Merge github.com:grpc/grpc into e2efuzz

97 files changed, 2227 insertions, 704 deletions

diff --git a/src/compiler/csharp_generator.cc b/src/compiler/csharp_generator.cc
index 5a8746df8d..69e2738d53 100644
--- a/src/compiler/csharp_generator.cc
+++ b/src/compiler/csharp_generator.cc
@@ -81,6 +81,10 @@ std::string GetServerInterfaceName(const ServiceDescriptor* service) {
   return "I" + service->name();
 }
 
+std::string GetServerClassName(const ServiceDescriptor* service) {
+  return service->name() + "Base";
+}
+
 std::string GetCSharpMethodType(MethodType method_type) {
   switch (method_type) {
     case METHODTYPE_NO_STREAMING:
@@ -108,10 +112,14 @@ std::string GetMethodFieldName(const MethodDescriptor *method) {
   return "__Method_" + method->name();
 }
 
-std::string GetMethodRequestParamMaybe(const MethodDescriptor *method) {
+std::string GetMethodRequestParamMaybe(const MethodDescriptor *method,
+                                       bool invocation_param=false) {
   if (method->client_streaming()) {
     return "";
   }
+  if (invocation_param) {
+    return "request, ";
+  }
   return GetClassName(method->input_type()) + " request, ";
 }
 
@@ -242,6 +250,8 @@ void GenerateServiceDescriptorProperty(Printer* out, const ServiceDescriptor *se
 
 void GenerateClientInterface(Printer* out, const ServiceDescriptor *service) {
   out->Print("// client interface\n");
+  out->Print("[System.Obsolete(\"Client side interfaced will be removed "
+             "in the next release. Use client class directly.\")]\n");
   out->Print("public interface $name$\n", "name",
              GetClientInterfaceName(service));
   out->Print("{\n");
@@ -290,6 +300,8 @@ void GenerateClientInterface(Printer* out, const ServiceDescriptor *service) {
 
 void GenerateServerInterface(Printer* out, const ServiceDescriptor *service) {
   out->Print("// server-side interface\n");
+  out->Print("[System.Obsolete(\"Service implementations should inherit"
+      " from the generated abstract base class instead.\")]\n");
   out->Print("public interface $name$\n", "name",
              GetServerInterfaceName(service));
   out->Print("{\n");
@@ -309,21 +321,64 @@ void GenerateServerInterface(Printer* out, const ServiceDescriptor *service) {
   out->Print("\n");
 }
 
+void GenerateServerClass(Printer* out, const ServiceDescriptor *service) {
+  out->Print("// server-side abstract class\n");
+  out->Print("public abstract class $name$\n", "name",
+             GetServerClassName(service));
+  out->Print("{\n");
+  out->Indent();
+  for (int i = 0; i < service->method_count(); i++) {
+    const MethodDescriptor *method = service->method(i);
+    out->Print(
+        "public virtual $returntype$ $methodname$($request$$response_stream_maybe$, "
+        "ServerCallContext context)\n",
+        "methodname", method->name(), "returntype",
+        GetMethodReturnTypeServer(method), "request",
+        GetMethodRequestParamServer(method), "response_stream_maybe",
+        GetMethodResponseStreamMaybe(method));
+    out->Print("{\n");
+    out->Indent();
+    out->Print("throw new RpcException("
+               "new Status(StatusCode.Unimplemented, \"\"));\n");
+    out->Outdent();
+    out->Print("}\n\n");
+  }
+  out->Outdent();
+  out->Print("}\n");
+  out->Print("\n");
+}
+
 void GenerateClientStub(Printer* out, const ServiceDescriptor *service) {
   out->Print("// client stub\n");
   out->Print(
-      "public class $name$ : ClientBase, $interface$\n",
-      "name", GetClientClassName(service), "interface",
-      GetClientInterfaceName(service));
+      "public class $name$ : ClientBase<$name$>, $interface$\n",
+      "name", GetClientClassName(service),
+      "interface", GetClientInterfaceName(service));
   out->Print("{\n");
   out->Indent();
 
   // constructors
-  out->Print(
-      "public $name$(Channel channel) : base(channel)\n",
-      "name", GetClientClassName(service));
+  out->Print("public $name$(Channel channel) : base(channel)\n",
+             "name", GetClientClassName(service));
+  out->Print("{\n");
+  out->Print("}\n");
+  out->Print("public $name$(CallInvoker callInvoker) : base(callInvoker)\n",
+             "name", GetClientClassName(service));
   out->Print("{\n");
   out->Print("}\n");
+  out->Print("///<summary>Protected parameterless constructor to allow creation"
+             " of test doubles.</summary>\n");
+  out->Print("protected $name$() : base()\n",
+             "name", GetClientClassName(service));
+  out->Print("{\n");
+  out->Print("}\n");
+  out->Print("///<summary>Protected constructor to allow creation of configured"
+             " clients.</summary>\n");
+  out->Print("protected $name$(ClientBaseConfiguration configuration)"
+             " : base(configuration)\n",
+             "name", GetClientClassName(service));
+  out->Print("{\n");
+  out->Print("}\n\n");
 
   for (int i = 0; i < service->method_count(); i++) {
     const MethodDescriptor *method = service->method(i);
@@ -331,30 +386,26 @@ void GenerateClientStub(Printer* out, const ServiceDescriptor *service) {
 
     if (method_type == METHODTYPE_NO_STREAMING) {
       // unary calls have an extra synchronous stub method
-      out->Print(
-          "public $response$ $methodname$($request$ request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))\n",
+      out->Print("public virtual $response$ $methodname$($request$ request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))\n",
           "methodname", method->name(), "request",
           GetClassName(method->input_type()), "response",
           GetClassName(method->output_type()));
       out->Print("{\n");
       out->Indent();
-      out->Print("var call = CreateCall($methodfield$, new CallOptions(headers, deadline, cancellationToken));\n",
-                 "methodfield", GetMethodFieldName(method));
-      out->Print("return Calls.BlockingUnaryCall(call, request);\n");
+      out->Print("return $methodname$(request, new CallOptions(headers, deadline, cancellationToken));\n",
+                 "methodname", method->name());
       out->Outdent();
       out->Print("}\n");
 
       // overload taking CallOptions as a param
-      out->Print(
-                "public $response$ $methodname$($request$ request, CallOptions options)\n",
-                "methodname", method->name(), "request",
-                GetClassName(method->input_type()), "response",
-                GetClassName(method->output_type()));
+      out->Print("public virtual $response$ $methodname$($request$ request, CallOptions options)\n",
+          "methodname", method->name(), "request",
+          GetClassName(method->input_type()), "response",
+          GetClassName(method->output_type()));
       out->Print("{\n");
       out->Indent();
-      out->Print("var call = CreateCall($methodfield$, options);\n",
+      out->Print("return CallInvoker.BlockingUnaryCall($methodfield$, null, options, request);\n",
                  "methodfield", GetMethodFieldName(method));
-      out->Print("return Calls.BlockingUnaryCall(call, request);\n");
       out->Outdent();
       out->Print("}\n");
     }
@@ -364,57 +415,44 @@ void GenerateClientStub(Printer* out, const ServiceDescriptor *service) {
       method_name += "Async";  // prevent name clash with synchronous method.
     }
     out->Print(
-        "public $returntype$ $methodname$($request_maybe$Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))\n",
-        "methodname", method_name, "request_maybe",
-        GetMethodRequestParamMaybe(method), "returntype",
-        GetMethodReturnTypeClient(method));
+            "public virtual $returntype$ $methodname$($request_maybe$Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))\n",
+            "methodname", method_name, "request_maybe",
+            GetMethodRequestParamMaybe(method), "returntype",
+            GetMethodReturnTypeClient(method));
     out->Print("{\n");
     out->Indent();
-    out->Print("var call = CreateCall($methodfield$, new CallOptions(headers, deadline, cancellationToken));\n",
-               "methodfield", GetMethodFieldName(method));
-    switch (GetMethodType(method)) {
-      case METHODTYPE_NO_STREAMING:
-        out->Print("return Calls.AsyncUnaryCall(call, request);\n");
-        break;
-      case METHODTYPE_CLIENT_STREAMING:
-        out->Print("return Calls.AsyncClientStreamingCall(call);\n");
-        break;
-      case METHODTYPE_SERVER_STREAMING:
-        out->Print(
-            "return Calls.AsyncServerStreamingCall(call, request);\n");
-        break;
-      case METHODTYPE_BIDI_STREAMING:
-        out->Print("return Calls.AsyncDuplexStreamingCall(call);\n");
-        break;
-      default:
-        GOOGLE_LOG(FATAL)<< "Can't get here.";
-    }
+
+    out->Print("return $methodname$($request_maybe$new CallOptions(headers, deadline, cancellationToken));\n",
+               "methodname", method_name,
+               "request_maybe", GetMethodRequestParamMaybe(method, true));
     out->Outdent();
     out->Print("}\n");
 
     // overload taking CallOptions as a param
     out->Print(
-        "public $returntype$ $methodname$($request_maybe$CallOptions options)\n",
+        "public virtual $returntype$ $methodname$($request_maybe$CallOptions options)\n",
         "methodname", method_name, "request_maybe",
         GetMethodRequestParamMaybe(method), "returntype",
         GetMethodReturnTypeClient(method));
     out->Print("{\n");
     out->Indent();
-    out->Print("var call = CreateCall($methodfield$, options);\n",
-               "methodfield", GetMethodFieldName(method));
     switch (GetMethodType(method)) {
       case METHODTYPE_NO_STREAMING:
-        out->Print("return Calls.AsyncUnaryCall(call, request);\n");
+        out->Print("return CallInvoker.AsyncUnaryCall($methodfield$, null, options, request);\n",
+                   "methodfield", GetMethodFieldName(method));
         break;
       case METHODTYPE_CLIENT_STREAMING:
-        out->Print("return Calls.AsyncClientStreamingCall(call);\n");
+        out->Print("return CallInvoker.AsyncClientStreamingCall($methodfield$, null, options);\n",
+                   "methodfield", GetMethodFieldName(method));
         break;
       case METHODTYPE_SERVER_STREAMING:
         out->Print(
-            "return Calls.AsyncServerStreamingCall(call, request);\n");
+            "return CallInvoker.AsyncServerStreamingCall($methodfield$, null, options, request);\n",
+            "methodfield", GetMethodFieldName(method));
         break;
       case METHODTYPE_BIDI_STREAMING:
-        out->Print("return Calls.AsyncDuplexStreamingCall(call);\n");
+        out->Print("return CallInvoker.AsyncDuplexStreamingCall($methodfield$, null, options);\n",
+                   "methodfield", GetMethodFieldName(method));
         break;
       default:
         GOOGLE_LOG(FATAL)<< "Can't get here.";
@@ -422,17 +460,30 @@ void GenerateClientStub(Printer* out, const ServiceDescriptor *service) {
     out->Outdent();
     out->Print("}\n");
   }
+
+  // override NewInstance method
+  out->Print("protected override $name$ NewInstance(ClientBaseConfiguration configuration)\n",
+             "name", GetClientClassName(service));
+  out->Print("{\n");
+  out->Indent();
+  out->Print("return new $name$(configuration);\n",
+             "name", GetClientClassName(service));
+  out->Outdent();
+  out->Print("}\n");
+
   out->Outdent();
   out->Print("}\n");
   out->Print("\n");
 }
 
-void GenerateBindServiceMethod(Printer* out, const ServiceDescriptor *service) {
+void GenerateBindServiceMethod(Printer* out, const ServiceDescriptor *service,
+                               bool use_server_class) {
   out->Print(
       "// creates service definition that can be registered with a server\n");
   out->Print(
       "public static ServerServiceDefinition BindService($interface$ serviceImpl)\n",
-      "interface", GetServerInterfaceName(service));
+      "interface", use_server_class ? GetServerClassName(service) :
+          GetServerInterfaceName(service));
   out->Print("{\n");
   out->Indent();
 
@@ -489,8 +540,10 @@ void GenerateService(Printer* out, const ServiceDescriptor *service) {
   GenerateServiceDescriptorProperty(out, service);
   GenerateClientInterface(out, service);
   GenerateServerInterface(out, service);
+  GenerateServerClass(out, service);
   GenerateClientStub(out, service);
-  GenerateBindServiceMethod(out, service);
+  GenerateBindServiceMethod(out, service, false);
+  GenerateBindServiceMethod(out, service, true);
   GenerateNewStubMethods(out, service);
 
   out->Outdent();
diff --git a/src/core/lib/client_config/README.md b/src/core/ext/client_config/README.md
index fff7a5af5b..7024fd540d 100644
--- a/src/core/lib/client_config/README.md
+++ b/src/core/ext/client_config/README.md
@@ -40,7 +40,7 @@ decisions (for example, by avoiding disconnected backends).
 Configured sub-channels are fully setup to participate in the grpc data plane.
 Their behavior is specified by a set of grpc channel filters defined at their
 construction. To customize this behavior, resolvers build
-grpc_subchannel_factory objects, which use the decorator pattern to customize
+grpc_client_channel_factory objects, which use the decorator pattern to customize
 construction arguments for concrete grpc_subchannel instances.
 
 
diff --git a/src/core/lib/surface/channel_connectivity.c b/src/core/ext/client_config/channel_connectivity.c
index 9a9ee422c2..3ebc333608 100644
--- a/src/core/lib/surface/channel_connectivity.c
+++ b/src/core/ext/client_config/channel_connectivity.c
@@ -36,7 +36,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 
-#include "src/core/lib/channel/client_channel.h"
+#include "src/core/ext/client_config/client_channel.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/completion_queue.h"
diff --git a/src/core/lib/channel/client_channel.c b/src/core/ext/client_config/client_channel.c
index 3f7cf1cf97..93d54fdcfe 100644
--- a/src/core/lib/channel/client_channel.c
+++ b/src/core/ext/client_config/client_channel.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/channel/client_channel.h"
+#include "src/core/ext/client_config/client_channel.h"
 
 #include <stdio.h>
 #include <string.h>
@@ -41,9 +41,9 @@
 #include <grpc/support/sync.h>
 #include <grpc/support/useful.h>
 
+#include "src/core/ext/client_config/subchannel_call_holder.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/connected_channel.h"
-#include "src/core/lib/channel/subchannel_call_holder.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/string.h"
@@ -114,6 +114,22 @@ static void watch_lb_policy(grpc_exec_ctx *exec_ctx, channel_data *chand,
                             grpc_lb_policy *lb_policy,
                             grpc_connectivity_state current_state);
 
+static void set_channel_connectivity_state_locked(grpc_exec_ctx *exec_ctx,
+                                                  channel_data *chand,
+                                                  grpc_connectivity_state state,
+                                                  const char *reason) {
+  if ((state == GRPC_CHANNEL_TRANSIENT_FAILURE ||
+       state == GRPC_CHANNEL_FATAL_FAILURE) &&
+      chand->lb_policy != NULL) {
+    /* cancel fail-fast picks */
+    grpc_lb_policy_cancel_picks(
+        exec_ctx, chand->lb_policy,
+        /* mask= */ GRPC_INITIAL_METADATA_IGNORE_CONNECTIVITY,
+        /* check= */ 0);
+  }
+  grpc_connectivity_state_set(exec_ctx, &chand->state_tracker, state, reason);
+}
+
 static void on_lb_policy_state_changed_locked(
     grpc_exec_ctx *exec_ctx, lb_policy_connectivity_watcher *w) {
   grpc_connectivity_state publish_state = w->state;
@@ -127,8 +143,8 @@ static void on_lb_policy_state_changed_locked(
     GRPC_LB_POLICY_UNREF(exec_ctx, w->chand->lb_policy, "channel");
     w->chand->lb_policy = NULL;
   }
-  grpc_connectivity_state_set(exec_ctx, &w->chand->state_tracker, publish_state,
-                              "lb_changed");
+  set_channel_connectivity_state_locked(exec_ctx, w->chand, publish_state,
+                                        "lb_changed");
   if (w->state != GRPC_CHANNEL_FATAL_FAILURE) {
     watch_lb_policy(exec_ctx, w->chand, w->lb_policy, w->state);
   }
@@ -200,8 +216,8 @@ static void cc_on_config_changed(grpc_exec_ctx *exec_ctx, void *arg,
   }
 
   if (iomgr_success && chand->resolver) {
-    grpc_connectivity_state_set(exec_ctx, &chand->state_tracker, state,
-                                "new_lb+resolver");
+    set_channel_connectivity_state_locked(exec_ctx, chand, state,
+                                          "new_lb+resolver");
     if (lb_policy != NULL) {
       watch_lb_policy(exec_ctx, chand, lb_policy, state);
     }
@@ -216,8 +232,8 @@ static void cc_on_config_changed(grpc_exec_ctx *exec_ctx, void *arg,
       GRPC_RESOLVER_UNREF(exec_ctx, chand->resolver, "channel");
       chand->resolver = NULL;
     }
-    grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
-                                GRPC_CHANNEL_FATAL_FAILURE, "resolver_gone");
+    set_channel_connectivity_state_locked(
+        exec_ctx, chand, GRPC_CHANNEL_FATAL_FAILURE, "resolver_gone");
     gpr_mu_unlock(&chand->mu_config);
   }
 
@@ -272,8 +288,8 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
   }
 
   if (op->disconnect && chand->resolver != NULL) {
-    grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
-                                GRPC_CHANNEL_FATAL_FAILURE, "disconnect");
+    set_channel_connectivity_state_locked(
+        exec_ctx, chand, GRPC_CHANNEL_FATAL_FAILURE, "disconnect");
     grpc_resolver_shutdown(exec_ctx, chand->resolver);
     GRPC_RESOLVER_UNREF(exec_ctx, chand->resolver, "channel");
     chand->resolver = NULL;
@@ -290,6 +306,7 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
 
 typedef struct {
   grpc_metadata_batch *initial_metadata;
+  uint32_t initial_metadata_flags;
   grpc_connected_subchannel **connected_subchannel;
   grpc_closure *on_ready;
   grpc_call_element *elem;
@@ -298,6 +315,7 @@ typedef struct {
 
 static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
                               grpc_metadata_batch *initial_metadata,
+                              uint32_t initial_metadata_flags,
                               grpc_connected_subchannel **connected_subchannel,
                               grpc_closure *on_ready);
 
@@ -308,6 +326,7 @@ static void continue_picking(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
   } else if (cpa->connected_subchannel == NULL) {
     /* cancelled, do nothing */
   } else if (cc_pick_subchannel(exec_ctx, cpa->elem, cpa->initial_metadata,
+                                cpa->initial_metadata_flags,
                                 cpa->connected_subchannel, cpa->on_ready)) {
     grpc_exec_ctx_enqueue(exec_ctx, cpa->on_ready, true, NULL);
   }
@@ -316,6 +335,7 @@ static void continue_picking(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
 
 static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
                               grpc_metadata_batch *initial_metadata,
+                              uint32_t initial_metadata_flags,
                               grpc_connected_subchannel **connected_subchannel,
                               grpc_closure *on_ready) {
   grpc_call_element *elem = elemp;
@@ -349,7 +369,8 @@ static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
     GRPC_LB_POLICY_REF(lb_policy, "cc_pick_subchannel");
     gpr_mu_unlock(&chand->mu_config);
     r = grpc_lb_policy_pick(exec_ctx, lb_policy, calld->pollset,
-                            initial_metadata, connected_subchannel, on_ready);
+                            initial_metadata, initial_metadata_flags,
+                            connected_subchannel, on_ready);
     GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "cc_pick_subchannel");
     return r;
   }
@@ -362,6 +383,7 @@ static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
   }
   cpa = gpr_malloc(sizeof(*cpa));
   cpa->initial_metadata = initial_metadata;
+  cpa->initial_metadata_flags = initial_metadata_flags;
   cpa->connected_subchannel = connected_subchannel;
   cpa->on_ready = on_ready;
   cpa->elem = elem;
diff --git a/src/core/lib/channel/client_channel.h b/src/core/ext/client_config/client_channel.h
index ac418c8c51..1e47ad34ad 100644
--- a/src/core/lib/channel/client_channel.h
+++ b/src/core/ext/client_config/client_channel.h
@@ -31,11 +31,11 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CHANNEL_CLIENT_CHANNEL_H
-#define GRPC_CORE_LIB_CHANNEL_CLIENT_CHANNEL_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H
 
+#include "src/core/ext/client_config/resolver.h"
 #include "src/core/lib/channel/channel_stack.h"
-#include "src/core/lib/client_config/resolver.h"
 
 /* A client channel is a channel that begins disconnected, and can connect
    to some endpoint on demand. If that endpoint disconnects, it will be
@@ -60,4 +60,4 @@ void grpc_client_channel_watch_connectivity_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
     grpc_connectivity_state *state, grpc_closure *on_complete);
 
-#endif /* GRPC_CORE_LIB_CHANNEL_CLIENT_CHANNEL_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H */
diff --git a/src/core/ext/client_config/client_channel_factory.c b/src/core/ext/client_config/client_channel_factory.c
new file mode 100644
index 0000000000..71c64c0da1
--- /dev/null
+++ b/src/core/ext/client_config/client_channel_factory.c
@@ -0,0 +1,57 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/ext/client_config/client_channel_factory.h"
+
+void grpc_client_channel_factory_ref(grpc_client_channel_factory* factory) {
+  factory->vtable->ref(factory);
+}
+
+void grpc_client_channel_factory_unref(grpc_exec_ctx* exec_ctx,
+                                       grpc_client_channel_factory* factory) {
+  factory->vtable->unref(exec_ctx, factory);
+}
+
+grpc_subchannel* grpc_client_channel_factory_create_subchannel(
+    grpc_exec_ctx* exec_ctx, grpc_client_channel_factory* factory,
+    grpc_subchannel_args* args) {
+  return factory->vtable->create_subchannel(exec_ctx, factory, args);
+}
+
+grpc_channel* grpc_client_channel_factory_create_channel(
+    grpc_exec_ctx* exec_ctx, grpc_client_channel_factory* factory,
+    const char* target, grpc_client_channel_type type,
+    grpc_channel_args* args) {
+  return factory->vtable->create_client_channel(exec_ctx, factory, target, type,
+                                                args);
+}
diff --git a/src/core/ext/client_config/client_channel_factory.h b/src/core/ext/client_config/client_channel_factory.h
new file mode 100644
index 0000000000..1241b9b781
--- /dev/null
+++ b/src/core/ext/client_config/client_channel_factory.h
@@ -0,0 +1,85 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_FACTORY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_FACTORY_H
+
+#include <grpc/impl/codegen/grpc_types.h>
+
+#include "src/core/ext/client_config/subchannel.h"
+#include "src/core/lib/channel/channel_stack.h"
+
+typedef struct grpc_client_channel_factory grpc_client_channel_factory;
+typedef struct grpc_client_channel_factory_vtable
+    grpc_client_channel_factory_vtable;
+
+typedef enum {
+  GRPC_CLIENT_CHANNEL_TYPE_REGULAR, /** for the user-level regular calls */
+  GRPC_CLIENT_CHANNEL_TYPE_LOAD_BALANCING, /** for communication with a load
+                                              balancing service */
+} grpc_client_channel_type;
+
+/** Constructor for new configured channels.
+    Creating decorators around this type is encouraged to adapt behavior. */
+struct grpc_client_channel_factory {
+  const grpc_client_channel_factory_vtable *vtable;
+};
+
+struct grpc_client_channel_factory_vtable {
+  void (*ref)(grpc_client_channel_factory *factory);
+  void (*unref)(grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *factory);
+  grpc_subchannel *(*create_subchannel)(grpc_exec_ctx *exec_ctx,
+                                        grpc_client_channel_factory *factory,
+                                        grpc_subchannel_args *args);
+  grpc_channel *(*create_client_channel)(grpc_exec_ctx *exec_ctx,
+                                         grpc_client_channel_factory *factory,
+                                         const char *target,
+                                         grpc_client_channel_type type,
+                                         grpc_channel_args *args);
+};
+
+void grpc_client_channel_factory_ref(grpc_client_channel_factory *factory);
+void grpc_client_channel_factory_unref(grpc_exec_ctx *exec_ctx,
+                                       grpc_client_channel_factory *factory);
+
+/** Create a new grpc_subchannel */
+grpc_subchannel *grpc_client_channel_factory_create_subchannel(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *factory,
+    grpc_subchannel_args *args);
+
+/** Create a new grpc_channel */
+grpc_channel *grpc_client_channel_factory_create_channel(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *factory,
+    const char *target, grpc_client_channel_type type, grpc_channel_args *args);
+
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_FACTORY_H */
diff --git a/src/core/lib/client_config/client_config.c b/src/core/ext/client_config/client_config.c
index 2521023364..f9b8e68698 100644
--- a/src/core/lib/client_config/client_config.c
+++ b/src/core/ext/client_config/client_config.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/client_config.h"
+#include "src/core/ext/client_config/client_config.h"
 
