockServiceHelper();
+
+            server = helper.GetServer();
+            server.Start();
+            channel = helper.GetChannel();
+        }
+
+        [TearDown]
+        public void Cleanup()
+        {
+            channel.Dispose();
+            server.ShutdownAsync().Wait();
+        }
+
+        [TestFixtureTearDown]
+        public void CleanupClass()
+        {
+            GrpcEnvironment.Shutdown();
+        }
+
+        [Test]
+        public void WriteOptions_Unary()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                context.WriteOptions = new WriteOptions(WriteFlags.NoCompress);
+                return request;
+            });
+
+            var callOptions = new CallOptions(writeOptions: new WriteOptions(WriteFlags.NoCompress));
+            Calls.BlockingUnaryCall(helper.CreateUnaryCall(callOptions), "abc");
+        }
+
+        [Test]
+        public async Task WriteOptions_DuplexStreaming()
+        {
+            helper.DuplexStreamingHandler = new DuplexStreamingServerMethod<string, string>(async (requestStream, responseStream, context) =>
+            {
+                await requestStream.ToListAsync();
+
+                context.WriteOptions = new WriteOptions(WriteFlags.NoCompress);
+
+                await context.WriteResponseHeadersAsync(new Metadata { { "ascii-header", "abcdefg" } });
+
+                await responseStream.WriteAsync("X");
+
+                responseStream.WriteOptions = null;
+                await responseStream.WriteAsync("Y");
+
+                responseStream.WriteOptions = new WriteOptions(WriteFlags.NoCompress);
+                await responseStream.WriteAsync("Z");
+            });
+
+            var callOptions = new CallOptions(writeOptions: new WriteOptions(WriteFlags.NoCompress));
+            var call = Calls.AsyncDuplexStreamingCall(helper.CreateDuplexStreamingCall(callOptions));
+
+            // check that write options from call options are propagated to request stream.
+            Assert.IsTrue((call.RequestStream.WriteOptions.Flags & WriteFlags.NoCompress) != 0);
+
+            call.RequestStream.WriteOptions = new WriteOptions();
+            await call.RequestStream.WriteAsync("A");
+
+            call.RequestStream.WriteOptions = null;
+            await call.RequestStream.WriteAsync("B");
+
+            call.RequestStream.WriteOptions = new WriteOptions(WriteFlags.NoCompress);
+            await call.RequestStream.WriteAsync("C");
+
+            await call.RequestStream.CompleteAsync();
+
+            await call.ResponseStream.ToListAsync();
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core.Tests/ContextPropagationTest.cs b/src/csharp/Grpc.Core.Tests/ContextPropagationTest.cs
new file mode 100644
index 0000000000..db5f953b0e
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/ContextPropagationTest.cs
@@ -0,0 +1,153 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    public class ContextPropagationTest
+    {
+        MockServiceHelper helper;
+        Server server;
+        Channel channel;
+
+        [SetUp]
+        public void Init()
+        {
+            helper = new MockServiceHelper();
+
+            server = helper.GetServer();
+            server.Start();
+            channel = helper.GetChannel();
+        }
+
+        [TearDown]
+        public void Cleanup()
+        {
+            channel.Dispose();
+            server.ShutdownAsync().Wait();
+        }
+
+        [TestFixtureTearDown]
+        public void CleanupClass()
+        {
+            GrpcEnvironment.Shutdown();
+        }
+
+        [Test]
+        public async Task PropagateCancellation()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                // check that we didn't obtain the default cancellation token.
+                Assert.IsTrue(context.CancellationToken.CanBeCanceled);
+                return "PASS";
+            });
+
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                var propagationToken = context.CreatePropagationToken();
+                Assert.IsNotNull(propagationToken.ParentCall);
+
+                var callOptions = new CallOptions(propagationToken: propagationToken);
+                return await Calls.AsyncUnaryCall(helper.CreateUnaryCall(callOptions), "xyz");
+            });
+                
+            var cts = new CancellationTokenSource();
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(cancellationToken: cts.Token)));
+            await call.RequestStream.CompleteAsync();
+            Assert.AreEqual("PASS", await call);
+        }
+
+        [Test]
+        public async Task PropagateDeadline()
+        {
+            var deadline = DateTime.UtcNow.AddDays(7);
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                Assert.IsTrue(context.Deadline < deadline.AddMinutes(1));
+                Assert.IsTrue(context.Deadline > deadline.AddMinutes(-1));
+                return "PASS";
+            });
+
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                Assert.Throws(typeof(ArgumentException), () =>
+                {
+                    // Trying to override deadline while propagating deadline from parent call will throw.
+                    Calls.BlockingUnaryCall(helper.CreateUnaryCall(
+                        new CallOptions(deadline: DateTime.UtcNow.AddDays(8),
+                                        propagationToken: context.CreatePropagationToken())), "");
+                });
+
+                var callOptions = new CallOptions(propagationToken: context.CreatePropagationToken());
+                return await Calls.AsyncUnaryCall(helper.CreateUnaryCall(callOptions), "xyz");
+            });
+                
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(deadline: deadline)));
+            await call.RequestStream.CompleteAsync();
+            Assert.AreEqual("PASS", await call);
+        }
+
+        [Test]
+        public async Task SuppressDeadlinePropagation()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                Assert.AreEqual(DateTime.MaxValue, context.Deadline);
+                return "PASS";
+            });
+
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                Assert.IsTrue(context.CancellationToken.CanBeCanceled);
+
+                var callOptions = new CallOptions(propagationToken: context.CreatePropagationToken(new ContextPropagationOptions(propagateDeadline: false)));
+                return await Calls.AsyncUnaryCall(helper.CreateUnaryCall(callOptions), "xyz");
+            });
+
+            var cts = new CancellationTokenSource();
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(deadline: DateTime.UtcNow.AddDays(7))));
+            await call.RequestStream.CompleteAsync();
+            Assert.AreEqual("PASS", await call);
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj b/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj
index f2bf459dc5..97ee0454bb 100644
--- a/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj
+++ b/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj
@@ -77,6 +77,10 @@
     <Compile Include="TimeoutsTest.cs" />
     <Compile Include="NUnitVersionTest.cs" />
     <Compile Include="ChannelTest.cs" />
+    <Compile Include="MockServiceHelper.cs" />
+    <Compile Include="ResponseHeadersTest.cs" />
+    <Compile Include="CompressionTest.cs" />
+    <Compile Include="ContextPropagationTest.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup>
diff --git a/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs b/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs
index 9ae12776f3..4ed93c7eca 100644
--- a/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs
+++ b/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs
@@ -69,5 +69,13 @@ namespace Grpc.Core.Tests
 
             Assert.IsFalse(object.ReferenceEquals(env1, env2));
         }
+
+        [Test]
+        public void GetCoreVersionString()
+        {
+            var coreVersion = GrpcEnvironment.GetCoreVersionString();
+            var parts = coreVersion.Split('.');
+            Assert.AreEqual(4, parts.Length);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core.Tests/Internal/MetadataArraySafeHandleTest.cs b/src/csharp/Grpc.Core.Tests/Internal/MetadataArraySafeHandleTest.cs
index 46469113c5..33534fdd3c 100644
--- a/src/csharp/Grpc.Core.Tests/Internal/MetadataArraySafeHandleTest.cs
+++ b/src/csharp/Grpc.Core.Tests/Internal/MetadataArraySafeHandleTest.cs
@@ -53,8 +53,8 @@ namespace Grpc.Core.Internal.Tests
         {
             var metadata = new Metadata
             {
-                new Metadata.Entry("host", "somehost"),
-                new Metadata.Entry("header2", "header value"),
+                { "host", "somehost" },
+                { "header2", "header value" },
             };
             var nativeMetadata = MetadataArraySafeHandle.Create(metadata);
             nativeMetadata.Dispose();
@@ -65,8 +65,8 @@ namespace Grpc.Core.Internal.Tests
         {
             var metadata = new Metadata
             {
-                new Metadata.Entry("host", "somehost"),
-                new Metadata.Entry("header2", "header value"),
+                { "host", "somehost" },
+                { "header2", "header value" }
             };
             var nativeMetadata = MetadataArraySafeHandle.Create(metadata);
 
diff --git a/src/csharp/Grpc.Core.Tests/MockServiceHelper.cs b/src/csharp/Grpc.Core.Tests/MockServiceHelper.cs
new file mode 100644
index 0000000000..bb69648d8b
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/MockServiceHelper.cs
@@ -0,0 +1,244 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    /// <summary>
+    /// Allows setting up a mock service in the client-server tests easily.
+    /// </summary>
+    public class MockServiceHelper
+    {
+        public const string ServiceName = "tests.Test";
+
+        public static readonly Method<string, string> UnaryMethod = new Method<string, string>(
+            MethodType.Unary,
+            ServiceName,
+            "Unary",
+            Marshallers.StringMarshaller,
+            Marshallers.StringMarshaller);
+
+        public static readonly Method<string, string> ClientStreamingMethod = new Method<string, string>(
+            MethodType.ClientStreaming,
+            ServiceName,
+            "ClientStreaming",
+            Marshallers.StringMarshaller,
+            Marshallers.StringMarshaller);
+
+        public static readonly Method<string, string> ServerStreamingMethod = new Method<string, string>(
+            MethodType.ServerStreaming,
+            ServiceName,
+            "ServerStreaming",
+            Marshallers.StringMarshaller,
+            Marshallers.StringMarshaller);
+
+        public static readonly Method<string, string> DuplexStreamingMethod = new Method<string, string>(
+            MethodType.DuplexStreaming,
+            ServiceName,
+            "DuplexStreaming",
+            Marshallers.StringMarshaller,
+            Marshallers.StringMarshaller);
+
+        readonly string host;
+        readonly ServerServiceDefinition serviceDefinition;
+
+        UnaryServerMethod<string, string> unaryHandler;
+        ClientStreamingServerMethod<string, string> clientStreamingHandler;
+        ServerStreamingServerMethod<string, string> serverStreamingHandler;
+        DuplexStreamingServerMethod<string, string> duplexStreamingHandler;
+
+        Server server;
+        Channel channel;
+
+        public MockServiceHelper(string host = null)
+        {
+            this.host = host ?? "localhost";
+
+            serviceDefinition = ServerServiceDefinition.CreateBuilder(ServiceName)
+                .AddMethod(UnaryMethod, (request, context) => unaryHandler(request, context))
+                .AddMethod(ClientStreamingMethod, (requestStream, context) => clientStreamingHandler(requestStream, context))
+                .AddMethod(ServerStreamingMethod, (request, responseStream, context) => serverStreamingHandler(request, responseStream, context))
+                .AddMethod(DuplexStreamingMethod, (requestStream, responseStream, context) => duplexStreamingHandler(requestStream, responseStream, context))
+                .Build();
+
+            var defaultStatus = new Status(StatusCode.Unknown, "Default mock implementation. Please provide your own.");
+
+            unaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                context.Status = defaultStatus;
+                return "";
+            });
+
+            clientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                context.Status = defaultStatus;
+                return "";
+            });
+
+            serverStreamingHandler = new ServerStreamingServerMethod<string, string>(async (request, responseStream, context) =>
+            {
+                context.Status = defaultStatus;
+            });
+
+            duplexStreamingHandler = new DuplexStreamingServerMethod<string, string>(async (requestStream, responseStream, context) =>
+            {
+                context.Status = defaultStatus;
+            });
+        }
+
+        /// <summary>
+        /// Returns the default server for this service and creates one if not yet created.
+        /// </summary>
+        public Server GetServer()
+        {
+            if (server == null)
+            {
+                server = new Server
+                {
+                    Services = { serviceDefinition },
+                    Ports = { { Host, ServerPort.PickUnused, ServerCredentials.Insecure } }
+                };
+            }
+            return server;
+        }
+
+        /// <summary>
+        /// Returns the default channel for this service and creates one if not yet created.
+        /// </summary>
+        public Channel GetChannel()
+        {
+            if (channel == null)
+            {
+                channel = new Channel(Host, GetServer().Ports.Single().BoundPort, Credentials.Insecure);
+            }
+            return channel;
+        }
+
+        public CallInvocationDetails<string, string> CreateUnaryCall(CallOptions options = default(CallOptions))
+        {
+            return new CallInvocationDetails<string, string>(channel, UnaryMethod, options);
+        }
+
+        public CallInvocationDetails<string, string> CreateClientStreamingCall(CallOptions options = default(CallOptions))
+        {
+            return new CallInvocationDetails<string, string>(channel, ClientStreamingMethod, options);
+        }
+
+        public CallInvocationDetails<string, string> CreateServerStreamingCall(CallOptions options = default(CallOptions))
+        {
+            return new CallInvocationDetails<string, string>(channel, ServerStreamingMethod, options);
+        }
+
+        public CallInvocationDetails<string, string> CreateDuplexStreamingCall(CallOptions options = default(CallOptions))
+        {
+            return new CallInvocationDetails<string, string>(channel, DuplexStreamingMethod, options);
+        }
+
+        public string Host
+        {
+            get
+            {
+                return this.host;
+            }
+        }
+
+        public ServerServiceDefinition ServiceDefinition
+        {
+            get
+            {
+                return this.serviceDefinition;
+            }
+        }
+      
+        public UnaryServerMethod<string, string> UnaryHandler
+        {
+            get
+            {
+                return this.unaryHandler;
+            }
+
+            set
+            {
+                unaryHandler = value;
+            }
+        }
+
+        public ClientStreamingServerMethod<string, string> ClientStreamingHandler
+        {
+            get
+            {
+                return this.clientStreamingHandler;
+            }
+
+            set
+            {
+                clientStreamingHandler = value;
+            }
+        }
+
+        public ServerStreamingServerMethod<string, string> ServerStreamingHandler
+        {
+            get
+            {
+                return this.serverStreamingHandler;
+            }
+
+            set
+            {
+                serverStreamingHandler = value;
+            }
+        }
+
+        public DuplexStreamingServerMethod<string, string> DuplexStreamingHandler
+        {
+            get
+            {
+                return this.duplexStreamingHandler;
+            }
+
+            set
+            {
+                duplexStreamingHandler = value;
+            }
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core.Tests/ResponseHeadersTest.cs b/src/csharp/Grpc.Core.Tests/ResponseHeadersTest.cs
new file mode 100644
index 0000000000..981b8ea3c8
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/ResponseHeadersTest.cs
@@ -0,0 +1,136 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    /// <summary>
+    /// Tests for response headers support.
+    /// </summary>
+    public class ResponseHeadersTest
+    {
+        MockServiceHelper helper;
+        Server server;
+        Channel channel;
+
+        Metadata headers;
+
+        [SetUp]
+        public void Init()
+        {
+            helper = new MockServiceHelper();
+
+            server = helper.GetServer();
+            server.Start();
+            channel = helper.GetChannel();
+
+            headers = new Metadata { { "ascii-header", "abcdefg" } };
+        }
+
+        [TearDown]
+        public void Cleanup()
+        {
+            channel.Dispose();
+            server.ShutdownAsync().Wait();
+        }
+
+        [TestFixtureTearDown]
+        public void CleanupClass()
+        {
+            GrpcEnvironment.Shutdown();
+        }
+
+        [Test]
+        public void WriteResponseHeaders_NullNotAllowed()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                Assert.Throws(typeof(ArgumentNullException), async () => await context.WriteResponseHeadersAsync(null));
+                return "PASS";
+            });
+
+            Assert.AreEqual("PASS", Calls.BlockingUnaryCall(helper.CreateUnaryCall(), ""));
+        }
+
+        [Test]
+        public void WriteResponseHeaders_AllowedOnlyOnce()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                await context.WriteResponseHeadersAsync(headers);
+                try
+                {
+                    await context.WriteResponseHeadersAsync(headers);
+                    Assert.Fail();
+                }
+                catch (InvalidOperationException expected)
+                {
+                }
+                return "PASS";
+            });
+                
+            Assert.AreEqual("PASS", Calls.BlockingUnaryCall(helper.CreateUnaryCall(), ""));
+        }
+
+        [Test]
+        public async Task WriteResponseHeaders_NotAllowedAfterWrite()
+        {
+            helper.ServerStreamingHandler = new ServerStreamingServerMethod<string, string>(async (request, responseStream, context) =>
+            {
+                await responseStream.WriteAsync("A");
+                try
+                {
+                    await context.WriteResponseHeadersAsync(headers);
+                    Assert.Fail();
+                }
+                catch (InvalidOperationException expected)
+                {
+                }
+                await responseStream.WriteAsync("B");
+            });
+
+            var call = Calls.AsyncServerStreamingCall(helper.CreateServerStreamingCall(), "");
+            var responses = await call.ResponseStream.ToListAsync();
+            CollectionAssert.AreEqual(new[] { "A", "B" }, responses);
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core.Tests/TimeoutsTest.cs b/src/csharp/Grpc.Core.Tests/TimeoutsTest.cs
index fc395b0acd..d875d601b9 100644
--- a/src/csharp/Grpc.Core.Tests/TimeoutsTest.cs
+++ b/src/csharp/Grpc.Core.Tests/TimeoutsTest.cs
@@ -48,38 +48,18 @@ namespace Grpc.Core.Tests
     /// </summary>
     public class TimeoutsTest
     {
-        const string Host = "localhost";
-        const string ServiceName = "tests.Test";
-
-        static readonly Method<string, string> TestMethod = new Method<string, string>(
-            MethodType.Unary,
-            ServiceName,
-            "Test",
-            Marshallers.StringMarshaller,
-            Marshallers.StringMarshaller);
-
-        static readonly ServerServiceDefinition ServiceDefinition = ServerServiceDefinition.CreateBuilder(ServiceName)
-            .AddMethod(TestMethod, TestMethodHandler)
-            .Build();
-
-        // provides a way how to retrieve an out-of-band result value from server handler
-        static TaskCompletionSource<string> stringFromServerHandlerTcs;
-
+        MockServiceHelper helper;
         Server server;
         Channel channel;
 
         [SetUp]
         public void Init()
         {
-            server = new Server
-            {
-                Services = { ServiceDefinition },
-                Ports = { { Host, ServerPort.PickUnused, ServerCredentials.Insecure } }
-            };
-            server.Start();
-            channel = new Channel(Host, server.Ports.Single().BoundPort, Credentials.Insecure);
+            helper = new MockServiceHelper();
 
-            stringFromServerHandlerTcs = new TaskCompletionSource<string>();
+            server = helper.GetServer();
+            server.Start();
+            channel = helper.GetChannel();
         }
 
         [TearDown]
@@ -98,115 +78,83 @@ namespace Grpc.Core.Tests
         [Test]
         public void InfiniteDeadline()
         {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                Assert.AreEqual(DateTime.MaxValue, context.Deadline);
+                return "PASS";
+            });
+
             // no deadline specified, check server sees infinite deadline
-            var callDetails = new CallInvocationDetails<string, string>(channel, TestMethod, new CallOptions());
-            Assert.AreEqual("DATETIME_MAXVALUE", Calls.BlockingUnaryCall(callDetails, "RETURN_DEADLINE"));
+            Assert.AreEqual("PASS", Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
 
             // DateTime.MaxValue deadline specified, check server sees infinite deadline
-            var callDetails2 = new CallInvocationDetails<string, string>(channel, TestMethod, new CallOptions());
-            Assert.AreEqual("DATETIME_MAXVALUE", Calls.BlockingUnaryCall(callDetails2, "RETURN_DEADLINE"));
+            Assert.AreEqual("PASS", Calls.BlockingUnaryCall(helper.CreateUnaryCall(new CallOptions(deadline: DateTime.MaxValue)), "abc"));
         }
 
         [Test]
         public void DeadlineTransferredToServer()
         {
-            var remainingTimeClient = TimeSpan.FromDays(7);
-            var deadline = DateTime.UtcNow + remainingTimeClient;
-            Thread.Sleep(1000);
-            var callDetails = new CallInvocationDetails<string, string>(channel, TestMethod, new CallOptions(deadline: deadline));
-
-            var serverDeadlineTicksString = Calls.BlockingUnaryCall(callDetails, "RETURN_DEADLINE");
-            var serverDeadline = new DateTime(long.Parse(serverDeadlineTicksString), DateTimeKind.Utc);
-
-            // A fairly relaxed check that the deadline set by client and deadline seen by server
-            // are in agreement. C core takes care of the work with transferring deadline over the wire,
-            // so we don't need an exact check here.
-            Assert.IsTrue(Math.Abs((deadline - serverDeadline).TotalMilliseconds) < 5000);
+            var clientDeadline = DateTime.UtcNow + TimeSpan.FromDays(7);
+
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                // A fairly relaxed check that the deadline set by client and deadline seen by server
+                // are in agreement. C core takes care of the work with transferring deadline over the wire,
+                // so we don't need an exact check here.
+                Assert.IsTrue(Math.Abs((clientDeadline - context.Deadline).TotalMilliseconds) < 5000);
+                return "PASS";
+            });
+            Calls.BlockingUnaryCall(helper.CreateUnaryCall(new CallOptions(deadline: clientDeadline)), "abc");
         }
 
         [Test]
         public void DeadlineInThePast()
         {
-            var callDetails = new CallInvocationDetails<string, string>(channel, TestMethod, new CallOptions(deadline: DateTime.MinValue));
-
-            try
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
             {
-                Calls.BlockingUnaryCall(callDetails, "TIMEOUT");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                // We can't guarantee the status code always DeadlineExceeded. See issue #2685.
-                Assert.Contains(e.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
-            }
+                await Task.Delay(60000);
+                return "FAIL";
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(new CallOptions(deadline: DateTime.MinValue)), "abc"));
+            // We can't guarantee the status code always DeadlineExceeded. See issue #2685.
+            Assert.Contains(ex.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
         }
 
         [Test]
         public void DeadlineExceededStatusOnTimeout()
         {
-            var deadline = DateTime.UtcNow.Add(TimeSpan.FromSeconds(5));
-            var callDetails = new CallInvocationDetails<string, string>(channel, TestMethod, new CallOptions(deadline: deadline));
-
-            try
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
             {
-                Calls.BlockingUnaryCall(callDetails, "TIMEOUT");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                // We can't guarantee the status code always DeadlineExceeded. See issue #2685.
-                Assert.Contains(e.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
-            }
+                await Task.Delay(60000);
+                return "FAIL";
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(new CallOptions(deadline: DateTime.UtcNow.Add(TimeSpan.FromSeconds(5)))), "abc"));
+            // We can't guarantee the status code always DeadlineExceeded. See issue #2685.
+            Assert.Contains(ex.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
         }
 
         [Test]
-        public void ServerReceivesCancellationOnTimeout()
+        public async Task ServerReceivesCancellationOnTimeout()
         {
-            var deadline = DateTime.UtcNow.Add(TimeSpan.FromSeconds(5));
-            var callDetails = new CallInvocationDetails<string, string>(channel, TestMethod, new CallOptions(deadline: deadline));
+            var serverReceivedCancellationTcs = new TaskCompletionSource<bool>();
 
-            try
-            {
-                Calls.BlockingUnaryCall(callDetails, "CHECK_CANCELLATION_RECEIVED");
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                // We can't guarantee the status code is always DeadlineExceeded. See issue #2685.
-                Assert.Contains(e.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
-            }
-            Assert.AreEqual("CANCELLED", stringFromServerHandlerTcs.Task.Result);
-        }
-            
-        private static async Task<string> TestMethodHandler(string request, ServerCallContext context)
-        {
-            if (request == "TIMEOUT")
-            {
-                await Task.Delay(60000);
-                return "";
-            }
-
-            if (request == "RETURN_DEADLINE")
-            {
-                if (context.Deadline == DateTime.MaxValue)
-                {
-                    return "DATETIME_MAXVALUE";
-                }
-
-                return context.Deadline.Ticks.ToString();
-            }
-
-            if (request == "CHECK_CANCELLATION_RECEIVED")
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) => 
             {
                 // wait until cancellation token is fired.
                 var tcs = new TaskCompletionSource<object>();
                 context.CancellationToken.Register(() => { tcs.SetResult(null); });
                 await tcs.Task;
-                stringFromServerHandlerTcs.SetResult("CANCELLED");
+                serverReceivedCancellationTcs.SetResult(true);
                 return "";
-            }
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(new CallOptions(deadline: DateTime.UtcNow.Add(TimeSpan.FromSeconds(5)))), "abc"));
+            // We can't guarantee the status code always DeadlineExceeded. See issue #2685.
+            Assert.Contains(ex.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
 
-            return "";
+            Assert.IsTrue(await serverReceivedCancellationTcs.Task);
         }
     }
 }
diff --git a/src/csharp/Grpc.Core/CallInvocationDetails.cs b/src/csharp/Grpc.Core/CallInvocationDetails.cs
index eb23a3a209..6565073fc5 100644
--- a/src/csharp/Grpc.Core/CallInvocationDetails.cs
+++ b/src/csharp/Grpc.Core/CallInvocationDetails.cs
@@ -40,30 +40,60 @@ namespace Grpc.Core
     /// <summary>
     /// Details about a client-side call to be invoked.
     /// </summary>
-    public class CallInvocationDetails<TRequest, TResponse>
+    public struct CallInvocationDetails<TRequest, TResponse>
     {
         readonly Channel channel;
         readonly string method;
         readonly string host;
         readonly Marshaller<TRequest> requestMarshaller;
         readonly Marshaller<TResponse> responseMarshaller;
-        readonly CallOptions options;
+        CallOptions options;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Grpc.Core.CallInvocationDetails`2"/> struct.
+        /// </summary>
+        /// <param name="channel">Channel to use for this call.</param>
+        /// <param name="method">Method to call.</param>
+        /// <param name="options">Call options.</param>
         public CallInvocationDetails(Channel channel, Method<TRequest, TResponse> method, CallOptions options) :
-            this(channel, method.FullName, null, method.RequestMarshaller, method.ResponseMarshaller, options)
+            this(channel, method, null, options)
         {
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Grpc.Core.CallInvocationDetails`2"/> struct.
+        /// </summary>
+        /// <param name="channel">Channel to use for this call.</param>
+        /// <param name="method">Method to call.</param>
+        /// <param name="host">Host that contains the method. if <c>null</c>, default host will be used.</param>
+        /// <param name="options">Call options.</param>
+        public CallInvocationDetails(Channel channel, Method<TRequest, TResponse> method, string host, CallOptions options) :
+            this(channel, method.FullName, host, method.RequestMarshaller, method.ResponseMarshaller, options)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Grpc.Core.CallInvocationDetails`2"/> struct.
+        /// </summary>
+        /// <param name="channel">Channel to use for this call.</param>
+        /// <param name="method">Qualified method name.</param>
+        /// <param name="host">Host that contains the method.</param>
+        /// <param name="requestMarshaller">Request marshaller.</param>
+        /// <param name="responseMarshaller">Response marshaller.</param>
+        /// <param name="options">Call options.</param>
         public CallInvocationDetails(Channel channel, string method, string host, Marshaller<TRequest> requestMarshaller, Marshaller<TResponse> responseMarshaller, CallOptions options)
         {
-            this.channel = Preconditions.CheckNotNull(channel);
-            this.method = Preconditions.CheckNotNull(method);
+            this.channel = Preconditions.CheckNotNull(channel, "channel");
+            this.method = Preconditions.CheckNotNull(method, "method");
             this.host = host;
-            this.requestMarshaller = Preconditions.CheckNotNull(requestMarshaller);
-            this.responseMarshaller = Preconditions.CheckNotNull(responseMarshaller);
-            this.options = Preconditions.CheckNotNull(options);
+            this.requestMarshaller = Preconditions.CheckNotNull(requestMarshaller, "requestMarshaller");
+            this.responseMarshaller = Preconditions.CheckNotNull(responseMarshaller, "responseMarshaller");
+            this.options = options;
         }
 
+        /// <summary>
+        /// Get channel associated with this call.
+        /// </summary>
         public Channel Channel
         {
             get
@@ -72,6 +102,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets name of method to be called.
+        /// </summary>
         public string Method
         {
             get
@@ -80,6 +113,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Get name of host.
+        /// </summary>
         public string Host
         {
             get
@@ -88,6 +124,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets marshaller used to serialize requests.
+        /// </summary>
         public Marshaller<TRequest> RequestMarshaller
         {
             get
@@ -96,6 +135,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets marshaller used to deserialized responses.
+        /// </summary>
         public Marshaller<TResponse> ResponseMarshaller
         {
             get
@@ -104,6 +146,9 @@ namespace Grpc.Core
             }
         }
             
+        /// <summary>
+        /// Gets the call options.
+        /// </summary>
         public CallOptions Options
         {
             get
@@ -111,5 +156,16 @@ namespace Grpc.Core
                 return options;
             }
         }
+
+        /// <summary>
+        /// Returns new instance of <see cref="CallInvocationDetails"/> with
+        /// <c>Options</c> set to the value provided. Values of all other fields are preserved.
+        /// </summary>
+        public CallInvocationDetails<TRequest, TResponse> WithOptions(CallOptions options)
+        {
+            var newDetails = this;
+            newDetails.options = options;
+            return newDetails;
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/CallOptions.cs b/src/csharp/Grpc.Core/CallOptions.cs
index 8e9739335f..3dfe80b48c 100644
--- a/src/csharp/Grpc.Core/CallOptions.cs
+++ b/src/csharp/Grpc.Core/CallOptions.cs
@@ -42,24 +42,30 @@ namespace Grpc.Core
     /// <summary>
     /// Options for calls made by client.
     /// </summary>
-    public class CallOptions
+    public struct CallOptions
     {
-        readonly Metadata headers;
-        readonly DateTime deadline;
-        readonly CancellationToken cancellationToken;
+        Metadata headers;
+        DateTime? deadline;
+        CancellationToken cancellationToken;
+        WriteOptions writeOptions;
+        ContextPropagationToken propagationToken;
 
         /// <summary>
-        /// Creates a new instance of <c>CallOptions</c>.
+        /// Creates a new instance of <c>CallOptions</c> struct.
         /// </summary>
         /// <param name="headers">Headers to be sent with the call.</param>
         /// <param name="deadline">Deadline for the call to finish. null means no deadline.</param>
         /// <param name="cancellationToken">Can be used to request cancellation of the call.</param>
-        public CallOptions(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+        /// <param name="writeOptions">Write options that will be used for this call.</param>
+        /// <param name="propagationToken">Context propagation token obtained from <see cref="ServerCallContext"/>.</param>
+        public CallOptions(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken),
+                           WriteOptions writeOptions = null, ContextPropagationToken propagationToken = null)
         {
-            // TODO(jtattermusch): consider only creating metadata object once it's really needed.
-            this.headers = headers != null ? headers : new Metadata();
-            this.deadline = deadline.HasValue ? deadline.Value : DateTime.MaxValue;
+            this.headers = headers;
+            this.deadline = deadline;
             this.cancellationToken = cancellationToken;
+            this.writeOptions = writeOptions;
+            this.propagationToken = propagationToken;
         }
 
         /// <summary>
@@ -73,7 +79,7 @@ namespace Grpc.Core
         /// <summary>
         /// Call deadline.
         /// </summary>
-        public DateTime Deadline
+        public DateTime? Deadline
         {
             get { return deadline; }
         }
@@ -85,5 +91,88 @@ namespace Grpc.Core
         {
             get { return cancellationToken; }
         }
+
+        /// <summary>
+        /// Write options that will be used for this call.
+        /// </summary>
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return this.writeOptions;
+            }
+        }
+
+        /// <summary>
+        /// Token for propagating parent call context.
+        /// </summary>
+        public ContextPropagationToken PropagationToken
+        {
+            get
+            {
+                return this.propagationToken;
+            }
+        }
+
+        /// <summary>
+        /// Returns new instance of <see cref="CallOptions"/> with
+        /// <c>Headers</c> set to the value provided. Values of all other fields are preserved.
+        /// </summary>
+        public CallOptions WithHeaders(Metadata headers)
+        {
+            var newOptions = this;
+            newOptions.headers = headers;
+            return newOptions;
+        }
+
+        /// <summary>
+        /// Returns new instance of <see cref="CallOptions"/> with
+        /// <c>Deadline</c> set to the value provided. Values of all other fields are preserved.
+        /// </summary>
+        public CallOptions WithDeadline(DateTime deadline)
+        {
+            var newOptions = this;
+            newOptions.deadline = deadline;
+            return newOptions;
+        }
+
+        /// <summary>
+        /// Returns new instance of <see cref="CallOptions"/> with
+        /// <c>CancellationToken</c> set to the value provided. Values of all other fields are preserved.
+        /// </summary>
+        public CallOptions WithCancellationToken(CancellationToken cancellationToken)
+        {
+            var newOptions = this;
+            newOptions.cancellationToken = cancellationToken;
+            return newOptions;
+        }
+
+        /// <summary>
+        /// Returns a new instance of <see cref="CallOptions"/> with 
+        /// all previously unset values set to their defaults and deadline and cancellation
+        /// token propagated when appropriate.
+        /// </summary>
+        internal CallOptions Normalize()
+        {
+            var newOptions = this;
+            if (propagationToken != null)
+            {
+                if (propagationToken.Options.IsPropagateDeadline)
+                {
+                    Preconditions.CheckArgument(!newOptions.deadline.HasValue,
+                        "Cannot propagate deadline from parent call. The deadline has already been set explicitly.");
+                    newOptions.deadline = propagationToken.ParentDeadline;
+                }
+                if (propagationToken.Options.IsPropagateCancellation)
+                {
+                    Preconditions.CheckArgument(!newOptions.cancellationToken.CanBeCanceled,
+                        "Cannot propagate cancellation token from parent call. The cancellation token has already been set to a non-default value.");
+                }
+            }
+                
+            newOptions.headers = newOptions.headers ?? Metadata.Empty;
+            newOptions.deadline = newOptions.deadline ?? DateTime.MaxValue;
+            return newOptions;
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/Calls.cs b/src/csharp/Grpc.Core/Calls.cs
index 00a8cabf82..7067456638 100644
--- a/src/csharp/Grpc.Core/Calls.cs
+++ b/src/csharp/Grpc.Core/Calls.cs
@@ -31,8 +31,6 @@
 