 #include <string.h>
 
diff --git a/src/core/lib/client_config/client_config.h b/src/core/ext/client_config/client_config.h
index 8dc2f6b299..a6290cbcf0 100644
--- a/src/core/lib/client_config/client_config.h
+++ b/src/core/ext/client_config/client_config.h
@@ -31,10 +31,10 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_CLIENT_CONFIG_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_CLIENT_CONFIG_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CONFIG_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CONFIG_H
 
-#include "src/core/lib/client_config/lb_policy.h"
+#include "src/core/ext/client_config/lb_policy.h"
 
 /** Total configuration for a client. Provided, and updated, by
     grpc_resolver */
@@ -50,4 +50,4 @@ void grpc_client_config_set_lb_policy(grpc_client_config *client_config,
 grpc_lb_policy *grpc_client_config_get_lb_policy(
     grpc_client_config *client_config);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_CLIENT_CONFIG_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CONFIG_H */
diff --git a/src/core/lib/client_config/connector.c b/src/core/ext/client_config/connector.c
index 4c7b823dac..5b629ed5fb 100644
--- a/src/core/lib/client_config/connector.c
+++ b/src/core/ext/client_config/connector.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/connector.h"
+#include "src/core/ext/client_config/connector.h"
 
 grpc_connector* grpc_connector_ref(grpc_connector* connector) {
   connector->vtable->ref(connector);
diff --git a/src/core/lib/client_config/connector.h b/src/core/ext/client_config/connector.h
index 39870a261c..dd85dfcb7d 100644
--- a/src/core/lib/client_config/connector.h
+++ b/src/core/ext/client_config/connector.h
@@ -31,8 +31,8 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_CONNECTOR_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_CONNECTOR_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_CONNECTOR_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_CONNECTOR_H
 
 #include "src/core/lib/channel/channel_stack.h"
 #include "src/core/lib/iomgr/sockaddr.h"
@@ -89,4 +89,4 @@ void grpc_connector_connect(grpc_exec_ctx *exec_ctx, grpc_connector *connector,
 void grpc_connector_shutdown(grpc_exec_ctx *exec_ctx,
                              grpc_connector *connector);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_CONNECTOR_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_CONNECTOR_H */
diff --git a/src/core/lib/client_config/default_initial_connect_string.c b/src/core/ext/client_config/default_initial_connect_string.c
index a70da4a84a..a70da4a84a 100644
--- a/src/core/lib/client_config/default_initial_connect_string.c
+++ b/src/core/ext/client_config/default_initial_connect_string.c
diff --git a/src/core/lib/client_config/initial_connect_string.c b/src/core/ext/client_config/initial_connect_string.c
index 4034ea2e87..41580d2106 100644
--- a/src/core/lib/client_config/initial_connect_string.c
+++ b/src/core/ext/client_config/initial_connect_string.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/initial_connect_string.h"
+#include "src/core/ext/client_config/initial_connect_string.h"
 
 #include <stddef.h>
 
diff --git a/src/core/lib/client_config/initial_connect_string.h b/src/core/ext/client_config/initial_connect_string.h
index 51302768c6..06f0767832 100644
--- a/src/core/lib/client_config/initial_connect_string.h
+++ b/src/core/ext/client_config/initial_connect_string.h
@@ -31,8 +31,8 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H
 
 #include <grpc/support/slice.h>
 #include "src/core/lib/iomgr/sockaddr.h"
@@ -47,4 +47,4 @@ void grpc_test_set_initial_connect_string_function(
 void grpc_set_initial_connect_string(struct sockaddr **addr, size_t *addr_len,
                                      gpr_slice *connect_string);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H */
diff --git a/src/core/lib/client_config/lb_policy.c b/src/core/ext/client_config/lb_policy.c
index 3d23669ec2..a7ad9842dc 100644
--- a/src/core/lib/client_config/lb_policy.c
+++ b/src/core/ext/client_config/lb_policy.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/lb_policy.h"
+#include "src/core/ext/client_config/lb_policy.h"
 
 #define WEAK_REF_BITS 16
 
@@ -101,10 +101,11 @@ void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx,
 int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                         grpc_pollset *pollset,
                         grpc_metadata_batch *initial_metadata,
+                        uint32_t initial_metadata_flags,
                         grpc_connected_subchannel **target,
                         grpc_closure *on_complete) {
   return policy->vtable->pick(exec_ctx, policy, pollset, initial_metadata,
-                              target, on_complete);
+                              initial_metadata_flags, target, on_complete);
 }
 
 void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
@@ -112,6 +113,14 @@ void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
   policy->vtable->cancel_pick(exec_ctx, policy, target);
 }
 
+void grpc_lb_policy_cancel_picks(grpc_exec_ctx *exec_ctx,
+                                 grpc_lb_policy *policy,
+                                 uint32_t initial_metadata_flags_mask,
+                                 uint32_t initial_metadata_flags_eq) {
+  policy->vtable->cancel_picks(exec_ctx, policy, initial_metadata_flags_mask,
+                               initial_metadata_flags_eq);
+}
+
 void grpc_lb_policy_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy) {
   policy->vtable->exit_idle(exec_ctx, policy);
 }
diff --git a/src/core/lib/client_config/lb_policy.h b/src/core/ext/client_config/lb_policy.h
index a63e8e68df..0384e0b2eb 100644
--- a/src/core/lib/client_config/lb_policy.h
+++ b/src/core/ext/client_config/lb_policy.h
@@ -31,10 +31,10 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_H
 
-#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/ext/client_config/subchannel.h"
 #include "src/core/lib/transport/connectivity_state.h"
 
 /** A load balancing policy: specified by a vtable and a struct (which
@@ -60,9 +60,13 @@ struct grpc_lb_policy_vtable {
   /** implement grpc_lb_policy_pick */
   int (*pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
               grpc_pollset *pollset, grpc_metadata_batch *initial_metadata,
+              uint32_t initial_metadata_flags,
               grpc_connected_subchannel **target, grpc_closure *on_complete);
   void (*cancel_pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                       grpc_connected_subchannel **target);
+  void (*cancel_picks)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                       uint32_t initial_metadata_flags_mask,
+                       uint32_t initial_metadata_flags_eq);
 
   void (*ping_one)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                    grpc_closure *closure);
@@ -122,6 +126,7 @@ void grpc_lb_policy_init(grpc_lb_policy *policy,
 int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                         grpc_pollset *pollset,
                         grpc_metadata_batch *initial_metadata,
+                        uint32_t initial_metadata_flags,
                         grpc_connected_subchannel **target,
                         grpc_closure *on_complete);
 
@@ -131,6 +136,14 @@ void grpc_lb_policy_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
 void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                                 grpc_connected_subchannel **target);
 
+/** Cancel all pending picks which have:
+    (initial_metadata_flags & initial_metadata_flags_mask) ==
+         initial_metadata_flags_eq */
+void grpc_lb_policy_cancel_picks(grpc_exec_ctx *exec_ctx,
+                                 grpc_lb_policy *policy,
+                                 uint32_t initial_metadata_flags_mask,
+                                 uint32_t initial_metadata_flags_eq);
+
 void grpc_lb_policy_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 
 void grpc_lb_policy_notify_on_state_change(grpc_exec_ctx *exec_ctx,
@@ -141,4 +154,4 @@ void grpc_lb_policy_notify_on_state_change(grpc_exec_ctx *exec_ctx,
 grpc_connectivity_state grpc_lb_policy_check_connectivity(
     grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_H */
diff --git a/src/core/lib/client_config/lb_policy_factory.c b/src/core/ext/client_config/lb_policy_factory.c
index 92e1f5f08b..70e46ef3cf 100644
--- a/src/core/lib/client_config/lb_policy_factory.c
+++ b/src/core/ext/client_config/lb_policy_factory.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/lb_policy_factory.h"
+#include "src/core/ext/client_config/lb_policy_factory.h"
 
 void grpc_lb_policy_factory_ref(grpc_lb_policy_factory* factory) {
   factory->vtable->ref(factory);
diff --git a/src/core/lib/client_config/lb_policy_factory.h b/src/core/ext/client_config/lb_policy_factory.h
index 6f21912821..1c89b28b59 100644
--- a/src/core/lib/client_config/lb_policy_factory.h
+++ b/src/core/ext/client_config/lb_policy_factory.h
@@ -31,11 +31,11 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_FACTORY_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_FACTORY_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_FACTORY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_FACTORY_H
 
-#include "src/core/lib/client_config/lb_policy.h"
-#include "src/core/lib/client_config/subchannel_factory.h"
+#include "src/core/ext/client_config/client_channel_factory.h"
+#include "src/core/ext/client_config/lb_policy.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 
 #include "src/core/lib/iomgr/exec_ctx.h"
@@ -51,7 +51,7 @@ struct grpc_lb_policy_factory {
 
 typedef struct grpc_lb_policy_args {
   grpc_resolved_addresses *addresses;
-  grpc_subchannel_factory *subchannel_factory;
+  grpc_client_channel_factory *client_channel_factory;
 } grpc_lb_policy_args;
 
 struct grpc_lb_policy_factory_vtable {
@@ -75,4 +75,4 @@ grpc_lb_policy *grpc_lb_policy_factory_create_lb_policy(
     grpc_exec_ctx *exec_ctx, grpc_lb_policy_factory *factory,
     grpc_lb_policy_args *args);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_FACTORY_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_FACTORY_H */
diff --git a/src/core/lib/client_config/lb_policy_registry.c b/src/core/ext/client_config/lb_policy_registry.c
index af396362a1..a23643ecc6 100644
--- a/src/core/lib/client_config/lb_policy_registry.c
+++ b/src/core/ext/client_config/lb_policy_registry.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
 
 #include <string.h>
 
diff --git a/src/core/lib/client_config/lb_policy_registry.h b/src/core/ext/client_config/lb_policy_registry.h
index 4b8495d8a1..92f38d6de6 100644
--- a/src/core/lib/client_config/lb_policy_registry.h
+++ b/src/core/ext/client_config/lb_policy_registry.h
@@ -31,10 +31,10 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_REGISTRY_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_REGISTRY_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_REGISTRY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_REGISTRY_H
 
-#include "src/core/lib/client_config/lb_policy_factory.h"
+#include "src/core/ext/client_config/lb_policy_factory.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
 
 /** Initialize the registry and set \a default_factory as the factory to be
@@ -52,4 +52,4 @@ void grpc_register_lb_policy(grpc_lb_policy_factory *factory);
 grpc_lb_policy *grpc_lb_policy_create(grpc_exec_ctx *exec_ctx, const char *name,
                                       grpc_lb_policy_args *args);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_REGISTRY_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_LB_POLICY_REGISTRY_H */
diff --git a/src/core/lib/client_config/resolver.c b/src/core/ext/client_config/resolver.c
index b9eef5575f..eb004455bd 100644
--- a/src/core/lib/client_config/resolver.c
+++ b/src/core/ext/client_config/resolver.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/resolver.h"
+#include "src/core/ext/client_config/resolver.h"
 
 void grpc_resolver_init(grpc_resolver *resolver,
                         const grpc_resolver_vtable *vtable) {
diff --git a/src/core/lib/client_config/resolver.h b/src/core/ext/client_config/resolver.h
index cf0bb2bc7a..6ecb5d2774 100644
--- a/src/core/lib/client_config/resolver.h
+++ b/src/core/ext/client_config/resolver.h
@@ -31,11 +31,11 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_H
 
-#include "src/core/lib/client_config/client_config.h"
-#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/ext/client_config/client_config.h"
+#include "src/core/ext/client_config/subchannel.h"
 #include "src/core/lib/iomgr/iomgr.h"
 
 typedef struct grpc_resolver grpc_resolver;
@@ -91,4 +91,4 @@ void grpc_resolver_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
                         grpc_client_config **target_config,
                         grpc_closure *on_complete);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_H */
diff --git a/src/core/lib/client_config/resolver_factory.c b/src/core/ext/client_config/resolver_factory.c
index 001fa28536..67832dcf59 100644
--- a/src/core/lib/client_config/resolver_factory.c
+++ b/src/core/ext/client_config/resolver_factory.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/resolver_factory.h"
+#include "src/core/ext/client_config/resolver_factory.h"
 
 void grpc_resolver_factory_ref(grpc_resolver_factory* factory) {
   factory->vtable->ref(factory);
diff --git a/src/core/lib/client_config/resolver_factory.h b/src/core/ext/client_config/resolver_factory.h
index a5bca06475..4eb6979aad 100644
--- a/src/core/lib/client_config/resolver_factory.h
+++ b/src/core/ext/client_config/resolver_factory.h
@@ -31,12 +31,12 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_FACTORY_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_FACTORY_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_FACTORY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_FACTORY_H
 
-#include "src/core/lib/client_config/resolver.h"
-#include "src/core/lib/client_config/subchannel_factory.h"
-#include "src/core/lib/client_config/uri_parser.h"
+#include "src/core/ext/client_config/client_channel_factory.h"
+#include "src/core/ext/client_config/resolver.h"
+#include "src/core/ext/client_config/uri_parser.h"
 
 typedef struct grpc_resolver_factory grpc_resolver_factory;
 typedef struct grpc_resolver_factory_vtable grpc_resolver_factory_vtable;
@@ -49,7 +49,7 @@ struct grpc_resolver_factory {
 
 typedef struct grpc_resolver_args {
   grpc_uri *uri;
-  grpc_subchannel_factory *subchannel_factory;
+  grpc_client_channel_factory *client_channel_factory;
 } grpc_resolver_args;
 
 struct grpc_resolver_factory_vtable {
@@ -79,4 +79,4 @@ grpc_resolver *grpc_resolver_factory_create_resolver(
 char *grpc_resolver_factory_get_default_authority(
     grpc_resolver_factory *factory, grpc_uri *uri);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_FACTORY_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_FACTORY_H */
diff --git a/src/core/lib/client_config/resolver_registry.c b/src/core/ext/client_config/resolver_registry.c
index 5f3db273b5..07f29bcb27 100644
--- a/src/core/lib/client_config/resolver_registry.c
+++ b/src/core/ext/client_config/resolver_registry.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/resolver_registry.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 
 #include <string.h>
 
@@ -123,14 +123,14 @@ static grpc_resolver_factory *resolve_factory(const char *target,
 }
 
 grpc_resolver *grpc_resolver_create(
-    const char *target, grpc_subchannel_factory *subchannel_factory) {
+    const char *target, grpc_client_channel_factory *client_channel_factory) {
   grpc_uri *uri = NULL;
   grpc_resolver_factory *factory = resolve_factory(target, &uri);
   grpc_resolver *resolver;
   grpc_resolver_args args;
   memset(&args, 0, sizeof(args));
   args.uri = uri;
-  args.subchannel_factory = subchannel_factory;
+  args.client_channel_factory = client_channel_factory;
   resolver = grpc_resolver_factory_create_resolver(factory, &args);
   grpc_uri_destroy(uri);
   return resolver;
diff --git a/src/core/lib/client_config/resolver_registry.h b/src/core/ext/client_config/resolver_registry.h
index 36c4f2fe03..5ef1383cd3 100644
--- a/src/core/lib/client_config/resolver_registry.h
+++ b/src/core/ext/client_config/resolver_registry.h
@@ -31,10 +31,10 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_REGISTRY_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_REGISTRY_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_REGISTRY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_REGISTRY_H
 
-#include "src/core/lib/client_config/resolver_factory.h"
+#include "src/core/ext/client_config/resolver_factory.h"
 
 void grpc_resolver_registry_init(const char *default_prefix);
 void grpc_resolver_registry_shutdown(void);
@@ -56,7 +56,7 @@ void grpc_register_resolver_type(grpc_resolver_factory *factory);
     return it.
     If a resolver factory was not found, return NULL. */
 grpc_resolver *grpc_resolver_create(
-    const char *target, grpc_subchannel_factory *subchannel_factory);
+    const char *target, grpc_client_channel_factory *client_channel_factory);
 
 /** Find a resolver factory given a name and return an (owned-by-the-caller)
  *  reference to it */
@@ -66,4 +66,4 @@ grpc_resolver_factory *grpc_resolver_factory_lookup(const char *name);
     representing the default authority to pass from a client. */
 char *grpc_get_default_authority(const char *target);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_REGISTRY_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_REGISTRY_H */
diff --git a/src/core/lib/client_config/subchannel.c b/src/core/ext/client_config/subchannel.c
index 47c53a16ba..20cf245a5b 100644
--- a/src/core/lib/client_config/subchannel.c
+++ b/src/core/ext/client_config/subchannel.c
@@ -31,18 +31,18 @@
  *
  */
 
-#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/ext/client_config/subchannel.h"
 
 #include <string.h>
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/avl.h>
 
+#include "src/core/ext/client_config/client_channel.h"
+#include "src/core/ext/client_config/initial_connect_string.h"
+#include "src/core/ext/client_config/subchannel_index.h"
 #include "src/core/lib/channel/channel_args.h"
-#include "src/core/lib/channel/client_channel.h"
 #include "src/core/lib/channel/connected_channel.h"
-#include "src/core/lib/client_config/initial_connect_string.h"
-#include "src/core/lib/client_config/subchannel_index.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/backoff.h"
@@ -54,7 +54,7 @@
 #define STRONG_REF_MASK (~(gpr_atm)((1 << INTERNAL_REF_BITS) - 1))
 
 #define GRPC_SUBCHANNEL_MIN_CONNECT_TIMEOUT_SECONDS 20
-#define GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS 1
+#define GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS 2
 #define GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER 1.6
 #define GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS 120
 #define GRPC_SUBCHANNEL_RECONNECT_JITTER 0.2
@@ -352,6 +352,25 @@ grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
                          c->args->args[i].value.integer,
                          c->args->args[i].value.integer);
       }
+      if (0 ==
+          strcmp(c->args->args[i].key, GRPC_ARG_MAX_RECONNECT_BACKOFF_MS)) {
+        if (c->args->args[i].type == GRPC_ARG_INTEGER) {
+          if (c->args->args[i].value.integer >= 0) {
+            gpr_backoff_init(
+                &c->backoff_state, GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
+                GRPC_SUBCHANNEL_RECONNECT_JITTER,
+                GPR_MIN(c->args->args[i].value.integer,
+                        GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000),
+                c->args->args[i].value.integer);
+          } else {
+            gpr_log(GPR_ERROR, GRPC_ARG_MAX_RECONNECT_BACKOFF_MS
+                    " : must be non-negative");
+          }
+        } else {
+          gpr_log(GPR_ERROR,
+                  GRPC_ARG_MAX_RECONNECT_BACKOFF_MS " : must be an integer");
+        }
+      }
     }
   }
   gpr_mu_init(&c->mu);
diff --git a/src/core/lib/client_config/subchannel.h b/src/core/ext/client_config/subchannel.h
index 68aeff39a1..0765a544e8 100644
--- a/src/core/lib/client_config/subchannel.h
+++ b/src/core/ext/client_config/subchannel.h
@@ -31,11 +31,11 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_H
 
+#include "src/core/ext/client_config/connector.h"
 #include "src/core/lib/channel/channel_stack.h"
-#include "src/core/lib/client_config/connector.h"
 #include "src/core/lib/transport/connectivity_state.h"
 
 /** A (sub-)channel that knows how to connect to exactly one target
@@ -171,4 +171,4 @@ grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
                                         grpc_connector *connector,
                                         grpc_subchannel_args *args);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_H */
diff --git a/src/core/lib/channel/subchannel_call_holder.c b/src/core/ext/client_config/subchannel_call_holder.c
index 22f3679bf5..3db462b246 100644
--- a/src/core/lib/channel/subchannel_call_holder.c
+++ b/src/core/ext/client_config/subchannel_call_holder.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/channel/subchannel_call_holder.h"
+#include "src/core/ext/client_config/subchannel_call_holder.h"
 
 #include <grpc/support/alloc.h>
 
@@ -127,7 +127,7 @@ retry:
           break;
         case GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL:
           holder->pick_subchannel(exec_ctx, holder->pick_subchannel_arg, NULL,
-                                  &holder->connected_subchannel, NULL);
+                                  0, &holder->connected_subchannel, NULL);
           break;
       }
       gpr_mu_unlock(&holder->mu);
@@ -145,7 +145,8 @@ retry:
     GRPC_CALL_STACK_REF(holder->owning_call, "pick_subchannel");
     if (holder->pick_subchannel(
             exec_ctx, holder->pick_subchannel_arg, op->send_initial_metadata,
-            &holder->connected_subchannel, &holder->next_step)) {
+            op->send_initial_metadata_flags, &holder->connected_subchannel,
+            &holder->next_step)) {
       holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
       GRPC_CALL_STACK_UNREF(exec_ctx, holder->owning_call, "pick_subchannel");
     }
diff --git a/src/core/lib/channel/subchannel_call_holder.h b/src/core/ext/client_config/subchannel_call_holder.h
index 5cf291a266..9299908788 100644
--- a/src/core/lib/channel/subchannel_call_holder.h
+++ b/src/core/ext/client_config/subchannel_call_holder.h
@@ -31,10 +31,10 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CHANNEL_SUBCHANNEL_CALL_HOLDER_H
-#define GRPC_CORE_LIB_CHANNEL_SUBCHANNEL_CALL_HOLDER_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_CALL_HOLDER_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_CALL_HOLDER_H
 
-#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/ext/client_config/subchannel.h"
 
 /** Pick a subchannel for grpc_subchannel_call_holder;
     Return 1 if subchannel is available immediately (in which case on_ready
@@ -42,6 +42,7 @@
     called when the subchannel is available) */
 typedef int (*grpc_subchannel_call_holder_pick_subchannel)(
     grpc_exec_ctx *exec_ctx, void *arg, grpc_metadata_batch *initial_metadata,
+    uint32_t initial_metadata_flags,
     grpc_connected_subchannel **connected_subchannel, grpc_closure *on_ready);
 
 typedef enum {
@@ -94,4 +95,4 @@ void grpc_subchannel_call_holder_perform_op(grpc_exec_ctx *exec_ctx,
 char *grpc_subchannel_call_holder_get_peer(grpc_exec_ctx *exec_ctx,
                                            grpc_subchannel_call_holder *holder);
 
-#endif /* GRPC_CORE_LIB_CHANNEL_SUBCHANNEL_CALL_HOLDER_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_CALL_HOLDER_H */
diff --git a/src/core/lib/client_config/subchannel_factory.c b/src/core/ext/client_config/subchannel_factory.c
index 541368ec96..d1e4d75a02 100644
--- a/src/core/lib/client_config/subchannel_factory.c
+++ b/src/core/ext/client_config/subchannel_factory.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/subchannel_factory.h"
+#include "src/core/ext/client_config/subchannel_factory.h"
 
 void grpc_subchannel_factory_ref(grpc_subchannel_factory* factory) {
   factory->vtable->ref(factory);
diff --git a/src/core/lib/client_config/subchannel_factory.h b/src/core/ext/client_config/subchannel_factory.h
index 96d68a2079..0fb806d081 100644
--- a/src/core/lib/client_config/subchannel_factory.h
+++ b/src/core/ext/client_config/subchannel_factory.h
@@ -31,11 +31,11 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H
 
+#include "src/core/ext/client_config/subchannel.h"
 #include "src/core/lib/channel/channel_stack.h"
-#include "src/core/lib/client_config/subchannel.h"
 
 typedef struct grpc_subchannel_factory grpc_subchannel_factory;
 typedef struct grpc_subchannel_factory_vtable grpc_subchannel_factory_vtable;
@@ -63,4 +63,4 @@ grpc_subchannel *grpc_subchannel_factory_create_subchannel(
     grpc_exec_ctx *exec_ctx, grpc_subchannel_factory *factory,
     grpc_subchannel_args *args);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H */
diff --git a/src/core/lib/client_config/subchannel_index.c b/src/core/ext/client_config/subchannel_index.c
index 2c545002a2..ab8d9bd91d 100644
--- a/src/core/lib/client_config/subchannel_index.c
+++ b/src/core/ext/client_config/subchannel_index.c
@@ -31,7 +31,7 @@
 //
 //
 
-#include "src/core/lib/client_config/subchannel_index.h"
+#include "src/core/ext/client_config/subchannel_index.h"
 
 #include <stdbool.h>
 #include <string.h>
diff --git a/src/core/lib/client_config/subchannel_index.h b/src/core/ext/client_config/subchannel_index.h
index bc5f03beb4..6b8d063855 100644
--- a/src/core/lib/client_config/subchannel_index.h
+++ b/src/core/ext/client_config/subchannel_index.h
@@ -31,11 +31,11 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
 
-#include "src/core/lib/client_config/connector.h"
-#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/ext/client_config/connector.h"
+#include "src/core/ext/client_config/subchannel.h"
 
 /** \file Provides an index of active subchannels so that they can be
     shared amongst channels */
@@ -74,4 +74,4 @@ void grpc_subchannel_index_init(void);
 /** Shutdown the subchannel index (global) */
 void grpc_subchannel_index_shutdown(void);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_INDEX_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_SUBCHANNEL_INDEX_H */
diff --git a/src/core/lib/client_config/uri_parser.c b/src/core/ext/client_config/uri_parser.c
index 6bec70da2d..3ca1a58e69 100644
--- a/src/core/lib/client_config/uri_parser.c
+++ b/src/core/ext/client_config/uri_parser.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/lib/client_config/uri_parser.h"
+#include "src/core/ext/client_config/uri_parser.h"
 
 #include <string.h>
 
diff --git a/src/core/lib/client_config/uri_parser.h b/src/core/ext/client_config/uri_parser.h
index 5d6785d293..875a7cb07c 100644
--- a/src/core/lib/client_config/uri_parser.h
+++ b/src/core/ext/client_config/uri_parser.h
@@ -31,8 +31,8 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_URI_PARSER_H
-#define GRPC_CORE_LIB_CLIENT_CONFIG_URI_PARSER_H
+#ifndef GRPC_CORE_EXT_CLIENT_CONFIG_URI_PARSER_H
+#define GRPC_CORE_EXT_CLIENT_CONFIG_URI_PARSER_H
 
 #include <stddef.h>
 
@@ -60,4 +60,4 @@ const char *grpc_uri_get_query_arg(const grpc_uri *uri, const char *key);
 /** destroy a uri */
 void grpc_uri_destroy(grpc_uri *uri);
 
-#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_URI_PARSER_H */
+#endif /* GRPC_CORE_EXT_CLIENT_CONFIG_URI_PARSER_H */
diff --git a/src/core/ext/lb_policy/grpclb/load_balancer_api.h b/src/core/ext/lb_policy/grpclb/load_balancer_api.h
index d329a2ffe8..968f7d278a 100644
--- a/src/core/ext/lb_policy/grpclb/load_balancer_api.h
+++ b/src/core/ext/lb_policy/grpclb/load_balancer_api.h
@@ -36,8 +36,8 @@
 
 #include <grpc/support/slice_buffer.h>
 
+#include "src/core/ext/client_config/lb_policy_factory.h"
 #include "src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.h"
-#include "src/core/lib/client_config/lb_policy_factory.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/core/ext/lb_policy/pick_first/pick_first.c b/src/core/ext/lb_policy/pick_first/pick_first.c
index cb5c40501e..5926f9d70b 100644
--- a/src/core/ext/lb_policy/pick_first/pick_first.c
+++ b/src/core/ext/lb_policy/pick_first/pick_first.c
@@ -34,12 +34,13 @@
 #include <string.h>
 
 #include <grpc/support/alloc.h>
-#include "src/core/lib/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/lib/transport/connectivity_state.h"
 
 typedef struct pending_pick {
   struct pending_pick *next;
   grpc_pollset *pollset;
+  uint32_t initial_metadata_flags;
   grpc_connected_subchannel **target;
   grpc_closure *on_complete;
 } pending_pick;
@@ -149,6 +150,31 @@ static void pf_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
   gpr_mu_unlock(&p->mu);
 }
 
+static void pf_cancel_picks(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                            uint32_t initial_metadata_flags_mask,
+                            uint32_t initial_metadata_flags_eq) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  pending_pick *pp;
+  gpr_mu_lock(&p->mu);
+  pp = p->pending_picks;
+  p->pending_picks = NULL;
+  while (pp != NULL) {
+    pending_pick *next = pp->next;
+    if ((pp->initial_metadata_flags & initial_metadata_flags_mask) ==
+        initial_metadata_flags_eq) {
+      grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                   pp->pollset);
+      grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, false, NULL);
+      gpr_free(pp);
+    } else {
+      pp->next = p->pending_picks;
+      p->pending_picks = pp;
+    }
+    pp = next;
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
 static void start_picking(grpc_exec_ctx *exec_ctx, pick_first_lb_policy *p) {
   p->started_picking = 1;
   p->checking_subchannel = 0;
@@ -171,6 +197,7 @@ static void pf_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 
 static int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
                    grpc_pollset *pollset, grpc_metadata_batch *initial_metadata,
+                   uint32_t initial_metadata_flags,
                    grpc_connected_subchannel **target,
                    grpc_closure *on_complete) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
@@ -199,6 +226,7 @@ static int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
     pp->next = p->pending_picks;
     pp->pollset = pollset;
     pp->target = target;
+    pp->initial_metadata_flags = initial_metadata_flags;
     pp->on_complete = on_complete;
     p->pending_picks = pp;
     gpr_mu_unlock(&p->mu);
@@ -286,11 +314,14 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
             &p->checking_connectivity, &p->connectivity_changed);
         break;
       case GRPC_CHANNEL_TRANSIENT_FAILURE:
-        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
-                                    GRPC_CHANNEL_TRANSIENT_FAILURE,
-                                    "connecting_transient_failure");
         p->checking_subchannel =
             (p->checking_subchannel + 1) % p->num_subchannels;
+        if (p->checking_subchannel == 0) {
+          /* only trigger transient failure when we've tried all alternatives */
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                      "connecting_transient_failure");
+        }
         p->checking_connectivity = grpc_subchannel_check_connectivity(
             p->subchannels[p->checking_subchannel]);
         if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
@@ -378,14 +409,9 @@ static void pf_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
 }
 
 static const grpc_lb_policy_vtable pick_first_lb_policy_vtable = {
-    pf_destroy,
-    pf_shutdown,
-    pf_pick,
-    pf_cancel_pick,
-    pf_ping_one,
-    pf_exit_idle,
-    pf_check_connectivity,
-    pf_notify_on_state_change};
+    pf_destroy,     pf_shutdown,           pf_pick,
+    pf_cancel_pick, pf_cancel_picks,       pf_ping_one,
+    pf_exit_idle,   pf_check_connectivity, pf_notify_on_state_change};
 
 static void pick_first_factory_ref(grpc_lb_policy_factory *factory) {}
 
@@ -395,7 +421,7 @@ static grpc_lb_policy *create_pick_first(grpc_exec_ctx *exec_ctx,
                                          grpc_lb_policy_factory *factory,
                                          grpc_lb_policy_args *args) {
   GPR_ASSERT(args->addresses != NULL);
-  GPR_ASSERT(args->subchannel_factory != NULL);
+  GPR_ASSERT(args->client_channel_factory != NULL);
 
   if (args->addresses->naddrs == 0) return NULL;
 
@@ -412,8 +438,8 @@ static grpc_lb_policy *create_pick_first(grpc_exec_ctx *exec_ctx,
     sc_args.addr = (struct sockaddr *)(args->addresses->addrs[i].addr);
     sc_args.addr_len = (size_t)args->addresses->addrs[i].len;
 
-    grpc_subchannel *subchannel = grpc_subchannel_factory_create_subchannel(
-        exec_ctx, args->subchannel_factory, &sc_args);
+    grpc_subchannel *subchannel = grpc_client_channel_factory_create_subchannel(
+        exec_ctx, args->client_channel_factory, &sc_args);
 
     if (subchannel != NULL) {
       p->subchannels[subchannel_idx++] = subchannel;
diff --git a/src/core/ext/lb_policy/round_robin/round_robin.c b/src/core/ext/lb_policy/round_robin/round_robin.c
index d94c081494..3f6051b892 100644
--- a/src/core/ext/lb_policy/round_robin/round_robin.c
+++ b/src/core/ext/lb_policy/round_robin/round_robin.c
@@ -35,7 +35,7 @@
 
 #include <grpc/support/alloc.h>
 
-#include "src/core/lib/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/transport/connectivity_state.h"
 
@@ -49,6 +49,7 @@ int grpc_lb_round_robin_trace = 0;
 typedef struct pending_pick {
   struct pending_pick *next;
   grpc_pollset *pollset;
+  uint32_t initial_metadata_flags;
   grpc_connected_subchannel **target;
   grpc_closure *on_complete;
 } pending_pick;
@@ -275,6 +276,32 @@ static void rr_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
   gpr_mu_unlock(&p->mu);
 }
 
+static void rr_cancel_picks(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                            uint32_t initial_metadata_flags_mask,
+                            uint32_t initial_metadata_flags_eq) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  pending_pick *pp;
+  gpr_mu_lock(&p->mu);
+  pp = p->pending_picks;
+  p->pending_picks = NULL;
+  while (pp != NULL) {
+    pending_pick *next = pp->next;
+    if ((pp->initial_metadata_flags & initial_metadata_flags_mask) ==
+        initial_metadata_flags_eq) {
+      grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                   pp->pollset);
+      *pp->target = NULL;
+      grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, false, NULL);
+      gpr_free(pp);
+    } else {
+      pp->next = p->pending_picks;
+      p->pending_picks = pp;
+    }
+    pp = next;
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
 static void start_picking(grpc_exec_ctx *exec_ctx, round_robin_lb_policy *p) {
   size_t i;
   p->started_picking = 1;
@@ -303,6 +330,7 @@ static void rr_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 
 static int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
                    grpc_pollset *pollset, grpc_metadata_batch *initial_metadata,
+                   uint32_t initial_metadata_flags,
                    grpc_connected_subchannel **target,
                    grpc_closure *on_complete) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
@@ -330,6 +358,7 @@ static int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
     pp->pollset = pollset;
     pp->target = target;
     pp->on_complete = on_complete;
+    pp->initial_metadata_flags = initial_metadata_flags;
     p->pending_picks = pp;
     gpr_mu_unlock(&p->mu);
     return 0;
@@ -485,14 +514,9 @@ static void rr_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
 }
 
 static const grpc_lb_policy_vtable round_robin_lb_policy_vtable = {
-    rr_destroy,
-    rr_shutdown,
-    rr_pick,
-    rr_cancel_pick,
-    rr_ping_one,
-    rr_exit_idle,
-    rr_check_connectivity,
-    rr_notify_on_state_change};
+    rr_destroy,     rr_shutdown,           rr_pick,
+    rr_cancel_pick, rr_cancel_picks,       rr_ping_one,
+    rr_exit_idle,   rr_check_connectivity, rr_notify_on_state_change};
 
 static void round_robin_factory_ref(grpc_lb_policy_factory *factory) {}
 
@@ -502,7 +526,7 @@ static grpc_lb_policy *create_round_robin(grpc_exec_ctx *exec_ctx,
                                           grpc_lb_policy_factory *factory,
                                           grpc_lb_policy_args *args) {
   GPR_ASSERT(args->addresses != NULL);
-  GPR_ASSERT(args->subchannel_factory != NULL);
+  GPR_ASSERT(args->client_channel_factory != NULL);
 
   round_robin_lb_policy *p = gpr_malloc(sizeof(*p));
   memset(p, 0, sizeof(*p));
@@ -518,8 +542,8 @@ static grpc_lb_policy *create_round_robin(grpc_exec_ctx *exec_ctx,
     sc_args.addr = (struct sockaddr *)(args->addresses->addrs[i].addr);
     sc_args.addr_len = (size_t)args->addresses->addrs[i].len;
 
-    grpc_subchannel *subchannel = grpc_subchannel_factory_create_subchannel(
-        exec_ctx, args->subchannel_factory, &sc_args);
+    grpc_subchannel *subchannel = grpc_client_channel_factory_create_subchannel(
+        exec_ctx, args->client_channel_factory, &sc_args);
 
     if (subchannel != NULL) {
       subchannel_data *sd = gpr_malloc(sizeof(*sd));
diff --git a/src/core/ext/resolver/dns/native/dns_resolver.c b/src/core/ext/resolver/dns/native/dns_resolver.c
index 70d8a3fe2d..2749b0ca01 100644
--- a/src/core/ext/resolver/dns/native/dns_resolver.c
+++ b/src/core/ext/resolver/dns/native/dns_resolver.c
@@ -37,8 +37,8 @@
 #include <grpc/support/host_port.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/lib/client_config/lb_policy_registry.h"
-#include "src/core/lib/client_config/resolver_registry.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/support/backoff.h"
@@ -59,7 +59,7 @@ typedef struct {
   /** default port to use */
   char *default_port;
   /** subchannel factory */
-  grpc_subchannel_factory *subchannel_factory;
+  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
@@ -170,7 +170,7 @@ static void dns_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
     config = grpc_client_config_create();
     memset(&lb_policy_args, 0, sizeof(lb_policy_args));
     lb_policy_args.addresses = addresses;
-    lb_policy_args.subchannel_factory = r->subchannel_factory;
+    lb_policy_args.client_channel_factory = r->client_channel_factory;
     lb_policy =
         grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
     if (lb_policy != NULL) {
@@ -228,7 +228,7 @@ static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   if (r->resolved_config) {
     grpc_client_config_unref(exec_ctx, r->resolved_config);
   }
-  grpc_subchannel_factory_unref(exec_ctx, r->subchannel_factory);
+  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
   gpr_free(r->name);
   gpr_free(r->default_port);
   gpr_free(r->lb_policy_name);
@@ -255,10 +255,10 @@ static grpc_resolver *dns_create(grpc_resolver_args *args,
   grpc_resolver_init(&r->base, &dns_resolver_vtable);
   r->name = gpr_strdup(path);
   r->default_port = gpr_strdup(default_port);
-  r->subchannel_factory = args->subchannel_factory;
+  r->client_channel_factory = args->client_channel_factory;
   gpr_backoff_init(&r->backoff_state, BACKOFF_MULTIPLIER, BACKOFF_JITTER,
                    BACKOFF_MIN_SECONDS * 1000, BACKOFF_MAX_SECONDS * 1000);
-  grpc_subchannel_factory_ref(r->subchannel_factory);
+  grpc_client_channel_factory_ref(r->client_channel_factory);
   r->lb_policy_name = gpr_strdup(lb_policy_name);
   return &r->base;
 }
diff --git a/src/core/ext/resolver/sockaddr/sockaddr_resolver.c b/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
index 69595ca3db..1f14b40e18 100644
--- a/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
+++ b/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,17 +31,17 @@
  *
  */
 
-#include <grpc/support/port_platform.h>
-
+#include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
+#include <grpc/support/port_platform.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/lib/client_config/lb_policy_registry.h"
-#include "src/core/lib/client_config/resolver_registry.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/unix_sockets_posix.h"
 #include "src/core/lib/support/string.h"
@@ -52,7 +52,7 @@ typedef struct {
   /** refcount */
   gpr_refcount refs;
   /** subchannel factory */
-  grpc_subchannel_factory *subchannel_factory;
+  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
@@ -125,7 +125,7 @@ static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
     grpc_lb_policy_args lb_policy_args;
     memset(&lb_policy_args, 0, sizeof(lb_policy_args));
     lb_policy_args.addresses = r->addresses;
-    lb_policy_args.subchannel_factory = r->subchannel_factory;
+    lb_policy_args.client_channel_factory = r->client_channel_factory;
     grpc_lb_policy *lb_policy =
         grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
     grpc_client_config_set_lb_policy(cfg, lb_policy);
@@ -140,7 +140,7 @@ static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
 static void sockaddr_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   sockaddr_resolver *r = (sockaddr_resolver *)gr;
   gpr_mu_destroy(&r->mu);
-  grpc_subchannel_factory_unref(exec_ctx, r->subchannel_factory);
+  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
   grpc_resolved_addresses_destroy(r->addresses);
   gpr_free(r->lb_policy_name);
   gpr_free(r);
@@ -263,22 +263,24 @@ static grpc_resolver *sockaddr_create(
   r = gpr_malloc(sizeof(sockaddr_resolver));
   memset(r, 0, sizeof(*r));
 
-  r->lb_policy_name = NULL;
-  if (0 != strcmp(args->uri->query, "")) {
-    gpr_slice query_slice;
-    gpr_slice_buffer query_parts;
-
-    query_slice =
-        gpr_slice_new(args->uri->query, strlen(args->uri->query), do_nothing);
-    gpr_slice_buffer_init(&query_parts);
-    gpr_slice_split(query_slice, "=", &query_parts);
-    GPR_ASSERT(query_parts.count == 2);
-    if (0 == gpr_slice_str_cmp(query_parts.slices[0], "lb_policy")) {
-      r->lb_policy_name = gpr_dump_slice(query_parts.slices[1], GPR_DUMP_ASCII);
-    }
-    gpr_slice_buffer_destroy(&query_parts);
-    gpr_slice_unref(query_slice);
+  r->lb_policy_name =
+      gpr_strdup(grpc_uri_get_query_arg(args->uri, "lb_policy"));
+  const char *lb_enabled_qpart =
+      grpc_uri_get_query_arg(args->uri, "lb_enabled");
+  /* anything other than "0" is interpreted as true */
+  const bool lb_enabled =
+      (lb_enabled_qpart != NULL && (strcmp("0", lb_enabled_qpart) != 0));
+
+  if (r->lb_policy_name != NULL && strcmp("grpclb", r->lb_policy_name) == 0 &&
+      !lb_enabled) {
+    /* we want grpclb but the "resolved" addresses aren't LB enabled. Bail
+     * out, as this is meant mostly for tests. */
+    gpr_log(GPR_ERROR,
+            "Requested 'grpclb' LB policy but resolved addresses don't "
+            "support load balancing.");
+    abort();
   }
+
   if (r->lb_policy_name == NULL) {
     r->lb_policy_name = gpr_strdup(default_lb_policy_name);
   }
@@ -318,8 +320,8 @@ static grpc_resolver *sockaddr_create(
   gpr_ref_init(&r->refs, 1);
   gpr_mu_init(&r->mu);
   grpc_resolver_init(&r->base, &sockaddr_resolver_vtable);
-  r->subchannel_factory = args->subchannel_factory;
-  grpc_subchannel_factory_ref(r->subchannel_factory);
+  r->client_channel_factory = args->client_channel_factory;
+  grpc_client_channel_factory_ref(r->client_channel_factory);
 
   return &r->base;
 }
diff --git a/src/core/ext/resolver/zookeeper/zookeeper_resolver.c b/src/core/ext/resolver/zookeeper/zookeeper_resolver.c
index 5acb0940c6..898632c3cd 100644
--- a/src/core/ext/resolver/zookeeper/zookeeper_resolver.c
+++ b/src/core/ext/resolver/zookeeper/zookeeper_resolver.c
@@ -39,8 +39,8 @@
 #include <grpc/grpc_zookeeper.h>
 #include <zookeeper/zookeeper.h>
 
-#include "src/core/lib/client_config/lb_policy_registry.h"
-#include "src/core/lib/client_config/resolver_registry.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/json/json.h"
 #include "src/core/lib/support/string.h"
@@ -57,7 +57,7 @@ typedef struct {
   /** name to resolve */
   char *name;
   /** subchannel factory */
-  grpc_subchannel_factory *subchannel_factory;
+  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
@@ -187,9 +187,8 @@ static void zookeeper_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
   if (addresses != NULL) {
     grpc_lb_policy_args lb_policy_args;
     config = grpc_client_config_create();
-
     lb_policy_args.addresses = addresses;
-    lb_policy_args.subchannel_factory = r->subchannel_factory;
+    lb_policy_args.client_channel_factory = r->client_channel_factory;
     lb_policy =
         grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
 
@@ -424,7 +423,7 @@ static void zookeeper_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   if (r->resolved_config != NULL) {
     grpc_client_config_unref(exec_ctx, r->resolved_config);
   }
-  grpc_subchannel_factory_unref(exec_ctx, r->subchannel_factory);
+  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
   gpr_free(r->name);
   gpr_free(r->lb_policy_name);
   gpr_free(r);
@@ -454,8 +453,8 @@ static grpc_resolver *zookeeper_create(grpc_resolver_args *args,
   grpc_resolver_init(&r->base, &zookeeper_resolver_vtable);
   r->name = gpr_strdup(path);
 
-  r->subchannel_factory = args->subchannel_factory;
-  grpc_subchannel_factory_ref(r->subchannel_factory);
+  r->client_channel_factory = args->client_channel_factory;
+  grpc_client_channel_factory_ref(r->client_channel_factory);
 
   r->lb_policy_name = gpr_strdup(lb_policy_name);
 
diff --git a/src/core/ext/transport/chttp2/client/insecure/channel_create.c b/src/core/ext/transport/chttp2/client/insecure/channel_create.c
index 606fff5fb4..5484438f0a 100644
--- a/src/core/ext/transport/chttp2/client/insecure/channel_create.c
+++ b/src/core/ext/transport/chttp2/client/insecure/channel_create.c
@@ -41,12 +41,12 @@
 #include <grpc/support/slice_buffer.h>
 
 #include "src/core/ext/census/grpc_filter.h"
+#include "src/core/ext/client_config/client_channel.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/channel/channel_args.h"
-#include "src/core/lib/channel/client_channel.h"
 #include "src/core/lib/channel/compress_filter.h"
 #include "src/core/lib/channel/http_client_filter.h"
-#include "src/core/lib/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/tcp_client.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/channel.h"
@@ -136,31 +136,35 @@ static const grpc_connector_vtable connector_vtable = {
     connector_ref, connector_unref, connector_shutdown, connector_connect};
 
 typedef struct {
-  grpc_subchannel_factory base;
+  grpc_client_channel_factory base;
   gpr_refcount refs;
   grpc_channel_args *merge_args;
   grpc_channel *master;
-} subchannel_factory;
+} client_channel_factory;
 