 #endregion
 
-using System;
-using System.Threading;
 using System.Threading.Tasks;
 using Grpc.Core.Internal;
 
@@ -40,9 +38,20 @@ namespace Grpc.Core
 {
     /// <summary>
     /// Helper methods for generated clients to make RPC calls.
+    /// Most users will use this class only indirectly and will be 
+    /// making calls using client object generated from protocol
+    /// buffer definition files.
     /// </summary>
     public static class Calls
     {
+        /// <summary>
+        /// Invokes a simple remote call in a blocking fashion.
+        /// </summary>
+        /// <returns>The response.</returns>
+        /// <param name="call">The call defintion.</param>
+        /// <param name="req">Request message.</param>
+        /// <typeparam name="TRequest">Type of request message.</typeparam>
+        /// <typeparam name="TResponse">The of response message.</typeparam>
         public static TResponse BlockingUnaryCall<TRequest, TResponse>(CallInvocationDetails<TRequest, TResponse> call, TRequest req)
             where TRequest : class
             where TResponse : class
@@ -51,6 +60,14 @@ namespace Grpc.Core
             return asyncCall.UnaryCall(req);
         }
 
+        /// <summary>
+        /// Invokes a simple remote call asynchronously.
+        /// </summary>
+        /// <returns>An awaitable call object providing access to the response.</returns>
+        /// <param name="call">The call defintion.</param>
+        /// <param name="req">Request message.</param>
+        /// <typeparam name="TRequest">Type of request message.</typeparam>
+        /// <typeparam name="TResponse">The of response message.</typeparam>
         public static AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(CallInvocationDetails<TRequest, TResponse> call, TRequest req)
             where TRequest : class
             where TResponse : class
@@ -60,6 +77,15 @@ namespace Grpc.Core
             return new AsyncUnaryCall<TResponse>(asyncResult, asyncCall.GetStatus, asyncCall.GetTrailers, asyncCall.Cancel);
         }
 
+        /// <summary>
+        /// Invokes a server streaming call asynchronously.
+        /// In server streaming scenario, client sends on request and server responds with a stream of responses.
+        /// </summary>
+        /// <returns>A call object providing access to the asynchronous response stream.</returns>
+        /// <param name="call">The call defintion.</param>
+        /// <param name="req">Request message.</param>
+        /// <typeparam name="TRequest">Type of request message.</typeparam>
+        /// <typeparam name="TResponse">The of response messages.</typeparam>
         public static AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(CallInvocationDetails<TRequest, TResponse> call, TRequest req)
             where TRequest : class
             where TResponse : class
@@ -70,6 +96,13 @@ namespace Grpc.Core
             return new AsyncServerStreamingCall<TResponse>(responseStream, asyncCall.GetStatus, asyncCall.GetTrailers, asyncCall.Cancel);
         }
 
+        /// <summary>
+        /// Invokes a client streaming call asynchronously.
+        /// In client streaming scenario, client sends a stream of requests and server responds with a single response.
+        /// </summary>
+        /// <returns>An awaitable call object providing access to the response.</returns>
+        /// <typeparam name="TRequest">Type of request messages.</typeparam>
+        /// <typeparam name="TResponse">The of response message.</typeparam>
         public static AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(CallInvocationDetails<TRequest, TResponse> call)
             where TRequest : class
             where TResponse : class
@@ -80,6 +113,15 @@ namespace Grpc.Core
             return new AsyncClientStreamingCall<TRequest, TResponse>(requestStream, resultTask, asyncCall.GetStatus, asyncCall.GetTrailers, asyncCall.Cancel);
         }
 
+        /// <summary>
+        /// Invokes a duplex streaming call asynchronously.
+        /// In duplex streaming scenario, client sends a stream of requests and server responds with a stream of responses.
+        /// The response stream is completely independent and both side can be sending messages at the same time.
+        /// </summary>
+        /// <returns>A call object providing access to the asynchronous request and response streams.</returns>
+        /// <param name="call">The call definition.</param>
+        /// <typeparam name="TRequest">Type of request messages.</typeparam>
+        /// <typeparam name="TResponse">Type of reponse messages.</typeparam>
         public static AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(CallInvocationDetails<TRequest, TResponse> call)
             where TRequest : class
             where TResponse : class
diff --git a/src/csharp/Grpc.Core/Channel.cs b/src/csharp/Grpc.Core/Channel.cs
index 9273ea4582..64c6adf2bf 100644
--- a/src/csharp/Grpc.Core/Channel.cs
+++ b/src/csharp/Grpc.Core/Channel.cs
@@ -49,6 +49,7 @@ namespace Grpc.Core
     {
         static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<Channel>();
 
+        readonly string target;
         readonly GrpcEnvironment environment;
         readonly ChannelSafeHandle handle;
         readonly List<ChannelOption> options;
@@ -58,12 +59,12 @@ namespace Grpc.Core
         /// Creates a channel that connects to a specific host.
         /// Port will default to 80 for an unsecure channel and to 443 for a secure channel.
         /// </summary>
-        /// <param name="host">The name or IP address of the host.</param>
+        /// <param name="target">Target of the channel.</param>
         /// <param name="credentials">Credentials to secure the channel.</param>
         /// <param name="options">Channel options.</param>
-        public Channel(string host, Credentials credentials, IEnumerable<ChannelOption> options = null)
+        public Channel(string target, Credentials credentials, IEnumerable<ChannelOption> options = null)
         {
-            Preconditions.CheckNotNull(host);
+            this.target = Preconditions.CheckNotNull(target, "target");
             this.environment = GrpcEnvironment.GetInstance();
             this.options = options != null ? new List<ChannelOption>(options) : new List<ChannelOption>();
 
@@ -73,11 +74,11 @@ namespace Grpc.Core
             {
                 if (nativeCredentials != null)
                 {
-                    this.handle = ChannelSafeHandle.CreateSecure(nativeCredentials, host, nativeChannelArgs);
+                    this.handle = ChannelSafeHandle.CreateSecure(nativeCredentials, target, nativeChannelArgs);
                 }
                 else
                 {
-                    this.handle = ChannelSafeHandle.CreateInsecure(host, nativeChannelArgs);
+                    this.handle = ChannelSafeHandle.CreateInsecure(target, nativeChannelArgs);
                 }
             }
         }
@@ -131,8 +132,8 @@ namespace Grpc.Core
             return tcs.Task;
         }
 
-        /// <summary> Address of the remote endpoint in URI format.</summary>
-        public string Target
+        /// <summary>Resolved address of the remote endpoint in URI format.</summary>
+        public string ResolvedTarget
         {
             get
             {
@@ -140,6 +141,15 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>The original target used to create the channel.</summary>
+        public string Target
+        {
+            get
+            {
+                return this.target;
+            }
+        }
+
         /// <summary>
         /// Allows explicitly requesting channel to connect without starting an RPC.
         /// Returned task completes once state Ready was seen. If the deadline is reached,
diff --git a/src/csharp/Grpc.Core/ChannelOptions.cs b/src/csharp/Grpc.Core/ChannelOptions.cs
index 1e0f90287a..0cb2953f2c 100644
--- a/src/csharp/Grpc.Core/ChannelOptions.cs
+++ b/src/csharp/Grpc.Core/ChannelOptions.cs
@@ -63,8 +63,8 @@ namespace Grpc.Core
         public ChannelOption(string name, string stringValue)
         {
             this.type = OptionType.String;
-            this.name = Preconditions.CheckNotNull(name);
-            this.stringValue = Preconditions.CheckNotNull(stringValue);
+            this.name = Preconditions.CheckNotNull(name, "name");
+            this.stringValue = Preconditions.CheckNotNull(stringValue, "stringValue");
         }
 
         /// <summary>
@@ -75,7 +75,7 @@ namespace Grpc.Core
         public ChannelOption(string name, int intValue)
         {
             this.type = OptionType.Integer;
-            this.name = Preconditions.CheckNotNull(name);
+            this.name = Preconditions.CheckNotNull(name, "name");
             this.intValue = intValue;
         }
 
diff --git a/src/csharp/Grpc.Core/ClientBase.cs b/src/csharp/Grpc.Core/ClientBase.cs
index 88494bb4ac..f46184406c 100644
--- a/src/csharp/Grpc.Core/ClientBase.cs
+++ b/src/csharp/Grpc.Core/ClientBase.cs
@@ -35,21 +35,26 @@ using System;
 using System.Collections.Generic;
 
 using Grpc.Core.Internal;
+using System.Text.RegularExpressions;
 
 namespace Grpc.Core
 {
-    public delegate void MetadataInterceptorDelegate(Metadata metadata);
+    public delegate void MetadataInterceptorDelegate(string authUri, Metadata metadata);
 
     /// <summary>
     /// Base class for client-side stubs.
     /// </summary>
     public abstract class ClientBase
     {
+        static readonly Regex TrailingPortPattern = new Regex(":[0-9]+/?$");
         readonly Channel channel;
+        readonly string authUriBase;
 
         public ClientBase(Channel channel)
         {
             this.channel = channel;
+            // TODO(jtattermush): we shouldn't need to hand-curate the channel.Target contents.
+            this.authUriBase = "https://" + TrailingPortPattern.Replace(channel.Target, "") + "/";
         }
 
         /// <summary>
@@ -63,6 +68,18 @@ namespace Grpc.Core
         }
 
         /// <summary>
+        /// gRPC supports multiple "hosts" being served by a single server. 
+        /// This property can be used to set the target host explicitly.
+        /// By default, this will be set to <c>null</c> with the meaning
+        /// "use default host".
+        /// </summary>
+        public string Host
+        {
+            get;
+            set;
+        }
+
+        /// <summary>
         /// Channel associated with this client.
         /// </summary>
         public Channel Channel
@@ -83,10 +100,14 @@ namespace Grpc.Core
             var interceptor = HeaderInterceptor;
             if (interceptor != null)
             {
-                interceptor(options.Headers);
-                options.Headers.Freeze();
+                if (options.Headers == null)
+                {
+                    options = options.WithHeaders(new Metadata());
+                }
+                var authUri = authUriBase + method.ServiceName;
+                interceptor(authUri, options.Headers);
             }
-            return new CallInvocationDetails<TRequest, TResponse>(channel, method, options);
+            return new CallInvocationDetails<TRequest, TResponse>(channel, method, Host, options);
         }
     }
 }
diff --git a/src/csharp/Grpc.Core/OperationFailedException.cs b/src/csharp/Grpc.Core/CompressionLevel.cs
index 9b1c24d0c1..399652b85e 100644
--- a/src/csharp/Grpc.Core/OperationFailedException.cs
+++ b/src/csharp/Grpc.Core/CompressionLevel.cs
@@ -36,12 +36,28 @@ using System;
 namespace Grpc.Core
 {
     /// <summary>
-    /// Thrown when gRPC operation fails.
+    /// Compression level based on grpc_compression_level from grpc/compression.h
     /// </summary>
-    public class OperationFailedException : Exception
+    public enum CompressionLevel
     {
-        public OperationFailedException(string message) : base(message)
-        {
-        }
+        /// <summary>
+        /// No compression.
+        /// </summary>
+        None = 0,
+
+        /// <summary>
+        /// Low compression.
+        /// </summary>
+        Low,
+
+        /// <summary>
+        /// Medium compression.
+        /// </summary>
+        Medium,
+
+        /// <summary>
+        /// High compression.
+        /// </summary>
+        High,
     }
 }
diff --git a/src/csharp/Grpc.Core/ContextPropagationToken.cs b/src/csharp/Grpc.Core/ContextPropagationToken.cs
new file mode 100644
index 0000000000..2e4bfc9e47
--- /dev/null
+++ b/src/csharp/Grpc.Core/ContextPropagationToken.cs
@@ -0,0 +1,171 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Threading;
+
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Token for propagating context of server side handlers to child calls.
+    /// In situations when a backend is making calls to another backend,
+    /// it makes sense to propagate properties like deadline and cancellation 
+    /// token of the server call to the child call.
+    /// C core provides some other contexts (like tracing context) that
+    /// are not accessible to C# layer, but this token still allows propagating them.
+    /// </summary>
+    public class ContextPropagationToken
+    {
+        /// <summary>
+        /// Default propagation mask used by C core.
+        /// </summary>
+        private const ContextPropagationFlags DefaultCoreMask = (ContextPropagationFlags)0xffff;
+
+        /// <summary>
+        /// Default propagation mask used by C# - we want to propagate deadline 
+        /// and cancellation token by our own means.
+        /// </summary>
+        internal const ContextPropagationFlags DefaultMask = DefaultCoreMask
+            & ~ContextPropagationFlags.Deadline & ~ContextPropagationFlags.Cancellation;
+
+        readonly CallSafeHandle parentCall;
+        readonly DateTime deadline;
+        readonly CancellationToken cancellationToken;
+        readonly ContextPropagationOptions options;
+
+        internal ContextPropagationToken(CallSafeHandle parentCall, DateTime deadline, CancellationToken cancellationToken, ContextPropagationOptions options)
+        {
+            this.parentCall = Preconditions.CheckNotNull(parentCall);
+            this.deadline = deadline;
+            this.cancellationToken = cancellationToken;
+            this.options = options ?? ContextPropagationOptions.Default;
+        }
+
+        /// <summary>
+        /// Gets the native handle of the parent call.
+        /// </summary>
+        internal CallSafeHandle ParentCall
+        {
+            get
+            {
+                return this.parentCall;
+            }
+        }
+
+        /// <summary>
+        /// Gets the parent call's deadline.
+        /// </summary>
+        internal DateTime ParentDeadline
+        {
+            get
+            {
+                return this.deadline;
+            }
+        }
+
+        /// <summary>
+        /// Gets the parent call's cancellation token.
+        /// </summary>
+        internal CancellationToken ParentCancellationToken
+        {
+            get
+            {
+                return this.cancellationToken;
+            }
+        }
+
+        /// <summary>
+        /// Get the context propagation options.
+        /// </summary>
+        internal ContextPropagationOptions Options
+        {
+            get
+            {
+                return this.options;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Options for <see cref="ContextPropagationToken"/>.
+    /// </summary>
+    public class ContextPropagationOptions
+    {
+        /// <summary>
+        /// The context propagation options that will be used by default.
+        /// </summary>
+        public static readonly ContextPropagationOptions Default = new ContextPropagationOptions();
+
+        bool propagateDeadline;
+        bool propagateCancellation;
+
+
+        /// <summary>
+        /// Creates new context propagation options.
+        /// </summary>
+        /// <param name="propagateDeadline">If set to <c>true</c> parent call's deadline will be propagated to the child call.</param>
+        /// <param name="propagateCancellation">If set to <c>true</c> parent call's cancellation token will be propagated to the child call.</param>
+        public ContextPropagationOptions(bool propagateDeadline = true, bool propagateCancellation = true)
+        {
+            this.propagateDeadline = propagateDeadline;
+            this.propagateCancellation = propagateCancellation;
+        }
+            
+        /// <value><c>true</c> if parent call's deadline should be propagated to the child call.</value>
+        public bool IsPropagateDeadline
+        {
+            get { return this.propagateDeadline; }
+        }
+
+        /// <value><c>true</c> if parent call's cancellation token should be propagated to the child call.</value>
+        public bool IsPropagateCancellation
+        {
+            get { return this.propagateCancellation; }
+        }
+    }
+
+    /// <summary>
+    /// Context propagation flags from grpc/grpc.h.
+    /// </summary>
+    [Flags]
+    internal enum ContextPropagationFlags
+    {
+        Deadline = 1,
+        CensusStatsContext = 2,
+        CensusTracingContext = 4,
+        Cancellation = 8
+    }
+}
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 52defd1965..055aff1444 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -77,14 +77,12 @@
     <Compile Include="ServerServiceDefinition.cs" />
     <Compile Include="Utils\AsyncStreamExtensions.cs" />
     <Compile Include="Utils\BenchmarkUtil.cs" />
-    <Compile Include="Utils\ExceptionHelper.cs" />
     <Compile Include="Internal\CredentialsSafeHandle.cs" />
     <Compile Include="Credentials.cs" />
     <Compile Include="Internal\ChannelArgsSafeHandle.cs" />
     <Compile Include="Internal\AsyncCompletion.cs" />
     <Compile Include="Internal\AsyncCallBase.cs" />
     <Compile Include="Internal\AsyncCallServer.cs" />
-    <Compile Include="OperationFailedException.cs" />
     <Compile Include="Internal\AsyncCall.cs" />
     <Compile Include="Utils\Preconditions.cs" />
     <Compile Include="Internal\ServerCredentialsSafeHandle.cs" />
@@ -115,6 +113,9 @@
     <Compile Include="ChannelState.cs" />
     <Compile Include="CallInvocationDetails.cs" />
     <Compile Include="CallOptions.cs" />
+    <Compile Include="CompressionLevel.cs" />
+    <Compile Include="WriteOptions.cs" />
+    <Compile Include="ContextPropagationToken.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Grpc.Core.nuspec" />
diff --git a/src/csharp/Grpc.Core/GrpcEnvironment.cs b/src/csharp/Grpc.Core/GrpcEnvironment.cs
index 034a66be3c..30d8c80235 100644
--- a/src/csharp/Grpc.Core/GrpcEnvironment.cs
+++ b/src/csharp/Grpc.Core/GrpcEnvironment.cs
@@ -53,6 +53,9 @@ namespace Grpc.Core
         [DllImport("grpc_csharp_ext.dll")]
         static extern void grpcsharp_shutdown();
 
+        [DllImport("grpc_csharp_ext.dll")]
+        static extern IntPtr grpcsharp_version_string();  // returns not-owned const char*
+
         static object staticLock = new object();
         static GrpcEnvironment instance;
 
@@ -112,7 +115,7 @@ namespace Grpc.Core
         /// </summary>
         public static void SetLogger(ILogger customLogger)
         {
-            Preconditions.CheckNotNull(customLogger);
+            Preconditions.CheckNotNull(customLogger, "customLogger");
             logger = customLogger;
         }
 
@@ -164,6 +167,15 @@ namespace Grpc.Core
         }
 
         /// <summary>
+        /// Gets version of gRPC C core.
+        /// </summary>
+        internal static string GetCoreVersionString()
+        {
+            var ptr = grpcsharp_version_string();  // the pointer is not owned
+            return Marshal.PtrToStringAnsi(ptr);
+        }
+
+        /// <summary>
         /// Shuts down this environment.
         /// </summary>
         private void Close()
@@ -180,23 +192,5 @@ namespace Grpc.Core
 
             Logger.Info("gRPC shutdown.");
         }
-
-        /// <summary>
-        /// Shuts down this environment asynchronously.
-        /// </summary>
-        private Task CloseAsync()
-        {
-            return Task.Run(() =>
-            {
-                try
-                {
-                    Close();
-                }
-                catch (Exception e)
-                {
-                    Logger.Error(e, "Error occured while shutting down GrpcEnvironment.");
-                }
-            });
-        }
     }
 }
diff --git a/src/csharp/Grpc.Core/IAsyncStreamReader.cs b/src/csharp/Grpc.Core/IAsyncStreamReader.cs
index 371fbf27ce..c0a0674e50 100644
--- a/src/csharp/Grpc.Core/IAsyncStreamReader.cs
+++ b/src/csharp/Grpc.Core/IAsyncStreamReader.cs
@@ -43,7 +43,7 @@ namespace Grpc.Core
     /// A stream of messages to be read.
     /// </summary>
     /// <typeparam name="T"></typeparam>
-    public interface IAsyncStreamReader<TResponse> : IAsyncEnumerator<TResponse>
+    public interface IAsyncStreamReader<T> : IAsyncEnumerator<T>
     {
         // TODO(jtattermusch): consider just using IAsyncEnumerator instead of this interface.
     }
diff --git a/src/csharp/Grpc.Core/IAsyncStreamWriter.cs b/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
index 2000210252..4e2acb9c71 100644
--- a/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
+++ b/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
@@ -50,5 +50,13 @@ namespace Grpc.Core
         /// </summary>
         /// <param name="message">the message to be written. Cannot be null.</param>
         Task WriteAsync(T message);
+
+        /// <summary>
+        /// Write options that will be used for the next write.
+        /// If null, default options will be used.
+        /// Once set, this property maintains its value across subsequent
+        /// writes.
+        /// <value>The write options.</value>
+        WriteOptions WriteOptions { get; set; }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index 414b5c4282..2c3e3d75ea 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -50,7 +50,7 @@ namespace Grpc.Core.Internal
     {
         static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<AsyncCall<TRequest, TResponse>>();
 
-        readonly CallInvocationDetails<TRequest, TResponse> callDetails;
+        readonly CallInvocationDetails<TRequest, TResponse> details;
 
         // Completion of a pending unary response if not null.
         TaskCompletionSource<TResponse> unaryResponseTcs;
@@ -63,7 +63,8 @@ namespace Grpc.Core.Internal
         public AsyncCall(CallInvocationDetails<TRequest, TResponse> callDetails)
             : base(callDetails.RequestMarshaller.Serializer, callDetails.ResponseMarshaller.Deserializer)
         {
-            this.callDetails = callDetails;
+            this.details = callDetails.WithOptions(callDetails.Options.Normalize());
+            this.initialMetadataSent = true;  // we always send metadata at the very beginning of the call.
         }
 
         // TODO: this method is not Async, so it shouldn't be in AsyncCall class, but 
@@ -89,11 +90,11 @@ namespace Grpc.Core.Internal
                     readingDone = true;
                 }
 
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
                     using (var ctx = BatchContextSafeHandle.Create())
                     {
-                        call.StartUnary(payload, ctx, metadataArray);
+                        call.StartUnary(ctx, payload, metadataArray, GetWriteFlagsForCall());
                         var ev = cq.Pluck(ctx.Handle);
 
                         bool success = (ev.success != 0);
@@ -108,15 +109,9 @@ namespace Grpc.Core.Internal
                     }
                 }
 
-                try
-                {
-                    // Once the blocking call returns, the result should be available synchronously.
-                    return unaryResponseTcs.Task.Result;
-                }
-                catch (AggregateException ae)
-                {
-                    throw ExceptionHelper.UnwrapRpcException(ae);
-                }
+                // Once the blocking call returns, the result should be available synchronously.
+                // Note that GetAwaiter().GetResult() doesn't wrap exceptions in AggregateException.
+                return unaryResponseTcs.Task.GetAwaiter().GetResult();
             }
         }
 
@@ -130,7 +125,7 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
                 halfcloseRequested = true;
                 readingDone = true;
@@ -138,9 +133,9 @@ namespace Grpc.Core.Internal
                 byte[] payload = UnsafeSerialize(msg);
 
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartUnary(payload, HandleUnaryResponse, metadataArray);
+                    call.StartUnary(HandleUnaryResponse, payload, metadataArray, GetWriteFlagsForCall());
                 }
                 return unaryResponseTcs.Task;
             }
@@ -157,12 +152,12 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
                 readingDone = true;
 
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
                     call.StartClientStreaming(HandleUnaryResponse, metadataArray);
                 }
@@ -181,16 +176,16 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
                 halfcloseRequested = true;
                 halfclosed = true;  // halfclose not confirmed yet, but it will be once finishedHandler is called.
 
                 byte[] payload = UnsafeSerialize(msg);
 
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartServerStreaming(payload, HandleFinished, metadataArray);
+                    call.StartServerStreaming(HandleFinished, payload, metadataArray, GetWriteFlagsForCall());
                 }
             }
         }
@@ -206,9 +201,9 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
                     call.StartDuplexStreaming(HandleFinished, metadataArray);
                 }
@@ -219,9 +214,9 @@ namespace Grpc.Core.Internal
         /// Sends a streaming request. Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendMessage(TRequest msg, AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendMessage(TRequest msg, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
-            StartSendMessageInternal(msg, completionDelegate);
+            StartSendMessageInternal(msg, writeFlags, completionDelegate);
         }
 
         /// <summary>
@@ -278,6 +273,14 @@ namespace Grpc.Core.Internal
             }
         }
 
+        public CallInvocationDetails<TRequest, TResponse> Details
+        {
+            get
+            {
+                return this.details;
+            }
+        }
+
         /// <summary>
         /// On client-side, we only fire readCompletionDelegate once all messages have been read 
         /// and status has been received.
@@ -310,14 +313,17 @@ namespace Grpc.Core.Internal
 
         protected override void OnReleaseResources()
         {
-            callDetails.Channel.Environment.DebugStats.ActiveClientCalls.Decrement();
+            details.Channel.Environment.DebugStats.ActiveClientCalls.Decrement();
         }
 
         private void Initialize(CompletionQueueSafeHandle cq)
         {
-            var call = callDetails.Channel.Handle.CreateCall(callDetails.Channel.Environment.CompletionRegistry, cq,
-                callDetails.Method, callDetails.Host, Timespec.FromDateTime(callDetails.Options.Deadline));
-            callDetails.Channel.Environment.DebugStats.ActiveClientCalls.Increment();
+            var parentCall = details.Options.PropagationToken != null ? details.Options.PropagationToken.ParentCall : CallSafeHandle.NullInstance;
+
+            var call = details.Channel.Handle.CreateCall(details.Channel.Environment.CompletionRegistry,
+                parentCall, ContextPropagationToken.DefaultMask, cq,
+                details.Method, details.Host, Timespec.FromDateTime(details.Options.Deadline.Value));
+            details.Channel.Environment.DebugStats.ActiveClientCalls.Increment();
             InitializeInternal(call);
             RegisterCancellationCallback();
         }
@@ -325,7 +331,7 @@ namespace Grpc.Core.Internal
         // Make sure that once cancellationToken for this call is cancelled, Cancel() will be called.
         private void RegisterCancellationCallback()
         {
-            var token = callDetails.Options.CancellationToken;
+            var token = details.Options.CancellationToken;
             if (token.CanBeCanceled)
             {
                 token.Register(() => this.Cancel());
@@ -333,6 +339,15 @@ namespace Grpc.Core.Internal
         }
 
         /// <summary>
+        /// Gets WriteFlags set in callDetails.Options.WriteOptions
+        /// </summary>
+        private WriteFlags GetWriteFlagsForCall()
+        {
+            var writeOptions = details.Options.WriteOptions;
+            return writeOptions != null ? writeOptions.Flags : default(WriteFlags);
+        }
+
+        /// <summary>
         /// Handler for unary response completion.
         /// </summary>
         private void HandleUnaryResponse(bool success, BatchContextSafeHandle ctx)
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
index 38f2a5baeb..6ca4bbdafc 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
@@ -71,6 +71,9 @@ namespace Grpc.Core.Internal
         protected bool halfclosed;
         protected bool finished;  // True if close has been received from the peer.
 
+        protected bool initialMetadataSent;
+        protected long streamingWritesCounter;
+
         public AsyncCallBase(Func<TWrite, byte[]> serializer, Func<byte[], TRead> deserializer)
         {
             this.serializer = Preconditions.CheckNotNull(serializer);
@@ -123,7 +126,7 @@ namespace Grpc.Core.Internal
         /// Initiates sending a message. Only one send operation can be active at a time.
         /// completionDelegate is invoked upon completion.
         /// </summary>
-        protected void StartSendMessageInternal(TWrite msg, AsyncCompletionDelegate<object> completionDelegate)
+        protected void StartSendMessageInternal(TWrite msg, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
             byte[] payload = UnsafeSerialize(msg);
 
@@ -132,8 +135,11 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
-                call.StartSendMessage(payload, HandleSendFinished);
+                call.StartSendMessage(HandleSendFinished, payload, writeFlags, !initialMetadataSent);
+
                 sendCompletionDelegate = completionDelegate;
+                initialMetadataSent = true;
+                streamingWritesCounter++;
             }
         }
 
@@ -287,7 +293,7 @@ namespace Grpc.Core.Internal
 
             if (!success)
             {
-                FireCompletion(origCompletionDelegate, null, new OperationFailedException("Send failed"));
+                FireCompletion(origCompletionDelegate, null, new InvalidOperationException("Send failed"));
             }
             else
             {
@@ -312,7 +318,7 @@ namespace Grpc.Core.Internal
 
             if (!success)
             {
-                FireCompletion(origCompletionDelegate, null, new OperationFailedException("Halfclose failed"));
+                FireCompletion(origCompletionDelegate, null, new InvalidOperationException("Halfclose failed"));
             }
             else
             {
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index 513902ee36..3710a65d6b 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -83,9 +83,9 @@ namespace Grpc.Core.Internal
         /// Sends a streaming response. Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendMessage(TResponse msg, AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendMessage(TResponse msg, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
-            StartSendMessageInternal(msg, completionDelegate);
+            StartSendMessageInternal(msg, writeFlags, completionDelegate);
         }
 
         /// <summary>
@@ -98,6 +98,35 @@ namespace Grpc.Core.Internal
         }
 
         /// <summary>
+        /// Initiates sending a initial metadata. 
+        /// Even though C-core allows sending metadata in parallel to sending messages, we will treat sending metadata as a send message operation
+        /// to make things simpler.
+        /// completionDelegate is invoked upon completion.
+        /// </summary>
+        public void StartSendInitialMetadata(Metadata headers, AsyncCompletionDelegate<object> completionDelegate)
+        {
+            lock (myLock)
+            {
+                Preconditions.CheckNotNull(headers, "metadata");
+                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+
+                Preconditions.CheckState(!initialMetadataSent, "Response headers can only be sent once per call.");
+                Preconditions.CheckState(streamingWritesCounter == 0, "Response headers can only be sent before the first write starts.");
+                CheckSendingAllowed();
+
+                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+
+                using (var metadataArray = MetadataArraySafeHandle.Create(headers))
+                {
+                    call.StartSendInitialMetadata(HandleSendFinished, metadataArray);
+                }
+
+                this.initialMetadataSent = true;
+                sendCompletionDelegate = completionDelegate;
+            }
+        }
+
+        /// <summary>
         /// Sends call result status, also indicating server is done with streaming responses.
         /// Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
@@ -111,7 +140,7 @@ namespace Grpc.Core.Internal
 
                 using (var metadataArray = MetadataArraySafeHandle.Create(trailers))
                 {
-                    call.StartSendStatusFromServer(status, HandleHalfclosed, metadataArray);
+                    call.StartSendStatusFromServer(HandleHalfclosed, status, metadataArray, !initialMetadataSent);
                 }
                 halfcloseRequested = true;
                 readingDone = true;
diff --git a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
index 714749b171..3cb01e29bd 100644
--- a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
@@ -42,6 +42,8 @@ namespace Grpc.Core.Internal
     /// </summary>
     internal class CallSafeHandle : SafeHandleZeroIsInvalid
     {
+        public static readonly CallSafeHandle NullInstance = new CallSafeHandle();
+
         const uint GRPC_WRITE_BUFFER_HINT = 1;
         CompletionRegistry completionRegistry;
 
@@ -53,7 +55,7 @@ namespace Grpc.Core.Internal
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_unary(CallSafeHandle call,
-            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, MetadataArraySafeHandle metadataArray);
+            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_client_streaming(CallSafeHandle call,
@@ -62,7 +64,7 @@ namespace Grpc.Core.Internal
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_server_streaming(CallSafeHandle call,
             BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len,
-            MetadataArraySafeHandle metadataArray);
+            MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_duplex_streaming(CallSafeHandle call,
@@ -70,7 +72,7 @@ namespace Grpc.Core.Internal
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_message(CallSafeHandle call,
-            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len);
+            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_close_from_client(CallSafeHandle call,
@@ -78,7 +80,7 @@ namespace Grpc.Core.Internal
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_status_from_server(CallSafeHandle call, 
-            BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray);
+            BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_recv_message(CallSafeHandle call,
@@ -89,6 +91,10 @@ namespace Grpc.Core.Internal
             BatchContextSafeHandle ctx);
 
         [DllImport("grpc_csharp_ext.dll")]
+        static extern GRPCCallError grpcsharp_call_send_initial_metadata(CallSafeHandle call,
+            BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+
+        [DllImport("grpc_csharp_ext.dll")]
         static extern CStringSafeHandle grpcsharp_call_get_peer(CallSafeHandle call);
 
         [DllImport("grpc_csharp_ext.dll")]
@@ -103,17 +109,17 @@ namespace Grpc.Core.Internal
             this.completionRegistry = completionRegistry;
         }
 
-        public void StartUnary(byte[] payload, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartUnary(BatchCompletionDelegate callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray)
+            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
                 .CheckOk();
         }
 
-        public void StartUnary(byte[] payload, BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray)
+        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
-            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray)
+            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
                 .CheckOk();
         }
 
@@ -124,11 +130,11 @@ namespace Grpc.Core.Internal
             grpcsharp_call_start_client_streaming(this, ctx, metadataArray).CheckOk();
         }
 