-static void subchannel_factory_ref(grpc_subchannel_factory *scf) {
-  subchannel_factory *f = (subchannel_factory *)scf;
+static void client_channel_factory_ref(
+    grpc_client_channel_factory *cc_factory) {
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
   gpr_ref(&f->refs);
 }
 
-static void subchannel_factory_unref(grpc_exec_ctx *exec_ctx,
-                                     grpc_subchannel_factory *scf) {
-  subchannel_factory *f = (subchannel_factory *)scf;
+static void client_channel_factory_unref(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory) {
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
   if (gpr_unref(&f->refs)) {
-    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master, "subchannel_factory");
+    if (f->master != NULL) {
+      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master,
+                                  "client_channel_factory");
+    }
     grpc_channel_args_destroy(f->merge_args);
     gpr_free(f);
   }
 }
 
-static grpc_subchannel *subchannel_factory_create_subchannel(
-    grpc_exec_ctx *exec_ctx, grpc_subchannel_factory *scf,
+static grpc_subchannel *client_channel_factory_create_subchannel(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory,
     grpc_subchannel_args *args) {
-  subchannel_factory *f = (subchannel_factory *)scf;
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
   connector *c = gpr_malloc(sizeof(*c));
   grpc_channel_args *final_args =
       grpc_channel_args_merge(args->args, f->merge_args);
@@ -175,9 +179,33 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
   return s;
 }
 
-static const grpc_subchannel_factory_vtable subchannel_factory_vtable = {
-    subchannel_factory_ref, subchannel_factory_unref,
-    subchannel_factory_create_subchannel};
+static grpc_channel *client_channel_factory_create_channel(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory,
+    const char *target, grpc_client_channel_type type,
+    grpc_channel_args *args) {
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
+  grpc_channel_args *final_args = grpc_channel_args_merge(args, f->merge_args);
+  grpc_channel *channel = grpc_channel_create(exec_ctx, target, final_args,
+                                              GRPC_CLIENT_CHANNEL, NULL);
+  grpc_channel_args_destroy(final_args);
+  grpc_resolver *resolver = grpc_resolver_create(target, &f->base);
+  if (!resolver) {
+    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel,
+                                "client_channel_factory_create_channel");
+    return NULL;
+  }
+
+  grpc_client_channel_set_resolver(
+      exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
+  GRPC_RESOLVER_UNREF(exec_ctx, resolver, "create_channel");
+
+  return channel;
+}
+
+static const grpc_client_channel_factory_vtable client_channel_factory_vtable =
+    {client_channel_factory_ref, client_channel_factory_unref,
+     client_channel_factory_create_subchannel,
+     client_channel_factory_create_channel};
 
 /* Create a client channel:
    Asynchronously: - resolve target
@@ -186,38 +214,27 @@ static const grpc_subchannel_factory_vtable subchannel_factory_vtable = {
 grpc_channel *grpc_insecure_channel_create(const char *target,
                                            const grpc_channel_args *args,
                                            void *reserved) {
-  grpc_channel *channel = NULL;
-  grpc_resolver *resolver;
-  subchannel_factory *f;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   GRPC_API_TRACE(
       "grpc_insecure_channel_create(target=%p, args=%p, reserved=%p)", 3,
       (target, args, reserved));
   GPR_ASSERT(!reserved);
 
-  channel =
-      grpc_channel_create(&exec_ctx, target, args, GRPC_CLIENT_CHANNEL, NULL);
-
-  f = gpr_malloc(sizeof(*f));
-  f->base.vtable = &subchannel_factory_vtable;
+  client_channel_factory *f = gpr_malloc(sizeof(*f));
+  memset(f, 0, sizeof(*f));
+  f->base.vtable = &client_channel_factory_vtable;
   gpr_ref_init(&f->refs, 1);
   f->merge_args = grpc_channel_args_copy(args);
-  f->master = channel;
-  GRPC_CHANNEL_INTERNAL_REF(f->master, "subchannel_factory");
-  resolver = grpc_resolver_create(target, &f->base);
-  if (!resolver) {
-    GRPC_CHANNEL_INTERNAL_UNREF(&exec_ctx, f->master, "subchannel_factory");
-    grpc_subchannel_factory_unref(&exec_ctx, &f->base);
-    grpc_exec_ctx_finish(&exec_ctx);
-    return NULL;
-  }
 
-  grpc_client_channel_set_resolver(
-      &exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
-  GRPC_RESOLVER_UNREF(&exec_ctx, resolver, "create");
-  grpc_subchannel_factory_unref(&exec_ctx, &f->base);
+  grpc_channel *channel = client_channel_factory_create_channel(
+      &exec_ctx, &f->base, target, GRPC_CLIENT_CHANNEL_TYPE_REGULAR, NULL);
+  if (channel != NULL) {
+    f->master = channel;
+    GRPC_CHANNEL_INTERNAL_REF(f->master, "grpc_insecure_channel_create");
+  }
+  grpc_client_channel_factory_unref(&exec_ctx, &f->base);
 
   grpc_exec_ctx_finish(&exec_ctx);
 
-  return channel;
+  return channel; /* may be NULL */
 }
diff --git a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
index 3465d2b6c4..58af6f995a 100644
--- a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
+++ b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
@@ -40,10 +40,10 @@
 #include <grpc/support/slice.h>
 #include <grpc/support/slice_buffer.h>
 
+#include "src/core/ext/client_config/client_channel.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/channel/channel_args.h"
-#include "src/core/lib/channel/client_channel.h"
-#include "src/core/lib/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/tcp_client.h"
 #include "src/core/lib/security/auth_filters.h"
 #include "src/core/lib/security/credentials.h"
@@ -192,34 +192,38 @@ static const grpc_connector_vtable connector_vtable = {
     connector_ref, connector_unref, connector_shutdown, connector_connect};
 
 typedef struct {
-  grpc_subchannel_factory base;
+  grpc_client_channel_factory base;
   gpr_refcount refs;
   grpc_channel_args *merge_args;
   grpc_channel_security_connector *security_connector;
   grpc_channel *master;
-} subchannel_factory;
+} client_channel_factory;
 
-static void subchannel_factory_ref(grpc_subchannel_factory *scf) {
-  subchannel_factory *f = (subchannel_factory *)scf;
+static void client_channel_factory_ref(
+    grpc_client_channel_factory *cc_factory) {
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
   gpr_ref(&f->refs);
 }
 
-static void subchannel_factory_unref(grpc_exec_ctx *exec_ctx,
-                                     grpc_subchannel_factory *scf) {
-  subchannel_factory *f = (subchannel_factory *)scf;
+static void client_channel_factory_unref(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory) {
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
   if (gpr_unref(&f->refs)) {
     GRPC_SECURITY_CONNECTOR_UNREF(&f->security_connector->base,
-                                  "subchannel_factory");
-    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master, "subchannel_factory");
+                                  "client_channel_factory");
+    if (f->master != NULL) {
+      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master,
+                                  "client_channel_factory");
+    }
     grpc_channel_args_destroy(f->merge_args);
     gpr_free(f);
   }
 }
 
-static grpc_subchannel *subchannel_factory_create_subchannel(
-    grpc_exec_ctx *exec_ctx, grpc_subchannel_factory *scf,
+static grpc_subchannel *client_channel_factory_create_subchannel(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory,
     grpc_subchannel_args *args) {
-  subchannel_factory *f = (subchannel_factory *)scf;
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
   connector *c = gpr_malloc(sizeof(*c));
   grpc_channel_args *final_args =
       grpc_channel_args_merge(args->args, f->merge_args);
@@ -236,9 +240,37 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
   return s;
 }
 
-static const grpc_subchannel_factory_vtable subchannel_factory_vtable = {
-    subchannel_factory_ref, subchannel_factory_unref,
-    subchannel_factory_create_subchannel};
+static grpc_channel *client_channel_factory_create_channel(
+    grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory,
+    const char *target, grpc_client_channel_type type,
+    grpc_channel_args *args) {
+  client_channel_factory *f = (client_channel_factory *)cc_factory;
+
+  grpc_channel_args *final_args = grpc_channel_args_merge(args, f->merge_args);
+  grpc_channel *channel = grpc_channel_create(exec_ctx, target, final_args,
+                                              GRPC_CLIENT_CHANNEL, NULL);
+  grpc_channel_args_destroy(final_args);
+
+  grpc_resolver *resolver = grpc_resolver_create(target, &f->base);
+  if (resolver != NULL) {
+    grpc_client_channel_set_resolver(
+        exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
+    GRPC_RESOLVER_UNREF(exec_ctx, resolver, "create");
+  } else {
+    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel,
+                                "client_channel_factory_create_channel");
+    channel = NULL;
+  }
+
+  GRPC_SECURITY_CONNECTOR_UNREF(&f->security_connector->base,
+                                "client_channel_factory_create_channel");
+  return channel;
+}
+
+static const grpc_client_channel_factory_vtable client_channel_factory_vtable =
+    {client_channel_factory_ref, client_channel_factory_unref,
+     client_channel_factory_create_subchannel,
+     client_channel_factory_create_channel};
 
 /* Create a secure client channel:
    Asynchronously: - resolve target
@@ -248,13 +280,11 @@ grpc_channel *grpc_secure_channel_create(grpc_channel_credentials *creds,
                                          const char *target,
                                          const grpc_channel_args *args,
                                          void *reserved) {
-  grpc_channel *channel;
   grpc_arg connector_arg;
   grpc_channel_args *args_copy;
   grpc_channel_args *new_args_from_connector;
   grpc_channel_security_connector *security_connector;
-  grpc_resolver *resolver;
-  subchannel_factory *f;
+  client_channel_factory *f;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
   GRPC_API_TRACE(
@@ -284,35 +314,30 @@ grpc_channel *grpc_secure_channel_create(grpc_channel_credentials *creds,
       new_args_from_connector != NULL ? new_args_from_connector : args,
       &connector_arg, 1);
 
-  channel = grpc_channel_create(&exec_ctx, target, args_copy,
-                                GRPC_CLIENT_CHANNEL, NULL);
-
   f = gpr_malloc(sizeof(*f));
-  f->base.vtable = &subchannel_factory_vtable;
+  memset(f, 0, sizeof(*f));
+  f->base.vtable = &client_channel_factory_vtable;
   gpr_ref_init(&f->refs, 1);
-  GRPC_SECURITY_CONNECTOR_REF(&security_connector->base, "subchannel_factory");
-  f->security_connector = security_connector;
+
   f->merge_args = grpc_channel_args_copy(args_copy);
-  f->master = channel;
-  GRPC_CHANNEL_INTERNAL_REF(channel, "subchannel_factory");
-  resolver = grpc_resolver_create(target, &f->base);
-  if (resolver) {
-    grpc_client_channel_set_resolver(
-        &exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
-    GRPC_RESOLVER_UNREF(&exec_ctx, resolver, "create");
-  }
-  grpc_subchannel_factory_unref(&exec_ctx, &f->base);
-  GRPC_SECURITY_CONNECTOR_UNREF(&security_connector->base, "channel_create");
   grpc_channel_args_destroy(args_copy);
   if (new_args_from_connector != NULL) {
     grpc_channel_args_destroy(new_args_from_connector);
   }
 
-  if (!resolver) {
-    GRPC_CHANNEL_INTERNAL_UNREF(&exec_ctx, channel, "subchannel_factory");
-    channel = NULL;
+  GRPC_SECURITY_CONNECTOR_REF(&security_connector->base,
+                              "grpc_secure_channel_create");
+  f->security_connector = security_connector;
+
+  grpc_channel *channel = client_channel_factory_create_channel(
+      &exec_ctx, &f->base, target, GRPC_CLIENT_CHANNEL_TYPE_REGULAR, NULL);
+  if (channel != NULL) {
+    f->master = channel;
+    GRPC_CHANNEL_INTERNAL_REF(f->master, "grpc_secure_channel_create");
   }
+
+  grpc_client_channel_factory_unref(&exec_ctx, &f->base);
   grpc_exec_ctx_finish(&exec_ctx);
 
-  return channel;
+  return channel; /* may be NULL */
 }
diff --git a/src/core/lib/channel/http_client_filter.c b/src/core/lib/channel/http_client_filter.c
index deba23e21f..211f537c69 100644
--- a/src/core/lib/channel/http_client_filter.c
+++ b/src/core/lib/channel/http_client_filter.c
@@ -111,10 +111,12 @@ static void hc_mutate_op(grpc_call_element *elem,
                                elem);
     /* Send : prefixed headers, which have to be before any application
        layer headers. */
-    grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->method,
-                                 op->send_idempotent_request
-                                     ? GRPC_MDELEM_METHOD_PUT
-                                     : GRPC_MDELEM_METHOD_POST);
+    grpc_metadata_batch_add_head(
+        op->send_initial_metadata, &calld->method,
+        op->send_initial_metadata_flags &
+                GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST
+            ? GRPC_MDELEM_METHOD_PUT
+            : GRPC_MDELEM_METHOD_POST);
     grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->scheme,
                                  channeld->static_scheme);
     grpc_metadata_batch_add_tail(op->send_initial_metadata, &calld->te_trailers,
diff --git a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
index dba335490b..3c8127e1a8 100644
--- a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015-2016, Google Inc.
+ * Copyright 2015, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index 235a7df08d..0eb95a2e09 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015-2016, Google Inc.
+ * Copyright 2015, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/src/core/lib/iomgr/ev_posix.h b/src/core/lib/iomgr/ev_posix.h
index 9d27b2bcda..1fa9f5ef2d 100644
--- a/src/core/lib/iomgr/ev_posix.h
+++ b/src/core/lib/iomgr/ev_posix.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015-2016, Google Inc.
+ * Copyright 2015, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/src/core/lib/iomgr/unix_sockets_posix.h b/src/core/lib/iomgr/unix_sockets_posix.h
index 752cab85a5..22d6af5044 100644
--- a/src/core/lib/iomgr/unix_sockets_posix.h
+++ b/src/core/lib/iomgr/unix_sockets_posix.h
@@ -38,8 +38,8 @@
 
 #include <grpc/support/string_util.h>
 
-#include "src/core/lib/client_config/resolver_factory.h"
-#include "src/core/lib/client_config/uri_parser.h"
+#include "src/core/ext/client_config/resolver_factory.h"
+#include "src/core/ext/client_config/uri_parser.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/sockaddr.h"
 
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index b22bd69f44..6581bbd3d1 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -81,11 +81,11 @@ typedef enum {
   /* Status came from the application layer overriding whatever
      the wire says */
   STATUS_FROM_API_OVERRIDE = 0,
-  /* Status was created by some internal channel stack operation */
-  STATUS_FROM_CORE,
   /* Status came from 'the wire' - or somewhere below the surface
      layer */
   STATUS_FROM_WIRE,
+  /* Status was created by some internal channel stack operation */
+  STATUS_FROM_CORE,
   /* Status came from the server sending status */
   STATUS_FROM_SERVER_STATUS,
   STATUS_SOURCE_COUNT
@@ -1115,6 +1115,9 @@ static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp, bool success) {
 
   gpr_mu_lock(&call->mu);
   if (bctl->send_initial_metadata) {
+    if (!success) {
+      set_status_code(call, STATUS_FROM_CORE, GRPC_STATUS_UNAVAILABLE);
+    }
     grpc_metadata_batch_destroy(
         &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */]);
   }
@@ -1237,8 +1240,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->metadata_batch[0][0].deadline = call->send_deadline;
         stream_op.send_initial_metadata =
             &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */];
-        stream_op.send_idempotent_request =
-            (op->flags & GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) != 0;
+        stream_op.send_initial_metadata_flags = op->flags;
         break;
       case GRPC_OP_SEND_MESSAGE:
         if (!are_write_flags_valid(op->flags)) {
diff --git a/src/core/lib/surface/channel.c b/src/core/lib/surface/channel.c
index 06f991b085..332f504507 100644
--- a/src/core/lib/surface/channel.c
+++ b/src/core/lib/surface/channel.c
@@ -40,7 +40,7 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/lib/client_config/resolver_registry.h"
+#include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/surface/api_trace.h"
diff --git a/src/core/lib/surface/channel.h b/src/core/lib/surface/channel.h
index 640fd7e137..22dae930e4 100644
--- a/src/core/lib/surface/channel.h
+++ b/src/core/lib/surface/channel.h
@@ -35,7 +35,6 @@
 #define GRPC_CORE_LIB_SURFACE_CHANNEL_H
 
 #include "src/core/lib/channel/channel_stack.h"
-#include "src/core/lib/client_config/subchannel_factory.h"
 #include "src/core/lib/surface/channel_stack_type.h"
 
 grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
diff --git a/src/core/lib/surface/init.c b/src/core/lib/surface/init.c
index aca4ce9d07..f221d8db35 100644
--- a/src/core/lib/surface/init.c
+++ b/src/core/lib/surface/init.c
@@ -39,17 +39,17 @@
 #include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/time.h>
+#include "src/core/ext/client_config/client_channel.h"
+#include "src/core/ext/client_config/lb_policy_registry.h"
+#include "src/core/ext/client_config/resolver_registry.h"
+#include "src/core/ext/client_config/subchannel.h"
+#include "src/core/ext/client_config/subchannel_index.h"
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/channel/channel_stack.h"
-#include "src/core/lib/channel/client_channel.h"
 #include "src/core/lib/channel/compress_filter.h"
 #include "src/core/lib/channel/connected_channel.h"
 #include "src/core/lib/channel/http_client_filter.h"
 #include "src/core/lib/channel/http_server_filter.h"
-#include "src/core/lib/client_config/lb_policy_registry.h"
-#include "src/core/lib/client_config/resolver_registry.h"
-#include "src/core/lib/client_config/subchannel.h"
-#include "src/core/lib/client_config/subchannel_index.h"
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/iomgr/iomgr.h"
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index a78d71322c..1eb446312b 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -101,9 +101,9 @@ typedef struct grpc_transport_stream_op {
   /** Send initial metadata to the peer, from the provided metadata batch.
       idempotent_request MUST be set if this is non-null */
   grpc_metadata_batch *send_initial_metadata;
-  /** Iff send_initial_metadata != NULL, flags if this is an idempotent request
-      or not */
-  bool send_idempotent_request;
+  /** Iff send_initial_metadata != NULL, flags associated with
+      send_initial_metadata: a bitfield of GRPC_INITIAL_METADATA_xxx */
+  uint32_t send_initial_metadata_flags;
 
   /** Send trailing metadata to the peer, from the provided metadata batch. */
   grpc_metadata_batch *send_trailing_metadata;
diff --git a/src/cpp/client/client_context.cc b/src/cpp/client/client_context.cc
index bf6423128a..c277d7ebe8 100644
--- a/src/cpp/client/client_context.cc
+++ b/src/cpp/client/client_context.cc
@@ -60,6 +60,8 @@ static ClientContext::GlobalCallbacks* g_client_callbacks =
 
 ClientContext::ClientContext()
     : initial_metadata_received_(false),
+      fail_fast_(true),
+      idempotent_(false),
       call_(nullptr),
       call_canceled_(false),
       deadline_(gpr_inf_future(GPR_CLOCK_REALTIME)),
diff --git a/src/csharp/Grpc.Core/CallInvoker.cs b/src/csharp/Grpc.Core/CallInvoker.cs
new file mode 100644
index 0000000000..39199b1fd5
--- /dev/null
+++ b/src/csharp/Grpc.Core/CallInvoker.cs
@@ -0,0 +1,84 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, 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.Threading.Tasks;
+using Grpc.Core.Internal;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Abstraction of client-side RPC invocation.
+    /// </summary>
+    /// <seealso cref="Calls"/>
+    public abstract class CallInvoker
+    {
+        /// <summary>
+        /// Invokes a simple remote call in a blocking fashion.
+        /// </summary>
+        public abstract TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+            where TRequest : class
+            where TResponse : class;
+
+        /// <summary>
+        /// Invokes a simple remote call asynchronously.
+        /// </summary>
+        public abstract AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+            where TRequest : class
+            where TResponse : class;
+
+        /// <summary>
+        /// Invokes a server streaming call asynchronously.
+        /// In server streaming scenario, client sends on request and server responds with a stream of responses.
+        /// </summary>
+        public abstract AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+            where TRequest : class
+            where TResponse : class;
+
+        /// <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>
+        public abstract AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+            where TRequest : class
+            where TResponse : class;
+
+        /// <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>
+        public abstract AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+            where TRequest : class
+            where TResponse : class;
+    }
+}
diff --git a/src/csharp/Grpc.Core/ClientBase.cs b/src/csharp/Grpc.Core/ClientBase.cs
index e5b398062b..5517233e3c 100644
--- a/src/csharp/Grpc.Core/ClientBase.cs
+++ b/src/csharp/Grpc.Core/ClientBase.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -31,93 +31,156 @@
 
 #endregion
 
-using System;
-using System.Text.RegularExpressions;
-using System.Threading.Tasks;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
 
 namespace Grpc.Core
 {
     /// <summary>
-    /// Interceptor for call headers.
+    /// Generic base class for client-side stubs.
     /// </summary>
-    /// <remarks>Header interceptor is no longer to recommented way to perform authentication.
-    /// For header (initial metadata) based auth such as OAuth2 or JWT access token, use <see cref="MetadataCredentials"/>.
-    /// </remarks>
-    public delegate void HeaderInterceptor(IMethod method, Metadata metadata);
+    public abstract class ClientBase<T> : ClientBase
+        where T : ClientBase<T>
+    {
+        /// <summary>
+        /// Initializes a new instance of <c>ClientBase</c> class that
+        /// throws <c>NotImplementedException</c> upon invocation of any RPC.
+        /// This constructor is only provided to allow creation of test doubles
+        /// for client classes (e.g. mocking requires a parameterless constructor).
+        /// </summary>
+        protected ClientBase() : base()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of <c>ClientBase</c> class.
+        /// </summary>
+        /// <param name="configuration">The configuration.</param>
+        protected ClientBase(ClientBaseConfiguration configuration) : base(configuration)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of <c>ClientBase</c> class.
+        /// </summary>
+        /// <param name="channel">The channel to use for remote call invocation.</param>
+        public ClientBase(Channel channel) : base(channel)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of <c>ClientBase</c> class.
+        /// </summary>
+        /// <param name="callInvoker">The <c>CallInvoker</c> for remote call invocation.</param>
+        public ClientBase(CallInvoker callInvoker) : base(callInvoker)
+        {
+        }
+
+        /// <summary>
+        /// Creates a new client that sets host field for calls explicitly.
+        /// gRPC supports multiple "hosts" being served by a single server.
+        /// By default (if a client was not created by calling this method),
+        /// host <c>null</c> with the meaning "use default host" is used.
+        /// </summary>
+        public T WithHost(string host)
+        {
+            var newConfiguration = this.Configuration.WithHost(host);
+            return NewInstance(newConfiguration);
+        }
+
+        /// <summary>
+        /// Creates a new instance of client from given <c>ClientBaseConfiguration</c>.
+        /// </summary>
+        protected abstract T NewInstance(ClientBaseConfiguration configuration);
+    }
 
     /// <summary>
     /// Base class for client-side stubs.
     /// </summary>
     public abstract class ClientBase
     {
-        readonly Channel channel;
+        readonly ClientBaseConfiguration configuration;
+        readonly CallInvoker callInvoker;
+
+        /// <summary>
+        /// Initializes a new instance of <c>ClientBase</c> class that
+        /// throws <c>NotImplementedException</c> upon invocation of any RPC.
+        /// This constructor is only provided to allow creation of test doubles
+        /// for client classes (e.g. mocking requires a parameterless constructor).
+        /// </summary>
+        protected ClientBase() : this(new UnimplementedCallInvoker())
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of <c>ClientBase</c> class.
+        /// </summary>
+        /// <param name="configuration">The configuration.</param>
+        protected ClientBase(ClientBaseConfiguration configuration)
+        {
+            this.configuration = GrpcPreconditions.CheckNotNull(configuration, "configuration");
+            this.callInvoker = configuration.CreateDecoratedCallInvoker();
+        }
 
         /// <summary>
         /// Initializes a new instance of <c>ClientBase</c> class.
         /// </summary>
         /// <param name="channel">The channel to use for remote call invocation.</param>
-        public ClientBase(Channel channel)
+        public ClientBase(Channel channel) : this(new DefaultCallInvoker(channel))
         {
-            this.channel = channel;
         }
 
         /// <summary>
-        /// Can be used to register a custom header interceptor.
-        /// The interceptor is invoked each time a new call on this client is started.
-        /// It is not recommented to use header interceptor to add auth headers to RPC calls.
+        /// Initializes a new instance of <c>ClientBase</c> class.
         /// </summary>
-        /// <seealso cref="HeaderInterceptor"/>
-        public HeaderInterceptor HeaderInterceptor
+        /// <param name="callInvoker">The <c>CallInvoker</c> for remote call invocation.</param>
+        public ClientBase(CallInvoker callInvoker) : this(new ClientBaseConfiguration(callInvoker, null))
         {
-            get;
-            set;
         }
 
         /// <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".
+        /// Gets the call invoker.
         /// </summary>
-        public string Host
+        protected CallInvoker CallInvoker
         {
-            get;
-            set;
+            get { return this.callInvoker; }
         }
 
         /// <summary>
-        /// Channel associated with this client.
+        /// Gets the configuration.
         /// </summary>
-        public Channel Channel
+        internal ClientBaseConfiguration Configuration
         {
-            get
-            {
-                return this.channel;
-            }
+            get { return this.configuration; }
         }
 
         /// <summary>
-        /// Creates a new call to given method.
+        /// Represents configuration of ClientBase. The class itself is visible to
+        /// subclasses, but contents are marked as internal to make the instances opaque.
+        /// The verbose name of this class was chosen to make name clash in generated code 
+        /// less likely.
         /// </summary>
-        /// <param name="method">The method to invoke.</param>
-        /// <param name="options">The call options.</param>
-        /// <typeparam name="TRequest">Request message type.</typeparam>
-        /// <typeparam name="TResponse">Response message type.</typeparam>
-        /// <returns>The call invocation details.</returns>
-        protected CallInvocationDetails<TRequest, TResponse> CreateCall<TRequest, TResponse>(Method<TRequest, TResponse> method, CallOptions options)
-            where TRequest : class
-            where TResponse : class
+        protected internal class ClientBaseConfiguration
         {
-            var interceptor = HeaderInterceptor;
-            if (interceptor != null)
+            readonly CallInvoker undecoratedCallInvoker;
+            readonly string host;
+
+            internal ClientBaseConfiguration(CallInvoker undecoratedCallInvoker, string host)
+            {
+                this.undecoratedCallInvoker = GrpcPreconditions.CheckNotNull(undecoratedCallInvoker);
+                this.host = host;
+            }
+
+            internal CallInvoker CreateDecoratedCallInvoker()
+            {
+                return new InterceptingCallInvoker(undecoratedCallInvoker, hostInterceptor: (h) => host);
+            }
+
+            internal ClientBaseConfiguration WithHost(string host)
             {
-                if (options.Headers == null)
-                {
-                    options = options.WithHeaders(new Metadata());
-                }
-                interceptor(method, options.Headers);
+                GrpcPreconditions.CheckNotNull(host, "host");
+                return new ClientBaseConfiguration(this.undecoratedCallInvoker, host);
             }
-            return new CallInvocationDetails<TRequest, TResponse>(channel, method, Host, options);
         }
     }
 }
diff --git a/src/csharp/Grpc.Core/DefaultCallInvoker.cs b/src/csharp/Grpc.Core/DefaultCallInvoker.cs
new file mode 100644
index 0000000000..1a99e41153
--- /dev/null
+++ b/src/csharp/Grpc.Core/DefaultCallInvoker.cs
@@ -0,0 +1,112 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, 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.Threading.Tasks;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Invokes client RPCs using <see cref="Calls"/>.
+    /// </summary>
+    public class DefaultCallInvoker : CallInvoker
+    {
+        readonly Channel channel;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Grpc.Core.DefaultCallInvoker"/> class.
+        /// </summary>
+        /// <param name="channel">Channel to use.</param>
+        public DefaultCallInvoker(Channel channel)
+        {
+            this.channel = GrpcPreconditions.CheckNotNull(channel);
+        }
+
+        /// <summary>
+        /// Invokes a simple remote call in a blocking fashion.
+        /// </summary>
+        public override TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            var call = CreateCall(method, host, options);
+            return Calls.BlockingUnaryCall(call, request);
+        }
+
+        /// <summary>
+        /// Invokes a simple remote call asynchronously.
+        /// </summary>
+        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            var call = CreateCall(method, host, options);
+            return Calls.AsyncUnaryCall(call, request);
+        }
+
+        /// <summary>
+        /// Invokes a server streaming call asynchronously.
+        /// In server streaming scenario, client sends on request and server responds with a stream of responses.
+        /// </summary>
+        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            var call = CreateCall(method, host, options);
+            return Calls.AsyncServerStreamingCall(call, request);
+        }
+
+        /// <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>
+        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+        {
+            var call = CreateCall(method, host, options);
+            return Calls.AsyncClientStreamingCall(call);
+        }
+
+        /// <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>
+        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+        {
+            var call = CreateCall(method, host, options);
+            return Calls.AsyncDuplexStreamingCall(call);
+        }
+
+        protected virtual CallInvocationDetails<TRequest, TResponse> CreateCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+                where TRequest : class
+                where TResponse : class
+        {
+            return new CallInvocationDetails<TRequest, TResponse>(channel, method, host, options);
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 3189835ccd..251a688946 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -129,6 +129,10 @@
     <Compile Include="Profiling\Profilers.cs" />
     <Compile Include="Internal\DefaultSslRootsOverride.cs" />
     <Compile Include="Utils\GrpcPreconditions.cs" />
+    <Compile Include="CallInvoker.cs" />
+    <Compile Include="DefaultCallInvoker.cs" />
+    <Compile Include="Internal\UnimplementedCallInvoker.cs" />
+    <Compile Include="Internal\InterceptingCallInvoker.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Grpc.Core.nuspec" />
diff --git a/src/csharp/Grpc.Core/Internal/InterceptingCallInvoker.cs b/src/csharp/Grpc.Core/Internal/InterceptingCallInvoker.cs
new file mode 100644
index 0000000000..ef48dc7121
--- /dev/null
+++ b/src/csharp/Grpc.Core/Internal/InterceptingCallInvoker.cs
@@ -0,0 +1,134 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, 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.Tasks;
+using Grpc.Core;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core.Internal
+{
+    /// <summary>
+    /// Decorates an underlying <c>CallInvoker</c> to intercept call invocations.
+    /// </summary>
+    internal class InterceptingCallInvoker : CallInvoker
+    {
+        readonly CallInvoker callInvoker;
+        readonly Func<string, string> hostInterceptor;
+        readonly Func<CallOptions, CallOptions> callOptionsInterceptor;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Grpc.Core.InterceptingCallInvoker"/> class.
+        /// </summary>
+        public InterceptingCallInvoker(CallInvoker callInvoker,
+            Func<string, string> hostInterceptor = null,
+            Func<CallOptions, CallOptions> callOptionsInterceptor = null)
+        {
+            this.callInvoker = GrpcPreconditions.CheckNotNull(callInvoker);
+            this.hostInterceptor = hostInterceptor;
+            this.callOptionsInterceptor = callOptionsInterceptor;
+        }
+
+        /// <summary>
+        /// Intercepts a unary call.
+        /// </summary>
+        public override TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            host = InterceptHost(host);
+            options = InterceptCallOptions(options);
+            return callInvoker.BlockingUnaryCall(method, host, options, request);
+        }
+
+        /// <summary>
+        /// Invokes a simple remote call asynchronously.
+        /// </summary>
+        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            host = InterceptHost(host);
+            options = InterceptCallOptions(options);
+            return callInvoker.AsyncUnaryCall(method, host, options, request);
+        }
+
+        /// <summary>
+        /// Invokes a server streaming call asynchronously.
+        /// In server streaming scenario, client sends on request and server responds with a stream of responses.
+        /// </summary>
+        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            host = InterceptHost(host);
+            options = InterceptCallOptions(options);
+            return callInvoker.AsyncServerStreamingCall(method, host, options, request);
+        }
+
+        /// <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>
+        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+        {
+            host = InterceptHost(host);
+            options = InterceptCallOptions(options);
+            return callInvoker.AsyncClientStreamingCall(method, host, options);
+        }
+
+        /// <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>
+        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+        {
+            host = InterceptHost(host);
+            options = InterceptCallOptions(options);
+            return callInvoker.AsyncDuplexStreamingCall(method, host, options);
+        }
+
+        private string InterceptHost(string host)
+        {
+            if (hostInterceptor == null)
+            {
+                return host;
+            }
+            return hostInterceptor(host);
+        }
+
+        private CallOptions InterceptCallOptions(CallOptions options)
+        {
+            if (callOptionsInterceptor == null)
+            {
+                return options;
+            }
+            return callOptionsInterceptor(options);
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core/Internal/UnimplementedCallInvoker.cs b/src/csharp/Grpc.Core/Internal/UnimplementedCallInvoker.cs
new file mode 100644
index 0000000000..0c7340873b
--- /dev/null
+++ b/src/csharp/Grpc.Core/Internal/UnimplementedCallInvoker.cs
@@ -0,0 +1,75 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, 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.Tasks;
+using Grpc.Core;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core.Internal
+{
+    /// <summary>
+    /// Call invoker that throws <c>NotImplementedException</c> for all requests.
+    /// </summary>
+    internal class UnimplementedCallInvoker : CallInvoker
+    {
+        public UnimplementedCallInvoker()
+        {
+        }
+
+        public override TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Examples.MathClient/MathClient.cs b/src/csharp/Grpc.Examples.MathClient/MathClient.cs
index 64e429ed5a..aadef6833d 100644
--- a/src/csharp/Grpc.Examples.MathClient/MathClient.cs
+++ b/src/csharp/Grpc.Examples.MathClient/MathClient.cs
@@ -1,5 +1,5 @@
 #region Copyright notice and license
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -40,7 +40,7 @@ namespace Math
         public static void Main(string[] args)
         {
             var channel = new Channel("127.0.0.1", 23456, ChannelCredentials.Insecure);
-            Math.IMathClient client = new Math.MathClient(channel);
+            Math.MathClient client = new Math.MathClient(channel);
             MathExamples.DivExample(client);
 
             MathExamples.DivAsyncExample(client).Wait();
diff --git a/src/csharp/Grpc.Examples/MathExamples.cs b/src/csharp/Grpc.Examples/MathExamples.cs
index 8009ccbbfa..6075420974 100644
--- a/src/csharp/Grpc.Examples/MathExamples.cs
+++ b/src/csharp/Grpc.Examples/MathExamples.cs
@@ -1,5 +1,5 @@
 #region Copyright notice and license
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -38,19 +38,19 @@ namespace Math
 {
     public static class MathExamples
     {
-        public static void DivExample(Math.IMathClient client)
+        public static void DivExample(Math.MathClient client)
         {
             DivReply result = client.Div(new DivArgs { Dividend = 10, Divisor = 3 });
             Console.WriteLine("Div Result: " + result);
         }
 
-        public static async Task DivAsyncExample(Math.IMathClient client)
+        public static async Task DivAsyncExample(Math.MathClient client)
         {
             DivReply result = await client.DivAsync(new DivArgs { Dividend = 4, Divisor = 5 });
             Console.WriteLine("DivAsync Result: " + result);
         }
 
-        public static async Task FibExample(Math.IMathClient client)
+        public static async Task FibExample(Math.MathClient client)
         {
             using (var call = client.Fib(new FibArgs { Limit = 5 }))
             {
@@ -59,7 +59,7 @@ namespace Math
             }
         }
 
-        public static async Task SumExample(Math.IMathClient client)
+        public static async Task SumExample(Math.MathClient client)
         {
             var numbers = new List<Num>
             {
@@ -75,7 +75,7 @@ namespace Math
             }
         }
 
-        public static async Task DivManyExample(Math.IMathClient client)
+        public static async Task DivManyExample(Math.MathClient client)
         {
             var divArgsList = new List<DivArgs>
             {
@@ -90,7 +90,7 @@ namespace Math
             }
         }
 
-        public static async Task DependendRequestsExample(Math.IMathClient client)
+        public static async Task DependendRequestsExample(Math.MathClient client)
         {
             var numbers = new List<Num>
             {
diff --git a/src/csharp/Grpc.Examples/MathGrpc.cs b/src/csharp/Grpc.Examples/MathGrpc.cs
index a6e878d0f4..f3bb0d1cdc 100644
--- a/src/csharp/Grpc.Examples/MathGrpc.cs
+++ b/src/csharp/Grpc.Examples/MathGrpc.cs
@@ -52,6 +52,7 @@ namespace Math {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface IMathClient
     {
       global::Math.DivReply Div(global::Math.DivArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -67,6 +68,7 @@ namespace Math {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface IMath
     {
       Task<global::Math.DivReply> Div(global::Math.DivArgs request, ServerCallContext context);
@@ -75,61 +77,92 @@ namespace Math {
       Task<global::Math.Num> Sum(IAsyncStreamReader<global::Math.Num> requestStream, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class MathBase
+    {
+      public virtual Task<global::Math.DivReply> Div(global::Math.DivArgs request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task DivMany(IAsyncStreamReader<global::Math.DivArgs> requestStream, IServerStreamWriter<global::Math.DivReply> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task Fib(global::Math.FibArgs request, IServerStreamWriter<global::Math.Num> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task<global::Math.Num> Sum(IAsyncStreamReader<global::Math.Num> requestStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class MathClient : ClientBase, IMathClient
+    public class MathClient : ClientBase<MathClient>, IMathClient
     {
       public MathClient(Channel channel) : base(channel)
       {
       }
-      public global::Math.DivReply Div(global::Math.DivArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public MathClient(CallInvoker callInvoker) : base(callInvoker)
       {
-        var call = CreateCall(__Method_Div, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public global::Math.DivReply Div(global::Math.DivArgs request, CallOptions options)
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected MathClient() : base()
       {
-        var call = CreateCall(__Method_Div, options);
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public AsyncUnaryCall<global::Math.DivReply> DivAsync(global::Math.DivArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected MathClient(ClientBaseConfiguration configuration) : base(configuration)
       {
-        var call = CreateCall(__Method_Div, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
       }
-      public AsyncUnaryCall<global::Math.DivReply> DivAsync(global::Math.DivArgs request, CallOptions options)
+
+      public virtual global::Math.DivReply Div(global::Math.DivArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Div, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return Div(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncDuplexStreamingCall<global::Math.DivArgs, global::Math.DivReply> DivMany(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Math.DivReply Div(global::Math.DivArgs request, CallOptions options)
       {
-        var call = CreateCall(__Method_DivMany, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncDuplexStreamingCall(call);
+        return CallInvoker.BlockingUnaryCall(__Method_Div, null, options, request);
       }
-      public AsyncDuplexStreamingCall<global::Math.DivArgs, global::Math.DivReply> DivMany(CallOptions options)
+      public virtual AsyncUnaryCall<global::Math.DivReply> DivAsync(global::Math.DivArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_DivMany, options);
-        return Calls.AsyncDuplexStreamingCall(call);
+        return DivAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncServerStreamingCall<global::Math.Num> Fib(global::Math.FibArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Math.DivReply> DivAsync(global::Math.DivArgs request, CallOptions options)
       {
-        var call = CreateCall(__Method_Fib, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncServerStreamingCall(call, request);
+        return CallInvoker.AsyncUnaryCall(__Method_Div, null, options, request);
       }
-      public AsyncServerStreamingCall<global::Math.Num> Fib(global::Math.FibArgs request, CallOptions options)
+      public virtual AsyncDuplexStreamingCall<global::Math.DivArgs, global::Math.DivReply> DivMany(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Fib, options);
-        return Calls.AsyncServerStreamingCall(call, request);
+        return DivMany(new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncClientStreamingCall<global::Math.Num, global::Math.Num> Sum(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncDuplexStreamingCall<global::Math.DivArgs, global::Math.DivReply> DivMany(CallOptions options)
       {
-        var call = CreateCall(__Method_Sum, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncClientStreamingCall(call);
+        return CallInvoker.AsyncDuplexStreamingCall(__Method_DivMany, null, options);
       }
-      public AsyncClientStreamingCall<global::Math.Num, global::Math.Num> Sum(CallOptions options)
+      public virtual AsyncServerStreamingCall<global::Math.Num> Fib(global::Math.FibArgs request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Sum, options);
-        return Calls.AsyncClientStreamingCall(call);
+        return Fib(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual AsyncServerStreamingCall<global::Math.Num> Fib(global::Math.FibArgs request, CallOptions options)
+      {
+        return CallInvoker.AsyncServerStreamingCall(__Method_Fib, null, options, request);
+      }
+      public virtual AsyncClientStreamingCall<global::Math.Num, global::Math.Num> Sum(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      {
+        return Sum(new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual AsyncClientStreamingCall<global::Math.Num, global::Math.Num> Sum(CallOptions options)
+      {
+        return CallInvoker.AsyncClientStreamingCall(__Method_Sum, null, options);
+      }
+      protected override MathClient NewInstance(ClientBaseConfiguration configuration)
+      {
+        return new MathClient(configuration);
       }
     }
 
@@ -143,6 +176,16 @@ namespace Math {
           .AddMethod(__Method_Sum, serviceImpl.Sum).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(MathBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_Div, serviceImpl.Div)
+          .AddMethod(__Method_DivMany, serviceImpl.DivMany)
+          .AddMethod(__Method_Fib, serviceImpl.Fib)
+          .AddMethod(__Method_Sum, serviceImpl.Sum).Build();
+    }
+
     // creates a new client
     public static MathClient NewClient(Channel channel)
     {
diff --git a/src/csharp/Grpc.Examples/MathServiceImpl.cs b/src/csharp/Grpc.Examples/MathServiceImpl.cs
index 71dc655e46..79c56e57a8 100644
--- a/src/csharp/Grpc.Examples/MathServiceImpl.cs
+++ b/src/csharp/Grpc.Examples/MathServiceImpl.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -43,14 +43,14 @@ namespace Math
     /// <summary>
     /// Implementation of MathService server
     /// </summary>
-    public class MathServiceImpl : Math.IMath
+    public class MathServiceImpl : Math.MathBase
     {
-        public Task<DivReply> Div(DivArgs request, ServerCallContext context)
+        public override Task<DivReply> Div(DivArgs request, ServerCallContext context)
         {
             return Task.FromResult(DivInternal(request));
         }
 
-        public async Task Fib(FibArgs request, IServerStreamWriter<Num> responseStream, ServerCallContext context)
+        public override async Task Fib(FibArgs request, IServerStreamWriter<Num> responseStream, ServerCallContext context)
         {
             if (request.Limit <= 0)
             {
@@ -72,7 +72,7 @@ namespace Math
             }
         }
 
-        public async Task<Num> Sum(IAsyncStreamReader<Num> requestStream, ServerCallContext context)
+        public override async Task<Num> Sum(IAsyncStreamReader<Num> requestStream, ServerCallContext context)
         {
             long sum = 0;
             await requestStream.ForEachAsync(async num =>
@@ -82,7 +82,7 @@ namespace Math
             return new Num { Num_ = sum };
         }
 
-        public async Task DivMany(IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream, ServerCallContext context)
+        public override async Task DivMany(IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream, ServerCallContext context)
         {
             await requestStream.ForEachAsync(async divArgs => await responseStream.WriteAsync(DivInternal(divArgs)));
         }
diff --git a/src/csharp/Grpc.HealthCheck.Tests/HealthClientServerTest.cs b/src/csharp/Grpc.HealthCheck.Tests/HealthClientServerTest.cs
index 8318e84277..fb292945a6 100644
--- a/src/csharp/Grpc.HealthCheck.Tests/HealthClientServerTest.cs
+++ b/src/csharp/Grpc.HealthCheck.Tests/HealthClientServerTest.cs
@@ -49,7 +49,7 @@ namespace Grpc.HealthCheck.Tests
         const string Host = "localhost";
         Server server;
         Channel channel;
-        Grpc.Health.V1.Health.IHealthClient client;
+        Grpc.Health.V1.Health.HealthClient client;
         Grpc.HealthCheck.HealthServiceImpl serviceImpl;
 
         [TestFixtureSetUp]
diff --git a/src/csharp/Grpc.HealthCheck/HealthGrpc.cs b/src/csharp/Grpc.HealthCheck/HealthGrpc.cs
index 68320eb5c2..72e11cca3a 100644
--- a/src/csharp/Grpc.HealthCheck/HealthGrpc.cs
+++ b/src/csharp/Grpc.HealthCheck/HealthGrpc.cs
@@ -29,6 +29,7 @@ namespace Grpc.Health.V1 {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface IHealthClient
     {
       global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -38,36 +39,59 @@ namespace Grpc.Health.V1 {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface IHealth
     {
       Task<global::Grpc.Health.V1.HealthCheckResponse> Check(global::Grpc.Health.V1.HealthCheckRequest request, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class HealthBase
+    {
+      public virtual Task<global::Grpc.Health.V1.HealthCheckResponse> Check(global::Grpc.Health.V1.HealthCheckRequest request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class HealthClient : ClientBase, IHealthClient
+    public class HealthClient : ClientBase<HealthClient>, IHealthClient
     {
       public HealthClient(Channel channel) : base(channel)
       {
       }
-      public global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public HealthClient(CallInvoker callInvoker) : base(callInvoker)
       {
-        var call = CreateCall(__Method_Check, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, CallOptions options)
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected HealthClient() : base()
+      {
+      }
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected HealthClient(ClientBaseConfiguration configuration) : base(configuration)
+      {
+      }
+
+      public virtual global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Check, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return Check(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Health.V1.HealthCheckResponse> CheckAsync(global::Grpc.Health.V1.HealthCheckRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_Check, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_Check, null, options, request);
       }
-      public AsyncUnaryCall<global::Grpc.Health.V1.HealthCheckResponse> CheckAsync(global::Grpc.Health.V1.HealthCheckRequest request, CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Health.V1.HealthCheckResponse> CheckAsync(global::Grpc.Health.V1.HealthCheckRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Check, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return CheckAsync(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual AsyncUnaryCall<global::Grpc.Health.V1.HealthCheckResponse> CheckAsync(global::Grpc.Health.V1.HealthCheckRequest request, CallOptions options)
+      {
+        return CallInvoker.AsyncUnaryCall(__Method_Check, null, options, request);
+      }
+      protected override HealthClient NewInstance(ClientBaseConfiguration configuration)
+      {
+        return new HealthClient(configuration);
       }
     }
 