-        public void StartServerStreaming(byte[] payload, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartServerStreaming(BatchCompletionDelegate callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray).CheckOk();
+            grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags).CheckOk();
         }
 
         public void StartDuplexStreaming(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
@@ -138,11 +144,11 @@ namespace Grpc.Core.Internal
             grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray).CheckOk();
         }
 
-        public void StartSendMessage(byte[] payload, BatchCompletionDelegate callback)
+        public void StartSendMessage(BatchCompletionDelegate callback, byte[] payload, WriteFlags writeFlags, bool sendEmptyInitialMetadata)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_send_message(this, ctx, payload, new UIntPtr((ulong)payload.Length)).CheckOk();
+            grpcsharp_call_send_message(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, sendEmptyInitialMetadata).CheckOk();
         }
 
         public void StartSendCloseFromClient(BatchCompletionDelegate callback)
@@ -152,11 +158,11 @@ namespace Grpc.Core.Internal
             grpcsharp_call_send_close_from_client(this, ctx).CheckOk();
         }
 
-        public void StartSendStatusFromServer(Status status, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartSendStatusFromServer(BatchCompletionDelegate callback, Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray).CheckOk();
+            grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray, sendEmptyInitialMetadata).CheckOk();
         }
 
         public void StartReceiveMessage(BatchCompletionDelegate callback)
@@ -173,6 +179,13 @@ namespace Grpc.Core.Internal
             grpcsharp_call_start_serverside(this, ctx).CheckOk();
         }
 
+        public void StartSendInitialMetadata(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        {
+            var ctx = BatchContextSafeHandle.Create();
+            completionRegistry.RegisterBatchCompletion(ctx, callback);
+            grpcsharp_call_send_initial_metadata(this, ctx, metadataArray).CheckOk();
+        }
+
         public void Cancel()
         {
             grpcsharp_call_cancel(this).CheckOk();
diff --git a/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs b/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs
index 7324ebdf57..7f03bf4ea5 100644
--- a/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs
@@ -47,7 +47,7 @@ namespace Grpc.Core.Internal
         static extern ChannelSafeHandle grpcsharp_secure_channel_create(CredentialsSafeHandle credentials, string target, ChannelArgsSafeHandle channelArgs);
 
         [DllImport("grpc_csharp_ext.dll")]
-        static extern CallSafeHandle grpcsharp_channel_create_call(ChannelSafeHandle channel, CompletionQueueSafeHandle cq, string method, string host, Timespec deadline);
+        static extern CallSafeHandle grpcsharp_channel_create_call(ChannelSafeHandle channel, CallSafeHandle parentCall, ContextPropagationFlags propagationMask, CompletionQueueSafeHandle cq, string method, string host, Timespec deadline);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern ChannelState grpcsharp_channel_check_connectivity_state(ChannelSafeHandle channel, int tryToConnect);
@@ -76,9 +76,9 @@ namespace Grpc.Core.Internal
             return grpcsharp_secure_channel_create(credentials, target, channelArgs);
         }
 
-        public CallSafeHandle CreateCall(CompletionRegistry registry, CompletionQueueSafeHandle cq, string method, string host, Timespec deadline)
+        public CallSafeHandle CreateCall(CompletionRegistry registry, CallSafeHandle parentCall, ContextPropagationFlags propagationMask, CompletionQueueSafeHandle cq, string method, string host, Timespec deadline)
         {
-            var result = grpcsharp_channel_create_call(this, cq, method, host, deadline);
+            var result = grpcsharp_channel_create_call(this, parentCall, propagationMask, cq, method, host, deadline);
             result.SetCompletionRegistry(registry);
             return result;
         }
diff --git a/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs b/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
index 58f493463b..013f00ff6f 100644
--- a/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
@@ -40,16 +40,18 @@ namespace Grpc.Core.Internal
     internal class ClientRequestStream<TRequest, TResponse> : IClientStreamWriter<TRequest>
     {
         readonly AsyncCall<TRequest, TResponse> call;
+        WriteOptions writeOptions;
 
         public ClientRequestStream(AsyncCall<TRequest, TResponse> call)
         {
             this.call = call;
+            this.writeOptions = call.Details.Options.WriteOptions;
         }
 
         public Task WriteAsync(TRequest message)
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendMessage(message, taskSource.CompletionDelegate);
+            call.StartSendMessage(message, GetWriteFlags(), taskSource.CompletionDelegate);
             return taskSource.Task;
         }
 
@@ -59,5 +61,24 @@ namespace Grpc.Core.Internal
             call.StartSendCloseFromClient(taskSource.CompletionDelegate);
             return taskSource.Task;
         }
+
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return this.writeOptions;
+            }
+
+            set
+            {
+                writeOptions = value;
+            }
+        }
+
+        private WriteFlags GetWriteFlags()
+        {
+            var options = writeOptions;
+            return options != null ? options.Flags : default(WriteFlags);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
index 19f0e3c57f..688f9f6fec 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
@@ -75,7 +75,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 Preconditions.CheckArgument(await requestStream.MoveNext());
@@ -131,7 +131,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 Preconditions.CheckArgument(await requestStream.MoveNext());
@@ -187,7 +187,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 var result = await handler(requestStream, context);
@@ -247,7 +247,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 await handler(requestStream, responseStream, context);
@@ -304,13 +304,14 @@ namespace Grpc.Core.Internal
             return new Status(StatusCode.Unknown, "Exception was thrown by handler.");
         }
 
-        public static ServerCallContext NewContext(ServerRpcNew newRpc, string peer, CancellationToken cancellationToken)
+        public static ServerCallContext NewContext<TRequest, TResponse>(ServerRpcNew newRpc, string peer, ServerResponseStream<TRequest, TResponse> serverResponseStream, CancellationToken cancellationToken)
+            where TRequest : class
+            where TResponse : class
         {
             DateTime realtimeDeadline = newRpc.Deadline.ToClockType(GPRClockType.Realtime).ToDateTime();
 
-            return new ServerCallContext(
-                newRpc.Method, newRpc.Host, peer, realtimeDeadline,
-                newRpc.RequestMetadata, cancellationToken);
+            return new ServerCallContext(newRpc.Call, newRpc.Method, newRpc.Host, peer, realtimeDeadline,
+                newRpc.RequestMetadata, cancellationToken, serverResponseStream.WriteResponseHeadersAsync, serverResponseStream);
         }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs b/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
index 756dcee87f..03e39efc02 100644
--- a/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
@@ -38,11 +38,12 @@ namespace Grpc.Core.Internal
     /// <summary>
     /// Writes responses asynchronously to an underlying AsyncCallServer object.
     /// </summary>
-    internal class ServerResponseStream<TRequest, TResponse> : IServerStreamWriter<TResponse>
+    internal class ServerResponseStream<TRequest, TResponse> : IServerStreamWriter<TResponse>, IHasWriteOptions
         where TRequest : class
         where TResponse : class
     {
         readonly AsyncCallServer<TRequest, TResponse> call;
+        WriteOptions writeOptions;
 
         public ServerResponseStream(AsyncCallServer<TRequest, TResponse> call)
         {
@@ -52,7 +53,7 @@ namespace Grpc.Core.Internal
         public Task WriteAsync(TResponse message)
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendMessage(message, taskSource.CompletionDelegate);
+            call.StartSendMessage(message, GetWriteFlags(), taskSource.CompletionDelegate);
             return taskSource.Task;
         }
 
@@ -62,5 +63,31 @@ namespace Grpc.Core.Internal
             call.StartSendStatusFromServer(status, trailers, taskSource.CompletionDelegate);
             return taskSource.Task;
         }
+
+        public Task WriteResponseHeadersAsync(Metadata responseHeaders)
+        {
+            var taskSource = new AsyncCompletionTaskSource<object>();
+            call.StartSendInitialMetadata(responseHeaders, taskSource.CompletionDelegate);
+            return taskSource.Task;
+        }
+
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return writeOptions;
+            }
+
+            set
+            {
+                writeOptions = value;
+            }
+        }
+
+        private WriteFlags GetWriteFlags()
+        {
+            var options = writeOptions;
+            return options != null ? options.Flags : default(WriteFlags);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/Timespec.cs b/src/csharp/Grpc.Core/Internal/Timespec.cs
index e83d21f4a4..daf85d5f61 100644
--- a/src/csharp/Grpc.Core/Internal/Timespec.cs
+++ b/src/csharp/Grpc.Core/Internal/Timespec.cs
@@ -211,7 +211,7 @@ namespace Grpc.Core.Internal
                 return Timespec.InfPast;
             }
 
-            Preconditions.CheckArgument(dateTime.Kind == DateTimeKind.Utc, "dateTime");
+            Preconditions.CheckArgument(dateTime.Kind == DateTimeKind.Utc, "dateTime needs of kind DateTimeKind.Utc or be equal to DateTime.MaxValue or DateTime.MinValue.");
 
             try
             {
diff --git a/src/csharp/Grpc.Core/KeyCertificatePair.cs b/src/csharp/Grpc.Core/KeyCertificatePair.cs
index 5def15a656..6f691975e9 100644
--- a/src/csharp/Grpc.Core/KeyCertificatePair.cs
+++ b/src/csharp/Grpc.Core/KeyCertificatePair.cs
@@ -54,8 +54,8 @@ namespace Grpc.Core
         /// <param name="privateKey">PEM encoded private key.</param>
         public KeyCertificatePair(string certificateChain, string privateKey)
         {
-            this.certificateChain = Preconditions.CheckNotNull(certificateChain);
-            this.privateKey = Preconditions.CheckNotNull(privateKey);
+            this.certificateChain = Preconditions.CheckNotNull(certificateChain, "certificateChain");
+            this.privateKey = Preconditions.CheckNotNull(privateKey, "privateKey");
         }
 
         /// <summary>
diff --git a/src/csharp/Grpc.Core/Logging/ConsoleLogger.cs b/src/csharp/Grpc.Core/Logging/ConsoleLogger.cs
index c67765c78d..382481d871 100644
--- a/src/csharp/Grpc.Core/Logging/ConsoleLogger.cs
+++ b/src/csharp/Grpc.Core/Logging/ConsoleLogger.cs
@@ -42,16 +42,21 @@ namespace Grpc.Core.Logging
         readonly Type forType;
         readonly string forTypeString;
 
+        /// <summary>Creates a console logger not associated to any specific type.</summary>
         public ConsoleLogger() : this(null)
         {
         }
 
+        /// <summary>Creates a console logger that logs messsage specific for given type.</summary>
         private ConsoleLogger(Type forType)
         {
             this.forType = forType;
             this.forTypeString = forType != null ? forType.FullName + " " : "";
         }
-
+ 
+        /// <summary>
+        /// Returns a logger associated with the specified type.
+        /// </summary>
         public ILogger ForType<T>()
         {
             if (typeof(T) == forType)
@@ -61,31 +66,37 @@ namespace Grpc.Core.Logging
             return new ConsoleLogger(typeof(T));
         }
 
+        /// <summary>Logs a message with severity Debug.</summary>
         public void Debug(string message, params object[] formatArgs)
         {
             Log("D", message, formatArgs);
         }
 
+        /// <summary>Logs a message with severity Info.</summary>
         public void Info(string message, params object[] formatArgs)
         {
             Log("I", message, formatArgs);
         }
 
+        /// <summary>Logs a message with severity Warning.</summary>
         public void Warning(string message, params object[] formatArgs)
         {
             Log("W", message, formatArgs);
         }
 
+        /// <summary>Logs a message and an associated exception with severity Warning.</summary>
         public void Warning(Exception exception, string message, params object[] formatArgs)
         {
             Log("W", message + " " + exception, formatArgs);
         }
 
+        /// <summary>Logs a message with severity Error.</summary>
         public void Error(string message, params object[] formatArgs)
         {
             Log("E", message, formatArgs);
         }
 
+        /// <summary>Logs a message and an associated exception with severity Error.</summary>
         public void Error(Exception exception, string message, params object[] formatArgs)
         {
             Log("E", message + " " + exception, formatArgs);
diff --git a/src/csharp/Grpc.Core/Logging/ILogger.cs b/src/csharp/Grpc.Core/Logging/ILogger.cs
index 0d58f133e3..61e0c91388 100644
--- a/src/csharp/Grpc.Core/Logging/ILogger.cs
+++ b/src/csharp/Grpc.Core/Logging/ILogger.cs
@@ -42,16 +42,22 @@ namespace Grpc.Core.Logging
         /// <summary>Returns a logger associated with the specified type.</summary>
         ILogger ForType<T>();
 
+        /// <summary>Logs a message with severity Debug.</summary>
         void Debug(string message, params object[] formatArgs);
 
+        /// <summary>Logs a message with severity Info.</summary>
         void Info(string message, params object[] formatArgs);
 
+        /// <summary>Logs a message with severity Warning.</summary>
         void Warning(string message, params object[] formatArgs);
 
+        /// <summary>Logs a message and an associated exception with severity Warning.</summary>
         void Warning(Exception exception, string message, params object[] formatArgs);
 
+        /// <summary>Logs a message with severity Error.</summary>
         void Error(string message, params object[] formatArgs);
 
+        /// <summary>Logs a message and an associated exception with severity Error.</summary>
         void Error(Exception exception, string message, params object[] formatArgs);
     }
 }
diff --git a/src/csharp/Grpc.Core/Marshaller.cs b/src/csharp/Grpc.Core/Marshaller.cs
index 8b1a929074..f38cb0863f 100644
--- a/src/csharp/Grpc.Core/Marshaller.cs
+++ b/src/csharp/Grpc.Core/Marshaller.cs
@@ -37,19 +37,27 @@ using Grpc.Core.Utils;
 namespace Grpc.Core
 {
     /// <summary>
-    /// For serializing and deserializing messages.
+    /// Encapsulates the logic for serializing and deserializing messages.
     /// </summary>
     public struct Marshaller<T>
     {
         readonly Func<T, byte[]> serializer;
         readonly Func<byte[], T> deserializer;
 
+        /// <summary>
+        /// Initializes a new marshaller.
+        /// </summary>
+        /// <param name="serializer">Function that will be used to serialize messages.</param>
+        /// <param name="deserializer">Function that will be used to deserialize messages.</param>
         public Marshaller(Func<T, byte[]> serializer, Func<byte[], T> deserializer)
         {
-            this.serializer = Preconditions.CheckNotNull(serializer);
-            this.deserializer = Preconditions.CheckNotNull(deserializer);
+            this.serializer = Preconditions.CheckNotNull(serializer, "serializer");
+            this.deserializer = Preconditions.CheckNotNull(deserializer, "deserializer");
         }
 
+        /// <summary>
+        /// Gets the serializer function.
+        /// </summary>
         public Func<T, byte[]> Serializer
         {
             get
@@ -58,6 +66,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets the deserializer function.
+        /// </summary>
         public Func<byte[], T> Deserializer
         {
             get
@@ -72,11 +83,17 @@ namespace Grpc.Core
     /// </summary>
     public static class Marshallers
     {
+        /// <summary>
+        /// Creates a marshaller from specified serializer and deserializer.
+        /// </summary>
         public static Marshaller<T> Create<T>(Func<T, byte[]> serializer, Func<byte[], T> deserializer)
         {
             return new Marshaller<T>(serializer, deserializer);
         }
 
+        /// <summary>
+        /// Returns a marshaller for <c>string</c> type. This is useful for testing.
+        /// </summary>
         public static Marshaller<string> StringMarshaller
         {
             get
diff --git a/src/csharp/Grpc.Core/Metadata.cs b/src/csharp/Grpc.Core/Metadata.cs
index 6fd0a7109d..9db2abf46e 100644
--- a/src/csharp/Grpc.Core/Metadata.cs
+++ b/src/csharp/Grpc.Core/Metadata.cs
@@ -114,6 +114,16 @@ namespace Grpc.Core
             entries.Add(item);
         }
 
+        public void Add(string key, string value)
+        {
+            Add(new Entry(key, value));
+        }
+
+        public void Add(string key, byte[] valueBytes)
+        {
+            Add(new Entry(key, valueBytes));
+        }
+
         public void Clear()
         {
             CheckWriteable();
@@ -176,15 +186,15 @@ namespace Grpc.Core
 
             public Entry(string key, byte[] valueBytes)
             {
-                this.key = Preconditions.CheckNotNull(key);
+                this.key = Preconditions.CheckNotNull(key, "key");
                 this.value = null;
-                this.valueBytes = Preconditions.CheckNotNull(valueBytes);
+                this.valueBytes = Preconditions.CheckNotNull(valueBytes, "valueBytes");
             }
 
             public Entry(string key, string value)
             {
-                this.key = Preconditions.CheckNotNull(key);
-                this.value = Preconditions.CheckNotNull(value);
+                this.key = Preconditions.CheckNotNull(key, "key");
+                this.value = Preconditions.CheckNotNull(value, "value");
                 this.valueBytes = null;
             }
 
diff --git a/src/csharp/Grpc.Core/Method.cs b/src/csharp/Grpc.Core/Method.cs
index cc047ac9f8..4c208b4a26 100644
--- a/src/csharp/Grpc.Core/Method.cs
+++ b/src/csharp/Grpc.Core/Method.cs
@@ -41,14 +41,21 @@ namespace Grpc.Core
     /// </summary>
     public enum MethodType
     {
-        Unary,  // Unary request, unary response.
-        ClientStreaming,  // Streaming request, unary response.
-        ServerStreaming,  // Unary request, streaming response.
-        DuplexStreaming  // Streaming request, streaming response.
+        /// <summary>Single request sent from client, single response received from server.</summary>
+        Unary,
+
+        /// <summary>Stream of request sent from client, single response received from server.</summary>
+        ClientStreaming,
+
+        /// <summary>Single request sent from client, stream of responses received from server.</summary>
+        ServerStreaming,
+
+        /// <summary>Both server and client can stream arbitrary number of requests and responses simultaneously.</summary>
+        DuplexStreaming
     }
 
     /// <summary>
-    /// A description of a service method.
+    /// A description of a remote method.
     /// </summary>
     public class Method<TRequest, TResponse>
     {
@@ -59,16 +66,27 @@ namespace Grpc.Core
         readonly Marshaller<TResponse> responseMarshaller;
         readonly string fullName;
 
+        /// <summary>
+        /// Initializes a new instance of the <c>Method</c> class.
+        /// </summary>
+        /// <param name="type">Type of method.</param>
+        /// <param name="serviceName">Name of service this method belongs to.</param>
+        /// <param name="name">Unqualified name of the method.</param>
+        /// <param name="requestMarshaller">Marshaller used for request messages.</param>
+        /// <param name="responseMarshaller">Marshaller used for response messages.</param>
         public Method(MethodType type, string serviceName, string name, Marshaller<TRequest> requestMarshaller, Marshaller<TResponse> responseMarshaller)
         {
             this.type = type;
-            this.serviceName = Preconditions.CheckNotNull(serviceName);
-            this.name = Preconditions.CheckNotNull(name);
-            this.requestMarshaller = Preconditions.CheckNotNull(requestMarshaller);
-            this.responseMarshaller = Preconditions.CheckNotNull(responseMarshaller);
-            this.fullName = GetFullName(serviceName);
+            this.serviceName = Preconditions.CheckNotNull(serviceName, "serviceName");
+            this.name = Preconditions.CheckNotNull(name, "name");
+            this.requestMarshaller = Preconditions.CheckNotNull(requestMarshaller, "requestMarshaller");
+            this.responseMarshaller = Preconditions.CheckNotNull(responseMarshaller, "responseMarshaller");
+            this.fullName = GetFullName(serviceName, name);
         }
 
+        /// <summary>
+        /// Gets the type of the method.
+        /// </summary>
         public MethodType Type
         {
             get
@@ -77,6 +95,9 @@ namespace Grpc.Core
             }
         }
             
+        /// <summary>
+        /// Gets the name of the service to which this method belongs.
+        /// </summary>
         public string ServiceName
         {
             get
@@ -85,6 +106,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets the unqualified name of the method.
+        /// </summary>
         public string Name
         {
             get
@@ -93,6 +117,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets the marshaller used for request messages.
+        /// </summary>
         public Marshaller<TRequest> RequestMarshaller
         {
             get
@@ -101,6 +128,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Gets the marshaller used for response messages.
+        /// </summary>
         public Marshaller<TResponse> ResponseMarshaller
         {
             get
@@ -108,7 +138,11 @@ namespace Grpc.Core
                 return this.responseMarshaller;
             }
         }
-
+            
+        /// <summary>
+        /// Gets the fully qualified name of the method. On the server side, methods are dispatched
+        /// based on this name.
+        /// </summary>
         public string FullName
         {
             get
@@ -120,9 +154,9 @@ namespace Grpc.Core
         /// <summary>
         /// Gets full name of the method including the service name.
         /// </summary>
-        internal string GetFullName(string serviceName)
+        internal static string GetFullName(string serviceName, string methodName)
         {
-            return "/" + Preconditions.CheckNotNull(serviceName) + "/" + this.Name;
+            return "/" + serviceName + "/" + methodName;
         }
     }
 }
diff --git a/src/csharp/Grpc.Core/RpcException.cs b/src/csharp/Grpc.Core/RpcException.cs
index c58578286b..cac417e626 100644
--- a/src/csharp/Grpc.Core/RpcException.cs
+++ b/src/csharp/Grpc.Core/RpcException.cs
@@ -36,22 +36,34 @@ using System;
 namespace Grpc.Core
 {
     /// <summary>
-    /// Thrown when remote procedure call fails.
+    /// Thrown when remote procedure call fails. Every <c>RpcException</c> is associated with a resulting <see cref="Status"/> of the call.
     /// </summary>
     public class RpcException : Exception
     {
         private readonly Status status;
 
+        /// <summary>
+        /// Creates a new <c>RpcException</c> associated with given status.
+        /// </summary>
+        /// <param name="status">Resulting status of a call.</param>
         public RpcException(Status status) : base(status.ToString())
         {
             this.status = status;
         }
 
+        /// <summary>
+        /// Creates a new <c>RpcException</c> associated with given status and message.
+        /// </summary>
+        /// <param name="status">Resulting status of a call.</param>
+        /// <param name="message">The exception message.</param> 
         public RpcException(Status status, string message) : base(message)
         {
             this.status = status;
         }
 
+        /// <summary>
+        /// Resulting status of the call.
+        /// </summary>
         public Status Status
         {
             get
diff --git a/src/csharp/Grpc.Core/Server.cs b/src/csharp/Grpc.Core/Server.cs
index eb5b043d1c..c76f126026 100644
--- a/src/csharp/Grpc.Core/Server.cs
+++ b/src/csharp/Grpc.Core/Server.cs
@@ -192,7 +192,7 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(serverPort.Credentials);
+                Preconditions.CheckNotNull(serverPort.Credentials, "serverPort");
                 Preconditions.CheckState(!startRequested);
                 var address = string.Format("{0}:{1}", serverPort.Host, serverPort.Port);
                 int boundPort;
diff --git a/src/csharp/Grpc.Core/ServerCallContext.cs b/src/csharp/Grpc.Core/ServerCallContext.cs
index 032b1390db..75d81c64f3 100644
--- a/src/csharp/Grpc.Core/ServerCallContext.cs
+++ b/src/csharp/Grpc.Core/ServerCallContext.cs
@@ -36,15 +36,16 @@ using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 
+using Grpc.Core.Internal;
+
 namespace Grpc.Core
 {
     /// <summary>
     /// Context for a server-side call.
     /// </summary>
-    public sealed class ServerCallContext
+    public class ServerCallContext
     {
-        // TODO(jtattermusch): expose method to send initial metadata back to client
-
+        private readonly CallSafeHandle callHandle;
         private readonly string method;
         private readonly string host;
         private readonly string peer;
@@ -54,15 +55,34 @@ namespace Grpc.Core
         private readonly Metadata responseTrailers = new Metadata();
 
         private Status status = Status.DefaultSuccess;
+        private Func<Metadata, Task> writeHeadersFunc;
+        private IHasWriteOptions writeOptionsHolder;
 
-        public ServerCallContext(string method, string host, string peer, DateTime deadline, Metadata requestHeaders, CancellationToken cancellationToken)
+        internal ServerCallContext(CallSafeHandle callHandle, string method, string host, string peer, DateTime deadline, Metadata requestHeaders, CancellationToken cancellationToken,
+            Func<Metadata, Task> writeHeadersFunc, IHasWriteOptions writeOptionsHolder)
         {
+            this.callHandle = callHandle;
             this.method = method;
             this.host = host;
             this.peer = peer;
             this.deadline = deadline;
             this.requestHeaders = requestHeaders;
             this.cancellationToken = cancellationToken;
+            this.writeHeadersFunc = writeHeadersFunc;
+            this.writeOptionsHolder = writeOptionsHolder;
+        }
+
+        public Task WriteResponseHeadersAsync(Metadata responseHeaders)
+        {
+            return writeHeadersFunc(responseHeaders);
+        }
+
+        /// <summary>
+        /// Creates a propagation token to be used to propagate call context to a child call.
+        /// </summary>
+        public ContextPropagationToken CreatePropagationToken(ContextPropagationOptions options = null)
+        {
+            return new ContextPropagationToken(callHandle, deadline, cancellationToken, options);
         }
             
         /// <summary>Name of method called in this RPC.</summary>
@@ -110,7 +130,7 @@ namespace Grpc.Core
             }
         }
 
-        ///<summary>Cancellation token signals when call is cancelled.</summary>
+        /// <summary>Cancellation token signals when call is cancelled.</summary>
         public CancellationToken CancellationToken
         {
             get
@@ -141,5 +161,31 @@ namespace Grpc.Core
                 status = value;
             }
         }
+
+        /// <summary>
+        /// Allows setting write options for the following write.
+        /// For streaming response calls, this property is also exposed as on IServerStreamWriter for convenience.
+        /// Both properties are backed by the same underlying value.
+        /// </summary>
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return writeOptionsHolder.WriteOptions;
+            }
+
+            set
+            {
+                writeOptionsHolder.WriteOptions = value;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Allows sharing write options between ServerCallContext and other objects.
+    /// </summary>
+    public interface IHasWriteOptions
+    {
+        WriteOptions WriteOptions { get; set; }
     }
 }
diff --git a/src/csharp/Grpc.Core/ServerCredentials.cs b/src/csharp/Grpc.Core/ServerCredentials.cs
index c11a1ede08..3c6703d30e 100644
--- a/src/csharp/Grpc.Core/ServerCredentials.cs
+++ b/src/csharp/Grpc.Core/ServerCredentials.cs
@@ -91,7 +91,7 @@ namespace Grpc.Core
         {
             this.keyCertificatePairs = new List<KeyCertificatePair>(keyCertificatePairs).AsReadOnly();
             Preconditions.CheckArgument(this.keyCertificatePairs.Count > 0,
-                "At least one KeyCertificatePair needs to be provided");
+                "At least one KeyCertificatePair needs to be provided.");
             if (forceClientAuth)
             {
                 Preconditions.CheckNotNull(rootCertificates,
diff --git a/src/csharp/Grpc.Core/ServerMethods.cs b/src/csharp/Grpc.Core/ServerMethods.cs
index d457770203..1f119a80ff 100644
--- a/src/csharp/Grpc.Core/ServerMethods.cs
+++ b/src/csharp/Grpc.Core/ServerMethods.cs
@@ -31,12 +31,8 @@
 
 #endregion
 
-using System;
-using System.Threading;
 using System.Threading.Tasks;
 
-using Grpc.Core.Internal;
-
 namespace Grpc.Core
 {
     /// <summary>
diff --git a/src/csharp/Grpc.Core/ServerPort.cs b/src/csharp/Grpc.Core/ServerPort.cs
index 55e4bd0062..598404d045 100644
--- a/src/csharp/Grpc.Core/ServerPort.cs
+++ b/src/csharp/Grpc.Core/ServerPort.cs
@@ -62,9 +62,9 @@ namespace Grpc.Core
         /// <param name="credentials">credentials to use to secure this port.</param>
         public ServerPort(string host, int port, ServerCredentials credentials)
         {
-            this.host = Preconditions.CheckNotNull(host);
+            this.host = Preconditions.CheckNotNull(host, "host");
             this.port = port;
-            this.credentials = Preconditions.CheckNotNull(credentials);
+            this.credentials = Preconditions.CheckNotNull(credentials, "credentials");
         }
 
         /// <summary>
diff --git a/src/csharp/Grpc.Core/ServerServiceDefinition.cs b/src/csharp/Grpc.Core/ServerServiceDefinition.cs
index a00d156e52..94b0a320c3 100644
--- a/src/csharp/Grpc.Core/ServerServiceDefinition.cs
+++ b/src/csharp/Grpc.Core/ServerServiceDefinition.cs
@@ -79,7 +79,7 @@ namespace Grpc.Core
                     where TRequest : class
                     where TResponse : class
             {
-                callHandlers.Add(method.GetFullName(serviceName), ServerCalls.UnaryCall(method, handler));
+                callHandlers.Add(method.FullName, ServerCalls.UnaryCall(method, handler));
                 return this;
             }
 
@@ -89,7 +89,7 @@ namespace Grpc.Core
                     where TRequest : class
                     where TResponse : class
             {
-                callHandlers.Add(method.GetFullName(serviceName), ServerCalls.ClientStreamingCall(method, handler));
+                callHandlers.Add(method.FullName, ServerCalls.ClientStreamingCall(method, handler));
                 return this;
             }
 
@@ -99,7 +99,7 @@ namespace Grpc.Core
                     where TRequest : class
                     where TResponse : class
             {
-                callHandlers.Add(method.GetFullName(serviceName), ServerCalls.ServerStreamingCall(method, handler));
+                callHandlers.Add(method.FullName, ServerCalls.ServerStreamingCall(method, handler));
                 return this;
             }
 
@@ -109,7 +109,7 @@ namespace Grpc.Core
                     where TRequest : class
                     where TResponse : class
             {
-                callHandlers.Add(method.GetFullName(serviceName), ServerCalls.DuplexStreamingCall(method, handler));
+                callHandlers.Add(method.FullName, ServerCalls.DuplexStreamingCall(method, handler));
                 return this;
             }
 
diff --git a/src/csharp/Grpc.Core/Status.cs b/src/csharp/Grpc.Core/Status.cs
index 754f6cb3ca..6bd8dc820b 100644
--- a/src/csharp/Grpc.Core/Status.cs
+++ b/src/csharp/Grpc.Core/Status.cs
@@ -29,13 +29,12 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endregion
 
-using System;
-using System.Runtime.InteropServices;
+using Grpc.Core.Utils;
 
 namespace Grpc.Core
 {
     /// <summary>
-    /// Represents RPC result.
+    /// Represents RPC result, which consists of <see cref="StatusCode"/> and an optional detail string. 
     /// </summary>
     public struct Status
     {
@@ -52,6 +51,11 @@ namespace Grpc.Core
         readonly StatusCode statusCode;
         readonly string detail;
 
+        /// <summary>
+        /// Creates a new instance of <c>Status</c>.
+        /// </summary>
+        /// <param name="statusCode">Status code.</param>
+        /// <param name="detail">Detail.</param>
         public Status(StatusCode statusCode, string detail)
         {
             this.statusCode = statusCode;
@@ -80,6 +84,9 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Returns a <see cref="System.String"/> that represents the current <see cref="Grpc.Core.Status"/>.
+        /// </summary>
         public override string ToString()
         {
             return string.Format("Status(StatusCode={0}, Detail=\"{1}\")", statusCode, detail);
diff --git a/src/csharp/Grpc.Core/StatusCode.cs b/src/csharp/Grpc.Core/StatusCode.cs
index a9696fa469..90606955af 100644
--- a/src/csharp/Grpc.Core/StatusCode.cs
+++ b/src/csharp/Grpc.Core/StatusCode.cs
@@ -31,8 +31,6 @@
 
 #endregion
 
-using System;
-
 namespace Grpc.Core
 {
     /// <summary>
@@ -41,101 +39,101 @@ namespace Grpc.Core
     /// </summary>
     public enum StatusCode
     {
-        /* Not an error; returned on success */
+        /// <summary>Not an error; returned on success.</summary>
         OK = 0,
-        /* The operation was cancelled (typically by the caller). */
+
+        /// <summary>The operation was cancelled (typically by the caller).</summary>
         Cancelled = 1,
-        /* Unknown error.  An example of where this error may be returned is
-     if a Status value received from another address space belongs to
-     an error-space that is not known in this address space.  Also
-     errors raised by APIs that do not return enough error information
-     may be converted to this error. */
+
+        /// <summary>
+        /// Unknown error.  An example of where this error may be returned is
+        /// if a Status value received from another address space belongs to
+        /// an error-space that is not known in this address space.  Also
+        /// errors raised by APIs that do not return enough error information
+        /// may be converted to this error.
+        /// </summary>
         Unknown = 2,
-        /* Client specified an invalid argument.  Note that this differs
-     from FAILED_PRECONDITION.  INVALID_ARGUMENT indicates arguments
-     that are problematic regardless of the state of the system
-     (e.g., a malformed file name). */
+
+        /// <summary>
+        /// Client specified an invalid argument.  Note that this differs
+        /// from FAILED_PRECONDITION.  INVALID_ARGUMENT indicates arguments
+        /// that are problematic regardless of the state of the system
+        /// (e.g., a malformed file name).
+        /// </summary>
         InvalidArgument = 3,
-        /* Deadline expired before operation could complete.  For operations
-     that change the state of the system, this error may be returned
-     even if the operation has completed successfully.  For example, a
-     successful response from a server could have been delayed long
-     enough for the deadline to expire. */
+
+        /// <summary>
+        /// Deadline expired before operation could complete.  For operations
+        /// that change the state of the system, this error may be returned
+        /// even if the operation has completed successfully.  For example, a
+        /// successful response from a server could have been delayed long
+        /// enough for the deadline to expire.
+        /// </summary>
         DeadlineExceeded = 4,
-        /* Some requested entity (e.g., file or directory) was not found. */
+
+        /// <summary>Some requested entity (e.g., file or directory) was not found.</summary>
         NotFound = 5,
-        /* Some entity that we attempted to create (e.g., file or directory)
-     already exists. */
+
+        /// <summary>Some entity that we attempted to create (e.g., file or directory) already exists.</summary>
         AlreadyExists = 6,
-        /* The caller does not have permission to execute the specified
-     operation.  PERMISSION_DENIED must not be used for rejections
-     caused by exhausting some resource (use RESOURCE_EXHAUSTED
-     instead for those errors).  PERMISSION_DENIED must not be
-     used if the caller can not be identified (use UNAUTHENTICATED
-     instead for those errors). */
+
+        /// <summary>
+        /// The caller does not have permission to execute the specified
+        /// operation.  PERMISSION_DENIED must not be used for rejections
+        /// caused by exhausting some resource (use RESOURCE_EXHAUSTED
+        /// instead for those errors).  PERMISSION_DENIED must not be
+        /// used if the caller can not be identified (use UNAUTHENTICATED
+        /// instead for those errors).
+        /// </summary>
         PermissionDenied = 7,
-        /* The request does not have valid authentication credentials for the
-     operation. */
+
+        /// <summary>The request does not have valid authentication credentials for the operation.</summary>
         Unauthenticated = 16,
-        /* Some resource has been exhausted, perhaps a per-user quota, or
-     perhaps the entire file system is out of space. */
+
+        /// <summary>
+        /// Some resource has been exhausted, perhaps a per-user quota, or
+        /// perhaps the entire file system is out of space.
+        /// </summary>
         ResourceExhausted = 8,
-        /* Operation was rejected because the system is not in a state
-     required for the operation's execution.  For example, directory
-     to be deleted may be non-empty, an rmdir operation is applied to
-     a non-directory, etc.
-
-     A litmus test that may help a service implementor in deciding
-     between FAILED_PRECONDITION, ABORTED, and UNAVAILABLE:
-      (a) Use UNAVAILABLE if the client can retry just the failing call.
-      (b) Use ABORTED if the client should retry at a higher-level
-          (e.g., restarting a read-modify-write sequence).
-      (c) Use FAILED_PRECONDITION if the client should not retry until
-          the system state has been explicitly fixed.  E.g., if an "rmdir"
-          fails because the directory is non-empty, FAILED_PRECONDITION
-          should be returned since the client should not retry unless
-          they have first fixed up the directory by deleting files from it.
-      (d) Use FAILED_PRECONDITION if the client performs conditional
-          REST Get/Update/Delete on a resource and the resource on the
-          server does not match the condition. E.g., conflicting
-          read-modify-write on the same resource. */
+
+        /// <summary>
+        /// Operation was rejected because the system is not in a state
+        /// required for the operation's execution.  For example, directory
+        /// to be deleted may be non-empty, an rmdir operation is applied to
+        /// a non-directory, etc.
+        /// </summary>
         FailedPrecondition = 9,
-        /* The operation was aborted, typically due to a concurrency issue
-     like sequencer check failures, transaction aborts, etc.
 