@@ -78,6 +102,13 @@ namespace Grpc.Health.V1 {
           .AddMethod(__Method_Check, serviceImpl.Check).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(HealthBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_Check, serviceImpl.Check).Build();
+    }
+
     // creates a new client
     public static HealthClient NewClient(Channel channel)
     {
diff --git a/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs b/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs
index a6e82aa0d4..d0406ece00 100644
--- a/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs
+++ b/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs
@@ -51,7 +51,7 @@ namespace Grpc.HealthCheck
     /// server.AddServiceDefinition(Grpc.Health.V1.Health.BindService(serviceImpl));
     /// </code>
     /// </summary>
-    public class HealthServiceImpl : Grpc.Health.V1.Health.IHealth
+    public class HealthServiceImpl : Grpc.Health.V1.Health.HealthBase
     {
         private readonly object myLock = new object();
         private readonly Dictionary<string, HealthCheckResponse.Types.ServingStatus> statusMap = 
@@ -99,7 +99,7 @@ namespace Grpc.HealthCheck
         /// <param name="request">The check request.</param>
         /// <param name="context">The call context.</param>
         /// <returns>The asynchronous response.</returns>
-        public Task<HealthCheckResponse> Check(HealthCheckRequest request, ServerCallContext context)
+        public override Task<HealthCheckResponse> Check(HealthCheckRequest request, ServerCallContext context)
         {
             lock (myLock)
             {
diff --git a/src/csharp/Grpc.IntegrationTesting/BenchmarkServiceImpl.cs b/src/csharp/Grpc.IntegrationTesting/BenchmarkServiceImpl.cs
index 7e7bc713a0..07f2703d4a 100644
--- a/src/csharp/Grpc.IntegrationTesting/BenchmarkServiceImpl.cs
+++ b/src/csharp/Grpc.IntegrationTesting/BenchmarkServiceImpl.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -44,19 +44,19 @@ namespace Grpc.Testing
     /// <summary>
     /// Implementation of BenchmarkService server
     /// </summary>
-    public class BenchmarkServiceImpl : BenchmarkService.IBenchmarkService
+    public class BenchmarkServiceImpl : BenchmarkService.BenchmarkServiceBase
     {
         public BenchmarkServiceImpl()
         {
         }
 
-        public Task<SimpleResponse> UnaryCall(SimpleRequest request, ServerCallContext context)
+        public override Task<SimpleResponse> UnaryCall(SimpleRequest request, ServerCallContext context)
         {
             var response = new SimpleResponse { Payload = CreateZerosPayload(request.ResponseSize) };
             return Task.FromResult(response);
         }
 
-        public async Task StreamingCall(IAsyncStreamReader<SimpleRequest> requestStream, IServerStreamWriter<SimpleResponse> responseStream, ServerCallContext context)
+        public override async Task StreamingCall(IAsyncStreamReader<SimpleRequest> requestStream, IServerStreamWriter<SimpleResponse> responseStream, ServerCallContext context)
         {
             await requestStream.ForEachAsync(async request =>
             {
diff --git a/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs b/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
index 5bfc89d591..f954ca5f34 100644
--- a/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
+++ b/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
@@ -61,15 +61,7 @@ namespace Grpc.IntegrationTesting
         public static IClientRunner CreateStarted(ClientConfig config)
         {
             Logger.Debug("ClientConfig: {0}", config);
-            string target = config.ServerTargets.Single();
-            GrpcPreconditions.CheckArgument(config.LoadParams.LoadCase == LoadParams.LoadOneofCase.ClosedLoop,
-                "Only closed loop scenario supported for C#");
-            GrpcPreconditions.CheckArgument(config.ClientChannels == 1, "ClientConfig.ClientChannels needs to be 1");
 
-            if (config.OutstandingRpcsPerChannel != 0)
-            {
-                Logger.Warning("ClientConfig.OutstandingRpcsPerChannel is not supported for C#. Ignoring the value");
-            }
             if (config.AsyncClientThreads != 0)
             {
                 Logger.Warning("ClientConfig.AsyncClientThreads is not supported for C#. Ignoring the value");
@@ -83,22 +75,40 @@ namespace Grpc.IntegrationTesting
                 Logger.Warning("ClientConfig.CoreList is not supported for C#. Ignoring the value");
             }
 
-            var credentials = config.SecurityParams != null ? TestCredentials.CreateSslCredentials() : ChannelCredentials.Insecure;
+            var channels = CreateChannels(config.ClientChannels, config.ServerTargets, config.SecurityParams);
+
+            return new ClientRunnerImpl(channels,
+                config.ClientType,
+                config.RpcType,
+                config.OutstandingRpcsPerChannel,
+                config.LoadParams,
+                config.PayloadConfig,
+                config.HistogramParams);
+        }
+
+        private static List<Channel> CreateChannels(int clientChannels, IEnumerable<string> serverTargets, SecurityParams securityParams)
+        {
+            GrpcPreconditions.CheckArgument(clientChannels > 0, "clientChannels needs to be at least 1.");
+            GrpcPreconditions.CheckArgument(serverTargets.Count() > 0, "at least one serverTarget needs to be specified.");
+
+            var credentials = securityParams != null ? TestCredentials.CreateSslCredentials() : ChannelCredentials.Insecure;
             List<ChannelOption> channelOptions = null;
-            if (config.SecurityParams != null && config.SecurityParams.ServerHostOverride != "")
+            if (securityParams != null && securityParams.ServerHostOverride != "")
             {
                 channelOptions = new List<ChannelOption>
                 {
-                    new ChannelOption(ChannelOptions.SslTargetNameOverride, config.SecurityParams.ServerHostOverride)
+                    new ChannelOption(ChannelOptions.SslTargetNameOverride, securityParams.ServerHostOverride)
                 };
             }
-            var channel = new Channel(target, credentials, channelOptions);
 
-            return new ClientRunnerImpl(channel,
-                config.ClientType,
-                config.RpcType,
-                config.PayloadConfig,
-                config.HistogramParams);
+            var result = new List<Channel>();
+            for (int i = 0; i < clientChannels; i++)
+            {
+                var target = serverTargets.ElementAt(i % serverTargets.Count());
+                var channel = new Channel(target, credentials, channelOptions);
+                result.Add(channel);
+            }
+            return result;
         }
     }
 
@@ -106,30 +116,35 @@ namespace Grpc.IntegrationTesting
     {
         const double SecondsToNanos = 1e9;
 
-        readonly Channel channel;
+        readonly List<Channel> channels;
         readonly ClientType clientType;
         readonly RpcType rpcType;
         readonly PayloadConfig payloadConfig;
         readonly Histogram histogram;
 
-        readonly BenchmarkService.IBenchmarkServiceClient client;
-        readonly Task runnerTask;
-        readonly CancellationTokenSource stoppedCts;
+        readonly List<Task> runnerTasks;
+        readonly CancellationTokenSource stoppedCts = new CancellationTokenSource();
         readonly WallClockStopwatch wallClockStopwatch = new WallClockStopwatch();
         
-        public ClientRunnerImpl(Channel channel, ClientType clientType, RpcType rpcType, PayloadConfig payloadConfig, HistogramParams histogramParams)
+        public ClientRunnerImpl(List<Channel> channels, ClientType clientType, RpcType rpcType, int outstandingRpcsPerChannel, LoadParams loadParams, PayloadConfig payloadConfig, HistogramParams histogramParams)
         {
-            this.channel = GrpcPreconditions.CheckNotNull(channel);
+            GrpcPreconditions.CheckArgument(outstandingRpcsPerChannel > 0, "outstandingRpcsPerChannel");
+            this.channels = new List<Channel>(channels);
             this.clientType = clientType;
             this.rpcType = rpcType;
             this.payloadConfig = payloadConfig;
             this.histogram = new Histogram(histogramParams.Resolution, histogramParams.MaxPossible);
 
-            this.stoppedCts = new CancellationTokenSource();
-            this.client = BenchmarkService.NewClient(channel);
-
-            var threadBody = GetThreadBody();
-            this.runnerTask = Task.Factory.StartNew(threadBody, TaskCreationOptions.LongRunning);
+            this.runnerTasks = new List<Task>();
+            foreach (var channel in this.channels)
+            {
+                for (int i = 0; i < outstandingRpcsPerChannel; i++)
+                {
+                    var timer = CreateTimer(loadParams, 1.0 / this.channels.Count / outstandingRpcsPerChannel);
+                    var threadBody = GetThreadBody(channel, timer);
+                    this.runnerTasks.Add(Task.Factory.StartNew(threadBody, TaskCreationOptions.LongRunning));
+                }
+            }
         }
 
         public ClientStats GetStats(bool reset)
@@ -150,12 +165,19 @@ namespace Grpc.IntegrationTesting
         public async Task StopAsync()
         {
             stoppedCts.Cancel();
-            await runnerTask;
-            await channel.ShutdownAsync();
+            foreach (var runnerTask in runnerTasks)
+            {
+                await runnerTask;
+            }
+            foreach (var channel in channels)
+            {
+                await channel.ShutdownAsync();
+            }
         }
 
-        private void RunClosedLoopUnary()
+        private void RunUnary(Channel channel, IInterarrivalTimer timer)
         {
+            var client = BenchmarkService.NewClient(channel);
             var request = CreateSimpleRequest();
             var stopwatch = new Stopwatch();
 
@@ -167,11 +189,14 @@ namespace Grpc.IntegrationTesting
 
                 // spec requires data point in nanoseconds.
                 histogram.AddObservation(stopwatch.Elapsed.TotalSeconds * SecondsToNanos);
+
+                timer.WaitForNext();
             }
         }
 
-        private async Task RunClosedLoopUnaryAsync()
+        private async Task RunUnaryAsync(Channel channel, IInterarrivalTimer timer)
         {
+            var client = BenchmarkService.NewClient(channel);
             var request = CreateSimpleRequest();
             var stopwatch = new Stopwatch();
 
@@ -183,11 +208,14 @@ namespace Grpc.IntegrationTesting
 
                 // spec requires data point in nanoseconds.
                 histogram.AddObservation(stopwatch.Elapsed.TotalSeconds * SecondsToNanos);
+
+                await timer.WaitForNextAsync();
             }
         }
 
-        private async Task RunClosedLoopStreamingAsync()
+        private async Task RunStreamingPingPongAsync(Channel channel, IInterarrivalTimer timer)
         {
+            var client = BenchmarkService.NewClient(channel);
             var request = CreateSimpleRequest();
             var stopwatch = new Stopwatch();
 
@@ -202,6 +230,8 @@ namespace Grpc.IntegrationTesting
 
                     // spec requires data point in nanoseconds.
                     histogram.AddObservation(stopwatch.Elapsed.TotalSeconds * SecondsToNanos);
+
+                    await timer.WaitForNextAsync();
                 }
 
                 // finish the streaming call
@@ -210,7 +240,7 @@ namespace Grpc.IntegrationTesting
             }
         }
 
-        private async Task RunGenericClosedLoopStreamingAsync()
+        private async Task RunGenericStreamingAsync(Channel channel, IInterarrivalTimer timer)
         {
             var request = CreateByteBufferRequest();
             var stopwatch = new Stopwatch();
@@ -228,6 +258,8 @@ namespace Grpc.IntegrationTesting
 
                     // spec requires data point in nanoseconds.
                     histogram.AddObservation(stopwatch.Elapsed.TotalSeconds * SecondsToNanos);
+
+                    await timer.WaitForNextAsync();
                 }
 
                 // finish the streaming call
@@ -236,7 +268,7 @@ namespace Grpc.IntegrationTesting
             }
         }
 
-        private Action GetThreadBody()
+        private Action GetThreadBody(Channel channel, IInterarrivalTimer timer)
         {
             if (payloadConfig.PayloadCase == PayloadConfig.PayloadOneofCase.BytebufParams)
             {
@@ -244,7 +276,7 @@ namespace Grpc.IntegrationTesting
                 GrpcPreconditions.CheckArgument(rpcType == RpcType.STREAMING, "Generic client only supports streaming calls");
                 return () =>
                 {
-                    RunGenericClosedLoopStreamingAsync().Wait();
+                    RunGenericStreamingAsync(channel, timer).Wait();
                 };
             }
 
@@ -252,7 +284,7 @@ namespace Grpc.IntegrationTesting
             if (clientType == ClientType.SYNC_CLIENT)
             {
                 GrpcPreconditions.CheckArgument(rpcType == RpcType.UNARY, "Sync client can only be used for Unary calls in C#");
-                return RunClosedLoopUnary;
+                return () => RunUnary(channel, timer);
             }
             else if (clientType == ClientType.ASYNC_CLIENT)
             {
@@ -261,12 +293,12 @@ namespace Grpc.IntegrationTesting
                     case RpcType.UNARY:
                         return () =>
                         {
-                            RunClosedLoopUnaryAsync().Wait();
+                            RunUnaryAsync(channel, timer).Wait();
                         };
                     case RpcType.STREAMING:
                         return () =>
                         {
-                            RunClosedLoopStreamingAsync().Wait();
+                            RunStreamingPingPongAsync(channel, timer).Wait();
                         };
                 }
             }
@@ -292,5 +324,18 @@ namespace Grpc.IntegrationTesting
         {
             return new Payload { Body = ByteString.CopyFrom(new byte[size]) };
         }
+
+        private static IInterarrivalTimer CreateTimer(LoadParams loadParams, double loadMultiplier)
+        {
+            switch (loadParams.LoadCase)
+            {
+                case LoadParams.LoadOneofCase.ClosedLoop:
+                    return new ClosedLoopInterarrivalTimer();
+                case LoadParams.LoadOneofCase.Poisson:
+                    return new PoissonInterarrivalTimer(loadParams.Poisson.OfferedLoad * loadMultiplier);
+                default:
+                    throw new ArgumentException("Unknown load type");
+            }
+        }
     }
 }
diff --git a/src/csharp/Grpc.IntegrationTesting/GeneratedClientTest.cs b/src/csharp/Grpc.IntegrationTesting/GeneratedClientTest.cs
new file mode 100644
index 0000000000..37786b6c30
--- /dev/null
+++ b/src/csharp/Grpc.IntegrationTesting/GeneratedClientTest.cs
@@ -0,0 +1,106 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, 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.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Utils;
+using Grpc.Testing;
+using Moq;
+using NUnit.Framework;
+
+namespace Grpc.IntegrationTesting
+{
+    public class GeneratedClientTest
+    {
+        TestService.TestServiceClient unimplementedClient = new UnimplementedTestServiceClient();
+
+        [Test]
+        public void ExpandedParamOverloadCanBeMocked()
+        {
+            var expected = new SimpleResponse();
+
+            var mockClient = new Mock<TestService.TestServiceClient>();
+            // mocking is relatively clumsy because one needs to specify value for all the optional params.
+            mockClient.Setup(m => m.UnaryCall(It.IsAny<SimpleRequest>(), null, null, CancellationToken.None)).Returns(expected);
+
+            Assert.AreSame(expected, mockClient.Object.UnaryCall(new SimpleRequest()));
+        }
+
+        [Test]
+        public void CallOptionsOverloadCanBeMocked()
+        {
+            var expected = new SimpleResponse();
+
+            var mockClient = new Mock<TestService.TestServiceClient>();
+            mockClient.Setup(m => m.UnaryCall(It.IsAny<SimpleRequest>(), It.IsAny<CallOptions>())).Returns(expected);
+
+            Assert.AreSame(expected, mockClient.Object.UnaryCall(new SimpleRequest(), new CallOptions()));
+        }
+
+        [Test]
+        public void DefaultMethodStubThrows_UnaryCall()
+        {
+            Assert.Throws(typeof(NotImplementedException), () => unimplementedClient.UnaryCall(new SimpleRequest()));
+        }
+
+        [Test]
+        public void DefaultMethodStubThrows_ClientStreaming()
+        {
+            Assert.Throws(typeof(NotImplementedException), () => unimplementedClient.StreamingInputCall());
+        }
+
+        [Test]
+        public void DefaultMethodStubThrows_ServerStreaming()
+        {
+            Assert.Throws(typeof(NotImplementedException), () => unimplementedClient.StreamingOutputCall(new StreamingOutputCallRequest()));
+        }
+
+        [Test]
+        public void DefaultMethodStubThrows_DuplexStreaming()
+        {
+            Assert.Throws(typeof(NotImplementedException), () => unimplementedClient.FullDuplexCall());
+        }
+
+        /// <summary>
+        /// Subclass of the generated client that doesn't override any method stubs.
+        /// </summary>
+        private class UnimplementedTestServiceClient : TestService.TestServiceClient
+        {
+        }
+    }
+}
diff --git a/src/csharp/Grpc.IntegrationTesting/GeneratedServiceBaseTest.cs b/src/csharp/Grpc.IntegrationTesting/GeneratedServiceBaseTest.cs
new file mode 100644
index 0000000000..99aa729030
--- /dev/null
+++ b/src/csharp/Grpc.IntegrationTesting/GeneratedServiceBaseTest.cs
@@ -0,0 +1,116 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, 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.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Utils;
+using Grpc.Testing;
+using Moq;
+using NUnit.Framework;
+
+namespace Grpc.IntegrationTesting
+{
+    public class GeneratedServiceBaseTest
+    {
+        const string Host = "localhost";
+        Server server;
+        Channel channel;
+        TestService.TestServiceClient client;
+
+        [SetUp]
+        public void Init()
+        {
+            server = new Server
+            {
+                Services = { TestService.BindService(new UnimplementedTestServiceImpl()) },
+                Ports = { { Host, ServerPort.PickUnused, SslServerCredentials.Insecure } }
+            };
+            server.Start();
+            channel = new Channel(Host, server.Ports.Single().BoundPort, ChannelCredentials.Insecure);
+            client = TestService.NewClient(channel);
+        }
+
+        [TearDown]
+        public void Cleanup()
+        {
+            channel.ShutdownAsync().Wait();
+            server.ShutdownAsync().Wait();
+        }
+
+        [Test]
+        public void UnimplementedByDefault_Unary()
+        {
+            var ex = Assert.Throws<RpcException>(() => client.UnaryCall(new SimpleRequest { }));
+            Assert.AreEqual(StatusCode.Unimplemented, ex.Status.StatusCode);
+        }
+
+        [Test]
+        public async Task UnimplementedByDefault_ClientStreaming()
+        {
+            var call = client.StreamingInputCall();
+
+            var ex = Assert.Throws<RpcException>(async () => await call);
+            Assert.AreEqual(StatusCode.Unimplemented, ex.Status.StatusCode);
+        }
+
+        [Test]
+        public async Task UnimplementedByDefault_ServerStreamingCall()
+        {
+            var call = client.StreamingOutputCall(new StreamingOutputCallRequest());
+
+            var ex = Assert.Throws<RpcException>(async () => await call.ResponseStream.MoveNext());
+            Assert.AreEqual(StatusCode.Unimplemented, ex.Status.StatusCode);
+        }
+
+        [Test]
+        public async Task UnimplementedByDefault_DuplexStreamingCall()
+        {
+            var call = client.FullDuplexCall();
+
+            var ex = Assert.Throws<RpcException>(async () => await call.ResponseStream.MoveNext());
+            Assert.AreEqual(StatusCode.Unimplemented, ex.Status.StatusCode);
+        }
+
+        /// <summary>
+        /// Implementation of TestService that doesn't override any methods.
+        /// </summary>
+        private class UnimplementedTestServiceImpl : TestService.TestServiceBase
+        {
+        }
+    }
+}
diff --git a/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj b/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj
index d3c572fe27..7ea80b11f0 100644
--- a/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj
+++ b/src/csharp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj
@@ -84,7 +84,6 @@
     <Compile Include="..\Grpc.Core\Version.cs">
       <Link>Version.cs</Link>
     </Compile>
-    <Compile Include="HeaderInterceptorTest.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Empty.cs" />
     <Compile Include="Messages.cs" />
@@ -114,6 +113,9 @@
     <Compile Include="QpsWorker.cs" />
     <Compile Include="WallClockStopwatch.cs" />
     <Compile Include="GenericService.cs" />
+    <Compile Include="GeneratedServiceBaseTest.cs" />
+    <Compile Include="GeneratedClientTest.cs" />
+    <Compile Include="InterarrivalTimers.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup>
diff --git a/src/csharp/Grpc.IntegrationTesting/InterarrivalTimers.cs b/src/csharp/Grpc.IntegrationTesting/InterarrivalTimers.cs
new file mode 100644
index 0000000000..6492d34890
--- /dev/null
+++ b/src/csharp/Grpc.IntegrationTesting/InterarrivalTimers.cs
@@ -0,0 +1,148 @@
+#region Copyright notice and license
+
+// Copyright 2016, 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.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Threading.Tasks;
+using Google.Protobuf;
+using Grpc.Core;
+using Grpc.Core.Utils;
+using Grpc.Testing;
+
+namespace Grpc.IntegrationTesting
+{
+    public interface IInterarrivalTimer
+    {
+        void WaitForNext();
+
+        Task WaitForNextAsync();
+    }
+
+    /// <summary>
+    /// Interarrival timer that doesn't wait at all.
+    /// </summary>
+    public class ClosedLoopInterarrivalTimer : IInterarrivalTimer
+    {
+        public ClosedLoopInterarrivalTimer()
+        {
+        }
+
+        public void WaitForNext()
+        {
+            // NOP
+        }
+
+        public Task WaitForNextAsync()
+        {
+            return Task.FromResult<object>(null);
+        }
+    }
+
+    /// <summary>
+    /// Interarrival timer that generates Poisson process load.
+    /// </summary>
+    public class PoissonInterarrivalTimer : IInterarrivalTimer
+    {
+        readonly ExponentialDistribution exponentialDistribution;
+        DateTime? lastEventTime;
+
+        public PoissonInterarrivalTimer(double offeredLoad)
+        {
+            this.exponentialDistribution = new ExponentialDistribution(new Random(), offeredLoad);
+            this.lastEventTime = DateTime.UtcNow;
+        }
+
+        public void WaitForNext()
+        {
+            var waitDuration = GetNextWaitDuration();
+            int millisTimeout = (int) Math.Round(waitDuration.TotalMilliseconds);
+            if (millisTimeout > 0)
+            {
+                // TODO(jtattermusch): probably only works well for a relatively low interarrival rate
+                Thread.Sleep(millisTimeout);
+            }
+        }
+
+        public async Task WaitForNextAsync()
+        {
+            var waitDuration = GetNextWaitDuration();
+            int millisTimeout = (int) Math.Round(waitDuration.TotalMilliseconds);
+            if (millisTimeout > 0)
+            {
+                // TODO(jtattermusch): probably only works well for a relatively low interarrival rate
+                await Task.Delay(millisTimeout);
+            }
+        }
+
+        private TimeSpan GetNextWaitDuration()
+        {
+            if (!lastEventTime.HasValue)
+            {
+                this.lastEventTime = DateTime.Now;
+            }
+
+            var origLastEventTime = this.lastEventTime.Value;
+            this.lastEventTime = origLastEventTime + TimeSpan.FromSeconds(exponentialDistribution.Next());
+            return this.lastEventTime.Value - origLastEventTime;
+        }
+
+        /// <summary>
+        /// Exp generator.
+        /// </summary>
+        private class ExponentialDistribution
+        {
+            readonly Random random;
+            readonly double lambda;
+            readonly double lambdaReciprocal;
+
+            public ExponentialDistribution(Random random, double lambda)
+            {
+                this.random = random;
+                this.lambda = lambda;
+                this.lambdaReciprocal = 1.0 / lambda;
+            }
+
+            public double Next()
+            {
+                double uniform = random.NextDouble();
+                // Use 1.0-uni above to avoid NaN if uni is 0
+                return lambdaReciprocal * (-Math.Log(1.0 - uniform));
+            }
+        }
+    }
+}
diff --git a/src/csharp/Grpc.IntegrationTesting/InteropClient.cs b/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
index b0e33e49f7..7ca5221936 100644
--- a/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
+++ b/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -217,7 +217,7 @@ namespace Grpc.IntegrationTesting
             }
         }
 