-     See litmus test above for deciding between FAILED_PRECONDITION,
-     ABORTED, and UNAVAILABLE. */
+        /// <summary>
+        /// The operation was aborted, typically due to a concurrency issue
+        /// like sequencer check failures, transaction aborts, etc.
+        /// </summary>
         Aborted = 10,
-        /* Operation was attempted past the valid range.  E.g., seeking or
-     reading past end of file.
-
-     Unlike INVALID_ARGUMENT, this error indicates a problem that may
-     be fixed if the system state changes. For example, a 32-bit file
-     system will generate INVALID_ARGUMENT if asked to read at an
-     offset that is not in the range [0,2^32-1], but it will generate
-     OUT_OF_RANGE if asked to read from an offset past the current
-     file size.
-
-     There is a fair bit of overlap between FAILED_PRECONDITION and
-     OUT_OF_RANGE.  We recommend using OUT_OF_RANGE (the more specific
-     error) when it applies so that callers who are iterating through
-     a space can easily look for an OUT_OF_RANGE error to detect when
-     they are done. */
+
+        /// <summary>
+        /// Operation was attempted past the valid range.  E.g., seeking or
+        /// reading past end of file.
+        /// </summary>
         OutOfRange = 11,
-        /* Operation is not implemented or not supported/enabled in this service. */
+
+        /// <summary>Operation is not implemented or not supported/enabled in this service.</summary>
         Unimplemented = 12,
-        /* Internal errors.  Means some invariants expected by underlying
-     system has been broken.  If you see one of these errors,
-     something is very broken. */
+
+        /// <summary>
+        /// Internal errors.  Means some invariants expected by underlying
+        /// system has been broken.  If you see one of these errors,
+        /// something is very broken.
+        /// </summary>
         Internal = 13,
-        /* The service is currently unavailable.  This is a most likely a
-     transient condition and may be corrected by retrying with
-     a backoff.
 
-     See litmus test above for deciding between FAILED_PRECONDITION,
-     ABORTED, and UNAVAILABLE. */
+        /// <summary>
+        /// The service is currently unavailable.  This is a most likely a
+        /// transient condition and may be corrected by retrying with
+        /// a backoff.
+        /// </summary>
         Unavailable = 14,
-        /* Unrecoverable data loss or corruption. */
+
+        /// <summary>Unrecoverable data loss or corruption.</summary>
         DataLoss = 15
     }
 }
diff --git a/src/csharp/Grpc.Core/Utils/AsyncStreamExtensions.cs b/src/csharp/Grpc.Core/Utils/AsyncStreamExtensions.cs
index 8a748b45a8..cdf1e51026 100644
--- a/src/csharp/Grpc.Core/Utils/AsyncStreamExtensions.cs
+++ b/src/csharp/Grpc.Core/Utils/AsyncStreamExtensions.cs
@@ -33,7 +33,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading.Tasks;
 
 namespace Grpc.Core.Utils
@@ -46,7 +45,7 @@ namespace Grpc.Core.Utils
         /// <summary>
         /// Reads the entire stream and executes an async action for each element.
         /// </summary>
-        public static async Task ForEach<T>(this IAsyncStreamReader<T> streamReader, Func<T, Task> asyncAction)
+        public static async Task ForEachAsync<T>(this IAsyncStreamReader<T> streamReader, Func<T, Task> asyncAction)
             where T : class
         {
             while (await streamReader.MoveNext())
@@ -58,7 +57,7 @@ namespace Grpc.Core.Utils
         /// <summary>
         /// Reads the entire stream and creates a list containing all the elements read.
         /// </summary>
-        public static async Task<List<T>> ToList<T>(this IAsyncStreamReader<T> streamReader)
+        public static async Task<List<T>> ToListAsync<T>(this IAsyncStreamReader<T> streamReader)
             where T : class
         {
             var result = new List<T>();
@@ -73,7 +72,7 @@ namespace Grpc.Core.Utils
         /// Writes all elements from given enumerable to the stream.
         /// Completes the stream afterwards unless close = false.
         /// </summary>
-        public static async Task WriteAll<T>(this IClientStreamWriter<T> streamWriter, IEnumerable<T> elements, bool complete = true)
+        public static async Task WriteAllAsync<T>(this IClientStreamWriter<T> streamWriter, IEnumerable<T> elements, bool complete = true)
             where T : class
         {
             foreach (var element in elements)
@@ -89,7 +88,7 @@ namespace Grpc.Core.Utils
         /// <summary>
         /// Writes all elements from given enumerable to the stream.
         /// </summary>
-        public static async Task WriteAll<T>(this IServerStreamWriter<T> streamWriter, IEnumerable<T> elements)
+        public static async Task WriteAllAsync<T>(this IServerStreamWriter<T> streamWriter, IEnumerable<T> elements)
             where T : class
         {
             foreach (var element in elements)
diff --git a/src/csharp/Grpc.Core/Utils/BenchmarkUtil.cs b/src/csharp/Grpc.Core/Utils/BenchmarkUtil.cs
index 82653c3a1f..eb3a5b16e3 100644
--- a/src/csharp/Grpc.Core/Utils/BenchmarkUtil.cs
+++ b/src/csharp/Grpc.Core/Utils/BenchmarkUtil.cs
@@ -39,6 +39,9 @@ using System.Threading.Tasks;
 
 namespace Grpc.Core.Utils
 {
+    /// <summary>
+    /// Utility methods to run microbenchmarks.
+    /// </summary>
     public static class BenchmarkUtil
     {
         /// <summary>
diff --git a/src/csharp/Grpc.Core/Utils/Preconditions.cs b/src/csharp/Grpc.Core/Utils/Preconditions.cs
index aeb5d210a7..374262f87a 100644
--- a/src/csharp/Grpc.Core/Utils/Preconditions.cs
+++ b/src/csharp/Grpc.Core/Utils/Preconditions.cs
@@ -32,17 +32,16 @@
 #endregion
 
 using System;
-using System.Collections.Concurrent;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.Threading.Tasks;
 
 namespace Grpc.Core.Utils
 {
+    /// <summary>
+    /// Utility methods to simplify checking preconditions in the code.
+    /// </summary>
     public static class Preconditions
     {
         /// <summary>
-        /// Throws ArgumentException if condition is false.
+        /// Throws <see cref="ArgumentException"/> if condition is false.
         /// </summary>
         public static void CheckArgument(bool condition)
         {
@@ -53,7 +52,7 @@ namespace Grpc.Core.Utils
         }
 
         /// <summary>
-        /// Throws ArgumentException with given message if condition is false.
+        /// Throws <see cref="ArgumentException"/> with given message if condition is false.
         /// </summary>
         public static void CheckArgument(bool condition, string errorMessage)
         {
@@ -64,31 +63,31 @@ namespace Grpc.Core.Utils
         }
 
         /// <summary>
-        /// Throws NullReferenceException if reference is null.
+        /// Throws <see cref="ArgumentNullException"/> if reference is null.
         /// </summary>
         public static T CheckNotNull<T>(T reference)
         {
             if (reference == null)
             {
-                throw new NullReferenceException();
+                throw new ArgumentNullException();
             }
             return reference;
         }
 
         /// <summary>
-        /// Throws NullReferenceException with given message if reference is null.
+        /// Throws <see cref="ArgumentNullException"/> if reference is null.
         /// </summary>
-        public static T CheckNotNull<T>(T reference, string errorMessage)
+        public static T CheckNotNull<T>(T reference, string paramName)
         {
             if (reference == null)
             {
-                throw new NullReferenceException(errorMessage);
+                throw new ArgumentNullException(paramName);
             }
             return reference;
         }
 
         /// <summary>
-        /// Throws InvalidOperationException if condition is false.
+        /// Throws <see cref="InvalidOperationException"/> if condition is false.
         /// </summary>
         public static void CheckState(bool condition)
         {
@@ -99,7 +98,7 @@ namespace Grpc.Core.Utils
         }
 
         /// <summary>
-        /// Throws InvalidOperationException with given message if condition is false.
+        /// Throws <see cref="InvalidOperationException"/> with given message if condition is false.
         /// </summary>
         public static void CheckState(bool condition, string errorMessage)
         {
diff --git a/src/csharp/Grpc.Core/Version.cs b/src/csharp/Grpc.Core/Version.cs
index b5cb652945..d02b301cac 100644
--- a/src/csharp/Grpc.Core/Version.cs
+++ b/src/csharp/Grpc.Core/Version.cs
@@ -1,5 +1,37 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
 using System.Reflection;
-using System.Runtime.CompilerServices;
 
 // The current version of gRPC C#.
-[assembly: AssemblyVersion(Grpc.Core.VersionInfo.CurrentVersion + ".*")]
+[assembly: AssemblyVersion(Grpc.Core.VersionInfo.CurrentVersion + ".0")]
diff --git a/src/csharp/Grpc.Core/VersionInfo.cs b/src/csharp/Grpc.Core/VersionInfo.cs
index 656a3d47bb..b6dbd3b49c 100644
--- a/src/csharp/Grpc.Core/VersionInfo.cs
+++ b/src/csharp/Grpc.Core/VersionInfo.cs
@@ -1,13 +1,46 @@
-using System.Reflection;
-using System.Runtime.CompilerServices;
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
 
 namespace Grpc.Core
 {
+    /// <summary>
+    /// Provides info about current version of gRPC.
+    /// </summary>
     public static class VersionInfo
     {
         /// <summary>
         /// Current version of gRPC
         /// </summary>
-        public const string CurrentVersion = "0.6.0";
+        public const string CurrentVersion = "0.6.1";
     }
 }
diff --git a/src/csharp/Grpc.Core/Utils/ExceptionHelper.cs b/src/csharp/Grpc.Core/WriteOptions.cs
index c4d6bee058..7ef3189d76 100644
--- a/src/csharp/Grpc.Core/Utils/ExceptionHelper.cs
+++ b/src/csharp/Grpc.Core/WriteOptions.cs
@@ -33,25 +33,50 @@
 
 using System;
 
-namespace Grpc.Core.Utils
+namespace Grpc.Core
 {
-    public static class ExceptionHelper
+    /// <summary>
+    /// Flags for write operations.
+    /// </summary>
+    [Flags]
+    public enum WriteFlags
     {
         /// <summary>
-        /// If inner exceptions contain RpcException, rethrows it.
-        /// Otherwise, rethrows the original aggregate exception.
-        /// Always throws, the exception return type is here only to make the.
+        /// Hint that the write may be buffered and need not go out on the wire immediately.
+        /// gRPC is free to buffer the message until the next non-buffered
+        /// write, or until write stream completion, but it need not buffer completely or at all.
         /// </summary>
-        public static Exception UnwrapRpcException(AggregateException ae)
+        BufferHint = 0x1,
+
+        /// <summary>
+        /// Force compression to be disabled for a particular write.
+        /// </summary>
+        NoCompress = 0x2
+    }
+
+    /// <summary>
+    /// Options for write operations.
+    /// </summary>
+    public class WriteOptions
+    {
+        /// <summary>
+        /// Default write options.
+        /// </summary>
+        public static readonly WriteOptions Default = new WriteOptions();
+            
+        private WriteFlags flags;
+
+        public WriteOptions(WriteFlags flags = default(WriteFlags))
+        {
+            this.flags = flags;
+        }
+
+        public WriteFlags Flags
         {
-            foreach (var e in ae.InnerExceptions)
+            get
             {
-                if (e is RpcException)
-                {
-                    throw e;
-                }
+                return this.flags;
             }
-            throw ae;
         }
     }
 }
diff --git a/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs b/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs
index 08aece7ef2..fdef950f09 100644
--- a/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs
+++ b/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs
@@ -92,15 +92,8 @@ namespace math.Tests
         [Test]
         public void DivByZero()
         {
-            try
-            {
-                DivReply response = client.Div(new DivArgs.Builder { Dividend = 0, Divisor = 0 }.Build());
-                Assert.Fail();
-            }
-            catch (RpcException e)
-            {
-                Assert.AreEqual(StatusCode.Unknown, e.Status.StatusCode);
-            }   
+            var ex = Assert.Throws<RpcException>(() => client.Div(new DivArgs.Builder { Dividend = 0, Divisor = 0 }.Build()));
+            Assert.AreEqual(StatusCode.Unknown, ex.Status.StatusCode);
         }
 
         [Test]
@@ -116,7 +109,7 @@ namespace math.Tests
         {
             using (var call = client.Fib(new FibArgs.Builder { Limit = 6 }.Build()))
             {
-                var responses = await call.ResponseStream.ToList();
+                var responses = await call.ResponseStream.ToListAsync();
                 CollectionAssert.AreEqual(new List<long> { 1, 1, 2, 3, 5, 8 },
                     responses.ConvertAll((n) => n.Num_));
             }
@@ -158,15 +151,10 @@ namespace math.Tests
             using (var call = client.Fib(new FibArgs.Builder { Limit = 0 }.Build(), 
                 deadline: DateTime.UtcNow.AddMilliseconds(500)))
             {
-                try
-                {
-                    await call.ResponseStream.ToList();
-                    Assert.Fail();
-                }
-                catch (RpcException e)
-                {
-                    Assert.AreEqual(StatusCode.DeadlineExceeded, e.Status.StatusCode);
-                }
+                var ex = Assert.Throws<RpcException>(async () => await call.ResponseStream.ToListAsync());
+
+                // We can't guarantee the status code always DeadlineExceeded. See issue #2685.
+                Assert.Contains(ex.Status.StatusCode, new[] { StatusCode.DeadlineExceeded, StatusCode.Internal });
             }
         }
 
@@ -179,7 +167,7 @@ namespace math.Tests
                 var numbers = new List<long> { 10, 20, 30 }.ConvertAll(
                             n => Num.CreateBuilder().SetNum_(n).Build());
 
-                await call.RequestStream.WriteAll(numbers);
+                await call.RequestStream.WriteAllAsync(numbers);
                 var result = await call.ResponseAsync;
                 Assert.AreEqual(60, result.Num_);
             }
@@ -197,8 +185,8 @@ namespace math.Tests
 
             using (var call = client.DivMany())
             {
-                await call.RequestStream.WriteAll(divArgsList);
-                var result = await call.ResponseStream.ToList();
+                await call.RequestStream.WriteAllAsync(divArgsList);
+                var result = await call.ResponseStream.ToListAsync();
 
                 CollectionAssert.AreEqual(new long[] { 3, 4, 3 }, result.ConvertAll((divReply) => divReply.Quotient));
                 CollectionAssert.AreEqual(new long[] { 1, 16, 1 }, result.ConvertAll((divReply) => divReply.Remainder));
diff --git a/src/csharp/Grpc.Examples/MathExamples.cs b/src/csharp/Grpc.Examples/MathExamples.cs
index 06d81a4d83..dc1bf43995 100644
--- a/src/csharp/Grpc.Examples/MathExamples.cs
+++ b/src/csharp/Grpc.Examples/MathExamples.cs
@@ -54,7 +54,7 @@ namespace math
         {
             using (var call = client.Fib(new FibArgs.Builder { Limit = 5 }.Build()))
             {
-                List<Num> result = await call.ResponseStream.ToList();
+                List<Num> result = await call.ResponseStream.ToListAsync();
                 Console.WriteLine("Fib Result: " + string.Join("|", result));
             }
         }
@@ -70,7 +70,7 @@ namespace math
 
             using (var call = client.Sum())
             {
-                await call.RequestStream.WriteAll(numbers);
+                await call.RequestStream.WriteAllAsync(numbers);
                 Console.WriteLine("Sum Result: " + await call.ResponseAsync);
             }
         }
@@ -85,8 +85,8 @@ namespace math
             };
             using (var call = client.DivMany())
             { 
-                await call.RequestStream.WriteAll(divArgsList);
-                Console.WriteLine("DivMany Result: " + string.Join("|", await call.ResponseStream.ToList()));
+                await call.RequestStream.WriteAllAsync(divArgsList);
+                Console.WriteLine("DivMany Result: " + string.Join("|", await call.ResponseStream.ToListAsync()));
             }
         }
 
@@ -102,7 +102,7 @@ namespace math
             Num sum;
             using (var sumCall = client.Sum())
             {
-                await sumCall.RequestStream.WriteAll(numbers);
+                await sumCall.RequestStream.WriteAllAsync(numbers);
                 sum = await sumCall.ResponseAsync;
             }
 
diff --git a/src/csharp/Grpc.Examples/MathServiceImpl.cs b/src/csharp/Grpc.Examples/MathServiceImpl.cs
index dd26b1d350..7b2684615c 100644
--- a/src/csharp/Grpc.Examples/MathServiceImpl.cs
+++ b/src/csharp/Grpc.Examples/MathServiceImpl.cs
@@ -75,7 +75,7 @@ namespace math
         public async Task<Num> Sum(IAsyncStreamReader<Num> requestStream, ServerCallContext context)
         {
             long sum = 0;
-            await requestStream.ForEach(async num =>
+            await requestStream.ForEachAsync(async num =>
             {
                 sum += num.Num_;
             });
@@ -84,10 +84,7 @@ namespace math
 
         public async Task DivMany(IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream, ServerCallContext context)
         {
-            await requestStream.ForEach(async divArgs =>
-            {
-                await responseStream.WriteAsync(DivInternal(divArgs));
-            });
+            await requestStream.ForEachAsync(async divArgs => await responseStream.WriteAsync(DivInternal(divArgs)));
         }
 
         static DivReply DivInternal(DivArgs args)
diff --git a/src/csharp/Grpc.HealthCheck.Tests/HealthServiceImplTest.cs b/src/csharp/Grpc.HealthCheck.Tests/HealthServiceImplTest.cs
index 7184415655..c4caa3b57a 100644
--- a/src/csharp/Grpc.HealthCheck.Tests/HealthServiceImplTest.cs
+++ b/src/csharp/Grpc.HealthCheck.Tests/HealthServiceImplTest.cs
@@ -92,11 +92,11 @@ namespace Grpc.HealthCheck.Tests
         public void NullsRejected()
         {
             var impl = new HealthServiceImpl();
-            Assert.Throws(typeof(NullReferenceException), () => impl.SetStatus(null, "", HealthCheckResponse.Types.ServingStatus.SERVING));
-            Assert.Throws(typeof(NullReferenceException), () => impl.SetStatus("", null, HealthCheckResponse.Types.ServingStatus.SERVING));
+            Assert.Throws(typeof(ArgumentNullException), () => impl.SetStatus(null, "", HealthCheckResponse.Types.ServingStatus.SERVING));
+            Assert.Throws(typeof(ArgumentNullException), () => impl.SetStatus("", null, HealthCheckResponse.Types.ServingStatus.SERVING));
 
-            Assert.Throws(typeof(NullReferenceException), () => impl.ClearStatus(null, ""));
-            Assert.Throws(typeof(NullReferenceException), () => impl.ClearStatus("", null));
+            Assert.Throws(typeof(ArgumentNullException), () => impl.ClearStatus(null, ""));
+            Assert.Throws(typeof(ArgumentNullException), () => impl.ClearStatus("", null));
         }
 
         private static HealthCheckResponse.Types.ServingStatus GetStatusHelper(HealthServiceImpl impl, string host, string service)
diff --git a/src/csharp/Grpc.IntegrationTesting.Client/app.config b/src/csharp/Grpc.IntegrationTesting.Client/app.config
index 0a82bb4f16..84d7534d65 100644
--- a/src/csharp/Grpc.IntegrationTesting.Client/app.config
+++ b/src/csharp/Grpc.IntegrationTesting.Client/app.config
@@ -10,6 +10,10 @@
         <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
         <bindingRedirect oldVersion="0.0.0.0-4.2.28.0" newVersion="4.0.0.0" />
       </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="Google.Apis.Core" publicKeyToken="4b01fa6e34db77ab" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-1.9.2.38523" newVersion="1.9.2.38523" />
+      </dependentAssembly>
     </assemblyBinding>
   </runtime>
 </configuration>
\ No newline at end of file
diff --git a/src/csharp/Grpc.IntegrationTesting.Server/app.config b/src/csharp/Grpc.IntegrationTesting.Server/app.config
index 0a82bb4f16..84d7534d65 100644
--- a/src/csharp/Grpc.IntegrationTesting.Server/app.config
+++ b/src/csharp/Grpc.IntegrationTesting.Server/app.config
@@ -10,6 +10,10 @@
         <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
         <bindingRedirect oldVersion="0.0.0.0-4.2.28.0" newVersion="4.0.0.0" />
       </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="Google.Apis.Core" publicKeyToken="4b01fa6e34db77ab" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-1.9.2.38523" newVersion="1.9.2.38523" />
+      </dependentAssembly>
     </assemblyBinding>
   </runtime>
 </configuration>
\ No newline at end of file
diff --git a/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj b/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj
index 06a75a3351..2020a76d39 100644
--- a/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj
+++ b/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj
@@ -8,7 +8,7 @@
     <RootNamespace>Grpc.IntegrationTesting</RootNamespace>
     <AssemblyName>Grpc.IntegrationTesting</AssemblyName>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
-    <NuGetPackageImportStamp>041c163e</NuGetPackageImportStamp>
+    <NuGetPackageImportStamp>6566287f</NuGetPackageImportStamp>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -38,20 +38,33 @@
     <AssemblyOriginatorKeyFile>C:\keys\Grpc.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="BouncyCastle.Crypto">
+    <Reference Include="BouncyCastle.Crypto, Version=1.7.4137.9688, Culture=neutral, PublicKeyToken=a4292a325f69b123, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
       <HintPath>..\packages\BouncyCastle.1.7.0\lib\Net40-Client\BouncyCastle.Crypto.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Auth, Version=1.9.2.27817, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+    <Reference Include="Google.Apis.Auth, Version=1.9.3.19379, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
+      <HintPath>..\packages\Google.Apis.Auth.1.9.3\lib\net40\Google.Apis.Auth.dll</HintPath>
+    </Reference>
+    <Reference Include="Google.Apis.Auth.PlatformServices, Version=1.9.3.19383, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
+      <HintPath>..\packages\Google.Apis.Auth.1.9.3\lib\net40\Google.Apis.Auth.PlatformServices.dll</HintPath>
+    </Reference>
+    <Reference Include="Google.Apis.Core, Version=1.9.3.19379, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
+      <HintPath>..\packages\Google.Apis.Core.1.9.3\lib\portable-net40+sl50+win+wpa81+wp80\Google.Apis.Core.dll</HintPath>
+    </Reference>
+    <Reference Include="Microsoft.Threading.Tasks, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Google.Apis.Auth.1.9.2\lib\net40\Google.Apis.Auth.dll</HintPath>
+      <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Auth.PlatformServices, Version=1.9.2.27820, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+    <Reference Include="Microsoft.Threading.Tasks.Extensions, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Google.Apis.Auth.1.9.2\lib\net40\Google.Apis.Auth.PlatformServices.dll</HintPath>
+      <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.dll</HintPath>
     </Reference>
-    <Reference Include="Google.Apis.Core, Version=1.9.2.27816, Culture=neutral, PublicKeyToken=4b01fa6e34db77ab, processorArchitecture=MSIL">
+    <Reference Include="Microsoft.Threading.Tasks.Extensions.Desktop, Version=1.0.168.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Google.Apis.Core.1.9.2\lib\portable-net40+sl50+win+wpa81+wp80\Google.Apis.Core.dll</HintPath>
+      <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.Desktop.dll</HintPath>
     </Reference>
     <Reference Include="Newtonsoft.Json, Version=7.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
@@ -78,15 +91,6 @@
       <HintPath>..\packages\Microsoft.Net.Http.2.2.29\lib\net45\System.Net.Http.Primitives.dll</HintPath>
     </Reference>
     <Reference Include="System.Net.Http.WebRequest" />
-    <Reference Include="Microsoft.Threading.Tasks">
-      <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.dll</HintPath>
-    </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions">
-      <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.dll</HintPath>
-    </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions.Desktop">
-      <HintPath>..\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.Desktop.dll</HintPath>
-    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\Grpc.Core\Version.cs">
diff --git a/src/csharp/Grpc.IntegrationTesting/InteropClient.cs b/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
index 7411d91d5a..385ca92086 100644
--- a/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
+++ b/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
@@ -43,6 +43,7 @@ using Grpc.Auth;
 using Grpc.Core;
 using Grpc.Core.Utils;
 using NUnit.Framework;
+using Google.Apis.Auth.OAuth2;
 
 namespace Grpc.IntegrationTesting
 {
@@ -97,10 +98,10 @@ namespace Grpc.IntegrationTesting
             }
 
             var interopClient = new InteropClient(options);
-            interopClient.Run();
+            interopClient.Run().Wait();
         }
 
-        private void Run()
+        private async Task Run()
         {
             Credentials credentials = null;
             if (options.useTls)
@@ -120,17 +121,7 @@ namespace Grpc.IntegrationTesting
             using (Channel channel = new Channel(options.serverHost, options.serverPort.Value, credentials, channelOptions))
             {
                 TestService.TestServiceClient client = new TestService.TestServiceClient(channel);
-                if (options.testCase == "service_account_creds" || options.testCase == "compute_engine_creds")
-                {
-                    var credential = GoogleCredential.GetApplicationDefault();
-                    if (credential.IsCreateScopedRequired)
-                    {
-                        credential = credential.CreateScoped(new[] { AuthScope });
-                    }
-                    client.HeaderInterceptor = OAuth2Interceptors.FromCredential(credential);
-                }
-
-                RunTestCaseAsync(options.testCase, client).Wait();
+                await RunTestCaseAsync(options.testCase, client);
             }
             GrpcEnvironment.Shutdown();
         }
@@ -158,16 +149,19 @@ namespace Grpc.IntegrationTesting
                     await RunEmptyStreamAsync(client);
                     break;
                 case "service_account_creds":
-                    RunServiceAccountCreds(client);
+                    await RunServiceAccountCredsAsync(client);
                     break;
                 case "compute_engine_creds":
-                    RunComputeEngineCreds(client);
+                    await RunComputeEngineCredsAsync(client);
+                    break;
+                case "jwt_token_creds":
+                    await RunJwtTokenCredsAsync(client);
                     break;
                 case "oauth2_auth_token":
-                    RunOAuth2AuthToken(client);
+                    await RunOAuth2AuthTokenAsync(client);
                     break;
                 case "per_rpc_creds":
-                    RunPerRpcCreds(client);
+                    await RunPerRpcCredsAsync(client);
                     break;
                 case "cancel_after_begin":
                     await RunCancelAfterBeginAsync(client);
@@ -215,7 +209,7 @@ namespace Grpc.IntegrationTesting
 
             using (var call = client.StreamingInputCall())
             {
-                await call.RequestStream.WriteAll(bodySizes);
+                await call.RequestStream.WriteAllAsync(bodySizes);
 
                 var response = await call.ResponseAsync;
                 Assert.AreEqual(74922, response.AggregatedPayloadSize);
@@ -237,7 +231,7 @@ namespace Grpc.IntegrationTesting
 
             using (var call = client.StreamingOutputCall(request))
             {
-                var responseList = await call.ResponseStream.ToList();
+                var responseList = await call.ResponseStream.ToListAsync();
                 foreach (var res in responseList)
                 {
                     Assert.AreEqual(PayloadType.COMPRESSABLE, res.Payload.Type);
@@ -303,15 +297,19 @@ namespace Grpc.IntegrationTesting
             {
                 await call.RequestStream.CompleteAsync();
 
-                var responseList = await call.ResponseStream.ToList();
+                var responseList = await call.ResponseStream.ToListAsync();
                 Assert.AreEqual(0, responseList.Count);
             }
             Console.WriteLine("Passed!");
         }
 
-        public static void RunServiceAccountCreds(TestService.ITestServiceClient client)
+        public static async Task RunServiceAccountCredsAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running service_account_creds");
+            var credential = await GoogleCredential.GetApplicationDefaultAsync();
+            credential = credential.CreateScoped(new[] { AuthScope });
+            client.HeaderInterceptor = OAuth2Interceptors.FromCredential(credential);
+
             var request = SimpleRequest.CreateBuilder()
                 .SetResponseType(PayloadType.COMPRESSABLE)
                     .SetResponseSize(314159)
@@ -329,9 +327,13 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static void RunComputeEngineCreds(TestService.ITestServiceClient client)
+        public static async Task RunComputeEngineCredsAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running compute_engine_creds");
+            var credential = await GoogleCredential.GetApplicationDefaultAsync();
+            Assert.IsFalse(credential.IsCreateScopedRequired);
+            client.HeaderInterceptor = OAuth2Interceptors.FromCredential(credential);
+            
             var request = SimpleRequest.CreateBuilder()
                 .SetResponseType(PayloadType.COMPRESSABLE)
                     .SetResponseSize(314159)
@@ -349,12 +351,35 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static void RunOAuth2AuthToken(TestService.TestServiceClient client)
+        public static async Task RunJwtTokenCredsAsync(TestService.TestServiceClient client)
+        {
+            Console.WriteLine("running jwt_token_creds");
+            var credential = await GoogleCredential.GetApplicationDefaultAsync();
+            // check this a credential with scope support, but don't add the scope.
+            Assert.IsTrue(credential.IsCreateScopedRequired);
+            client.HeaderInterceptor = OAuth2Interceptors.FromCredential(credential);
+
+            var request = SimpleRequest.CreateBuilder()
+                .SetResponseType(PayloadType.COMPRESSABLE)
+                    .SetResponseSize(314159)
+                    .SetPayload(CreateZerosPayload(271828))
+                    .SetFillUsername(true)
+                    .SetFillOauthScope(true)
+                    .Build();
+
+            var response = client.UnaryCall(request);
+
+            Assert.AreEqual(PayloadType.COMPRESSABLE, response.Payload.Type);
+            Assert.AreEqual(314159, response.Payload.Body.Length);
+            Assert.AreEqual(ServiceAccountUser, response.Username);
+            Console.WriteLine("Passed!");
+        }
+
+        public static async Task RunOAuth2AuthTokenAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running oauth2_auth_token");
-            var credential = GoogleCredential.GetApplicationDefault().CreateScoped(new[] { AuthScope });
-            Assert.IsTrue(credential.RequestAccessTokenAsync(CancellationToken.None).Result);
-            string oauth2Token = credential.Token.AccessToken;
+            ITokenAccess credential = (await GoogleCredential.GetApplicationDefaultAsync()).CreateScoped(new[] { AuthScope });
+            string oauth2Token = await credential.GetAccessTokenForRequestAsync();
 
             client.HeaderInterceptor = OAuth2Interceptors.FromAccessToken(oauth2Token);
 