-        public static void RunEmptyUnary(TestService.ITestServiceClient client)
+        public static void RunEmptyUnary(TestService.TestServiceClient client)
         {
             Console.WriteLine("running empty_unary");
             var response = client.EmptyCall(new Empty());
@@ -225,7 +225,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static void RunLargeUnary(TestService.ITestServiceClient client)
+        public static void RunLargeUnary(TestService.TestServiceClient client)
         {
             Console.WriteLine("running large_unary");
             var request = new SimpleRequest
@@ -241,7 +241,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunClientStreamingAsync(TestService.ITestServiceClient client)
+        public static async Task RunClientStreamingAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running client_streaming");
 
@@ -257,7 +257,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunServerStreamingAsync(TestService.ITestServiceClient client)
+        public static async Task RunServerStreamingAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running server_streaming");
 
@@ -281,7 +281,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunPingPongAsync(TestService.ITestServiceClient client)
+        public static async Task RunPingPongAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running ping_pong");
 
@@ -338,7 +338,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunEmptyStreamAsync(TestService.ITestServiceClient client)
+        public static async Task RunEmptyStreamAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running empty_stream");
             using (var call = client.FullDuplexCall())
@@ -434,7 +434,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunCancelAfterBeginAsync(TestService.ITestServiceClient client)
+        public static async Task RunCancelAfterBeginAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running cancel_after_begin");
 
@@ -451,7 +451,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunCancelAfterFirstResponseAsync(TestService.ITestServiceClient client)
+        public static async Task RunCancelAfterFirstResponseAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running cancel_after_first_response");
 
@@ -477,7 +477,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunTimeoutOnSleepingServerAsync(TestService.ITestServiceClient client)
+        public static async Task RunTimeoutOnSleepingServerAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running timeout_on_sleeping_server");
 
@@ -499,7 +499,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunCustomMetadataAsync(TestService.ITestServiceClient client)
+        public static async Task RunCustomMetadataAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running custom_metadata");
             {
@@ -546,7 +546,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static async Task RunStatusCodeAndMessageAsync(TestService.ITestServiceClient client)
+        public static async Task RunStatusCodeAndMessageAsync(TestService.TestServiceClient client)
         {
             Console.WriteLine("running status_code_and_message");
             var echoStatus = new EchoStatus
@@ -580,7 +580,7 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
-        public static void RunUnimplementedMethod(UnimplementedService.IUnimplementedServiceClient client)
+        public static void RunUnimplementedMethod(UnimplementedService.UnimplementedServiceClient client)
         {
             Console.WriteLine("running unimplemented_method");
             var e = Assert.Throws<RpcException>(() => client.UnimplementedCall(new Empty()));
diff --git a/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs b/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs
index 5facb87971..4ee1ff5ec8 100644
--- a/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs
+++ b/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs
@@ -51,7 +51,7 @@ namespace Grpc.IntegrationTesting
         const string Host = "localhost";
         Server server;
         Channel channel;
-        TestService.ITestServiceClient client;
+        TestService.TestServiceClient client;
 
         [TestFixtureSetUp]
         public void Init()
diff --git a/src/csharp/Grpc.IntegrationTesting/MetadataCredentialsTest.cs b/src/csharp/Grpc.IntegrationTesting/MetadataCredentialsTest.cs
index 1c8bfed1f6..f95af5008f 100644
--- a/src/csharp/Grpc.IntegrationTesting/MetadataCredentialsTest.cs
+++ b/src/csharp/Grpc.IntegrationTesting/MetadataCredentialsTest.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -50,15 +50,15 @@ namespace Grpc.IntegrationTesting
         const string Host = "localhost";
         Server server;
         Channel channel;
-        TestService.ITestServiceClient client;
+        TestService.TestServiceClient client;
         List<ChannelOption> options;
-        Mock<TestService.ITestService> serviceMock;
+        Mock<TestService.TestServiceBase> serviceMock;
         AsyncAuthInterceptor asyncAuthInterceptor;
 
         [SetUp]
         public void Init()
         {
-            serviceMock = new Mock<TestService.ITestService>();
+            serviceMock = new Mock<TestService.TestServiceBase>();
             serviceMock.Setup(m => m.UnaryCall(It.IsAny<SimpleRequest>(), It.IsAny<ServerCallContext>()))
                 .Returns(new Func<SimpleRequest, ServerCallContext, Task<SimpleResponse>>(UnaryCallHandler));
 
diff --git a/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs b/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs
index 996439afbf..46b16cf202 100644
--- a/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs
+++ b/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs
@@ -36,6 +36,7 @@ namespace Grpc.Testing {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface IBenchmarkServiceClient
     {
       global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -47,47 +48,73 @@ namespace Grpc.Testing {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface IBenchmarkService
     {
       Task<global::Grpc.Testing.SimpleResponse> UnaryCall(global::Grpc.Testing.SimpleRequest request, ServerCallContext context);
       Task StreamingCall(IAsyncStreamReader<global::Grpc.Testing.SimpleRequest> requestStream, IServerStreamWriter<global::Grpc.Testing.SimpleResponse> responseStream, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class BenchmarkServiceBase
+    {
+      public virtual Task<global::Grpc.Testing.SimpleResponse> UnaryCall(global::Grpc.Testing.SimpleRequest request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task StreamingCall(IAsyncStreamReader<global::Grpc.Testing.SimpleRequest> requestStream, IServerStreamWriter<global::Grpc.Testing.SimpleResponse> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class BenchmarkServiceClient : ClientBase, IBenchmarkServiceClient
+    public class BenchmarkServiceClient : ClientBase<BenchmarkServiceClient>, IBenchmarkServiceClient
     {
       public BenchmarkServiceClient(Channel channel) : base(channel)
       {
       }
-      public global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public BenchmarkServiceClient(CallInvoker callInvoker) : base(callInvoker)
+      {
+      }
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected BenchmarkServiceClient() : base()
       {
-        var call = CreateCall(__Method_UnaryCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, CallOptions options)
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(configuration)
       {
-        var call = CreateCall(__Method_UnaryCall, options);
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+
+      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_UnaryCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return UnaryCall(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, CallOptions options)
+      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_UnaryCall, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_UnaryCall, null, options, request);
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_StreamingCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncDuplexStreamingCall(call);
+        return UnaryCallAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingCall(CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_StreamingCall, options);
-        return Calls.AsyncDuplexStreamingCall(call);
+        return CallInvoker.AsyncUnaryCall(__Method_UnaryCall, null, options, request);
+      }
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      {
+        return StreamingCall(new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingCall(CallOptions options)
+      {
+        return CallInvoker.AsyncDuplexStreamingCall(__Method_StreamingCall, null, options);
+      }
+      protected override BenchmarkServiceClient NewInstance(ClientBaseConfiguration configuration)
+      {
+        return new BenchmarkServiceClient(configuration);
       }
     }
 
@@ -99,6 +126,14 @@ namespace Grpc.Testing {
           .AddMethod(__Method_StreamingCall, serviceImpl.StreamingCall).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(BenchmarkServiceBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_UnaryCall, serviceImpl.UnaryCall)
+          .AddMethod(__Method_StreamingCall, serviceImpl.StreamingCall).Build();
+    }
+
     // creates a new client
     public static BenchmarkServiceClient NewClient(Channel channel)
     {
@@ -153,6 +188,7 @@ namespace Grpc.Testing {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface IWorkerServiceClient
     {
       AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -170,6 +206,7 @@ namespace Grpc.Testing {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface IWorkerService
     {
       Task RunServer(IAsyncStreamReader<global::Grpc.Testing.ServerArgs> requestStream, IServerStreamWriter<global::Grpc.Testing.ServerStatus> responseStream, ServerCallContext context);
@@ -178,71 +215,100 @@ namespace Grpc.Testing {
       Task<global::Grpc.Testing.Void> QuitWorker(global::Grpc.Testing.Void request, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class WorkerServiceBase
+    {
+      public virtual Task RunServer(IAsyncStreamReader<global::Grpc.Testing.ServerArgs> requestStream, IServerStreamWriter<global::Grpc.Testing.ServerStatus> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task RunClient(IAsyncStreamReader<global::Grpc.Testing.ClientArgs> requestStream, IServerStreamWriter<global::Grpc.Testing.ClientStatus> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task<global::Grpc.Testing.CoreResponse> CoreCount(global::Grpc.Testing.CoreRequest request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task<global::Grpc.Testing.Void> QuitWorker(global::Grpc.Testing.Void request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class WorkerServiceClient : ClientBase, IWorkerServiceClient
+    public class WorkerServiceClient : ClientBase<WorkerServiceClient>, IWorkerServiceClient
     {
       public WorkerServiceClient(Channel channel) : base(channel)
       {
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public WorkerServiceClient(CallInvoker callInvoker) : base(callInvoker)
       {
-        var call = CreateCall(__Method_RunServer, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncDuplexStreamingCall(call);
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(CallOptions options)
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected WorkerServiceClient() : base()
       {
-        var call = CreateCall(__Method_RunServer, options);
-        return Calls.AsyncDuplexStreamingCall(call);
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.ClientArgs, global::Grpc.Testing.ClientStatus> RunClient(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(configuration)
       {
-        var call = CreateCall(__Method_RunClient, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncDuplexStreamingCall(call);
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.ClientArgs, global::Grpc.Testing.ClientStatus> RunClient(CallOptions options)
+
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_RunClient, options);
-        return Calls.AsyncDuplexStreamingCall(call);
+        return RunServer(new CallOptions(headers, deadline, cancellationToken));
       }
-      public global::Grpc.Testing.CoreResponse CoreCount(global::Grpc.Testing.CoreRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(CallOptions options)
       {
-        var call = CreateCall(__Method_CoreCount, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
+        return CallInvoker.AsyncDuplexStreamingCall(__Method_RunServer, null, options);
       }
-      public global::Grpc.Testing.CoreResponse CoreCount(global::Grpc.Testing.CoreRequest request, CallOptions options)
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.ClientArgs, global::Grpc.Testing.ClientStatus> RunClient(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_CoreCount, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return RunClient(new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.CoreResponse> CoreCountAsync(global::Grpc.Testing.CoreRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.ClientArgs, global::Grpc.Testing.ClientStatus> RunClient(CallOptions options)
       {
-        var call = CreateCall(__Method_CoreCount, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.AsyncDuplexStreamingCall(__Method_RunClient, null, options);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.CoreResponse> CoreCountAsync(global::Grpc.Testing.CoreRequest request, CallOptions options)
+      public virtual global::Grpc.Testing.CoreResponse CoreCount(global::Grpc.Testing.CoreRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_CoreCount, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return CoreCount(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public global::Grpc.Testing.Void QuitWorker(global::Grpc.Testing.Void request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.CoreResponse CoreCount(global::Grpc.Testing.CoreRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_QuitWorker, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_CoreCount, null, options, request);
       }
-      public global::Grpc.Testing.Void QuitWorker(global::Grpc.Testing.Void request, CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Testing.CoreResponse> CoreCountAsync(global::Grpc.Testing.CoreRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_QuitWorker, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return CoreCountAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Void> QuitWorkerAsync(global::Grpc.Testing.Void request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Grpc.Testing.CoreResponse> CoreCountAsync(global::Grpc.Testing.CoreRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_QuitWorker, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.AsyncUnaryCall(__Method_CoreCount, null, options, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Void> QuitWorkerAsync(global::Grpc.Testing.Void request, CallOptions options)
+      public virtual global::Grpc.Testing.Void QuitWorker(global::Grpc.Testing.Void request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_QuitWorker, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return QuitWorker(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual global::Grpc.Testing.Void QuitWorker(global::Grpc.Testing.Void request, CallOptions options)
+      {
+        return CallInvoker.BlockingUnaryCall(__Method_QuitWorker, null, options, request);
+      }
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Void> QuitWorkerAsync(global::Grpc.Testing.Void request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      {
+        return QuitWorkerAsync(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Void> QuitWorkerAsync(global::Grpc.Testing.Void request, CallOptions options)
+      {
+        return CallInvoker.AsyncUnaryCall(__Method_QuitWorker, null, options, request);
+      }
+      protected override WorkerServiceClient NewInstance(ClientBaseConfiguration configuration)
+      {
+        return new WorkerServiceClient(configuration);
       }
     }
 
@@ -256,6 +322,16 @@ namespace Grpc.Testing {
           .AddMethod(__Method_QuitWorker, serviceImpl.QuitWorker).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(WorkerServiceBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_RunServer, serviceImpl.RunServer)
+          .AddMethod(__Method_RunClient, serviceImpl.RunClient)
+          .AddMethod(__Method_CoreCount, serviceImpl.CoreCount)
+          .AddMethod(__Method_QuitWorker, serviceImpl.QuitWorker).Build();
+    }
+
     // creates a new client
     public static WorkerServiceClient NewClient(Channel channel)
     {
diff --git a/src/csharp/Grpc.IntegrationTesting/SslCredentialsTest.cs b/src/csharp/Grpc.IntegrationTesting/SslCredentialsTest.cs
index 37b2518c21..3df45b5f70 100644
--- a/src/csharp/Grpc.IntegrationTesting/SslCredentialsTest.cs
+++ b/src/csharp/Grpc.IntegrationTesting/SslCredentialsTest.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -53,7 +53,7 @@ namespace Grpc.IntegrationTesting
         const string Host = "localhost";
         Server server;
         Channel channel;
-        TestService.ITestServiceClient client;
+        TestService.TestServiceClient client;
 
         [TestFixtureSetUp]
         public void Init()
diff --git a/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs b/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs
index 2c469080d9..b84ec2d984 100644
--- a/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs
+++ b/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs
@@ -69,6 +69,7 @@ namespace Grpc.Testing {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface ITestServiceClient
     {
       global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -90,6 +91,7 @@ namespace Grpc.Testing {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface ITestService
     {
       Task<global::Grpc.Testing.Empty> EmptyCall(global::Grpc.Testing.Empty request, ServerCallContext context);
@@ -100,91 +102,126 @@ namespace Grpc.Testing {
       Task HalfDuplexCall(IAsyncStreamReader<global::Grpc.Testing.StreamingOutputCallRequest> requestStream, IServerStreamWriter<global::Grpc.Testing.StreamingOutputCallResponse> responseStream, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class TestServiceBase
+    {
+      public virtual Task<global::Grpc.Testing.Empty> EmptyCall(global::Grpc.Testing.Empty request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task<global::Grpc.Testing.SimpleResponse> UnaryCall(global::Grpc.Testing.SimpleRequest request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, IServerStreamWriter<global::Grpc.Testing.StreamingOutputCallResponse> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task<global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<global::Grpc.Testing.StreamingInputCallRequest> requestStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task FullDuplexCall(IAsyncStreamReader<global::Grpc.Testing.StreamingOutputCallRequest> requestStream, IServerStreamWriter<global::Grpc.Testing.StreamingOutputCallResponse> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task HalfDuplexCall(IAsyncStreamReader<global::Grpc.Testing.StreamingOutputCallRequest> requestStream, IServerStreamWriter<global::Grpc.Testing.StreamingOutputCallResponse> responseStream, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class TestServiceClient : ClientBase, ITestServiceClient
+    public class TestServiceClient : ClientBase<TestServiceClient>, ITestServiceClient
     {
       public TestServiceClient(Channel channel) : base(channel)
       {
       }
-      public global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public TestServiceClient(CallInvoker callInvoker) : base(callInvoker)
+      {
+      }
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected TestServiceClient() : base()
+      {
+      }
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected TestServiceClient(ClientBaseConfiguration configuration) : base(configuration)
+      {
+      }
+
+      public virtual global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_EmptyCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
+        return EmptyCall(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, CallOptions options)
+      public virtual global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, CallOptions options)
       {
-        var call = CreateCall(__Method_EmptyCall, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_EmptyCall, null, options, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Empty> EmptyCallAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Empty> EmptyCallAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_EmptyCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return EmptyCallAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Empty> EmptyCallAsync(global::Grpc.Testing.Empty request, CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Empty> EmptyCallAsync(global::Grpc.Testing.Empty request, CallOptions options)
       {
-        var call = CreateCall(__Method_EmptyCall, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.AsyncUnaryCall(__Method_EmptyCall, null, options, request);
       }
-      public global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_UnaryCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
+        return UnaryCall(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, CallOptions options)
+      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_UnaryCall, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_UnaryCall, null, options, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_UnaryCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return UnaryCallAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_UnaryCall, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.AsyncUnaryCall(__Method_UnaryCall, null, options, request);
       }
-      public AsyncServerStreamingCall<global::Grpc.Testing.StreamingOutputCallResponse> StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncServerStreamingCall<global::Grpc.Testing.StreamingOutputCallResponse> StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_StreamingOutputCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncServerStreamingCall(call, request);
+        return StreamingOutputCall(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncServerStreamingCall<global::Grpc.Testing.StreamingOutputCallResponse> StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, CallOptions options)
+      public virtual AsyncServerStreamingCall<global::Grpc.Testing.StreamingOutputCallResponse> StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, CallOptions options)
       {
-        var call = CreateCall(__Method_StreamingOutputCall, options);
-        return Calls.AsyncServerStreamingCall(call, request);
+        return CallInvoker.AsyncServerStreamingCall(__Method_StreamingOutputCall, null, options, request);
       }
-      public AsyncClientStreamingCall<global::Grpc.Testing.StreamingInputCallRequest, global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncClientStreamingCall<global::Grpc.Testing.StreamingInputCallRequest, global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_StreamingInputCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncClientStreamingCall(call);
+        return StreamingInputCall(new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncClientStreamingCall<global::Grpc.Testing.StreamingInputCallRequest, global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(CallOptions options)
+      public virtual AsyncClientStreamingCall<global::Grpc.Testing.StreamingInputCallRequest, global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(CallOptions options)
       {
-        var call = CreateCall(__Method_StreamingInputCall, options);
-        return Calls.AsyncClientStreamingCall(call);
+        return CallInvoker.AsyncClientStreamingCall(__Method_StreamingInputCall, null, options);
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> FullDuplexCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> FullDuplexCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_FullDuplexCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncDuplexStreamingCall(call);
+        return FullDuplexCall(new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> FullDuplexCall(CallOptions options)
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> FullDuplexCall(CallOptions options)
       {
-        var call = CreateCall(__Method_FullDuplexCall, options);
-        return Calls.AsyncDuplexStreamingCall(call);
+        return CallInvoker.AsyncDuplexStreamingCall(__Method_FullDuplexCall, null, options);
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> HalfDuplexCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> HalfDuplexCall(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_HalfDuplexCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncDuplexStreamingCall(call);
+        return HalfDuplexCall(new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> HalfDuplexCall(CallOptions options)
+      public virtual AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> HalfDuplexCall(CallOptions options)
       {
-        var call = CreateCall(__Method_HalfDuplexCall, options);
-        return Calls.AsyncDuplexStreamingCall(call);
+        return CallInvoker.AsyncDuplexStreamingCall(__Method_HalfDuplexCall, null, options);
+      }
+      protected override TestServiceClient NewInstance(ClientBaseConfiguration configuration)
+      {
+        return new TestServiceClient(configuration);
       }
     }
 
@@ -200,6 +237,18 @@ namespace Grpc.Testing {
           .AddMethod(__Method_HalfDuplexCall, serviceImpl.HalfDuplexCall).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(TestServiceBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_EmptyCall, serviceImpl.EmptyCall)
+          .AddMethod(__Method_UnaryCall, serviceImpl.UnaryCall)
+          .AddMethod(__Method_StreamingOutputCall, serviceImpl.StreamingOutputCall)
+          .AddMethod(__Method_StreamingInputCall, serviceImpl.StreamingInputCall)
+          .AddMethod(__Method_FullDuplexCall, serviceImpl.FullDuplexCall)
+          .AddMethod(__Method_HalfDuplexCall, serviceImpl.HalfDuplexCall).Build();
+    }
+
     // creates a new client
     public static TestServiceClient NewClient(Channel channel)
     {
@@ -227,6 +276,7 @@ namespace Grpc.Testing {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface IUnimplementedServiceClient
     {
       global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -236,36 +286,59 @@ namespace Grpc.Testing {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface IUnimplementedService
     {
       Task<global::Grpc.Testing.Empty> UnimplementedCall(global::Grpc.Testing.Empty request, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class UnimplementedServiceBase
+    {
+      public virtual Task<global::Grpc.Testing.Empty> UnimplementedCall(global::Grpc.Testing.Empty request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class UnimplementedServiceClient : ClientBase, IUnimplementedServiceClient
+    public class UnimplementedServiceClient : ClientBase<UnimplementedServiceClient>, IUnimplementedServiceClient
     {
       public UnimplementedServiceClient(Channel channel) : base(channel)
       {
       }
-      public global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public UnimplementedServiceClient(CallInvoker callInvoker) : base(callInvoker)
+      {
+      }
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected UnimplementedServiceClient() : base()
+      {
+      }
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected UnimplementedServiceClient(ClientBaseConfiguration configuration) : base(configuration)
+      {
+      }
+
+      public virtual global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      {
+        return UnimplementedCall(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, CallOptions options)
       {
-        var call = CreateCall(__Method_UnimplementedCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_UnimplementedCall, null, options, request);
       }
-      public global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_UnimplementedCall, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return UnimplementedCallAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, CallOptions options)
       {
-        var call = CreateCall(__Method_UnimplementedCall, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.AsyncUnaryCall(__Method_UnimplementedCall, null, options, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, CallOptions options)
+      protected override UnimplementedServiceClient NewInstance(ClientBaseConfiguration configuration)
       {
-        var call = CreateCall(__Method_UnimplementedCall, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return new UnimplementedServiceClient(configuration);
       }
     }
 
@@ -276,6 +349,13 @@ namespace Grpc.Testing {
           .AddMethod(__Method_UnimplementedCall, serviceImpl.UnimplementedCall).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(UnimplementedServiceBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_UnimplementedCall, serviceImpl.UnimplementedCall).Build();
+    }
+
     // creates a new client
     public static UnimplementedServiceClient NewClient(Channel channel)
     {
@@ -311,6 +391,7 @@ namespace Grpc.Testing {
     }
 
     // client interface
+    [System.Obsolete("Client side interfaced will be removed in the next release. Use client class directly.")]
     public interface IReconnectServiceClient
     {
       global::Grpc.Testing.Empty Start(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken));
@@ -324,57 +405,81 @@ namespace Grpc.Testing {
     }
 
     // server-side interface
+    [System.Obsolete("Service implementations should inherit from the generated abstract base class instead.")]
     public interface IReconnectService
     {
       Task<global::Grpc.Testing.Empty> Start(global::Grpc.Testing.Empty request, ServerCallContext context);
       Task<global::Grpc.Testing.ReconnectInfo> Stop(global::Grpc.Testing.Empty request, ServerCallContext context);
     }
 