@@ -370,13 +395,12 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static void RunPerRpcCreds(TestService.TestServiceClient client)
+        public static async Task RunPerRpcCredsAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running per_rpc_creds");
 
-            var credential = GoogleCredential.GetApplicationDefault().CreateScoped(new[] { AuthScope });
-            Assert.IsTrue(credential.RequestAccessTokenAsync(CancellationToken.None).Result);
-            string oauth2Token = credential.Token.AccessToken;
+            ITokenAccess credential = (await GoogleCredential.GetApplicationDefaultAsync()).CreateScoped(new[] { AuthScope });
+            string oauth2Token = await credential.GetAccessTokenForRequestAsync();
             var headerInterceptor = OAuth2Interceptors.FromAccessToken(oauth2Token);
 
             var request = SimpleRequest.CreateBuilder()
@@ -385,7 +409,7 @@ namespace Grpc.IntegrationTesting
                 .Build();
 
             var headers = new Metadata();
-            headerInterceptor(headers);
+            headerInterceptor("", headers);
             var response = client.UnaryCall(request, headers: headers);
 
             Assert.AreEqual(AuthScopeResponse, response.OauthScope);
@@ -404,15 +428,8 @@ namespace Grpc.IntegrationTesting
                 await Task.Delay(1000);
                 cts.Cancel();
 
-                try
-                {
-                    var response = await call.ResponseAsync;
-                    Assert.Fail();
-                }
-                catch (RpcException e)
-                {
-                    Assert.AreEqual(StatusCode.Cancelled, e.Status.StatusCode);
-                }
+                var ex = Assert.Throws<RpcException>(async () => await call.ResponseAsync);
+                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
             }
             Console.WriteLine("Passed!");
         }
@@ -435,15 +452,8 @@ namespace Grpc.IntegrationTesting
 
                 cts.Cancel();
 
-                try
-                {
-                    await call.ResponseStream.MoveNext();
-                    Assert.Fail();
-                }
-                catch (RpcException e)
-                {
-                    Assert.AreEqual(StatusCode.Cancelled, e.Status.StatusCode);
-                }
+                var ex = Assert.Throws<RpcException>(async () => await call.ResponseStream.MoveNext());
+                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
             }
             Console.WriteLine("Passed!");
         }
diff --git a/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs b/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
index ccf9fe6ced..ceebd5dd8c 100644
--- a/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
+++ b/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
@@ -71,7 +71,7 @@ namespace grpc.testing
         public async Task<StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<StreamingInputCallRequest> requestStream, ServerCallContext context)
         {
             int sum = 0;
-            await requestStream.ForEach(async request =>
+            await requestStream.ForEachAsync(async request =>
             {
                 sum += request.Payload.Body.Length;
             });
@@ -80,7 +80,7 @@ namespace grpc.testing
 
         public async Task FullDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
         {
-            await requestStream.ForEach(async request =>
+            await requestStream.ForEachAsync(async request =>
             {
                 foreach (var responseParam in request.ResponseParametersList)
                 {
diff --git a/src/csharp/Grpc.IntegrationTesting/app.config b/src/csharp/Grpc.IntegrationTesting/app.config
index 0a82bb4f16..84d7534d65 100644
--- a/src/csharp/Grpc.IntegrationTesting/app.config
+++ b/src/csharp/Grpc.IntegrationTesting/app.config
@@ -10,6 +10,10 @@
         <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
         <bindingRedirect oldVersion="0.0.0.0-4.2.28.0" newVersion="4.0.0.0" />
       </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="Google.Apis.Core" publicKeyToken="4b01fa6e34db77ab" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-1.9.2.38523" newVersion="1.9.2.38523" />
+      </dependentAssembly>
     </assemblyBinding>
   </runtime>
 </configuration>
\ No newline at end of file
diff --git a/src/csharp/Grpc.IntegrationTesting/packages.config b/src/csharp/Grpc.IntegrationTesting/packages.config
index 7d1f84f303..0867b091b9 100644
--- a/src/csharp/Grpc.IntegrationTesting/packages.config
+++ b/src/csharp/Grpc.IntegrationTesting/packages.config
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
   <package id="BouncyCastle" version="1.7.0" targetFramework="net45" />
-  <package id="Google.Apis.Auth" version="1.9.2" targetFramework="net45" />
-  <package id="Google.Apis.Core" version="1.9.2" targetFramework="net45" />
+  <package id="Google.Apis.Auth" version="1.9.3" targetFramework="net45" />
+  <package id="Google.Apis.Core" version="1.9.3" targetFramework="net45" />
   <package id="Google.ProtocolBuffers" version="2.4.1.521" targetFramework="net45" />
   <package id="Ix-Async" version="1.2.3" targetFramework="net45" />
   <package id="Microsoft.Bcl" version="1.1.10" targetFramework="net45" />
diff --git a/src/csharp/build_packages.bat b/src/csharp/build_packages.bat
index 9e1253bf0b..8a11d01430 100644
--- a/src/csharp/build_packages.bat
+++ b/src/csharp/build_packages.bat
@@ -1,8 +1,8 @@
 @rem Builds gRPC NuGet packages
 
 @rem Current package versions
-set VERSION=0.6.0
-set CORE_VERSION=0.10.0
+set VERSION=0.6.1
+set CORE_VERSION=0.10.1
 
 @rem Adjust the location of nuget.exe
 set NUGET=C:\nuget\nuget.exe
diff --git a/src/csharp/doc/README.md b/src/csharp/doc/README.md
new file mode 100644
index 0000000000..585500b5ca
--- /dev/null
+++ b/src/csharp/doc/README.md
@@ -0,0 +1,2 @@
+
+SandCastle project files to generate HTML reference documentation.
\ No newline at end of file
diff --git a/src/csharp/doc/grpc_csharp_public.shfbproj b/src/csharp/doc/grpc_csharp_public.shfbproj
new file mode 100644
index 0000000000..05c93f4a13
--- /dev/null
+++ b/src/csharp/doc/grpc_csharp_public.shfbproj
@@ -0,0 +1,70 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <!-- The configuration and platform will be used to determine which assemblies to include from solution and
+				 project documentation sources -->
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{77e3da09-fc92-486f-a90a-99ca788e8b59}</ProjectGuid>
+    <SHFBSchemaVersion>2015.6.5.0</SHFBSchemaVersion>
+    <!-- AssemblyName, Name, and RootNamespace are not used by SHFB but Visual Studio adds them anyway -->
+    <AssemblyName>Documentation</AssemblyName>
+    <RootNamespace>Documentation</RootNamespace>
+    <Name>Documentation</Name>
+    <!-- SHFB properties -->
+    <FrameworkVersion>.NET Framework 4.5</FrameworkVersion>
+    <OutputPath>..\..\..\doc\ref\csharp\html</OutputPath>
+    <Language>en-US</Language>
+    <DocumentationSources>
+      <DocumentationSource sourceFile="..\Grpc.Auth\Grpc.Auth.csproj" />
+<DocumentationSource sourceFile="..\Grpc.Core\Grpc.Core.csproj" /></DocumentationSources>
+    <BuildAssemblerVerbosity>OnlyWarningsAndErrors</BuildAssemblerVerbosity>
+    <HelpFileFormat>Website</HelpFileFormat>
+    <IndentHtml>False</IndentHtml>
+    <KeepLogFile>True</KeepLogFile>
+    <DisableCodeBlockComponent>False</DisableCodeBlockComponent>
+    <CleanIntermediates>True</CleanIntermediates>
+    <HelpFileVersion>1.0.0.0</HelpFileVersion>
+    <MaximumGroupParts>2</MaximumGroupParts>
+    <NamespaceGrouping>False</NamespaceGrouping>
+    <SyntaxFilters>Standard</SyntaxFilters>
+    <SdkLinkTarget>Blank</SdkLinkTarget>
+    <RootNamespaceContainer>True</RootNamespaceContainer>
+    <PresentationStyle>VS2013</PresentationStyle>
+    <Preliminary>False</Preliminary>
+    <NamingMethod>MemberName</NamingMethod>
+    <HelpTitle>gRPC C#</HelpTitle>
+    <ContentPlacement>AboveNamespaces</ContentPlacement>
+    <HtmlHelpName>Documentation</HtmlHelpName>
+  </PropertyGroup>
+  <!-- There are no properties for these groups.  AnyCPU needs to appear in order for Visual Studio to perform
+			 the build.  The others are optional common platform types that may appear. -->
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x86' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x64' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x64' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|Win32' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|Win32' ">
+  </PropertyGroup>
+  <!-- Import the SHFB build targets -->
+  <Import Project="$(SHFBROOT)\SandcastleHelpFileBuilder.targets" />
+  <!-- The pre-build and post-build event properties must appear *after* the targets file import in order to be
+			 evaluated correctly. -->
+  <PropertyGroup>
+    <PreBuildEvent>
+    </PreBuildEvent>
+    <PostBuildEvent>
+    </PostBuildEvent>
+    <RunPostBuildEvent>OnBuildSuccess</RunPostBuildEvent>
+  </PropertyGroup>
+</Project>
\ No newline at end of file
diff --git a/src/csharp/ext/grpc_csharp_ext.c b/src/csharp/ext/grpc_csharp_ext.c
index 048887bc12..9379ae01f1 100644
--- a/src/csharp/ext/grpc_csharp_ext.c
+++ b/src/csharp/ext/grpc_csharp_ext.c
@@ -376,10 +376,12 @@ GPR_EXPORT void GPR_CALLTYPE grpcsharp_channel_destroy(grpc_channel *channel) {
 }
 
 GPR_EXPORT grpc_call *GPR_CALLTYPE
-grpcsharp_channel_create_call(grpc_channel *channel, grpc_completion_queue *cq,
+grpcsharp_channel_create_call(grpc_channel *channel, grpc_call *parent_call,
+                              gpr_uint32 propagation_mask,
+                              grpc_completion_queue *cq,
                               const char *method, const char *host,
                               gpr_timespec deadline) {
-  return grpc_channel_create_call(channel, NULL, GRPC_PROPAGATE_DEFAULTS, cq,
+  return grpc_channel_create_call(channel, parent_call, propagation_mask, cq,
                                   method, host, deadline);
 }
 
@@ -497,7 +499,7 @@ GPR_EXPORT void GPR_CALLTYPE grpcsharp_call_destroy(grpc_call *call) {
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
                            const char *send_buffer, size_t send_buffer_len,
-                           grpc_metadata_array *initial_metadata) {
+                           grpc_metadata_array *initial_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[6];
   ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
@@ -511,7 +513,7 @@ grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
   ops[1].op = GRPC_OP_SEND_MESSAGE;
   ctx->send_message = string_to_byte_buffer(send_buffer, send_buffer_len);
   ops[1].data.send_message = ctx->send_message;
-  ops[1].flags = 0;
+  ops[1].flags = write_flags;
 
   ops[2].op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
   ops[2].flags = 0;
@@ -578,7 +580,7 @@ grpcsharp_call_start_client_streaming(grpc_call *call,
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
     grpc_call *call, grpcsharp_batch_context *ctx, const char *send_buffer,
-    size_t send_buffer_len, grpc_metadata_array *initial_metadata) {
+    size_t send_buffer_len, grpc_metadata_array *initial_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[5];
   ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
@@ -592,7 +594,7 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
   ops[1].op = GRPC_OP_SEND_MESSAGE;
   ctx->send_message = string_to_byte_buffer(send_buffer, send_buffer_len);
   ops[1].data.send_message = ctx->send_message;
-  ops[1].flags = 0;
+  ops[1].flags = write_flags;
 
   ops[2].op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
   ops[2].flags = 0;
@@ -651,15 +653,22 @@ grpcsharp_call_start_duplex_streaming(grpc_call *call,
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_send_message(grpc_call *call, grpcsharp_batch_context *ctx,
-                            const char *send_buffer, size_t send_buffer_len) {
+                            const char *send_buffer, size_t send_buffer_len,
+                            gpr_uint32 write_flags,
+                            gpr_int32 send_empty_initial_metadata) {
   /* TODO: don't use magic number */
-  grpc_op ops[1];
+  grpc_op ops[2];
+  size_t nops = send_empty_initial_metadata ? 2 : 1;
   ops[0].op = GRPC_OP_SEND_MESSAGE;
   ctx->send_message = string_to_byte_buffer(send_buffer, send_buffer_len);
   ops[0].data.send_message = ctx->send_message;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
+  ops[1].op = GRPC_OP_SEND_INITIAL_METADATA;
+  ops[1].data.send_initial_metadata.count = 0;
+  ops[1].data.send_initial_metadata.metadata = NULL;
+  ops[1].flags = 0;
 
-  return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
+  return grpc_call_start_batch(call, ops, nops, ctx);
 }
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
@@ -675,9 +684,11 @@ grpcsharp_call_send_close_from_client(grpc_call *call,
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_send_status_from_server(
     grpc_call *call, grpcsharp_batch_context *ctx, grpc_status_code status_code,
-    const char *status_details, grpc_metadata_array *trailing_metadata) {
+    const char *status_details, grpc_metadata_array *trailing_metadata,
+    gpr_int32 send_empty_initial_metadata) {
   /* TODO: don't use magic number */
-  grpc_op ops[1];
+  grpc_op ops[2];
+  size_t nops = send_empty_initial_metadata ? 2 : 1;
   ops[0].op = GRPC_OP_SEND_STATUS_FROM_SERVER;
   ops[0].data.send_status_from_server.status = status_code;
   ops[0].data.send_status_from_server.status_details =
@@ -689,8 +700,12 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_send_status_from_server(
   ops[0].data.send_status_from_server.trailing_metadata =
       ctx->send_status_from_server.trailing_metadata.metadata;
   ops[0].flags = 0;
+  ops[1].op = GRPC_OP_SEND_INITIAL_METADATA;
+  ops[1].data.send_initial_metadata.count = 0;
+  ops[1].data.send_initial_metadata.metadata = NULL;
+  ops[1].flags = 0;
 
-  return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
+  return grpc_call_start_batch(call, ops, nops, ctx);
 }
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
@@ -706,16 +721,28 @@ grpcsharp_call_recv_message(grpc_call *call, grpcsharp_batch_context *ctx) {
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_serverside(grpc_call *call, grpcsharp_batch_context *ctx) {
   /* TODO: don't use magic number */
-  grpc_op ops[2];
-  ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
-  ops[0].data.send_initial_metadata.count = 0;
-  ops[0].data.send_initial_metadata.metadata = NULL;
+  grpc_op ops[1];
+  ops[0].op = GRPC_OP_RECV_CLOSE_ON_SERVER;
+  ops[0].data.recv_close_on_server.cancelled =
+      (&ctx->recv_close_on_server_cancelled);
   ops[0].flags = 0;
 
-  ops[1].op = GRPC_OP_RECV_CLOSE_ON_SERVER;
-  ops[1].data.recv_close_on_server.cancelled =
-      (&ctx->recv_close_on_server_cancelled);
-  ops[1].flags = 0;
+  return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
+}
+
+GPR_EXPORT grpc_call_error GPR_CALLTYPE
+grpcsharp_call_send_initial_metadata(grpc_call *call,
+                                     grpcsharp_batch_context *ctx,
+                                     grpc_metadata_array *initial_metadata) {
+  /* TODO: don't use magic number */
+  grpc_op ops[1];
+  ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
+  grpcsharp_metadata_array_move(&(ctx->send_initial_metadata),
+                                initial_metadata);
+  ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
+  ops[0].data.send_initial_metadata.metadata =
+      ctx->send_initial_metadata.metadata;
+  ops[0].flags = 0;
 
   return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
 }
@@ -849,6 +876,11 @@ GPR_EXPORT void GPR_CALLTYPE grpcsharp_redirect_log(grpcsharp_log_func func) {
 
 typedef void(GPR_CALLTYPE *test_callback_funcptr)(gpr_int32 success);
 
+/* Version info */
+GPR_EXPORT const char *GPR_CALLTYPE grpcsharp_version_string() {
+  return grpc_version_string();
+}
+
 /* For testing */
 GPR_EXPORT void GPR_CALLTYPE
 grpcsharp_test_callback(test_callback_funcptr callback) {
diff --git a/src/node/binding.gyp b/src/node/binding.gyp
index 6ba233388a..734dc8410b 100644
--- a/src/node/binding.gyp
+++ b/src/node/binding.gyp
@@ -11,7 +11,8 @@
         '-pedantic',
         '-g',
         '-zdefs',
-        '-Werror'
+        '-Werror',
+        '-Wno-error=deprecated-declarations'
       ],
       'ldflags': [
         '-g'
diff --git a/src/node/examples/perf_test.js b/src/node/examples/perf_test.js
index 0f38725f72..214b9384d5 100644
--- a/src/node/examples/perf_test.js
+++ b/src/node/examples/perf_test.js
@@ -63,7 +63,7 @@ function runTest(iterations, callback) {
           var timeDiff = process.hrtime(startTime);
           intervals[i] = timeDiff[0] * 1000000 + timeDiff[1] / 1000;
           next(i+1);
-        }, {}, deadline);
+        }, {}, {deadline: deadline});
       }
     }
     next(0);
diff --git a/src/node/ext/call.cc b/src/node/ext/call.cc
index fe585a0d4f..c5c8313385 100644
--- a/src/node/ext/call.cc
+++ b/src/node/ext/call.cc
@@ -510,10 +510,21 @@ NAN_METHOD(Call::New) {
       NanUtf8String method(args[1]);
       double deadline = args[2]->NumberValue();
       grpc_channel *wrapped_channel = channel->GetWrappedChannel();
-      grpc_call *wrapped_call = grpc_channel_create_call(
-          wrapped_channel, NULL, GRPC_PROPAGATE_DEFAULTS,
-          CompletionQueueAsyncWorker::GetQueue(), *method, channel->GetHost(),
-          MillisecondsToTimespec(deadline));
+      grpc_call *wrapped_call;
+      if (args[3]->IsString()) {
+        NanUtf8String host_override(args[3]);
+        wrapped_call = grpc_channel_create_call(
+            wrapped_channel, NULL, GRPC_PROPAGATE_DEFAULTS,
+            CompletionQueueAsyncWorker::GetQueue(), *method,
+            *host_override, MillisecondsToTimespec(deadline));
+      } else if (args[3]->IsUndefined() || args[3]->IsNull()) {
+        wrapped_call = grpc_channel_create_call(
+            wrapped_channel, NULL, GRPC_PROPAGATE_DEFAULTS,
+            CompletionQueueAsyncWorker::GetQueue(), *method,
+            NULL, MillisecondsToTimespec(deadline));
+      } else {
+        return NanThrowTypeError("Call's fourth argument must be a string");
+      }
       call = new Call(wrapped_call);
       args.This()->SetHiddenValue(NanNew("channel_"), channel_object);
     }
diff --git a/src/node/ext/channel.cc b/src/node/ext/channel.cc
index d02ed95672..457a58c057 100644
--- a/src/node/ext/channel.cc
+++ b/src/node/ext/channel.cc
@@ -59,14 +59,12 @@ using v8::Value;
 NanCallback *Channel::constructor;
 Persistent<FunctionTemplate> Channel::fun_tpl;
 
-Channel::Channel(grpc_channel *channel, NanUtf8String *host)
-    : wrapped_channel(channel), host(host) {}
+Channel::Channel(grpc_channel *channel) : wrapped_channel(channel) {}
 
 Channel::~Channel() {
   if (wrapped_channel != NULL) {
     grpc_channel_destroy(wrapped_channel);
   }
-  delete host;
 }
 
 void Channel::Init(Handle<Object> exports) {
@@ -91,8 +89,6 @@ bool Channel::HasInstance(Handle<Value> val) {
 
 grpc_channel *Channel::GetWrappedChannel() { return this->wrapped_channel; }
 
-char *Channel::GetHost() { return **this->host; }
-
 NAN_METHOD(Channel::New) {
   NanScope();
 
@@ -103,8 +99,7 @@ NAN_METHOD(Channel::New) {
     }
     grpc_channel *wrapped_channel;
     // Owned by the Channel object
-    NanUtf8String *host = new NanUtf8String(args[0]);
-    NanUtf8String *host_override = NULL;
+    NanUtf8String host(args[0]);
     grpc_credentials *creds;
     if (!Credentials::HasInstance(args[1])) {
       return NanThrowTypeError(
@@ -116,12 +111,9 @@ NAN_METHOD(Channel::New) {
     grpc_channel_args *channel_args_ptr;
     if (args[2]->IsUndefined()) {
       channel_args_ptr = NULL;
-      wrapped_channel = grpc_insecure_channel_create(**host, NULL);
+      wrapped_channel = grpc_insecure_channel_create(*host, NULL);
     } else if (args[2]->IsObject()) {
       Handle<Object> args_hash(args[2]->ToObject()->Clone());
-      if (args_hash->HasOwnProperty(NanNew(GRPC_SSL_TARGET_NAME_OVERRIDE_ARG))) {
-        host_override = new NanUtf8String(args_hash->Get(NanNew(GRPC_SSL_TARGET_NAME_OVERRIDE_ARG)));
-      }
       Handle<Array> keys(args_hash->GetOwnPropertyNames());
       grpc_channel_args channel_args;
       channel_args.num_args = keys->Length();
@@ -153,20 +145,15 @@ NAN_METHOD(Channel::New) {
       return NanThrowTypeError("Channel expects a string and an object");
     }
     if (creds == NULL) {
-      wrapped_channel = grpc_insecure_channel_create(**host, channel_args_ptr);
+      wrapped_channel = grpc_insecure_channel_create(*host, channel_args_ptr);
     } else {
       wrapped_channel =
-          grpc_secure_channel_create(creds, **host, channel_args_ptr);
+          grpc_secure_channel_create(creds, *host, channel_args_ptr);
     }
     if (channel_args_ptr != NULL) {
       free(channel_args_ptr->args);
     }
-    Channel *channel;
-    if (host_override == NULL) {
-      channel = new Channel(wrapped_channel, host);
-    } else {
-      channel = new Channel(wrapped_channel, host_override);
-    }
+    Channel *channel = new Channel(wrapped_channel);
     channel->Wrap(args.This());
     NanReturnValue(args.This());
   } else {
diff --git a/src/node/ext/channel.h b/src/node/ext/channel.h
index 6725ebb03f..e2182cb45c 100644
--- a/src/node/ext/channel.h
+++ b/src/node/ext/channel.h
@@ -53,11 +53,8 @@ class Channel : public ::node::ObjectWrap {
   /* Returns the grpc_channel struct that this object wraps */
   grpc_channel *GetWrappedChannel();
 
-  /* Return the hostname that this channel connects to */
-  char *GetHost();
-
  private:
-  explicit Channel(grpc_channel *channel, NanUtf8String *host);
+  explicit Channel(grpc_channel *channel);
   ~Channel();
 
   // Prevent copying
@@ -71,7 +68,6 @@ class Channel : public ::node::ObjectWrap {
   static v8::Persistent<v8::FunctionTemplate> fun_tpl;
 
   grpc_channel *wrapped_channel;
-  NanUtf8String *host;
 };
 
 }  // namespace node
diff --git a/src/node/interop/interop_client.js b/src/node/interop/interop_client.js
index 236b36616c..27f6c19c13 100644
--- a/src/node/interop/interop_client.js
+++ b/src/node/interop/interop_client.js
@@ -67,11 +67,8 @@ function zeroBuffer(size) {
  *     primarily for use with mocha
  */
 function emptyUnary(client, done) {
-  var call = client.emptyCall({}, function(err, resp) {
+  client.emptyCall({}, function(err, resp) {
     assert.ifError(err);
-  });
-  call.on('status', function(status) {
-    assert.strictEqual(status.code, grpc.status.OK);
     if (done) {
       done();
     }
@@ -92,13 +89,10 @@ function largeUnary(client, done) {
       body: zeroBuffer(271828)
     }
   };
-  var call = client.unaryCall(arg, function(err, resp) {
+  client.unaryCall(arg, function(err, resp) {
     assert.ifError(err);
     assert.strictEqual(resp.payload.type, 'COMPRESSABLE');
     assert.strictEqual(resp.payload.body.length, 314159);
-  });
-  call.on('status', function(status) {
-    assert.strictEqual(status.code, grpc.status.OK);
     if (done) {
       done();
     }
@@ -115,9 +109,6 @@ function clientStreaming(client, done) {
   var call = client.streamingInputCall(function(err, resp) {
     assert.ifError(err);
     assert.strictEqual(resp.aggregated_payload_size, 74922);
-  });
-  call.on('status', function(status) {
-    assert.strictEqual(status.code, grpc.status.OK);
     if (done) {
       done();
     }
@@ -268,7 +259,7 @@ function cancelAfterFirstResponse(client, done) {
 function timeoutOnSleepingServer(client, done) {
   var deadline = new Date();
   deadline.setMilliseconds(deadline.getMilliseconds() + 1);
-  var call = client.fullDuplexCall(null, deadline);
+  var call = client.fullDuplexCall(null, {deadline: deadline});
   call.write({
     payload: {body: zeroBuffer(27182)}
   });
@@ -302,15 +293,12 @@ function authTest(expected_user, scope, client, done) {
       fill_username: true,
       fill_oauth_scope: true
     };
-    var call = client.unaryCall(arg, function(err, resp) {
+    client.unaryCall(arg, function(err, resp) {
       assert.ifError(err);
       assert.strictEqual(resp.payload.type, 'COMPRESSABLE');
       assert.strictEqual(resp.payload.body.length, 314159);
       assert.strictEqual(resp.username, expected_user);
       assert.strictEqual(resp.oauth_scope, AUTH_SCOPE_RESPONSE);
-    });
-    call.on('status', function(status) {
-      assert.strictEqual(status.code, grpc.status.OK);
       if (done) {
         done();
       }
@@ -340,13 +328,10 @@ function oauth2Test(expected_user, scope, per_rpc, client, done) {
       };
       var makeTestCall = function(error, client_metadata) {
         assert.ifError(error);
-        var call = client.unaryCall(arg, function(err, resp) {
+        client.unaryCall(arg, function(err, resp) {
           assert.ifError(err);
           assert.strictEqual(resp.username, expected_user);
           assert.strictEqual(resp.oauth_scope, AUTH_SCOPE_RESPONSE);
-        });
-        call.on('status', function(status) {
-          assert.strictEqual(status.code, grpc.status.OK);
           if (done) {
             done();
           }
@@ -358,7 +343,6 @@ function oauth2Test(expected_user, scope, per_rpc, client, done) {
         client.updateMetadata = updateMetadata;
         makeTestCall(null, {});
       }
-
     });
   });
 }
@@ -409,6 +393,7 @@ function runTest(address, host_override, test_case, tls, test_ca, done) {
     creds = grpc.Credentials.createSsl(ca_data);
     if (host_override) {
       options['grpc.ssl_target_name_override'] = host_override;
+      options['grpc.default_authority'] = host_override;
     }
   } else {
     creds = grpc.Credentials.createInsecure();
diff --git a/src/node/src/client.js b/src/node/src/client.js
index b2b4423707..87c7690dc0 100644
--- a/src/node/src/client.js
+++ b/src/node/src/client.js
@@ -208,6 +208,25 @@ ClientWritableStream.prototype.getPeer = getPeer;
 ClientDuplexStream.prototype.getPeer = getPeer;
 
 /**
+ * Get a call object built with the provided options. Keys for options are
+ * 'deadline', which takes a date or number, and 'host', which takes a string
+ * and overrides the hostname to connect to.
+ * @param {Object} options Options map.
+ */
+function getCall(channel, method, options) {
+  var deadline;
+  var host;
+  if (options) {
+    deadline = options.deadline;
+    host = options.host;
+  }
+  if (deadline === undefined) {
+    deadline = Infinity;
+  }
+  return new grpc.Call(channel, method, deadline, host);
+}
+
+/**
  * Get a function that can make unary requests to the specified method.
  * @param {string} method The name of the method to request
  * @param {function(*):Buffer} serialize The serialization function for inputs
@@ -226,17 +245,13 @@ function makeUnaryRequestFunction(method, serialize, deserialize) {
    *     response is received
    * @param {array=} metadata Array of metadata key/value pairs to add to the
    *     call
-   * @param {(number|Date)=} deadline The deadline for processing this request.
-   *     Defaults to infinite future
+   * @param {Object=} options Options map
    * @return {EventEmitter} An event emitter for stream related events
    */
-  function makeUnaryRequest(argument, callback, metadata, deadline) {
+  function makeUnaryRequest(argument, callback, metadata, options) {
     /* jshint validthis: true */
-    if (deadline === undefined) {
-      deadline = Infinity;
-    }
     var emitter = new EventEmitter();
-    var call = new grpc.Call(this.channel, method, deadline);
+    var call = getCall(this.channel, method, options);
     if (metadata === null || metadata === undefined) {
       metadata = {};
     }
@@ -300,16 +315,12 @@ function makeClientStreamRequestFunction(method, serialize, deserialize) {
    *     response is received
    * @param {array=} metadata Array of metadata key/value pairs to add to the
    *     call
-   * @param {(number|Date)=} deadline The deadline for processing this request.
-   *     Defaults to infinite future
+   * @param {Object=} options Options map
    * @return {EventEmitter} An event emitter for stream related events
    */
-  function makeClientStreamRequest(callback, metadata, deadline) {
+  function makeClientStreamRequest(callback, metadata, options) {
     /* jshint validthis: true */
-    if (deadline === undefined) {
-      deadline = Infinity;
-    }
-    var call = new grpc.Call(this.channel, method, deadline);
+    var call = getCall(this.channel, method, options);
     if (metadata === null || metadata === undefined) {
       metadata = {};
     }
@@ -374,16 +385,12 @@ function makeServerStreamRequestFunction(method, serialize, deserialize) {
    *     serialize
    * @param {array=} metadata Array of metadata key/value pairs to add to the
    *     call
-   * @param {(number|Date)=} deadline The deadline for processing this request.
-   *     Defaults to infinite future
+   * @param {Object} options Options map
    * @return {EventEmitter} An event emitter for stream related events
    */
-  function makeServerStreamRequest(argument, metadata, deadline) {
+  function makeServerStreamRequest(argument, metadata, options) {
     /* jshint validthis: true */
-    if (deadline === undefined) {
-      deadline = Infinity;
-    }
-    var call = new grpc.Call(this.channel, method, deadline);
+    var call = getCall(this.channel, method, options);
     if (metadata === null || metadata === undefined) {
       metadata = {};
     }
@@ -446,16 +453,12 @@ function makeBidiStreamRequestFunction(method, serialize, deserialize) {
    * @this {SurfaceClient} Client object. Must have a channel member.
    * @param {array=} metadata Array of metadata key/value pairs to add to the
    *     call
-   * @param {(number|Date)=} deadline The deadline for processing this request.
-   *     Defaults to infinite future
+   * @param {Options} options Options map
    * @return {EventEmitter} An event emitter for stream related events
    */
-  function makeBidiStreamRequest(metadata, deadline) {
+  function makeBidiStreamRequest(metadata, options) {
     /* jshint validthis: true */
-    if (deadline === undefined) {
-      deadline = Infinity;
-    }
-    var call = new grpc.Call(this.channel, method, deadline);
+    var call = getCall(this.channel, method, options);
     if (metadata === null || metadata === undefined) {
       metadata = {};
     }
diff --git a/src/node/test/call_test.js b/src/node/test/call_test.js
index 48d859a8ec..8d0f20b074 100644
--- a/src/node/test/call_test.js
+++ b/src/node/test/call_test.js
@@ -84,6 +84,11 @@ describe('call', function() {
            new grpc.Call(channel, 'method', 0);
          });
        });
+    it('should accept an optional fourth string parameter', function() {
+      assert.doesNotThrow(function() {
+        new grpc.Call(channel, 'method', new Date(), 'host_override');
+      });
+    });
     it('should fail with a closed channel', function() {
       var local_channel = new grpc.Channel('hostname', insecureCreds);
       local_channel.close();
diff --git a/src/node/test/end_to_end_test.js b/src/node/test/end_to_end_test.js
index ea41dfc28c..7574d98b8a 100644
--- a/src/node/test/end_to_end_test.js
+++ b/src/node/test/end_to_end_test.js
@@ -74,8 +74,6 @@ describe('end-to-end', function() {
   });
   it('should start and end a request without error', function(complete) {
     var done = multiDone(complete, 2);
-    var deadline = new Date();
-    deadline.setSeconds(deadline.getSeconds() + 3);
     var status_text = 'xyz';
     var call = new grpc.Call(channel,
                              'dummy_method',
@@ -126,8 +124,6 @@ describe('end-to-end', function() {
   });
   it('should successfully send and receive metadata', function(complete) {
     var done = multiDone(complete, 2);
-    var deadline = new Date();
-    deadline.setSeconds(deadline.getSeconds() + 3);
     var status_text = 'xyz';
     var call = new grpc.Call(channel,
                              'dummy_method',
@@ -184,8 +180,6 @@ describe('end-to-end', function() {
     var req_text = 'client_request';
     var reply_text = 'server_response';
     var done = multiDone(complete, 2);
-    var deadline = new Date();
-    deadline.setSeconds(deadline.getSeconds() + 3);
     var status_text = 'success';
     var call = new grpc.Call(channel,
                              'dummy_method',
@@ -241,8 +235,6 @@ describe('end-to-end', function() {
   it('should send multiple messages', function(complete) {
     var done = multiDone(complete, 2);
     var requests = ['req1', 'req2'];
-    var deadline = new Date();
-    deadline.setSeconds(deadline.getSeconds() + 3);
     var status_text = 'xyz';
     var call = new grpc.Call(channel,
                              'dummy_method',
diff --git a/src/objective-c/GRPCClient/GRPCCall+OAuth2.h b/src/objective-c/GRPCClient/GRPCCall+OAuth2.h
new file mode 100644
index 0000000000..2e379a7157
--- /dev/null
+++ b/src/objective-c/GRPCClient/GRPCCall+OAuth2.h
@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import "GRPCCall.h"
+
+// Helpers for setting and reading headers compatible with OAuth2.
+@interface GRPCCall (OAuth2)
+
+// Setting this property is equivalent to setting "Bearer <passed token>" as the value of the
+// request header with key "authorization" (the authorization header). Setting it to nil removes the
+// authorization header from the request.
+// The value obtained by getting the property is the OAuth2 bearer token if the authorization header
+// of the request has the form "Bearer <token>", or nil otherwise.
+@property(atomic, copy) NSString *oauth2AccessToken;
+
+// Returns the value (if any) of the "www-authenticate" response header (the challenge header).
+@property(atomic, readonly) NSString *oauth2ChallengeHeader;
+
+@end
diff --git a/src/objective-c/GRPCClient/GRPCCall+OAuth2.m b/src/objective-c/GRPCClient/GRPCCall+OAuth2.m
new file mode 100644
index 0000000000..ed39d4b0f7
--- /dev/null
+++ b/src/objective-c/GRPCClient/GRPCCall+OAuth2.m
@@ -0,0 +1,63 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import "GRPCCall+OAuth2.h"
+
+static NSString * const kAuthorizationHeader = @"authorization";
+static NSString * const kBearerPrefix = @"Bearer ";
+static NSString * const kChallengeHeader = @"www-authenticate";
+
+@implementation GRPCCall (OAuth2)
+
+- (NSString *)oauth2AccessToken {
+  NSString *headerValue = self.requestMetadata[kAuthorizationHeader];
+  if ([headerValue hasPrefix:kBearerPrefix]) {
+    return [headerValue substringFromIndex:kBearerPrefix.length];
+  } else {
+    return nil;
+  }
+}
+
+- (void)setOauth2AccessToken:(NSString *)token {
+  if (token) {
+    self.requestMetadata[kAuthorizationHeader] = [kBearerPrefix stringByAppendingString:token];
+  } else {
+    [self.requestMetadata removeObjectForKey:kAuthorizationHeader];
+  }
+}
+
+- (NSString *)oauth2ChallengeHeader {
+  return self.responseMetadata[kChallengeHeader];
+}
+
+@end
diff --git a/src/objective-c/GRPCClient/GRPCCall+Tests.h b/src/objective-c/GRPCClient/GRPCCall+Tests.h
index 3d617b05d9..cca1614606 100644
--- a/src/objective-c/GRPCClient/GRPCCall+Tests.h
+++ b/src/objective-c/GRPCClient/GRPCCall+Tests.h
@@ -33,13 +33,22 @@
 
 #import "GRPCCall.h"
 
+// Methods to let tune down the security of gRPC connections for specific hosts. These shouldn't be
+// used in releases, but are sometimes needed for testing.
 @interface GRPCCall (Tests)
 
 // Establish all SSL connections to the provided host using the passed SSL target name and the root
 // certificates found in the file at |certsPath|.
-// Must be called before any gRPC call to that host is made.
+//
+// Must be called before any gRPC call to that host is made. It's illegal to pass the same host to
+// more than one invocation of the methods of this category.
 + (void)useTestCertsPath:(NSString *)certsPath
                 testName:(NSString *)testName
                  forHost:(NSString *)host;
 
+// Establish all connections to the provided host using cleartext instead of SSL.
+//
+// Must be called before any gRPC call to that host is made. It's illegal to pass the same host to
+// more than one invocation of the methods of this category.
++ (void)useInsecureConnectionsForHost:(NSString *)host;
 @end
diff --git a/src/objective-c/GRPCClient/GRPCCall+Tests.m b/src/objective-c/GRPCClient/GRPCCall+Tests.m
index 7c5b81d661..bade0b2920 100644
--- a/src/objective-c/GRPCClient/GRPCCall+Tests.m
+++ b/src/objective-c/GRPCClient/GRPCCall+Tests.m
@@ -36,12 +36,18 @@
 #import "private/GRPCHost.h"
 
 @implementation GRPCCall (Tests)
+
 + (void)useTestCertsPath:(NSString *)certsPath
                 testName:(NSString *)testName
                  forHost:(NSString *)host {
   GRPCHost *hostConfig = [GRPCHost hostWithAddress:host];
-  hostConfig.secure = YES;
   hostConfig.pathToCertificates = certsPath;
   hostConfig.hostNameOverride = testName;
 }
+
++ (void)useInsecureConnectionsForHost:(NSString *)host {
+  GRPCHost *hostConfig = [GRPCHost hostWithAddress:host];
+  hostConfig.secure = NO;
+}
+
 @end
diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index 5f7d74bca8..0f4c811ce4 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -74,11 +74,20 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
   // all. This wrapper over our actual writeable ensures thread-safety and
   // correct ordering.
   GRXConcurrentWriteable *_responseWriteable;
+
+  // The network thread wants the requestWriter to resume (when the server is ready for more input),
+  // or to stop (on errors), concurrently with user threads that want to start it, pause it or stop
+  // it. Because a writer isn't thread-safe, we'll synchronize those operations on it.
+  // We don't use a dispatch queue for that purpose, because the writer can call writeValue: or
+  // writesFinishedWithError: on this GRPCCall as part of those operations. We want to be able to
+  // pause the writer immediately on writeValue:, so we need our locking to be recursive.
   GRXWriter *_requestWriter;
 
   // To create a retain cycle when a call is started, up until it finishes. See
-  // |startWithWriteable:| and |finishWithError:|.
-  GRPCCall *_self;
+  // |startWithWriteable:| and |finishWithError:|. This saves users from having to retain a
+  // reference to the call object if all they're interested in is the handler being executed when
+  // the response arrives.
+  GRPCCall *_retainSelf;
 
   NSMutableDictionary *_requestMetadata;
   NSMutableDictionary *_responseMetadata;
@@ -136,11 +145,12 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
 
 - (void)finishWithError:(NSError *)errorOrNil {
   // If the call isn't retained anywhere else, it can be deallocated now.
-  _self = nil;
+  _retainSelf = nil;
 
   // If there were still request messages coming, stop them.
-  _requestWriter.state = GRXWriterStateFinished;
-  _requestWriter = nil;
+  @synchronized(_requestWriter) {
+    _requestWriter.state = GRXWriterStateFinished;
+  }
 
   if (errorOrNil) {
     [_responseWriteable cancelWithError:errorOrNil];
@@ -240,12 +250,14 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
     // Resume the request writer.
     GRPCCall *strongSelf = weakSelf;
     if (strongSelf) {
-      strongSelf->_requestWriter.state = GRXWriterStateStarted;
+      @synchronized(strongSelf->_requestWriter) {
+        strongSelf->_requestWriter.state = GRXWriterStateStarted;
+      }
     }
   };
-  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMessage alloc]
-                                            initWithMessage:message
-                                            handler:resumingHandler]] errorHandler:errorHandler];
+  [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMessage alloc] initWithMessage:message
+                                                                              handler:resumingHandler]]
+                            errorHandler:errorHandler];
 }
 
 - (void)writeValue:(id)value {
@@ -253,7 +265,9 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
 
   // Pause the input and only resume it when the C layer notifies us that writes
   // can proceed.
-  _requestWriter.state = GRXWriterStatePaused;
+  @synchronized(_requestWriter) {
+    _requestWriter.state = GRXWriterStatePaused;
+  }
 
   __weak GRPCCall *weakSelf = self;
   dispatch_async(_callQueue, ^{
@@ -273,7 +287,6 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
 }
 
 - (void)writesFinishedWithError:(NSError *)errorOrNil {
-  _requestWriter = nil;
   if (errorOrNil) {
     [self cancel];
   } else {
@@ -327,7 +340,9 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
     }
   }];
   // Now that the RPC has been initiated, request writes can start.
-  [_requestWriter startWithWriteable:self];
+  @synchronized(_requestWriter) {
+    [_requestWriter startWithWriteable:self];
+  }
 }
 
 #pragma mark GRXWriter implementation
@@ -338,7 +353,7 @@ NSString * const kGRPCStatusMetadataKey = @"io.grpc.StatusMetadataKey";
   // before being autoreleased).
   // Care is taken not to retain self strongly in any of the blocks used in this implementation, so
   // that the life of the instance is determined by this retain cycle.
-  _self = self;
+  _retainSelf = self;
 
   _responseWriteable = [[GRXConcurrentWriteable alloc] initWithWriteable:writeable];
   [self sendHeaders:_requestMetadata];
diff --git a/src/objective-c/GRPCClient/private/GRPCHost.m b/src/objective-c/GRPCClient/private/GRPCHost.m
index 5d9c48a524..d902f95b51 100644
--- a/src/objective-c/GRPCClient/private/GRPCHost.m
+++ b/src/objective-c/GRPCClient/private/GRPCHost.m
@@ -58,22 +58,14 @@
 // Default initializer.
 - (instancetype)initWithAddress:(NSString *)address {
 
-  // Verify and normalize the address, and decide whether to use SSL.
-  if (![address rangeOfString:@"://"].length) {
-    // No scheme provided; assume https.
-    address = [@"https://" stringByAppendingString:address];
+  // To provide a default port, we try to interpret the address. If it's just a host name without
+  // scheme and without port, we'll use port 443. If it has a scheme, we pass it untouched to the C
+  // gRPC library.
+  // TODO(jcanizales): Add unit tests for the types of addresses we want to let pass untouched.
+  NSURL *hostURL = [NSURL URLWithString:[@"https://" stringByAppendingString:address]];
+  if (hostURL && !hostURL.port) {
+    address = [hostURL.host stringByAppendingString:@":443"];
   }
-  NSURL *hostURL = [NSURL URLWithString:address];
-  if (!hostURL) {
-    [NSException raise:NSInvalidArgumentException format:@"Invalid URL: %@", address];
-  }
-  NSString *scheme = hostURL.scheme;
-  if (![scheme isEqualToString:@"https"] && ![scheme isEqualToString:@"http"]) {
-    [NSException raise:NSInvalidArgumentException format:@"URL scheme %@ isn't supported.", scheme];
-  }
-  // If the user didn't specify a port (hostURL.port is nil), provide a default one.
-  NSNumber *port = hostURL.port ?: [scheme isEqualToString:@"https"] ? @443 : @80;
-  address = [@[hostURL.host, port] componentsJoinedByString:@":"];
 
   // Look up the GRPCHost in the cache.
   static NSMutableDictionary *hostCache;
@@ -84,19 +76,16 @@
   @synchronized(hostCache) {
     GRPCHost *cachedHost = hostCache[address];
     if (cachedHost) {
-      // We could verify here that the cached host uses the same protocol that we're expecting. But
-      // creating non-SSL channels by adding "http://" to the address is going away (to make the use
-      // of insecure channels less subtle), so it's not worth it now.
       return cachedHost;
     }
 
     if ((self = [super init])) {
       _address = address;
-      _secure = [scheme isEqualToString:@"https"];
+      _secure = YES;
       hostCache[address] = self;
     }
-    return self;
   }
+  return self;
 }
 
 - (grpc_call *)unmanagedCallWithPath:(NSString *)path completionQueue:(GRPCCompletionQueue *)queue {
@@ -131,4 +120,7 @@
   return _hostNameOverride ?: _address;
 }
 
+// TODO(jcanizales): Don't let set |secure| to |NO| if |pathToCertificates| or |hostNameOverride|
+// have been set. Don't let set either of the latter if |secure| has been set to |NO|.
+
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCSecureChannel.m b/src/objective-c/GRPCClient/private/GRPCSecureChannel.m
index 9b4b6768f8..0a54804bb2 100644
--- a/src/objective-c/GRPCClient/private/GRPCSecureChannel.m
+++ b/src/objective-c/GRPCClient/private/GRPCSecureChannel.m
@@ -38,15 +38,18 @@
 // Returns NULL if the file at path couldn't be read. In that case, if errorPtr isn't NULL,
 // *errorPtr will be an object describing what went wrong.
 static grpc_credentials *CertificatesAtPath(NSString *path, NSError **errorPtr) {
-  NSString *certsContent = [NSString stringWithContentsOfFile:path
-                                                     encoding:NSASCIIStringEncoding
+  // Files in PEM format can have non-ASCII characters in their comments (e.g. for the name of the
+  // issuer). Load them as UTF8 and produce an ASCII equivalent.
+  NSString *contentInUTF8 = [NSString stringWithContentsOfFile:path
+                                                     encoding:NSUTF8StringEncoding
                                                         error:errorPtr];
-  if (!certsContent) {
+  NSData *contentInASCII = [contentInUTF8 dataUsingEncoding:NSASCIIStringEncoding
+                                       allowLossyConversion:YES];
+  if (!contentInASCII.bytes) {
     // Passing NULL to grpc_ssl_credentials_create produces behavior we don't want, so return.
     return NULL;
   }
-  const char * asCString = [certsContent cStringUsingEncoding:NSASCIIStringEncoding];
-  return grpc_ssl_credentials_create(asCString, NULL);
+  return grpc_ssl_credentials_create(contentInASCII.bytes, NULL);
 }
 
 @implementation GRPCSecureChannel
diff --git a/src/objective-c/RxLibrary/GRXBufferedPipe.h b/src/objective-c/RxLibrary/GRXBufferedPipe.h
index b6296e1ed7..ca94ce275f 100644
--- a/src/objective-c/RxLibrary/GRXBufferedPipe.h
+++ b/src/objective-c/RxLibrary/GRXBufferedPipe.h
@@ -36,13 +36,11 @@
 #import "GRXWriteable.h"
 #import "GRXWriter.h"
 
-// A buffered pipe is a Writeable that also acts as a Writer (to whichever other writeable is passed
-// to -startWithWriteable:).
+// A buffered pipe is a Writer that also acts as a Writeable.
 // Once it is started, whatever values are written into it (via -writeValue:) will be propagated
 // immediately, unless flow control prevents it.
 // If it is throttled and keeps receiving values, as well as if it receives values before being
-// started, it will buffer them and propagate them in order as soon as its state becomes
-// GRXWriterStateStarted.
+// started, it will buffer them and propagate them in order as soon as its state becomes Started.
 // If it receives an error (via -writesFinishedWithError:), it will drop any buffered values and
 // propagate the error immediately.
 //
@@ -51,6 +49,9 @@
 // pipe will keep buffering all data written to it, your application could run out of memory and
 // crash. If you want to react to flow control signals to prevent that, instead of using this class
 // you can implement an object that conforms to GRXWriter.
+//
+// Thread-safety:
+// The methods of an object of this class should not be called concurrently from different threads.
 @interface GRXBufferedPipe : GRXWriter<GRXWriteable>
 
 // Convenience constructor.
diff --git a/src/objective-c/RxLibrary/GRXForwardingWriter.h b/src/objective-c/RxLibrary/GRXForwardingWriter.h
index d004333d2b..f310832284 100644
--- a/src/objective-c/RxLibrary/GRXForwardingWriter.h
+++ b/src/objective-c/RxLibrary/GRXForwardingWriter.h
@@ -33,11 +33,17 @@
 
 #import "GRXWriter.h"
 
-// A "proxy" class that simply forwards values, completion, and errors from its
-// input writer to its writeable.
+// A "proxy" class that simply forwards values, completion, and errors from its input writer to its
+// writeable.
 // It is useful as a superclass for pipes that act as a transformation of their
 // input writer, and for classes that represent objects with input and
 // output sequences of values, like an RPC.
+//
+// Thread-safety:
+// All messages sent to this object need to be serialized. When it is started, the writer it wraps
+// is started in the same thread. Manual state changes are propagated to the wrapped writer in the
+// same thread too. Importantly, all messages the wrapped writer sends to its writeable need to be
+// serialized with any message sent to this object.
 @interface GRXForwardingWriter : GRXWriter
 - (instancetype)initWithWriter:(GRXWriter *)writer NS_DESIGNATED_INITIALIZER;
 @end
diff --git a/src/objective-c/RxLibrary/GRXForwardingWriter.m b/src/objective-c/RxLibrary/GRXForwardingWriter.m
index 2342f51ab3..a72be9ace2 100644
--- a/src/objective-c/RxLibrary/GRXForwardingWriter.m
+++ b/src/objective-c/RxLibrary/GRXForwardingWriter.m
@@ -48,7 +48,11 @@
 // Designated initializer
 - (instancetype)initWithWriter:(GRXWriter *)writer {
   if (!writer) {
-    [NSException raise:NSInvalidArgumentException format:@"writer can't be nil."];
+    return nil;
+  }
+  if (writer.state != GRXWriterStateNotStarted) {
+    [NSException raise:NSInvalidArgumentException
+                format:@"The writer argument must not have already started."];
   }
   if ((self = [super init])) {
     _writer = writer;
diff --git a/src/objective-c/RxLibrary/GRXImmediateWriter.h b/src/objective-c/RxLibrary/GRXImmediateWriter.h
index b171f0c760..3fcc259434 100644
--- a/src/objective-c/RxLibrary/GRXImmediateWriter.h
+++ b/src/objective-c/RxLibrary/GRXImmediateWriter.h
@@ -36,10 +36,17 @@
 #import "GRXWriter.h"
 
 // Utility to construct GRXWriter instances from values that are immediately available when
-// required. The returned writers all support pausing and early termination.
+// required.
 //
-// Unless the writeable callback pauses them or stops them early, these writers will do all their
-// interactions with the writeable before the start method returns.
+// Thread-safety:
+//
+// An object of this class shouldn't be messaged concurrently by more than one thread. It will start
+// messaging the writeable before |startWithWriteable:| returns, in the same thread. That is the
+// only place where the writer can be paused or stopped prematurely.
+//
+// If a paused writer of this class is resumed, it will start messaging the writeable, in the same
+// thread, before |setState:| returns. Because the object can't be legally accessed concurrently,
+// that's the only place where it can be paused again (or stopped).
 @interface GRXImmediateWriter : GRXWriter
 
 // Returns a writer that pulls values from the passed NSEnumerator instance and pushes them to
diff --git a/src/objective-c/RxLibrary/GRXWriter.h b/src/objective-c/RxLibrary/GRXWriter.h
index 5d6e1a472a..b1c994aa38 100644
--- a/src/objective-c/RxLibrary/GRXWriter.h
+++ b/src/objective-c/RxLibrary/GRXWriter.h
@@ -35,84 +35,73 @@
 
 #import "GRXWriteable.h"
 
+// States of a writer.
 typedef NS_ENUM(NSInteger, GRXWriterState) {
 
-  // The writer has not yet been given a writeable to which it can push its
-  // values. To have an writer transition to the Started state, send it a
-  // startWithWriteable: message.
+  // The writer has not yet been given a writeable to which it can push its values. To have a writer
+  // transition to the Started state, send it a startWithWriteable: message.
   //
-  // An writer's state cannot be manually set to this value.
+  // A writer's state cannot be manually set to this value.
   GRXWriterStateNotStarted,
 
   // The writer might push values to the writeable at any moment.
   GRXWriterStateStarted,
 
-  // The writer is temporarily paused, and won't send any more values to the
-  // writeable unless its state is set back to Started. The writer might still
-  // transition to the Finished state at any moment, and is allowed to send
-  // writesFinishedWithError: to its writeable.
-  //
-  // Not all implementations of writer have to support pausing, and thus
-  // trying to set an writer's state to this value might have no effect.
+  // The writer is temporarily paused, and won't send any more values to the writeable unless its
+  // state is set back to Started. The writer might still transition to the Finished state at any
+  // moment, and is allowed to send writesFinishedWithError: to its writeable.
   GRXWriterStatePaused,
 
   // The writer has released its writeable and won't interact with it anymore.
   //
-  // One seldomly wants to set an writer's state to this value, as its
-  // writeable isn't notified with a writesFinishedWithError: message. Instead, sending
-  // finishWithError: to the writer will make it notify the writeable and then
-  // transition to this state.
+  // One seldomly wants to set a writer's state to this value, as its writeable isn't notified with
+  // a writesFinishedWithError: message. Instead, sending finishWithError: to the writer will make
+  // it notify the writeable and then transition to this state.
   GRXWriterStateFinished
 };
 
-// An object that conforms to this protocol can produce, on demand, a sequence
-// of values. The sequence may be produced asynchronously, and it may consist of
-// any number of elements, including none or an infinite number.
+// An GRXWriter object can produce, on demand, a sequence of values. The sequence may be produced
+// asynchronously, and it may consist of any number of elements, including none or an infinite
+// number.
+//
+// GRXWriter is the active dual of NSEnumerator. The difference between them is thus whether the
+// object plays an active or passive role during usage: A user of NSEnumerator pulls values off it,
+// and passes the values to a writeable. A user of GRXWriter, though, just gives it a writeable, and
+// the GRXWriter instance pushes values to the writeable. This makes this protocol suitable to
+// represent a sequence of future values, as well as collections with internal iteration.
 //
-// GRXWriter is the active dual of NSEnumerator. The difference between them
-// is thus whether the object plays an active or passive role during usage: A
-// user of NSEnumerator pulls values off it, and passes the values to a writeable.
-// A user of GRXWriter, though, just gives it a writeable, and the
-// GRXWriter instance pushes values to the writeable. This makes this protocol
-// suitable to represent a sequence of future values, as well as collections
-// with internal iteration.
+// An instance of GRXWriter can start producing values after a writeable is passed to it. It can
+// also be commanded to finish the sequence immediately (with an optional error). Finally, it can be
+// asked to pause, and resumed later. All GRXWriter objects support pausing and early termination.
 //
-// An instance of GRXWriter can start producing values after a writeable is
-// passed to it. It can also be commanded to finish the sequence immediately
-// (with an optional error). Finally, it can be asked to pause, but the
-// conforming instance is not required to oblige.
+// Thread-safety:
 //
-// Unless otherwise indicated by a conforming class, no messages should be sent
-// concurrently to a GRXWriter. I.e., conforming classes aren't required to
-// be thread-safe.
+// State transitions take immediate effect if the object is used from a single thread. Subclasses
+// might offer stronger guarantees.
+//
+// Unless otherwise indicated by a conforming subclass, no messages should be sent concurrently to a
+// GRXWriter. I.e., conforming classes aren't required to be thread-safe.
 @interface GRXWriter : NSObject
 
-// This property can be used to query the current state of the writer, which
-// determines how it might currently use its writeable. Some state transitions can
-// be triggered by setting this property to the corresponding value, and that's
-// useful for advanced use cases like pausing an writer. For more details,
-// see the documentation of the enum.
+// This property can be used to query the current state of the writer, which determines how it might
+// currently use its writeable. Some state transitions can be triggered by setting this property to
+// the corresponding value, and that's useful for advanced use cases like pausing an writer. For
+// more details, see the documentation of the enum further down.
 @property(nonatomic) GRXWriterState state;
 
-// Start sending messages to the writeable. Messages may be sent before the method
-// returns, or they may be sent later in the future. See GRXWriteable.h for the
-// different messages a writeable can receive.
+// Transition to the Started state, and start sending messages to the writeable (a reference to it
+// is retained). Messages to the writeable may be sent before the method returns, or they may be
+// sent later in the future. See GRXWriteable.h for the different messages a writeable can receive.
 //
-// If this writer draws its values from an external source (e.g. from the
-// filesystem or from a server), calling this method will commonly trigger side
-// effects (like network connections).
+// If this writer draws its values from an external source (e.g. from the filesystem or from a
+// server), calling this method will commonly trigger side effects (like network connections).
 //
 // This method might only be called on writers in the NotStarted state.
 - (void)startWithWriteable:(id<GRXWriteable>)writeable;
 
-// Send writesFinishedWithError:errorOrNil immediately to the writeable, and don't send
-// any more messages to it.
-//
-// This method might only be called on writers in the Started or Paused
-// state.
+// Send writesFinishedWithError:errorOrNil to the writeable. Then release the reference to it and
+// transition to the Finished state.
 //
-// TODO(jcanizales): Consider adding some guarantee about the immediacy of that
-// stopping. I know I've relied on it in part of the code that uses this, but
-// can't remember the details in the presence of concurrency.
+// This method might only be called on writers in the Started or Paused state.
 - (void)finishWithError:(NSError *)errorOrNil;
 @end
diff --git a/src/objective-c/tests/GRPCClientTests.m b/src/objective-c/tests/GRPCClientTests.m
index 103e5ca3d4..f23102988b 100644
--- a/src/objective-c/tests/GRPCClientTests.m
+++ b/src/objective-c/tests/GRPCClientTests.m
@@ -35,6 +35,8 @@
 #import <XCTest/XCTest.h>
 
 #import <GRPCClient/GRPCCall.h>
+#import <GRPCClient/GRPCCall+OAuth2.h>
+#import <GRPCClient/GRPCCall+Tests.h>
 #import <ProtoRPC/ProtoMethod.h>
 #import <RemoteTest/Messages.pbobjc.h>
 #import <RxLibrary/GRXWriteable.h>
@@ -43,8 +45,7 @@
 // These are a few tests similar to InteropTests, but which use the generic gRPC client (GRPCCall)
 // rather than a generated proto library on top of it.
 
-// grpc-test.sandbox.google.com
-static NSString * const kHostAddress = @"http://localhost:5050";
+static NSString * const kHostAddress = @"localhost:5050";
 static NSString * const kPackage = @"grpc.testing";
 static NSString * const kService = @"TestService";
 
@@ -58,6 +59,9 @@ static ProtoMethod *kUnaryCallMethod;
 @implementation GRPCClientTests
 
 - (void)setUp {
+  // Register test server as non-SSL.
+  [GRPCCall useInsecureConnectionsForHost:kHostAddress];
+
   // This method isn't implemented by the remote server.
   kInexistentMethod = [[ProtoMethod alloc] initWithPackage:kPackage
                                                    service:kService
@@ -110,7 +114,7 @@ static ProtoMethod *kUnaryCallMethod;
 
   [call startWithWriteable:responsesWriteable];
 
-  [self waitForExpectationsWithTimeout:4 handler:nil];
+  [self waitForExpectationsWithTimeout:8 handler:nil];
 }
 
 - (void)testSimpleProtoRPC {
@@ -142,7 +146,7 @@ static ProtoMethod *kUnaryCallMethod;
 
   [call startWithWriteable:responsesWriteable];
 
-  [self waitForExpectationsWithTimeout:4 handler:nil];
+  [self waitForExpectationsWithTimeout:8 handler:nil];
 }
 
 - (void)testMetadata {
@@ -157,7 +161,7 @@ static ProtoMethod *kUnaryCallMethod;
                                              path:kUnaryCallMethod.HTTPPath
                                    requestsWriter:requestsWriter];
 
-  call.requestMetadata[@"Authorization"] = @"Bearer bogusToken";
+  call.oauth2AccessToken = @"bogusToken";
 
   id<GRXWriteable> responsesWriteable = [[GRXWriteable alloc] initWithValueHandler:^(NSData *value) {
     XCTFail(@"Received unexpected response: %@", value);
@@ -166,7 +170,7 @@ static ProtoMethod *kUnaryCallMethod;
     XCTAssertEqual(errorOrNil.code, 16, @"Finished with unexpected error: %@", errorOrNil);
     XCTAssertEqualObjects(call.responseMetadata, errorOrNil.userInfo[kGRPCStatusMetadataKey],
                           @"Metadata in the NSError object and call object differ.");
-    NSString *challengeHeader = call.responseMetadata[@"www-authenticate"];
+    NSString *challengeHeader = call.oauth2ChallengeHeader;
     XCTAssertGreaterThan(challengeHeader.length, 0,
                          @"No challenge in response headers %@", call.responseMetadata);
     [expectation fulfill];
diff --git a/src/objective-c/tests/InteropTests.h b/src/objective-c/tests/InteropTests.h
index c675c8d241..1045c3d124 100644
--- a/src/objective-c/tests/InteropTests.h
+++ b/src/objective-c/tests/InteropTests.h
@@ -37,8 +37,7 @@
 // https://github.com/grpc/grpc/blob/master/doc/interop-test-descriptions.md
 
 @interface InteropTests : XCTestCase
-// Returns @"http://localhost:5050".
+// Returns @"grpc-test.sandbox.google.com".
 // Override in a subclass to perform the same tests against a different address.
-// For interop tests, use @"grpc-test.sandbox.google.com".
 + (NSString *)host;
 @end
diff --git a/src/objective-c/tests/InteropTests.m b/src/objective-c/tests/InteropTests.m
index a6611d27be..1b63fe2059 100644
--- a/src/objective-c/tests/InteropTests.m
+++ b/src/objective-c/tests/InteropTests.m
@@ -35,6 +35,7 @@
 
 #include <grpc/status.h>
 
+#import <GRPCClient/GRPCCall+Tests.h>
 #import <ProtoRPC/ProtoRPC.h>
 #import <RemoteTest/Empty.pbobjc.h>
 #import <RemoteTest/Messages.pbobjc.h>
@@ -75,12 +76,16 @@
 }
 @end
 
+#pragma mark Tests
+
+static NSString * const kRemoteSSLHost = @"grpc-test.sandbox.google.com";
+
 @implementation InteropTests {
   RMTTestService *_service;
 }
 
 + (NSString *)host {
-  return @"http://localhost:5050";
+  return kRemoteSSLHost;
 }
 
 - (void)setUp {
@@ -123,7 +128,7 @@
     [expectation fulfill];
   }];
 
-  [self waitForExpectationsWithTimeout:8 handler:nil];
+  [self waitForExpectationsWithTimeout:16 handler:nil];
 }
 
 - (void)testClientStreamingRPC {
diff --git a/src/core/httpcli/httpcli_security_connector.h b/src/objective-c/tests/InteropTestsLocalCleartext.m
index c50f25905e..2d7d3c4b2c 100644
--- a/src/core/httpcli/httpcli_security_connector.h
+++ b/src/objective-c/tests/InteropTestsLocalCleartext.m
@@ -31,13 +31,29 @@
  *
  */
 
-#ifndef GRPC_INTERNAL_CORE_HTTPCLI_HTTPCLI_SECURITY_CONNECTOR_H
-#define GRPC_INTERNAL_CORE_HTTPCLI_HTTPCLI_SECURITY_CONNECTOR_H
+// Repeat of the tests in InteropTests.m, but sending the RPCs to a local cleartext server instead
+// of the remote SSL one.
 
-#include "src/core/security/security_connector.h"
+#import <GRPCClient/GRPCCall+Tests.h>
 
-grpc_security_status grpc_httpcli_ssl_channel_security_connector_create(
-    const unsigned char *pem_root_certs, size_t pem_root_certs_size,
-    const char *secure_peer_name, grpc_channel_security_connector **sc);
+#import "InteropTests.h"
 
-#endif  /* GRPC_INTERNAL_CORE_HTTPCLI_HTTPCLI_SECURITY_CONNECTOR_H */
+static NSString * const kLocalCleartextHost = @"localhost:5050";
+
+@interface InteropTestsLocalCleartext : InteropTests
+@end
+
+@implementation InteropTestsLocalCleartext
+
++ (NSString *)host {
+  return kLocalCleartextHost;
+}
+
+- (void)setUp {
+  // Register test server as non-SSL.
+  [GRPCCall useInsecureConnectionsForHost:kLocalCleartextHost];
+
+  [super setUp];
+}
+
+@end
diff --git a/src/objective-c/tests/InteropTestsLocalSSL.m b/src/objective-c/tests/InteropTestsLocalSSL.m
index 227ca79659..f69f806dcf 100644
--- a/src/objective-c/tests/InteropTestsLocalSSL.m
+++ b/src/objective-c/tests/InteropTestsLocalSSL.m
@@ -31,8 +31,8 @@
  *
  */
 
-// Repeat of the tests in InteropTests.m, but using SSL to communicate with the local server instead
-// of cleartext.
+// Repeat of the tests in InteropTests.m, but sending the RPCs to a local SSL server instead of the
+// remote one.
 
 #import <GRPCClient/GRPCCall+Tests.h>
 
diff --git a/src/objective-c/tests/Tests.xcodeproj/project.pbxproj b/src/objective-c/tests/Tests.xcodeproj/project.pbxproj
index af98aba9c0..3a1c3d940a 100644
--- a/src/objective-c/tests/Tests.xcodeproj/project.pbxproj
+++ b/src/objective-c/tests/Tests.xcodeproj/project.pbxproj
@@ -13,6 +13,7 @@
 		63423F511B151B77006CF63C /* RxLibraryUnitTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 63423F501B151B77006CF63C /* RxLibraryUnitTests.m */; };
 		635697CD1B14FC11007A7283 /* Tests.m in Sources */ = {isa = PBXBuildFile; fileRef = 635697CC1B14FC11007A7283 /* Tests.m */; };
 		635ED2EC1B1A3BC400FDE5C3 /* InteropTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 635ED2EB1B1A3BC400FDE5C3 /* InteropTests.m */; };
+		63715F561B780C020029CB0B /* InteropTestsLocalCleartext.m in Sources */ = {isa = PBXBuildFile; fileRef = 63715F551B780C020029CB0B /* InteropTestsLocalCleartext.m */; };
 		63E240CE1B6C4E2B005F3B0E /* InteropTestsLocalSSL.m in Sources */ = {isa = PBXBuildFile; fileRef = 63E240CD1B6C4E2B005F3B0E /* InteropTestsLocalSSL.m */; };
 		63E240D01B6C63DC005F3B0E /* TestCertificates.bundle in Resources */ = {isa = PBXBuildFile; fileRef = 63E240CF1B6C63DC005F3B0E /* TestCertificates.bundle */; };
 		7D8A186224D39101F90230F6 /* libPods.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 35F2B6BF3BAE8F0DC4AFD76E /* libPods.a */; };
@@ -51,6 +52,7 @@
 		635697CC1B14FC11007A7283 /* Tests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = Tests.m; sourceTree = "<group>"; };
 		635697D81B14FC11007A7283 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		635ED2EB1B1A3BC400FDE5C3 /* InteropTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = InteropTests.m; sourceTree = "<group>"; };
+		63715F551B780C020029CB0B /* InteropTestsLocalCleartext.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = InteropTestsLocalCleartext.m; sourceTree = "<group>"; };
 		63E240CC1B6C4D3A005F3B0E /* InteropTests.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = InteropTests.h; sourceTree = "<group>"; };
 		63E240CD1B6C4E2B005F3B0E /* InteropTestsLocalSSL.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = InteropTestsLocalSSL.m; sourceTree = "<group>"; };
 		63E240CF1B6C63DC005F3B0E /* TestCertificates.bundle */ = {isa = PBXFileReference; lastKnownFileType = "wrapper.plug-in"; path = TestCertificates.bundle; sourceTree = "<group>"; };
@@ -117,14 +119,15 @@
 		635697C91B14FC11007A7283 /* Tests */ = {
 			isa = PBXGroup;
 			children = (
-				63E240CD1B6C4E2B005F3B0E /* InteropTestsLocalSSL.m */,
 				6312AE4D1B1BF49B00341DEE /* GRPCClientTests.m */,
-				63175DFE1B1B9FAF00027841 /* LocalClearTextTests.m */,
+				63E240CC1B6C4D3A005F3B0E /* InteropTests.h */,
 				635ED2EB1B1A3BC400FDE5C3 /* InteropTests.m */,
+				63E240CD1B6C4E2B005F3B0E /* InteropTestsLocalSSL.m */,
+				63715F551B780C020029CB0B /* InteropTestsLocalCleartext.m */,
 				63423F501B151B77006CF63C /* RxLibraryUnitTests.m */,
+				63175DFE1B1B9FAF00027841 /* LocalClearTextTests.m */,
 				635697CC1B14FC11007A7283 /* Tests.m */,
 				635697D71B14FC11007A7283 /* Supporting Files */,
-				63E240CC1B6C4D3A005F3B0E /* InteropTests.h */,
 			);
 			name = Tests;
 			sourceTree = SOURCE_ROOT;
@@ -261,6 +264,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				63715F561B780C020029CB0B /* InteropTestsLocalCleartext.m in Sources */,
 				63175DFF1B1B9FAF00027841 /* LocalClearTextTests.m in Sources */,
 				63423F511B151B77006CF63C /* RxLibraryUnitTests.m in Sources */,
 				63E240CE1B6C4E2B005F3B0E /* InteropTestsLocalSSL.m in Sources */,
diff --git a/src/python/grpcio/grpc/_adapter/_c/module.c b/src/python/grpcio/grpc/_adapter/_c/module.c
index 1f3aedd9d8..9b93b051f6 100644
--- a/src/python/grpcio/grpc/_adapter/_c/module.c
+++ b/src/python/grpcio/grpc/_adapter/_c/module.c
@@ -53,6 +53,12 @@ PyMODINIT_FUNC init_c(void) {
     return;
   }
 
+  if (PyModule_AddStringConstant(
+          module, "PRIMARY_USER_AGENT_KEY",
+          GRPC_ARG_PRIMARY_USER_AGENT_STRING) < 0) {
+    return;
+  }
+
   /* GRPC maintains an internal counter of how many times it has been
      initialized and handles multiple pairs of grpc_init()/grpc_shutdown()
      invocations accordingly. */
diff --git a/src/python/grpcio/grpc/_adapter/_c/types/server.c b/src/python/grpcio/grpc/_adapter/_c/types/server.c
index c2190ea672..2a11d09d21 100644
--- a/src/python/grpcio/grpc/_adapter/_c/types/server.c
+++ b/src/python/grpcio/grpc/_adapter/_c/types/server.c
@@ -96,7 +96,7 @@ Server *pygrpc_Server_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
   PyObject *py_args;
   grpc_channel_args c_args;
   char *keywords[] = {"cq", "args", NULL};
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O!O:Channel", keywords,
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O!O:Server", keywords,
         &pygrpc_CompletionQueue_type, &cq, &py_args)) {
     return NULL;
   }
diff --git a/src/python/grpcio/grpc/_adapter/_low.py b/src/python/grpcio/grpc/_adapter/_low.py
index dcf67dbc11..239aac81b2 100644
--- a/src/python/grpcio/grpc/_adapter/_low.py
+++ b/src/python/grpcio/grpc/_adapter/_low.py
@@ -27,9 +27,12 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+from grpc import _grpcio_metadata
 from grpc._adapter import _c
 from grpc._adapter import _types
 
+_USER_AGENT = 'Python-gRPC-{}'.format(_grpcio_metadata.__version__)
+
 ClientCredentials = _c.ClientCredentials
 ServerCredentials = _c.ServerCredentials
 
@@ -76,6 +79,7 @@ class Call(_types.Call):
 class Channel(_types.Channel):
 
   def __init__(self, target, args, creds=None):
+    args = list(args) + [(_c.PRIMARY_USER_AGENT_KEY, _USER_AGENT)]
     if creds is None:
       self.channel = _c.Channel(target, args)
     else:
diff --git a/src/python/grpcio_test/grpc_interop/_interop_test_case.py b/src/python/grpcio_test/grpc_interop/_interop_test_case.py
index ed8f7ef009..b6d06b300d 100644
--- a/src/python/grpcio_test/grpc_interop/_interop_test_case.py
+++ b/src/python/grpcio_test/grpc_interop/_interop_test_case.py
@@ -59,3 +59,6 @@ class InteropTestCase(object):
 
   def testCancelAfterFirstResponse(self):
     methods.TestCase.CANCEL_AFTER_FIRST_RESPONSE.test_interoperability(self.stub, None)
+
+  def testTimeoutOnSleepingServer(self):
+    methods.TestCase.TIMEOUT_ON_SLEEPING_SERVER.test_interoperability(self.stub, None)
diff --git a/src/python/grpcio_test/grpc_interop/methods.py b/src/python/grpcio_test/grpc_interop/methods.py
index f4c94685ee..7a831f3cbd 100644
--- a/src/python/grpcio_test/grpc_interop/methods.py
+++ b/src/python/grpcio_test/grpc_interop/methods.py
@@ -33,10 +33,12 @@ import enum
 import json
 import os
 import threading
+import time
 
 from oauth2client import client as oauth2client_client
 
 from grpc.framework.alpha import utilities
+from grpc.framework.alpha import exceptions
 
 from grpc_interop import empty_pb2
 from grpc_interop import messages_pb2
@@ -318,6 +320,24 @@ def _cancel_after_first_response(stub):
       raise ValueError('expected call to be cancelled')
 
 
+def _timeout_on_sleeping_server(stub):
+  request_payload_size = 27182
+  with stub, _Pipe() as pipe:
+    response_iterator = stub.FullDuplexCall(pipe, 0.001)
+
+    request = messages_pb2.StreamingOutputCallRequest(
+        response_type=messages_pb2.COMPRESSABLE,
+        payload=messages_pb2.Payload(body=b'\x00' * request_payload_size))
+    pipe.add(request)
+    time.sleep(0.1)
+    try:
+      next(response_iterator)
+    except exceptions.ExpirationError:
+      pass
+    else:
+      raise ValueError('expected call to exceed deadline')
+
+
 def _compute_engine_creds(stub, args):
   response = _large_unary_common_behavior(stub, True, True)
   if args.default_service_account != response.username:
@@ -351,6 +371,7 @@ class TestCase(enum.Enum):
   CANCEL_AFTER_FIRST_RESPONSE = 'cancel_after_first_response'
   COMPUTE_ENGINE_CREDS = 'compute_engine_creds'
   SERVICE_ACCOUNT_CREDS = 'service_account_creds'
+  TIMEOUT_ON_SLEEPING_SERVER = 'timeout_on_sleeping_server'
 
   def test_interoperability(self, stub, args):
     if self is TestCase.EMPTY_UNARY:
@@ -367,6 +388,8 @@ class TestCase(enum.Enum):
       _cancel_after_begin(stub)
     elif self is TestCase.CANCEL_AFTER_FIRST_RESPONSE:
       _cancel_after_first_response(stub)
+    elif self is TestCase.TIMEOUT_ON_SLEEPING_SERVER:
+      _timeout_on_sleeping_server(stub)
     elif self is TestCase.COMPUTE_ENGINE_CREDS:
       _compute_engine_creds(stub, args)
     elif self is TestCase.SERVICE_ACCOUNT_CREDS:
diff --git a/src/python/grpcio_test/grpc_protoc_plugin/__init__.py b/src/python/grpcio_test/grpc_protoc_plugin/__init__.py
new file mode 100644
index 0000000000..7086519106
--- /dev/null
+++ b/src/python/grpcio_test/grpc_protoc_plugin/__init__.py
@@ -0,0 +1,30 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
diff --git a/src/python/grpcio_test/grpc_protoc_plugin/python_plugin_test.py b/src/python/grpcio_test/grpc_protoc_plugin/python_plugin_test.py
new file mode 100644
index 0000000000..b200d129a9
--- /dev/null
+++ b/src/python/grpcio_test/grpc_protoc_plugin/python_plugin_test.py
@@ -0,0 +1,541 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+import argparse
+import contextlib
+import distutils.spawn
+import errno
+import itertools
+import os
+import pkg_resources
+import shutil
+import subprocess
+import sys
+import tempfile
+import threading
+import time
+import unittest
+
+from grpc.framework.alpha import exceptions
+from grpc.framework.foundation import future
+
+# Identifiers of entities we expect to find in the generated module.
+SERVICER_IDENTIFIER = 'EarlyAdopterTestServiceServicer'
+SERVER_IDENTIFIER = 'EarlyAdopterTestServiceServer'
+STUB_IDENTIFIER = 'EarlyAdopterTestServiceStub'
+SERVER_FACTORY_IDENTIFIER = 'early_adopter_create_TestService_server'
+STUB_FACTORY_IDENTIFIER = 'early_adopter_create_TestService_stub'
+
+# The timeout used in tests of RPCs that are supposed to expire.
+SHORT_TIMEOUT = 2
+# The timeout used in tests of RPCs that are not supposed to expire. The
+# absurdly large value doesn't matter since no passing execution of this test
+# module will ever wait the duration.
+LONG_TIMEOUT = 600
+NO_DELAY = 0
+
+
+class _ServicerMethods(object):
+
+  def __init__(self, test_pb2, delay):
+    self._condition = threading.Condition()
+    self._delay = delay
+    self._paused = False
+    self._fail = False
+    self._test_pb2 = test_pb2
+
+  @contextlib.contextmanager
+  def pause(self):  # pylint: disable=invalid-name
+    with self._condition:
+      self._paused = True
+    yield
+    with self._condition:
+      self._paused = False
+      self._condition.notify_all()
+
+  @contextlib.contextmanager
+  def fail(self):  # pylint: disable=invalid-name
+    with self._condition:
+      self._fail = True
+    yield
+    with self._condition:
+      self._fail = False
+
+  def _control(self):  # pylint: disable=invalid-name
+    with self._condition:
+      if self._fail:
+        raise ValueError()
+      while self._paused:
+        self._condition.wait()
+    time.sleep(self._delay)
+
+  def UnaryCall(self, request, unused_rpc_context):
+    response = self._test_pb2.SimpleResponse()
+    response.payload.payload_type = self._test_pb2.COMPRESSABLE
+    response.payload.payload_compressable = 'a' * request.response_size
+    self._control()
+    return response
+
+  def StreamingOutputCall(self, request, unused_rpc_context):
+    for parameter in request.response_parameters:
+      response = self._test_pb2.StreamingOutputCallResponse()
+      response.payload.payload_type = self._test_pb2.COMPRESSABLE
+      response.payload.payload_compressable = 'a' * parameter.size
+      self._control()
+      yield response
+
+  def StreamingInputCall(self, request_iter, unused_rpc_context):
+    response = self._test_pb2.StreamingInputCallResponse()
+    aggregated_payload_size = 0
+    for request in request_iter:
+      aggregated_payload_size += len(request.payload.payload_compressable)
+    response.aggregated_payload_size = aggregated_payload_size
+    self._control()
+    return response
+
+  def FullDuplexCall(self, request_iter, unused_rpc_context):
+    for request in request_iter:
+      for parameter in request.response_parameters:
+        response = self._test_pb2.StreamingOutputCallResponse()
+        response.payload.payload_type = self._test_pb2.COMPRESSABLE
+        response.payload.payload_compressable = 'a' * parameter.size
+        self._control()
+        yield response
+
+  def HalfDuplexCall(self, request_iter, unused_rpc_context):
+    responses = []
+    for request in request_iter:
+      for parameter in request.response_parameters:
+        response = self._test_pb2.StreamingOutputCallResponse()
+        response.payload.payload_type = self._test_pb2.COMPRESSABLE
+        response.payload.payload_compressable = 'a' * parameter.size
+        self._control()
+        responses.append(response)
+    for response in responses:
+      yield response
+
+
+@contextlib.contextmanager
+def _CreateService(test_pb2, delay):
+  """Provides a servicer backend and a stub.
+
+  The servicer is just the implementation
+  of the actual servicer passed to the face player of the python RPC
+  implementation; the two are detached.
+
+  Non-zero delay puts a delay on each call to the servicer, representative of
+  communication latency. Timeout is the default timeout for the stub while
+  waiting for the service.
+
+  Args:
+    test_pb2: The test_pb2 module generated by this test.
+    delay: Delay in seconds per response from the servicer.
+
+  Yields:
+    A (servicer_methods, servicer, stub) three-tuple where servicer_methods is
+      the back-end of the service bound to the stub and the server and stub
+      are both activated and ready for use.
+  """
+  servicer_methods = _ServicerMethods(test_pb2, delay)
+
+  class Servicer(getattr(test_pb2, SERVICER_IDENTIFIER)):
+
+    def UnaryCall(self, request, context):
+      return servicer_methods.UnaryCall(request, context)
+
+    def StreamingOutputCall(self, request, context):
+      return servicer_methods.StreamingOutputCall(request, context)
+
+    def StreamingInputCall(self, request_iter, context):
+      return servicer_methods.StreamingInputCall(request_iter, context)
+
+    def FullDuplexCall(self, request_iter, context):
+      return servicer_methods.FullDuplexCall(request_iter, context)
+
+    def HalfDuplexCall(self, request_iter, context):
+      return servicer_methods.HalfDuplexCall(request_iter, context)
+
+  servicer = Servicer()
+  server = getattr(
+      test_pb2, SERVER_FACTORY_IDENTIFIER)(servicer, 0)
+  with server:
+    port = server.port()
+    stub = getattr(test_pb2, STUB_FACTORY_IDENTIFIER)('localhost', port)
+    with stub:
+      yield servicer_methods, stub, server
+
+
+def _streaming_input_request_iterator(test_pb2):
+  for _ in range(3):
+    request = test_pb2.StreamingInputCallRequest()
+    request.payload.payload_type = test_pb2.COMPRESSABLE
+    request.payload.payload_compressable = 'a'
+    yield request
+
+
+def _streaming_output_request(test_pb2):
+  request = test_pb2.StreamingOutputCallRequest()
+  sizes = [1, 2, 3]
+  request.response_parameters.add(size=sizes[0], interval_us=0)
+  request.response_parameters.add(size=sizes[1], interval_us=0)
+  request.response_parameters.add(size=sizes[2], interval_us=0)
+  return request
+
+
+def _full_duplex_request_iterator(test_pb2):
+  request = test_pb2.StreamingOutputCallRequest()
+  request.response_parameters.add(size=1, interval_us=0)
+  yield request
+  request = test_pb2.StreamingOutputCallRequest()
+  request.response_parameters.add(size=2, interval_us=0)
+  request.response_parameters.add(size=3, interval_us=0)
+  yield request
+
+
+class PythonPluginTest(unittest.TestCase):
+  """Test case for the gRPC Python protoc-plugin.
+
+  While reading these tests, remember that the futures API
+  (`stub.method.async()`) only gives futures for the *non-streaming* responses,
+  else it behaves like its blocking cousin.
+  """
+
+  def setUp(self):
+    # Assume that the appropriate protoc and grpc_python_plugins are on the
+    # path.
+    protoc_command = 'protoc'
+    protoc_plugin_filename = distutils.spawn.find_executable(
+        'grpc_python_plugin')
+    test_proto_filename = pkg_resources.resource_filename(
+        'grpc_protoc_plugin', 'test.proto')
+    if not os.path.isfile(protoc_command):
+      # Assume that if we haven't built protoc that it's on the system.
+      protoc_command = 'protoc'
+
+    # Ensure that the output directory exists.
+    self.outdir = tempfile.mkdtemp()
+
+    # Invoke protoc with the plugin.
+    cmd = [
+        protoc_command,
+        '--plugin=protoc-gen-python-grpc=%s' % protoc_plugin_filename,
+        '-I .',
+        '--python_out=%s' % self.outdir,
+        '--python-grpc_out=%s' % self.outdir,
+        os.path.basename(test_proto_filename),
+    ]
+    subprocess.check_call(' '.join(cmd), shell=True, env=os.environ,
+                          cwd=os.path.dirname(test_proto_filename))
+    sys.path.append(self.outdir)
+
+  def tearDown(self):
+    try:
+      shutil.rmtree(self.outdir)
+    except OSError as exc:
+      if exc.errno != errno.ENOENT:
+        raise
+
+  # TODO(atash): Figure out which of these tests is hanging flakily with small
+  # probability.
+
+  def testImportAttributes(self):
+    # check that we can access the generated module and its members.
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    self.assertIsNotNone(getattr(test_pb2, SERVICER_IDENTIFIER, None))
+    self.assertIsNotNone(getattr(test_pb2, SERVER_IDENTIFIER, None))
+    self.assertIsNotNone(getattr(test_pb2, STUB_IDENTIFIER, None))
+    self.assertIsNotNone(getattr(test_pb2, SERVER_FACTORY_IDENTIFIER, None))
+    self.assertIsNotNone(getattr(test_pb2, STUB_FACTORY_IDENTIFIER, None))
+
+  def testUpDown(self):
+    import test_pb2
+    with _CreateService(
+        test_pb2, NO_DELAY) as (servicer, stub, unused_server):
+      request = test_pb2.SimpleRequest(response_size=13)
+
+  def testUnaryCall(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (methods, stub, unused_server):
+      timeout = 6  # TODO(issue 2039): LONG_TIMEOUT like the other methods.
+      request = test_pb2.SimpleRequest(response_size=13)
+      response = stub.UnaryCall(request, timeout)
+    expected_response = methods.UnaryCall(request, 'not a real RpcContext!')
+    self.assertEqual(expected_response, response)
+
+  def testUnaryCallAsync(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = test_pb2.SimpleRequest(response_size=13)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      # Check that the call does not block waiting for the server to respond.
+      with methods.pause():
+        response_future = stub.UnaryCall.async(request, LONG_TIMEOUT)
+      response = response_future.result()
+    expected_response = methods.UnaryCall(request, 'not a real RpcContext!')
+    self.assertEqual(expected_response, response)
+
+  def testUnaryCallAsyncExpired(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      request = test_pb2.SimpleRequest(response_size=13)
+      with methods.pause():
+        response_future = stub.UnaryCall.async(request, SHORT_TIMEOUT)
+        with self.assertRaises(exceptions.ExpirationError):
+          response_future.result()
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testUnaryCallAsyncCancelled(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = test_pb2.SimpleRequest(response_size=13)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.pause():
+        response_future = stub.UnaryCall.async(request, 1)
+        response_future.cancel()
+        self.assertTrue(response_future.cancelled())
+
+  def testUnaryCallAsyncFailed(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = test_pb2.SimpleRequest(response_size=13)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.fail():
+        response_future = stub.UnaryCall.async(request, LONG_TIMEOUT)
+        self.assertIsNotNone(response_future.exception())
+
+  def testStreamingOutputCall(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = _streaming_output_request(test_pb2)
+    with _CreateService(test_pb2, NO_DELAY) as (methods, stub, unused_server):
+      responses = stub.StreamingOutputCall(request, LONG_TIMEOUT)
+      expected_responses = methods.StreamingOutputCall(
+          request, 'not a real RpcContext!')
+      for expected_response, response in itertools.izip_longest(
+          expected_responses, responses):
+        self.assertEqual(expected_response, response)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testStreamingOutputCallExpired(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = _streaming_output_request(test_pb2)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.pause():
+        responses = stub.StreamingOutputCall(request, SHORT_TIMEOUT)
+        with self.assertRaises(exceptions.ExpirationError):
+          list(responses)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testStreamingOutputCallCancelled(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = _streaming_output_request(test_pb2)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        unused_methods, stub, unused_server):
+      responses = stub.StreamingOutputCall(request, SHORT_TIMEOUT)
+      next(responses)
+      responses.cancel()
+      with self.assertRaises(future.CancelledError):
+        next(responses)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this times out '
+                 'instead of raising the proper error.')
+  def testStreamingOutputCallFailed(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request = _streaming_output_request(test_pb2)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.fail():
+        responses = stub.StreamingOutputCall(request, 1)
+        self.assertIsNotNone(responses)
+        with self.assertRaises(exceptions.ServicerError):
+          next(responses)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testStreamingInputCall(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (methods, stub, unused_server):
+      response = stub.StreamingInputCall(
+          _streaming_input_request_iterator(test_pb2), LONG_TIMEOUT)
+    expected_response = methods.StreamingInputCall(
+        _streaming_input_request_iterator(test_pb2), 'not a real RpcContext!')
+    self.assertEqual(expected_response, response)
+
+  def testStreamingInputCallAsync(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.pause():
+        response_future = stub.StreamingInputCall.async(
+            _streaming_input_request_iterator(test_pb2), LONG_TIMEOUT)
+      response = response_future.result()
+    expected_response = methods.StreamingInputCall(
+        _streaming_input_request_iterator(test_pb2), 'not a real RpcContext!')
+    self.assertEqual(expected_response, response)
+
+  def testStreamingInputCallAsyncExpired(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.pause():
+        response_future = stub.StreamingInputCall.async(
+            _streaming_input_request_iterator(test_pb2), SHORT_TIMEOUT)
+        with self.assertRaises(exceptions.ExpirationError):
+          response_future.result()
+        self.assertIsInstance(
+            response_future.exception(), exceptions.ExpirationError)
+
+  def testStreamingInputCallAsyncCancelled(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.pause():
+        timeout = 6  # TODO(issue 2039): LONG_TIMEOUT like the other methods.
+        response_future = stub.StreamingInputCall.async(
+            _streaming_input_request_iterator(test_pb2), timeout)
+        response_future.cancel()
+        self.assertTrue(response_future.cancelled())
+      with self.assertRaises(future.CancelledError):
+        response_future.result()
+
+  def testStreamingInputCallAsyncFailed(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.fail():
+        response_future = stub.StreamingInputCall.async(
+            _streaming_input_request_iterator(test_pb2), SHORT_TIMEOUT)
+        self.assertIsNotNone(response_future.exception())
+
+  def testFullDuplexCall(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (methods, stub, unused_server):
+      responses = stub.FullDuplexCall(
+          _full_duplex_request_iterator(test_pb2), LONG_TIMEOUT)
+      expected_responses = methods.FullDuplexCall(
+          _full_duplex_request_iterator(test_pb2), 'not a real RpcContext!')
+      for expected_response, response in itertools.izip_longest(
+          expected_responses, responses):
+        self.assertEqual(expected_response, response)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testFullDuplexCallExpired(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request_iterator = _full_duplex_request_iterator(test_pb2)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.pause():
+        responses = stub.FullDuplexCall(request_iterator, SHORT_TIMEOUT)
+        with self.assertRaises(exceptions.ExpirationError):
+          list(responses)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testFullDuplexCallCancelled(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (methods, stub, unused_server):
+      request_iterator = _full_duplex_request_iterator(test_pb2)
+      responses = stub.FullDuplexCall(request_iterator, LONG_TIMEOUT)
+      next(responses)
+      responses.cancel()
+      with self.assertRaises(future.CancelledError):
+        next(responses)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this hangs forever '
+                 'and fix.')
+  def testFullDuplexCallFailed(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    request_iterator = _full_duplex_request_iterator(test_pb2)
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      with methods.fail():
+        responses = stub.FullDuplexCall(request_iterator, LONG_TIMEOUT)
+        self.assertIsNotNone(responses)
+        with self.assertRaises(exceptions.ServicerError):
+          next(responses)
+
+  @unittest.skip('TODO(atash,nathaniel): figure out why this flakily hangs '
+                 'forever and fix.')
+  def testHalfDuplexCall(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    with _CreateService(test_pb2, NO_DELAY) as (
+        methods, stub, unused_server):
+      def half_duplex_request_iterator():
+        request = test_pb2.StreamingOutputCallRequest()
+        request.response_parameters.add(size=1, interval_us=0)
+        yield request
+        request = test_pb2.StreamingOutputCallRequest()
+        request.response_parameters.add(size=2, interval_us=0)
+        request.response_parameters.add(size=3, interval_us=0)
+        yield request
+      responses = stub.HalfDuplexCall(
+          half_duplex_request_iterator(), LONG_TIMEOUT)
+      expected_responses = methods.HalfDuplexCall(
+          half_duplex_request_iterator(), 'not a real RpcContext!')
+      for check in itertools.izip_longest(expected_responses, responses):
+        expected_response, response = check
+        self.assertEqual(expected_response, response)
+
+  def testHalfDuplexCallWedged(self):
+    import test_pb2  # pylint: disable=g-import-not-at-top
+    condition = threading.Condition()
+    wait_cell = [False]
+    @contextlib.contextmanager
+    def wait():  # pylint: disable=invalid-name
+      # Where's Python 3's 'nonlocal' statement when you need it?
+      with condition:
+        wait_cell[0] = True
+      yield
+      with condition:
+        wait_cell[0] = False
+        condition.notify_all()
+    def half_duplex_request_iterator():
+      request = test_pb2.StreamingOutputCallRequest()
+      request.response_parameters.add(size=1, interval_us=0)
+      yield request
+      with condition:
+        while wait_cell[0]:
+          condition.wait()
+    with _CreateService(test_pb2, NO_DELAY) as (methods, stub, unused_server):
+      with wait():
+        responses = stub.HalfDuplexCall(
+            half_duplex_request_iterator(), SHORT_TIMEOUT)
+        # half-duplex waits for the client to send all info
+        with self.assertRaises(exceptions.ExpirationError):
+          next(responses)
+
+
+if __name__ == '__main__':
+  os.chdir(os.path.dirname(sys.argv[0]))
+  unittest.main(verbosity=2)
diff --git a/src/python/grpcio_test/grpc_protoc_plugin/test.proto b/src/python/grpcio_test/grpc_protoc_plugin/test.proto
new file mode 100644
index 0000000000..ed7c6a7b79
--- /dev/null
+++ b/src/python/grpcio_test/grpc_protoc_plugin/test.proto
@@ -0,0 +1,139 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// An integration test service that covers all the method signature permutations
+// of unary/streaming requests/responses.
+// This file is duplicated around the code base. See GitHub issue #526.
+syntax = "proto2";
+
+package grpc.testing;
+
+enum PayloadType {
+  // Compressable text format.
+  COMPRESSABLE= 1;
+
+  // Uncompressable binary format.
+  UNCOMPRESSABLE = 2;
+
+  // Randomly chosen from all other formats defined in this enum.
+  RANDOM = 3;
+}
+
+message Payload {
+  required PayloadType payload_type = 1;
+  oneof payload_body {
+    string payload_compressable = 2;
+    bytes payload_uncompressable = 3;
+  }
+}
+
+message SimpleRequest {
+  // Desired payload type in the response from the server.
+  // If response_type is RANDOM, server randomly chooses one from other formats.
+  optional PayloadType response_type = 1 [default=COMPRESSABLE];
+
+  // Desired payload size in the response from the server.
+  // If response_type is COMPRESSABLE, this denotes the size before compression.
+  optional int32 response_size = 2;
+
+  // Optional input payload sent along with the request.
+  optional Payload payload = 3;
+}
+
+message SimpleResponse {
+  optional Payload payload = 1;
+}
+
+message StreamingInputCallRequest {
+  // Optional input payload sent along with the request.
+  optional Payload payload = 1;
+
+  // Not expecting any payload from the response.
+}
+
+message StreamingInputCallResponse {
+  // Aggregated size of payloads received from the client.
+  optional int32 aggregated_payload_size = 1;
+}
+
+message ResponseParameters {
+  // Desired payload sizes in responses from the server.
+  // If response_type is COMPRESSABLE, this denotes the size before compression.
+  required int32 size = 1;
+
+  // Desired interval between consecutive responses in the response stream in
+  // microseconds.
+  required int32 interval_us = 2;
+}
+
+message StreamingOutputCallRequest {
+  // Desired payload type in the response from the server.
+  // If response_type is RANDOM, the payload from each response in the stream
+  // might be of different types. This is to simulate a mixed type of payload
+  // stream.
+  optional PayloadType response_type = 1 [default=COMPRESSABLE];
+
+  repeated ResponseParameters response_parameters = 2;
+
+  // Optional input payload sent along with the request.
+  optional Payload payload = 3;
+}
+
+message StreamingOutputCallResponse {
+  optional Payload payload = 1;
+}
+
+service TestService {
+  // One request followed by one response.
+  // The server returns the client payload as-is.
+  rpc UnaryCall(SimpleRequest) returns (SimpleResponse);
+
+  // One request followed by a sequence of responses (streamed download).
+  // The server returns the payload with client desired type and sizes.
+  rpc StreamingOutputCall(StreamingOutputCallRequest)
+      returns (stream StreamingOutputCallResponse);
+
+  // A sequence of requests followed by one response (streamed upload).
+  // The server returns the aggregated size of client payload as the result.
+  rpc StreamingInputCall(stream StreamingInputCallRequest)
+      returns (StreamingInputCallResponse);
+
+  // A sequence of requests with each request served by the server immediately.
+  // As one request could lead to multiple responses, this interface
+  // demonstrates the idea of full duplexing.
+  rpc FullDuplexCall(stream StreamingOutputCallRequest)
+      returns (stream StreamingOutputCallResponse);
+
+  // A sequence of requests followed by a sequence of responses.
+  // The server buffers all the client requests and then serves them in order. A
+  // stream of responses are returned to the client when the server starts with
+  // first request.
+  rpc HalfDuplexCall(stream StreamingOutputCallRequest)
+      returns (stream StreamingOutputCallResponse);
+}
diff --git a/src/python/grpcio_test/grpc_test/_adapter/_low_test.py b/src/python/grpcio_test/grpc_test/_adapter/_low_test.py
index 9a8edfad0c..b6583662f3 100644
--- a/src/python/grpcio_test/grpc_test/_adapter/_low_test.py
+++ b/src/python/grpcio_test/grpc_test/_adapter/_low_test.py
@@ -31,11 +31,12 @@ import threading
 import time
 import unittest
 
+from grpc import _grpcio_metadata
 from grpc._adapter import _types
 from grpc._adapter import _low
 
 
-def WaitForEvents(completion_queues, deadline):
+def wait_for_events(completion_queues, deadline):
   """
   Args:
     completion_queues: list of completion queues to wait for events on
@@ -62,6 +63,7 @@ def WaitForEvents(completion_queues, deadline):
     thread.join()
   return results
 
+
 class InsecureServerInsecureClient(unittest.TestCase):
 
   def setUp(self):
@@ -123,16 +125,21 @@ class InsecureServerInsecureClient(unittest.TestCase):
     ], client_call_tag)
     self.assertEquals(_types.CallError.OK, client_start_batch_result)
 
-    client_no_event, request_event, = WaitForEvents([self.client_completion_queue, self.server_completion_queue], time.time() + 2)
+    client_no_event, request_event, = wait_for_events([self.client_completion_queue, self.server_completion_queue], time.time() + 2)
     self.assertEquals(client_no_event, None)
     self.assertEquals(_types.EventType.OP_COMPLETE, request_event.type)
     self.assertIsInstance(request_event.call, _low.Call)
     self.assertIs(server_request_tag, request_event.tag)
     self.assertEquals(1, len(request_event.results))
-    got_initial_metadata = dict(request_event.results[0].initial_metadata)
+    received_initial_metadata = dict(request_event.results[0].initial_metadata)
+    # Check that our metadata were transmitted
     self.assertEquals(
         dict(client_initial_metadata),
-        dict((x, got_initial_metadata[x]) for x in zip(*client_initial_metadata)[0]))
+        dict((x, received_initial_metadata[x]) for x in zip(*client_initial_metadata)[0]))
+    # Check that Python's user agent string is a part of the full user agent
+    # string
+    self.assertIn('Python-gRPC-{}'.format(_grpcio_metadata.__version__),
+                  received_initial_metadata['user-agent'])
     self.assertEquals(METHOD, request_event.call_details.method)
     self.assertEquals(HOST, request_event.call_details.host)
     self.assertLess(abs(DEADLINE - request_event.call_details.deadline), DEADLINE_TOLERANCE)
@@ -150,7 +157,7 @@ class InsecureServerInsecureClient(unittest.TestCase):
     ], server_call_tag)
     self.assertEquals(_types.CallError.OK, server_start_batch_result)
 
-    client_event, server_event, = WaitForEvents([self.client_completion_queue, self.server_completion_queue], time.time() + 1)
+    client_event, server_event, = wait_for_events([self.client_completion_queue, self.server_completion_queue], time.time() + 1)
 
     self.assertEquals(6, len(client_event.results))
     found_client_op_types = set()
diff --git a/src/python/grpcio_test/grpc_test/framework/face/testing/blocking_invocation_inline_service_test_case.py b/src/python/grpcio_test/grpc_test/framework/face/testing/blocking_invocation_inline_service_test_case.py
index 7e1158f96b..251e1eb68e 100644
--- a/src/python/grpcio_test/grpc_test/framework/face/testing/blocking_invocation_inline_service_test_case.py
+++ b/src/python/grpcio_test/grpc_test/framework/face/testing/blocking_invocation_inline_service_test_case.py
@@ -34,15 +34,13 @@ import abc
 import unittest  # pylint: disable=unused-import
 
 from grpc.framework.face import exceptions
+from grpc_test.framework.common import test_constants
 from grpc_test.framework.face.testing import control
 from grpc_test.framework.face.testing import coverage
 from grpc_test.framework.face.testing import digest
 from grpc_test.framework.face.testing import stock_service
 from grpc_test.framework.face.testing import test_case
 
-_TIMEOUT = 3
-_LONG_TIMEOUT = 45
-
 
 class BlockingInvocationInlineServiceTestCase(
     test_case.FaceTestCase, coverage.BlockingCoverage):
@@ -79,7 +77,7 @@ class BlockingInvocationInlineServiceTestCase(
         request = test_messages.request()
 
         response = self.stub.blocking_value_in_value_out(
-            name, request, _LONG_TIMEOUT)
+            name, request, test_constants.LONG_TIMEOUT)
 
         test_messages.verify(request, response, self)
 
@@ -90,7 +88,7 @@ class BlockingInvocationInlineServiceTestCase(
         request = test_messages.request()
 
         response_iterator = self.stub.inline_value_in_stream_out(
-            name, request, _LONG_TIMEOUT)
+            name, request, test_constants.LONG_TIMEOUT)
         responses = list(response_iterator)
 
         test_messages.verify(request, responses, self)
@@ -102,7 +100,7 @@ class BlockingInvocationInlineServiceTestCase(
         requests = test_messages.requests()
 
         response = self.stub.blocking_stream_in_value_out(
-            name, iter(requests), _LONG_TIMEOUT)
+            name, iter(requests), test_constants.LONG_TIMEOUT)
 
         test_messages.verify(requests, response, self)
 
@@ -113,7 +111,7 @@ class BlockingInvocationInlineServiceTestCase(
         requests = test_messages.requests()
 
         response_iterator = self.stub.inline_stream_in_stream_out(
-            name, iter(requests), _LONG_TIMEOUT)
+            name, iter(requests), test_constants.LONG_TIMEOUT)
         responses = list(response_iterator)
 
         test_messages.verify(requests, responses, self)
@@ -126,12 +124,12 @@ class BlockingInvocationInlineServiceTestCase(
         second_request = test_messages.request()
 
         first_response = self.stub.blocking_value_in_value_out(
-            name, first_request, _TIMEOUT)
+            name, first_request, test_constants.SHORT_TIMEOUT)
 
         test_messages.verify(first_request, first_response, self)
 
         second_response = self.stub.blocking_value_in_value_out(
-            name, second_request, _TIMEOUT)
+            name, second_request, test_constants.SHORT_TIMEOUT)
 
         test_messages.verify(second_request, second_response, self)
 
@@ -144,7 +142,7 @@ class BlockingInvocationInlineServiceTestCase(
         with self.control.pause(), self.assertRaises(
             exceptions.ExpirationError):
           multi_callable = self.stub.unary_unary_multi_callable(name)
-          multi_callable(request, _TIMEOUT)
+          multi_callable(request, test_constants.SHORT_TIMEOUT)
 
   def testExpiredUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
@@ -155,7 +153,7 @@ class BlockingInvocationInlineServiceTestCase(
         with self.control.pause(), self.assertRaises(
             exceptions.ExpirationError):
           response_iterator = self.stub.inline_value_in_stream_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
           list(response_iterator)
 
   def testExpiredStreamRequestUnaryResponse(self):
@@ -167,7 +165,7 @@ class BlockingInvocationInlineServiceTestCase(
         with self.control.pause(), self.assertRaises(
             exceptions.ExpirationError):
           multi_callable = self.stub.stream_unary_multi_callable(name)
-          multi_callable(iter(requests), _TIMEOUT)
+          multi_callable(iter(requests), test_constants.SHORT_TIMEOUT)
 
   def testExpiredStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
@@ -178,7 +176,7 @@ class BlockingInvocationInlineServiceTestCase(
         with self.control.pause(), self.assertRaises(
             exceptions.ExpirationError):
           response_iterator = self.stub.inline_stream_in_stream_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
           list(response_iterator)
 
   def testFailedUnaryRequestUnaryResponse(self):
@@ -188,7 +186,8 @@ class BlockingInvocationInlineServiceTestCase(
         request = test_messages.request()
 
         with self.control.fail(), self.assertRaises(exceptions.ServicerError):
-          self.stub.blocking_value_in_value_out(name, request, _TIMEOUT)
+          self.stub.blocking_value_in_value_out(name, request,
+                                                test_constants.SHORT_TIMEOUT)
 
   def testFailedUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
@@ -198,7 +197,7 @@ class BlockingInvocationInlineServiceTestCase(
 
         with self.control.fail(), self.assertRaises(exceptions.ServicerError):
           response_iterator = self.stub.inline_value_in_stream_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
           list(response_iterator)
 
   def testFailedStreamRequestUnaryResponse(self):
@@ -208,7 +207,8 @@ class BlockingInvocationInlineServiceTestCase(
         requests = test_messages.requests()
 
         with self.control.fail(), self.assertRaises(exceptions.ServicerError):
-          self.stub.blocking_stream_in_value_out(name, iter(requests), _TIMEOUT)
+          self.stub.blocking_stream_in_value_out(name, iter(requests),
+                                                 test_constants.SHORT_TIMEOUT)
 
   def testFailedStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
@@ -218,5 +218,5 @@ class BlockingInvocationInlineServiceTestCase(
 
         with self.control.fail(), self.assertRaises(exceptions.ServicerError):
           response_iterator = self.stub.inline_stream_in_stream_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
           list(response_iterator)
diff --git a/src/python/grpcio_test/grpc_test/framework/face/testing/event_invocation_synchronous_event_service_test_case.py b/src/python/grpcio_test/grpc_test/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
index 18eed53d6e..9df77678eb 100644
--- a/src/python/grpcio_test/grpc_test/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
+++ b/src/python/grpcio_test/grpc_test/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
@@ -33,6 +33,7 @@ import abc
 import unittest
 
 from grpc.framework.face import interfaces
+from grpc_test.framework.common import test_constants
 from grpc_test.framework.face.testing import callback as testing_callback
 from grpc_test.framework.face.testing import control
 from grpc_test.framework.face.testing import coverage
@@ -40,8 +41,6 @@ from grpc_test.framework.face.testing import digest
 from grpc_test.framework.face.testing import stock_service
 from grpc_test.framework.face.testing import test_case
 
-_TIMEOUT = 3
-
 
 class EventInvocationSynchronousEventServiceTestCase(
     test_case.FaceTestCase, coverage.FullCoverage):
@@ -79,7 +78,8 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         self.stub.event_value_in_value_out(
-            name, request, callback.complete, callback.abort, _TIMEOUT)
+            name, request, callback.complete, callback.abort,
+            test_constants.SHORT_TIMEOUT)
         callback.block_until_terminated()
         response = callback.response()
 
@@ -93,7 +93,8 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         self.stub.event_value_in_stream_out(
-            name, request, callback, callback.abort, _TIMEOUT)
+            name, request, callback, callback.abort,
+            test_constants.SHORT_TIMEOUT)
         callback.block_until_terminated()
         responses = callback.responses()
 
@@ -107,7 +108,8 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         unused_call, request_consumer = self.stub.event_stream_in_value_out(
-            name, callback.complete, callback.abort, _TIMEOUT)
+            name, callback.complete, callback.abort,
+            test_constants.SHORT_TIMEOUT)
         for request in requests:
           request_consumer.consume(request)
         request_consumer.terminate()
@@ -124,7 +126,7 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         unused_call, request_consumer = self.stub.event_stream_in_stream_out(
-            name, callback, callback.abort, _TIMEOUT)
+            name, callback, callback.abort, test_constants.SHORT_TIMEOUT)
         for request in requests:
           request_consumer.consume(request)
         request_consumer.terminate()
@@ -147,11 +149,11 @@ class EventInvocationSynchronousEventServiceTestCase(
           first_callback.complete(first_response)
           self.stub.event_value_in_value_out(
               name, second_request, second_callback.complete,
-              second_callback.abort, _TIMEOUT)
+              second_callback.abort, test_constants.SHORT_TIMEOUT)
 
         self.stub.event_value_in_value_out(
             name, first_request, make_second_invocation, first_callback.abort,
-            _TIMEOUT)
+           test_constants.SHORT_TIMEOUT)
         second_callback.block_until_terminated()
 
         first_response = first_callback.response()
@@ -168,7 +170,8 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.pause():
           self.stub.event_value_in_value_out(
-              name, request, callback.complete, callback.abort, _TIMEOUT)
+              name, request, callback.complete, callback.abort,
+              test_constants.SHORT_TIMEOUT)
           callback.block_until_terminated()
 
         self.assertEqual(interfaces.Abortion.EXPIRED, callback.abortion())
@@ -182,7 +185,8 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.pause():
           self.stub.event_value_in_stream_out(
-              name, request, callback, callback.abort, _TIMEOUT)
+              name, request, callback, callback.abort,
+              test_constants.SHORT_TIMEOUT)
           callback.block_until_terminated()
 
         self.assertEqual(interfaces.Abortion.EXPIRED, callback.abortion())
@@ -194,7 +198,8 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         self.stub.event_stream_in_value_out(
-            name, callback.complete, callback.abort, _TIMEOUT)
+            name, callback.complete, callback.abort,
+            test_constants.SHORT_TIMEOUT)
         callback.block_until_terminated()
 
         self.assertEqual(interfaces.Abortion.EXPIRED, callback.abortion())
@@ -207,7 +212,7 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         unused_call, request_consumer = self.stub.event_stream_in_stream_out(
-            name, callback, callback.abort, _TIMEOUT)
+            name, callback, callback.abort, test_constants.SHORT_TIMEOUT)
         for request in requests:
           request_consumer.consume(request)
         callback.block_until_terminated()
@@ -223,10 +228,12 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.fail():
           self.stub.event_value_in_value_out(
-              name, request, callback.complete, callback.abort, _TIMEOUT)
+              name, request, callback.complete, callback.abort,
+              test_constants.SHORT_TIMEOUT)
           callback.block_until_terminated()
 
-        self.assertEqual(interfaces.Abortion.SERVICER_FAILURE, callback.abortion())
+        self.assertEqual(interfaces.Abortion.SERVICER_FAILURE,
+                         callback.abortion())
 
   def testFailedUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
@@ -237,10 +244,12 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.fail():
           self.stub.event_value_in_stream_out(
-              name, request, callback, callback.abort, _TIMEOUT)
+              name, request, callback, callback.abort,
+              test_constants.SHORT_TIMEOUT)
           callback.block_until_terminated()
 
-        self.assertEqual(interfaces.Abortion.SERVICER_FAILURE, callback.abortion())
+        self.assertEqual(interfaces.Abortion.SERVICER_FAILURE,
+                         callback.abortion())
 
   def testFailedStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
@@ -251,13 +260,15 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.fail():
           unused_call, request_consumer = self.stub.event_stream_in_value_out(
-              name, callback.complete, callback.abort, _TIMEOUT)
+              name, callback.complete, callback.abort,
+              test_constants.SHORT_TIMEOUT)
           for request in requests:
             request_consumer.consume(request)
           request_consumer.terminate()
           callback.block_until_terminated()
 
-        self.assertEqual(interfaces.Abortion.SERVICER_FAILURE, callback.abortion())
+        self.assertEqual(interfaces.Abortion.SERVICER_FAILURE,
+                         callback.abortion())
 
   def testFailedStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
@@ -268,7 +279,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.fail():
           unused_call, request_consumer = self.stub.event_stream_in_stream_out(
-              name, callback, callback.abort, _TIMEOUT)
+              name, callback, callback.abort, test_constants.SHORT_TIMEOUT)
           for request in requests:
             request_consumer.consume(request)
           request_consumer.terminate()
@@ -287,10 +298,10 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         self.stub.event_value_in_value_out(
             name, first_request, first_callback.complete, first_callback.abort,
-            _TIMEOUT)
+           test_constants.SHORT_TIMEOUT)
         self.stub.event_value_in_value_out(
             name, second_request, second_callback.complete,
-            second_callback.abort, _TIMEOUT)
+            second_callback.abort, test_constants.SHORT_TIMEOUT)
         first_callback.block_until_terminated()
         second_callback.block_until_terminated()
 
@@ -312,7 +323,8 @@ class EventInvocationSynchronousEventServiceTestCase(
 
         with self.control.pause():
           call = self.stub.event_value_in_value_out(
-              name, request, callback.complete, callback.abort, _TIMEOUT)
+              name, request, callback.complete, callback.abort,
+              test_constants.SHORT_TIMEOUT)
           call.cancel()
           callback.block_until_terminated()
 
@@ -326,7 +338,8 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         call = self.stub.event_value_in_stream_out(
-            name, request, callback, callback.abort, _TIMEOUT)
+            name, request, callback, callback.abort,
+            test_constants.SHORT_TIMEOUT)
         call.cancel()
         callback.block_until_terminated()
 
@@ -340,7 +353,8 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         call, request_consumer = self.stub.event_stream_in_value_out(
-            name, callback.complete, callback.abort, _TIMEOUT)
+            name, callback.complete, callback.abort,
+            test_constants.SHORT_TIMEOUT)
         for request in requests:
           request_consumer.consume(request)
         call.cancel()
@@ -355,7 +369,7 @@ class EventInvocationSynchronousEventServiceTestCase(
         callback = testing_callback.Callback()
 
         call, unused_request_consumer = self.stub.event_stream_in_stream_out(
-            name, callback, callback.abort, _TIMEOUT)
+            name, callback, callback.abort, test_constants.SHORT_TIMEOUT)
         call.cancel()
         callback.block_until_terminated()
 
diff --git a/src/python/grpcio_test/grpc_test/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py b/src/python/grpcio_test/grpc_test/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
index 3b42914342..70d86a0422 100644
--- a/src/python/grpcio_test/grpc_test/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
+++ b/src/python/grpcio_test/grpc_test/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
@@ -37,13 +37,13 @@ import unittest
 from grpc.framework.face import exceptions
 from grpc.framework.foundation import future
 from grpc.framework.foundation import logging_pool
+from grpc_test.framework.common import test_constants
 from grpc_test.framework.face.testing import control
 from grpc_test.framework.face.testing import coverage
 from grpc_test.framework.face.testing import digest
 from grpc_test.framework.face.testing import stock_service
 from grpc_test.framework.face.testing import test_case
 
-_TIMEOUT = 3
 _MAXIMUM_POOL_SIZE = 10
 
 
@@ -110,7 +110,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         request = test_messages.request()
 
         response_future = self.stub.future_value_in_value_out(
-            name, request, _TIMEOUT)
+            name, request, test_constants.SHORT_TIMEOUT)
         response = response_future.result()
 
         test_messages.verify(request, response, self)
@@ -122,7 +122,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         request = test_messages.request()
 
         response_iterator = self.stub.inline_value_in_stream_out(
-            name, request, _TIMEOUT)
+            name, request, test_constants.SHORT_TIMEOUT)
         responses = list(response_iterator)
 
         test_messages.verify(request, responses, self)
@@ -138,7 +138,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         # returned to calling code before the iterator yields any requests.
         with request_iterator.pause():
           response_future = self.stub.future_stream_in_value_out(
-              name, request_iterator, _TIMEOUT)
+              name, request_iterator, test_constants.SHORT_TIMEOUT)
         response = response_future.result()
 
         test_messages.verify(requests, response, self)
@@ -154,7 +154,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         # returned to calling code before the iterator yields any requests.
         with request_iterator.pause():
           response_iterator = self.stub.inline_stream_in_stream_out(
-              name, request_iterator, _TIMEOUT)
+              name, request_iterator, test_constants.SHORT_TIMEOUT)
         responses = list(response_iterator)
 
         test_messages.verify(requests, responses, self)
@@ -167,13 +167,13 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         second_request = test_messages.request()
 
         first_response_future = self.stub.future_value_in_value_out(
-            name, first_request, _TIMEOUT)
+            name, first_request, test_constants.SHORT_TIMEOUT)
         first_response = first_response_future.result()
 
         test_messages.verify(first_request, first_response, self)
 
         second_response_future = self.stub.future_value_in_value_out(
-            name, second_request, _TIMEOUT)
+            name, second_request, test_constants.SHORT_TIMEOUT)
         second_response = second_response_future.result()
 
         test_messages.verify(second_request, second_response, self)
@@ -186,7 +186,8 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           multi_callable = self.stub.unary_unary_multi_callable(name)
-          response_future = multi_callable.future(request, _TIMEOUT)
+          response_future = multi_callable.future(request,
+                                                  test_constants.SHORT_TIMEOUT)
           self.assertIsInstance(
               response_future.exception(), exceptions.ExpirationError)
           with self.assertRaises(exceptions.ExpirationError):
@@ -200,7 +201,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           response_iterator = self.stub.inline_value_in_stream_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
           with self.assertRaises(exceptions.ExpirationError):
             list(response_iterator)
 
@@ -212,7 +213,8 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           multi_callable = self.stub.stream_unary_multi_callable(name)
-          response_future = multi_callable.future(iter(requests), _TIMEOUT)
+          response_future = multi_callable.future(iter(requests),
+                                                  test_constants.SHORT_TIMEOUT)
           self.assertIsInstance(
               response_future.exception(), exceptions.ExpirationError)
           with self.assertRaises(exceptions.ExpirationError):
@@ -226,7 +228,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           response_iterator = self.stub.inline_stream_in_stream_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
           with self.assertRaises(exceptions.ExpirationError):
             list(response_iterator)
 
@@ -238,7 +240,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.fail():
           response_future = self.stub.future_value_in_value_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
 
           # Because the servicer fails outside of the thread from which the
           # servicer-side runtime called into it its failure is
@@ -261,7 +263,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         # expiration of the RPC.
         with self.control.fail(), self.assertRaises(exceptions.ExpirationError):
           response_iterator = self.stub.inline_value_in_stream_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
           list(response_iterator)
 
   def testFailedStreamRequestUnaryResponse(self):
@@ -272,7 +274,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.fail():
           response_future = self.stub.future_stream_in_value_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
 
           # Because the servicer fails outside of the thread from which the
           # servicer-side runtime called into it its failure is
@@ -295,7 +297,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         # expiration of the RPC.
         with self.control.fail(), self.assertRaises(exceptions.ExpirationError):
           response_iterator = self.stub.inline_stream_in_stream_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
           list(response_iterator)
 
   def testParallelInvocations(self):
@@ -305,10 +307,11 @@ class FutureInvocationAsynchronousEventServiceTestCase(
         first_request = test_messages.request()
         second_request = test_messages.request()
 
+        # TODO(bug 2039): use LONG_TIMEOUT instead
         first_response_future = self.stub.future_value_in_value_out(
-            name, first_request, _TIMEOUT)
+            name, first_request, test_constants.SHORT_TIMEOUT)
         second_response_future = self.stub.future_value_in_value_out(
-            name, second_request, _TIMEOUT)
+            name, second_request, test_constants.SHORT_TIMEOUT)
         first_response = first_response_future.result()
         second_response = second_response_future.result()
 
@@ -327,7 +330,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           response_future = self.stub.future_value_in_value_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
           cancel_method_return_value = response_future.cancel()
 
         self.assertFalse(cancel_method_return_value)
@@ -341,7 +344,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           response_iterator = self.stub.inline_value_in_stream_out(
-              name, request, _TIMEOUT)
+              name, request, test_constants.SHORT_TIMEOUT)
           response_iterator.cancel()
 
         with self.assertRaises(future.CancelledError):
@@ -355,7 +358,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           response_future = self.stub.future_stream_in_value_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
           cancel_method_return_value = response_future.cancel()
 
         self.assertFalse(cancel_method_return_value)
@@ -369,7 +372,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
         with self.control.pause():
           response_iterator = self.stub.inline_stream_in_stream_out(
-              name, iter(requests), _TIMEOUT)
+              name, iter(requests), test_constants.SHORT_TIMEOUT)
           response_iterator.cancel()
 
         with self.assertRaises(future.CancelledError):
diff --git a/src/python/grpcio_test/setup.py b/src/python/grpcio_test/setup.py
index 925c32720f..a6203cae2d 100644
--- a/src/python/grpcio_test/setup.py
+++ b/src/python/grpcio_test/setup.py
@@ -48,8 +48,13 @@ _PACKAGE_DIRECTORIES = {
 
 _PACKAGE_DATA = {
     'grpc_interop': [
-        'credentials/ca.pem', 'credentials/server1.key',
-        'credentials/server1.pem',]
+        'credentials/ca.pem',
+        'credentials/server1.key',
+        'credentials/server1.pem',
+    ],
+    'grpc_protoc_plugin': [
+        'test.proto',
+    ],
 }
 
 _SETUP_REQUIRES = (
@@ -75,5 +80,5 @@ setuptools.setup(
     package_data=_PACKAGE_DATA,
     install_requires=_INSTALL_REQUIRES + _SETUP_REQUIRES,
     setup_requires=_SETUP_REQUIRES,
-    cmdclass=_COMMAND_CLASS
+    cmdclass=_COMMAND_CLASS,
 )
diff --git a/src/ruby/ext/grpc/rb_call.c b/src/ruby/ext/grpc/rb_call.c
index a7607a83a3..88659da535 100644
--- a/src/ruby/ext/grpc/rb_call.c
+++ b/src/ruby/ext/grpc/rb_call.c
@@ -179,6 +179,19 @@ static VALUE grpc_rb_call_cancel(VALUE self) {
   return Qnil;
 }
 
+/* Called to obtain the peer that this call is connected to. */
+static VALUE grpc_rb_call_get_peer(VALUE self) {
+  VALUE res = Qnil;
+  grpc_call *call = NULL;
+  char *peer = NULL;
+  TypedData_Get_Struct(self, grpc_call, &grpc_call_data_type, call);
+  peer = grpc_call_get_peer(call);
+  res = rb_str_new2(peer);
+  gpr_free(peer);
+
+  return res;
+}
+
 /*
   call-seq:
   status = call.status
@@ -720,6 +733,7 @@ void Init_grpc_call() {
   /* Add ruby analogues of the Call methods. */
   rb_define_method(grpc_rb_cCall, "run_batch", grpc_rb_call_run_batch, 4);
   rb_define_method(grpc_rb_cCall, "cancel", grpc_rb_call_cancel, 0);
+  rb_define_method(grpc_rb_cCall, "peer", grpc_rb_call_get_peer, 0);
   rb_define_method(grpc_rb_cCall, "status", grpc_rb_call_get_status, 0);
   rb_define_method(grpc_rb_cCall, "status=", grpc_rb_call_set_status, 1);
   rb_define_method(grpc_rb_cCall, "metadata", grpc_rb_call_get_metadata, 0);
diff --git a/src/ruby/ext/grpc/rb_channel.c b/src/ruby/ext/grpc/rb_channel.c
index a0663607c2..ac591f1563 100644
--- a/src/ruby/ext/grpc/rb_channel.c
+++ b/src/ruby/ext/grpc/rb_channel.c
@@ -37,6 +37,7 @@
 
 #include <grpc/grpc.h>
 #include <grpc/grpc_security.h>
+#include <grpc/support/alloc.h>
 #include "rb_grpc.h"
 #include "rb_call.h"
 #include "rb_channel_args.h"
@@ -202,7 +203,10 @@ static VALUE grpc_rb_channel_create_call(VALUE self, VALUE cqueue, VALUE method,
   grpc_channel *ch = NULL;
   grpc_completion_queue *cq = NULL;
   char *method_chars = StringValueCStr(method);
-  char *host_chars = StringValueCStr(host);
+  char *host_chars = NULL;
+  if (host != Qnil) {
+    host_chars = StringValueCStr(host);
+  }
 
   cq = grpc_rb_get_wrapped_completion_queue(cqueue);
   TypedData_Get_Struct(self, grpc_rb_channel, &grpc_channel_data_type, wrapper);
@@ -249,6 +253,21 @@ static VALUE grpc_rb_channel_destroy(VALUE self) {
   return Qnil;
 }
 
+
+/* Called to obtain the target that this channel accesses. */
+static VALUE grpc_rb_channel_get_target(VALUE self) {
+  grpc_rb_channel *wrapper = NULL;
+  VALUE res = Qnil;
+  char* target = NULL;
+
+  TypedData_Get_Struct(self, grpc_rb_channel, &grpc_channel_data_type, wrapper);
+  target = grpc_channel_get_target(wrapper->wrapped);
+  res = rb_str_new2(target);
+  gpr_free(target);
+
+  return res;
+}
+
 void Init_grpc_channel() {
   grpc_rb_cChannelArgs = rb_define_class("TmpChannelArgs", rb_cObject);
   grpc_rb_cChannel =
@@ -265,6 +284,7 @@ void Init_grpc_channel() {
   /* Add ruby analogues of the Channel methods. */
   rb_define_method(grpc_rb_cChannel, "create_call",
                    grpc_rb_channel_create_call, 4);
+  rb_define_method(grpc_rb_cChannel, "target", grpc_rb_channel_get_target, 0);
   rb_define_method(grpc_rb_cChannel, "destroy", grpc_rb_channel_destroy, 0);
   rb_define_alias(grpc_rb_cChannel, "close", "destroy");
 
diff --git a/src/ruby/grpc.gemspec b/src/ruby/grpc.gemspec
index dd4e27df51..45f31329e9 100755
--- a/src/ruby/grpc.gemspec
+++ b/src/ruby/grpc.gemspec
@@ -16,12 +16,15 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 2.0.0'
   s.requirements << 'libgrpc ~> 0.10.0 needs to be installed'
 
-  s.files         = `git ls-files`.split("\n")
-  s.test_files    = `git ls-files -- spec/*`.split("\n")
-  s.executables   = `git ls-files -- bin/*.rb`.split("\n").map do |f|
-    File.basename(f)
+  s.files = %w( Rakefile )
+  s.files += Dir.glob('lib/**/*')
+  s.files += Dir.glob('ext/**/*')
+  s.files += Dir.glob('bin/**/*')
+  s.test_files = Dir.glob('spec/**/*')
+  %w(math noproto).each do |b|
+    s.executables += [ "#{b}_client.rb", "#{b}_server.rb" ]
   end
-  s.require_paths = ['lib']
+  s.require_paths = %w( bin lib )
   s.platform      = Gem::Platform::RUBY
 
   s.add_dependency 'google-protobuf', '~> 3.0.0alpha.1.1'
diff --git a/src/ruby/lib/grpc/generic/client_stub.rb b/src/ruby/lib/grpc/generic/client_stub.rb
index 7b2c04aa22..a2f1ec612d 100644
--- a/src/ruby/lib/grpc/generic/client_stub.rb
+++ b/src/ruby/lib/grpc/generic/client_stub.rb
@@ -28,6 +28,7 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 require 'grpc/generic/active_call'
+require 'grpc/version'
 
 # GRPC contains the General RPC module.
 module GRPC
@@ -36,8 +37,8 @@ module GRPC
     include Core::StatusCodes
     include Core::TimeConsts
 
-    # Default timeout is 5 seconds.
-    DEFAULT_TIMEOUT = 5
+    # Default timeout is infinity.
+    DEFAULT_TIMEOUT = INFINITE_FUTURE
 
     # setup_channel is used by #initialize to constuct a channel from its
     # arguments.
@@ -46,6 +47,7 @@ module GRPC
         fail(TypeError, '!Channel') unless alt_chan.is_a?(Core::Channel)
         return alt_chan
       end
+      kw['grpc.primary_user_agent'] = "grpc-ruby/#{VERSION}"
       return Core::Channel.new(host, kw) if creds.nil?
       fail(TypeError, '!Credentials') unless creds.is_a?(Core::Credentials)
       Core::Channel.new(host, kw, creds)
@@ -408,7 +410,7 @@ module GRPC
     # @param timeout [TimeConst]
     def new_active_call(method, marshal, unmarshal, timeout = nil)
       deadline = from_relative_time(timeout.nil? ? @timeout : timeout)
-      call = @ch.create_call(@queue, method, @host, deadline)
+      call = @ch.create_call(@queue, method, nil, deadline)
       ActiveCall.new(call, @queue, marshal, unmarshal, deadline, started: false)
     end
   end
diff --git a/src/ruby/spec/call_spec.rb b/src/ruby/spec/call_spec.rb
index 4977c10a7e..36a442faed 100644
--- a/src/ruby/spec/call_spec.rb
+++ b/src/ruby/spec/call_spec.rb
@@ -137,7 +137,7 @@ describe GRPC::Core::Call do
   end
 
   def make_test_call
-    @ch.create_call(client_queue, 'dummy_method', 'dummy_host', deadline)
+    @ch.create_call(client_queue, 'dummy_method', nil, deadline)
   end
 
   def deadline
diff --git a/src/ruby/spec/channel_spec.rb b/src/ruby/spec/channel_spec.rb
index d471ff5db6..9081f0e20c 100644
--- a/src/ruby/spec/channel_spec.rb
+++ b/src/ruby/spec/channel_spec.rb
@@ -117,7 +117,7 @@ describe GRPC::Core::Channel do
       deadline = Time.now + 5
 
       blk = proc do
-        ch.create_call(cq, 'dummy_method', 'dummy_host', deadline)
+        ch.create_call(cq, 'dummy_method', nil, deadline)
       end
       expect(&blk).to_not raise_error
     end
@@ -128,7 +128,7 @@ describe GRPC::Core::Channel do
 
       deadline = Time.now + 5
       blk = proc do
-        ch.create_call(cq, 'dummy_method', 'dummy_host', deadline)
+        ch.create_call(cq, 'dummy_method', nil, deadline)
       end
       expect(&blk).to raise_error(RuntimeError)
     end
diff --git a/src/ruby/spec/client_server_spec.rb b/src/ruby/spec/client_server_spec.rb
index 0e85441209..57c9a8de9b 100644
--- a/src/ruby/spec/client_server_spec.rb
+++ b/src/ruby/spec/client_server_spec.rb
@@ -61,7 +61,7 @@ shared_context 'setup: tags' do
   end
 
   def new_client_call
-    @ch.create_call(@client_queue, '/method', 'foo.test.google.fr', deadline)
+    @ch.create_call(@client_queue, '/method', nil, deadline)
   end
 end
 
@@ -69,6 +69,23 @@ shared_examples 'basic GRPC message delivery is OK' do
   include GRPC::Core
   include_context 'setup: tags'
 
+  context 'the test channel' do
+    it 'should have a target' do
+      expect(@ch.target).to be_a(String)
+    end
+  end
+
+  context 'a client call' do
+    it 'should have a peer' do
+      expect(new_client_call.peer).to be_a(String)
+    end
+  end
+
+  it 'calls have peer info' do
+    call = new_client_call
+    expect(call.peer).to be_a(String)
+  end
+
   it 'servers receive requests from clients and can respond' do
     call = new_client_call
     server_call = nil
diff --git a/src/ruby/spec/generic/active_call_spec.rb b/src/ruby/spec/generic/active_call_spec.rb
index bc3bee3d44..424b2dbdeb 100644
--- a/src/ruby/spec/generic/active_call_spec.rb
+++ b/src/ruby/spec/generic/active_call_spec.rb
@@ -338,7 +338,7 @@ describe GRPC::ActiveCall do
   end
 
   def make_test_call
-    @ch.create_call(@client_queue, '/method', 'a.dummy.host', deadline)
+    @ch.create_call(@client_queue, '/method', nil, deadline)
   end
 
   def deadline