+    // server-side abstract class
+    public abstract class ReconnectServiceBase
+    {
+      public virtual Task<global::Grpc.Testing.Empty> Start(global::Grpc.Testing.Empty request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+      public virtual Task<global::Grpc.Testing.ReconnectInfo> Stop(global::Grpc.Testing.Empty request, ServerCallContext context)
+      {
+        throw new RpcException(new Status(StatusCode.Unimplemented, ""));
+      }
+
+    }
+
     // client stub
-    public class ReconnectServiceClient : ClientBase, IReconnectServiceClient
+    public class ReconnectServiceClient : ClientBase<ReconnectServiceClient>, IReconnectServiceClient
     {
       public ReconnectServiceClient(Channel channel) : base(channel)
       {
       }
-      public global::Grpc.Testing.Empty Start(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public ReconnectServiceClient(CallInvoker callInvoker) : base(callInvoker)
       {
-        var call = CreateCall(__Method_Start, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public global::Grpc.Testing.Empty Start(global::Grpc.Testing.Empty request, CallOptions options)
+      ///<summary>Protected parameterless constructor to allow creation of test doubles.</summary>
+      protected ReconnectServiceClient() : base()
       {
-        var call = CreateCall(__Method_Start, options);
-        return Calls.BlockingUnaryCall(call, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Empty> StartAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      ///<summary>Protected constructor to allow creation of configured clients.</summary>
+      protected ReconnectServiceClient(ClientBaseConfiguration configuration) : base(configuration)
       {
-        var call = CreateCall(__Method_Start, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.Empty> StartAsync(global::Grpc.Testing.Empty request, CallOptions options)
+
+      public virtual global::Grpc.Testing.Empty Start(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Start, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return Start(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public global::Grpc.Testing.ReconnectInfo Stop(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Empty Start(global::Grpc.Testing.Empty request, CallOptions options)
       {
-        var call = CreateCall(__Method_Stop, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.BlockingUnaryCall(call, request);
+        return CallInvoker.BlockingUnaryCall(__Method_Start, null, options, request);
       }
-      public global::Grpc.Testing.ReconnectInfo Stop(global::Grpc.Testing.Empty request, CallOptions options)
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Empty> StartAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Stop, options);
-        return Calls.BlockingUnaryCall(call, request);
+        return StartAsync(request, new CallOptions(headers, deadline, cancellationToken));
       }
-      public AsyncUnaryCall<global::Grpc.Testing.ReconnectInfo> StopAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual AsyncUnaryCall<global::Grpc.Testing.Empty> StartAsync(global::Grpc.Testing.Empty request, CallOptions options)
       {
-        var call = CreateCall(__Method_Stop, new CallOptions(headers, deadline, cancellationToken));
-        return Calls.AsyncUnaryCall(call, request);
+        return CallInvoker.AsyncUnaryCall(__Method_Start, null, options, request);
       }
-      public AsyncUnaryCall<global::Grpc.Testing.ReconnectInfo> StopAsync(global::Grpc.Testing.Empty request, CallOptions options)
+      public virtual global::Grpc.Testing.ReconnectInfo Stop(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
       {
-        var call = CreateCall(__Method_Stop, options);
-        return Calls.AsyncUnaryCall(call, request);
+        return Stop(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual global::Grpc.Testing.ReconnectInfo Stop(global::Grpc.Testing.Empty request, CallOptions options)
+      {
+        return CallInvoker.BlockingUnaryCall(__Method_Stop, null, options, request);
+      }
+      public virtual AsyncUnaryCall<global::Grpc.Testing.ReconnectInfo> StopAsync(global::Grpc.Testing.Empty request, Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      {
+        return StopAsync(request, new CallOptions(headers, deadline, cancellationToken));
+      }
+      public virtual AsyncUnaryCall<global::Grpc.Testing.ReconnectInfo> StopAsync(global::Grpc.Testing.Empty request, CallOptions options)
+      {
+        return CallInvoker.AsyncUnaryCall(__Method_Stop, null, options, request);
+      }
+      protected override ReconnectServiceClient NewInstance(ClientBaseConfiguration configuration)
+      {
+        return new ReconnectServiceClient(configuration);
       }
     }
 
@@ -386,6 +491,14 @@ namespace Grpc.Testing {
           .AddMethod(__Method_Stop, serviceImpl.Stop).Build();
     }
 
+    // creates service definition that can be registered with a server
+    public static ServerServiceDefinition BindService(ReconnectServiceBase serviceImpl)
+    {
+      return ServerServiceDefinition.CreateBuilder(__ServiceName)
+          .AddMethod(__Method_Start, serviceImpl.Start)
+          .AddMethod(__Method_Stop, serviceImpl.Stop).Build();
+    }
+
     // creates a new client
     public static ReconnectServiceClient NewClient(Channel channel)
     {
diff --git a/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs b/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
index 5a1b4cf319..354318e80e 100644
--- a/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
+++ b/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -45,14 +45,14 @@ namespace Grpc.Testing
     /// <summary>
     /// Implementation of TestService server
     /// </summary>
-    public class TestServiceImpl : TestService.ITestService
+    public class TestServiceImpl : TestService.TestServiceBase
     {
-        public Task<Empty> EmptyCall(Empty request, ServerCallContext context)
+        public override Task<Empty> EmptyCall(Empty request, ServerCallContext context)
         {
             return Task.FromResult(new Empty());
         }
 
-        public async Task<SimpleResponse> UnaryCall(SimpleRequest request, ServerCallContext context)
+        public override async Task<SimpleResponse> UnaryCall(SimpleRequest request, ServerCallContext context)
         {
             await EnsureEchoMetadataAsync(context);
             EnsureEchoStatus(request.ResponseStatus, context);
@@ -61,7 +61,7 @@ namespace Grpc.Testing
             return response;
         }
 
-        public async Task StreamingOutputCall(StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
+        public override async Task StreamingOutputCall(StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
         {
             await EnsureEchoMetadataAsync(context);
             EnsureEchoStatus(request.ResponseStatus, context);
@@ -73,7 +73,7 @@ namespace Grpc.Testing
             }
         }
 
-        public async Task<StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<StreamingInputCallRequest> requestStream, ServerCallContext context)
+        public override async Task<StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<StreamingInputCallRequest> requestStream, ServerCallContext context)
         {
             await EnsureEchoMetadataAsync(context);
 
@@ -85,7 +85,7 @@ namespace Grpc.Testing
             return new StreamingInputCallResponse { AggregatedPayloadSize = sum };
         }
 
-        public async Task FullDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
+        public override async Task FullDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
         {
             await EnsureEchoMetadataAsync(context);
 
@@ -100,7 +100,7 @@ namespace Grpc.Testing
             });
         }
 
-        public async Task HalfDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
+        public override async Task HalfDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
         {
             throw new NotImplementedException();
         }
diff --git a/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs b/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs
index e5ad0caa03..80dad9fdd9 100644
--- a/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs
+++ b/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs
@@ -45,7 +45,7 @@ namespace Grpc.Testing
     /// <summary>
     /// Implementation of WorkerService server
     /// </summary>
-    public class WorkerServiceImpl : WorkerService.IWorkerService
+    public class WorkerServiceImpl : WorkerService.WorkerServiceBase
     {
         readonly Action stopRequestHandler;
 
@@ -54,7 +54,7 @@ namespace Grpc.Testing
             this.stopRequestHandler = GrpcPreconditions.CheckNotNull(stopRequestHandler);
         }
         
-        public async Task RunServer(IAsyncStreamReader<ServerArgs> requestStream, IServerStreamWriter<ServerStatus> responseStream, ServerCallContext context)
+        public override async Task RunServer(IAsyncStreamReader<ServerArgs> requestStream, IServerStreamWriter<ServerStatus> responseStream, ServerCallContext context)
         {
             GrpcPreconditions.CheckState(await requestStream.MoveNext());
             var serverConfig = requestStream.Current.Setup;
@@ -78,7 +78,7 @@ namespace Grpc.Testing
             await runner.StopAsync();
         }
 
-        public async Task RunClient(IAsyncStreamReader<ClientArgs> requestStream, IServerStreamWriter<ClientStatus> responseStream, ServerCallContext context)
+        public override async Task RunClient(IAsyncStreamReader<ClientArgs> requestStream, IServerStreamWriter<ClientStatus> responseStream, ServerCallContext context)
         {
             GrpcPreconditions.CheckState(await requestStream.MoveNext());
             var clientConfig = requestStream.Current.Setup;
@@ -100,12 +100,12 @@ namespace Grpc.Testing
             await runner.StopAsync();
         }
 
-        public Task<CoreResponse> CoreCount(CoreRequest request, ServerCallContext context)
+        public override Task<CoreResponse> CoreCount(CoreRequest request, ServerCallContext context)
         {
             return Task.FromResult(new CoreResponse { Cores = Environment.ProcessorCount });
         }
 
-        public Task<Void> QuitWorker(Void request, ServerCallContext context)
+        public override Task<Void> QuitWorker(Void request, ServerCallContext context)
         {
             stopRequestHandler();
             return Task.FromResult(new Void());
diff --git a/src/csharp/grpc.native.csharp/grpc.native.csharp.nuspec b/src/csharp/grpc.native.csharp/grpc.native.csharp.nuspec
index 6a1795b709..cc688e2bc7 100644
--- a/src/csharp/grpc.native.csharp/grpc.native.csharp.nuspec
+++ b/src/csharp/grpc.native.csharp/grpc.native.csharp.nuspec
@@ -10,7 +10,7 @@
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>Native extension needed by gRPC C# library. This is not the package you are looking for, it is only meant to be used as a dependency.</description>
     <releaseNotes>Release of gRPC C core $version$ libraries.</releaseNotes>
-    <copyright>Copyright 2015-2016</copyright>
+    <copyright>Copyright 2015</copyright>
     <title>gRPC C# Native Extension</title>
     <summary>Native library required by gRPC C#</summary>
     <tags>gRPC native</tags>
diff --git a/src/csharp/tests.json b/src/csharp/tests.json
index d66cb1b100..718bfa3287 100644
--- a/src/csharp/tests.json
+++ b/src/csharp/tests.json
@@ -36,8 +36,9 @@
     "Math.Tests.MathClientServerTest",
     "Grpc.HealthCheck.Tests.HealthClientServerTest",
     "Grpc.HealthCheck.Tests.HealthServiceImplTest",
-    "Grpc.IntegrationTesting.HeaderInterceptorTest",
     "Grpc.IntegrationTesting.HistogramTest",
+    "Grpc.IntegrationTesting.GeneratedClientTest",
+    "Grpc.IntegrationTesting.GeneratedServiceBaseTest",
     "Grpc.IntegrationTesting.InteropClientServerTest",
     "Grpc.IntegrationTesting.MetadataCredentialsTest",
     "Grpc.IntegrationTesting.RunnerClientServerTest",
diff --git a/src/proto/grpc/testing/messages.proto b/src/proto/grpc/testing/messages.proto
index 193b6c4171..a063b470c7 100644
--- a/src/proto/grpc/testing/messages.proto
+++ b/src/proto/grpc/testing/messages.proto
@@ -1,5 +1,5 @@
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -159,6 +159,12 @@ message StreamingOutputCallResponse {
 }
 
 // For reconnect interop test only.
+// Client tells server what reconnection parameters it used.
+message ReconnectParams {
+  int32 max_reconnect_backoff_ms = 1;
+}
+
+// For reconnect interop test only.
 // Server tells client whether its reconnects are following the spec and the
 // reconnect backoffs it saw.
 message ReconnectInfo {
diff --git a/src/proto/grpc/testing/metrics.proto b/src/proto/grpc/testing/metrics.proto
index 0cc4b60239..1202b20b8f 100644
--- a/src/proto/grpc/testing/metrics.proto
+++ b/src/proto/grpc/testing/metrics.proto
@@ -1,4 +1,4 @@
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -42,7 +42,7 @@ message GaugeResponse {
   string name = 1;
   oneof value {
     int64 long_value = 2;
-    double double_vale = 3;
+    double double_value = 3;
     string string_value = 4;
   }
 }
diff --git a/src/proto/grpc/testing/test.proto b/src/proto/grpc/testing/test.proto
index 9faba297a3..84369db4b8 100644
--- a/src/proto/grpc/testing/test.proto
+++ b/src/proto/grpc/testing/test.proto
@@ -1,5 +1,5 @@
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -80,6 +80,6 @@ service UnimplementedService {
 
 // A service used to control reconnect server.
 service ReconnectService {
-  rpc Start(grpc.testing.Empty) returns (grpc.testing.Empty);
+  rpc Start(grpc.testing.ReconnectParams) returns (grpc.testing.Empty);
   rpc Stop(grpc.testing.Empty) returns (grpc.testing.ReconnectInfo);
 }
diff --git a/src/python/grpcio/grpc/beta/implementations.py b/src/python/grpcio/grpc/beta/implementations.py
index 06ee7aa26e..742e94dc65 100644
--- a/src/python/grpcio/grpc/beta/implementations.py
+++ b/src/python/grpcio/grpc/beta/implementations.py
@@ -1,4 +1,4 @@
-# Copyright 2015-2016, Google Inc.
+# Copyright 2015, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 875ff49d30..2ed0b1e520 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -83,6 +83,23 @@ CORE_SOURCE_FILES = [
   'src/core/ext/census/operation.c',
   'src/core/ext/census/placeholders.c',
   'src/core/ext/census/tracing.c',
+  'src/core/ext/client_config/channel_connectivity.c',
+  'src/core/ext/client_config/client_channel.c',
+  'src/core/ext/client_config/client_channel_factory.c',
+  'src/core/ext/client_config/client_config.c',
+  'src/core/ext/client_config/connector.c',
+  'src/core/ext/client_config/default_initial_connect_string.c',
+  'src/core/ext/client_config/initial_connect_string.c',
+  'src/core/ext/client_config/lb_policy.c',
+  'src/core/ext/client_config/lb_policy_factory.c',
+  'src/core/ext/client_config/lb_policy_registry.c',
+  'src/core/ext/client_config/resolver.c',
+  'src/core/ext/client_config/resolver_factory.c',
+  'src/core/ext/client_config/resolver_registry.c',
+  'src/core/ext/client_config/subchannel.c',
+  'src/core/ext/client_config/subchannel_call_holder.c',
+  'src/core/ext/client_config/subchannel_index.c',
+  'src/core/ext/client_config/uri_parser.c',
   'src/core/ext/lb_policy/grpclb/load_balancer_api.c',
   'src/core/ext/lb_policy/grpclb/proto/grpc/lb/v0/load_balancer.pb.c',
   'src/core/ext/lb_policy/pick_first/pick_first.c',
@@ -117,26 +134,10 @@ CORE_SOURCE_FILES = [
   'src/core/lib/channel/channel_args.c',
   'src/core/lib/channel/channel_stack.c',
   'src/core/lib/channel/channel_stack_builder.c',
-  'src/core/lib/channel/client_channel.c',
   'src/core/lib/channel/compress_filter.c',
   'src/core/lib/channel/connected_channel.c',
   'src/core/lib/channel/http_client_filter.c',
   'src/core/lib/channel/http_server_filter.c',
-  'src/core/lib/channel/subchannel_call_holder.c',
-  'src/core/lib/client_config/client_config.c',
-  'src/core/lib/client_config/connector.c',
-  'src/core/lib/client_config/default_initial_connect_string.c',
-  'src/core/lib/client_config/initial_connect_string.c',
-  'src/core/lib/client_config/lb_policy.c',
-  'src/core/lib/client_config/lb_policy_factory.c',
-  'src/core/lib/client_config/lb_policy_registry.c',
-  'src/core/lib/client_config/resolver.c',
-  'src/core/lib/client_config/resolver_factory.c',
-  'src/core/lib/client_config/resolver_registry.c',
-  'src/core/lib/client_config/subchannel.c',
-  'src/core/lib/client_config/subchannel_factory.c',
-  'src/core/lib/client_config/subchannel_index.c',
-  'src/core/lib/client_config/uri_parser.c',
   'src/core/lib/compression/compression_algorithm.c',
   'src/core/lib/compression/message_compress.c',
   'src/core/lib/debug/trace.c',
@@ -209,7 +210,6 @@ CORE_SOURCE_FILES = [
   'src/core/lib/surface/call_details.c',
   'src/core/lib/surface/call_log_batch.c',
   'src/core/lib/surface/channel.c',
-  'src/core/lib/surface/channel_connectivity.c',
   'src/core/lib/surface/channel_init.c',
   'src/core/lib/surface/channel_ping.c',
   'src/core/lib/surface/channel_stack_type.c',
diff --git a/src/python/grpcio/tests/interop/_secure_interop_test.py b/src/python/grpcio/tests/interop/_secure_interop_test.py
index 1a1a063a6f..86d7e43351 100644
--- a/src/python/grpcio/tests/interop/_secure_interop_test.py
+++ b/src/python/grpcio/tests/interop/_secure_interop_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015-2016, Google Inc.
+# Copyright 2015, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
diff --git a/src/python/grpcio/tests/interop/client.py b/src/python/grpcio/tests/interop/client.py
index 02a37cc6bc..1d10d7e45d 100644
--- a/src/python/grpcio/tests/interop/client.py
+++ b/src/python/grpcio/tests/interop/client.py
@@ -1,4 +1,4 @@
-# Copyright 2015-2016, Google Inc.
+# Copyright 2015, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
diff --git a/src/python/grpcio/tests/unit/beta/_beta_features_test.py b/src/python/grpcio/tests/unit/beta/_beta_features_test.py
index b8b77a96c1..bb2893a21b 100644
--- a/src/python/grpcio/tests/unit/beta/_beta_features_test.py
+++ b/src/python/grpcio/tests/unit/beta/_beta_features_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015-2016, Google Inc.
+# Copyright 2015, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
diff --git a/src/python/grpcio/tests/unit/beta/_face_interface_test.py b/src/python/grpcio/tests/unit/beta/_face_interface_test.py
index ea19ee47ae..3a67516906 100644
--- a/src/python/grpcio/tests/unit/beta/_face_interface_test.py
+++ b/src/python/grpcio/tests/unit/beta/_face_interface_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015-2016, Google Inc.
+# Copyright 2015, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
diff --git a/src/ruby/ext/grpc/rb_call.c b/src/ruby/ext/grpc/rb_call.c
index dc80d18b45..f5fdbb2ffd 100644
--- a/src/ruby/ext/grpc/rb_call.c
+++ b/src/ruby/ext/grpc/rb_call.c
@@ -359,7 +359,7 @@ static int grpc_rb_md_ary_fill_hash_cb(VALUE key, VALUE val, VALUE md_ary_obj) {
       md_ary->metadata[md_ary->count].value_length = value_len;
       md_ary->count += 1;
     }
-  } else {
+  } else if (TYPE(val) == T_STRING) {
     value_str = RSTRING_PTR(val);
     value_len = RSTRING_LEN(val);
     if (!grpc_is_binary_header(key_str, key_len) &&
@@ -373,6 +373,10 @@ static int grpc_rb_md_ary_fill_hash_cb(VALUE key, VALUE val, VALUE md_ary_obj) {
     md_ary->metadata[md_ary->count].value = value_str;
     md_ary->metadata[md_ary->count].value_length = value_len;
     md_ary->count += 1;
+  } else {
+    rb_raise(rb_eArgError,
+               "Header values must be of type string or array");
+    return ST_STOP;
   }
 
   return ST_CONTINUE;
diff --git a/src/ruby/lib/grpc/generic/rpc_server.rb b/src/ruby/lib/grpc/generic/rpc_server.rb
index 4b5578b018..5ba77db173 100644
--- a/src/ruby/lib/grpc/generic/rpc_server.rb
+++ b/src/ruby/lib/grpc/generic/rpc_server.rb
@@ -403,7 +403,7 @@ module GRPC
       loop_handle_server_calls
     end
 
-    # Sends UNAVAILABLE if there are too many unprocessed jobs
+    # Sends RESOURCE_EXHAUSTED if there are too many unprocessed jobs
     def available?(an_rpc)
       jobs_count, max = @pool.jobs_waiting, @max_waiting_requests
       GRPC.logger.info("waiting: #{jobs_count}, max: #{max}")
@@ -411,7 +411,7 @@ module GRPC
       GRPC.logger.warn("NOT AVAILABLE: too many jobs_waiting: #{an_rpc}")
       noop = proc { |x| x }
       c = ActiveCall.new(an_rpc.call, @cq, noop, noop, an_rpc.deadline)
-      c.send_status(StatusCodes::UNAVAILABLE, '')
+      c.send_status(StatusCodes::RESOURCE_EXHAUSTED, '')
       nil
     end
 
diff --git a/src/ruby/spec/generic/client_stub_spec.rb b/src/ruby/spec/generic/client_stub_spec.rb
index 5e13c25fcf..dd8e2e9f7a 100644
--- a/src/ruby/spec/generic/client_stub_spec.rb
+++ b/src/ruby/spec/generic/client_stub_spec.rb
@@ -193,44 +193,45 @@ describe 'ClientStub' do
   describe '#client_streamer' do
     shared_examples 'client streaming' do
       before(:each) do
+        server_port = create_test_server
+        host = "localhost:#{server_port}"
+        @stub = GRPC::ClientStub.new(host, @cq, :this_channel_is_insecure)
+        @options = { k1: 'v1', k2: 'v2' }
         @sent_msgs = Array.new(3) { |i| 'msg_' + (i + 1).to_s }
         @resp = 'a_reply'
       end
 
       it 'should send requests to/receive a reply from a server' do
-        server_port = create_test_server
-        host = "localhost:#{server_port}"
         th = run_client_streamer(@sent_msgs, @resp, @pass)
-        stub = GRPC::ClientStub.new(host, @cq, :this_channel_is_insecure)
-        expect(get_response(stub)).to eq(@resp)
+        expect(get_response(@stub)).to eq(@resp)
         th.join
       end
 
       it 'should send metadata to the server ok' do
-        server_port = create_test_server
-        host = "localhost:#{server_port}"
-        th = run_client_streamer(@sent_msgs, @resp, @pass,
-                                 k1: 'v1', k2: 'v2')
-        stub = GRPC::ClientStub.new(host, @cq, :this_channel_is_insecure)
-        expect(get_response(stub)).to eq(@resp)
+        th = run_client_streamer(@sent_msgs, @resp, @pass, @options)
+        expect(get_response(@stub)).to eq(@resp)
         th.join
       end
 
       it 'should raise an error if the status is not ok' do
-        server_port = create_test_server
-        host = "localhost:#{server_port}"
         th = run_client_streamer(@sent_msgs, @resp, @fail)
-        stub = GRPC::ClientStub.new(host, @cq, :this_channel_is_insecure)
-        blk = proc { get_response(stub) }
+        blk = proc { get_response(@stub) }
         expect(&blk).to raise_error(GRPC::BadStatus)
         th.join
       end
+
+      it 'should raise ArgumentError if metadata contains invalid values' do
+        @options.merge!(k3: 3)
+        expect do
+          get_response(@stub)
+        end.to raise_error(ArgumentError,
+                           /Header values must be of type string or array/)
+      end
     end
 
     describe 'without a call operation' do
       def get_response(stub)
-        stub.client_streamer(@method, @sent_msgs, noop, noop,
-                             k1: 'v1', k2: 'v2')
+        stub.client_streamer(@method, @sent_msgs, noop, noop, @options)
       end
 
       it_behaves_like 'client streaming'
@@ -239,7 +240,7 @@ describe 'ClientStub' do
     describe 'via a call operation' do
       def get_response(stub)
         op = stub.client_streamer(@method, @sent_msgs, noop, noop,
-                                  return_op: true, k1: 'v1', k2: 'v2')
+                                  @options.merge(return_op: true))
         expect(op).to be_a(GRPC::ActiveCall::Operation)
         op.execute
       end
diff --git a/src/ruby/spec/generic/rpc_server_spec.rb b/src/ruby/spec/generic/rpc_server_spec.rb
index e16ba60387..e688057cb1 100644
--- a/src/ruby/spec/generic/rpc_server_spec.rb
+++ b/src/ruby/spec/generic/rpc_server_spec.rb
@@ -426,7 +426,7 @@ describe GRPC::RpcServer do
         threads.each(&:join)
       end
 
-      it 'should return UNAVAILABLE on too many jobs', server: true do
+      it 'should return RESOURCE_EXHAUSTED on too many jobs', server: true do
         opts = {
           a_channel_arg: 'an_arg',
           server_override: @server,
@@ -449,7 +449,8 @@ describe GRPC::RpcServer do
             begin
               stub.an_rpc(req)
             rescue GRPC::BadStatus => e
-              one_failed_as_unavailable = e.code == StatusCodes::UNAVAILABLE
+              one_failed_as_unavailable =
+                e.code == StatusCodes::RESOURCE_EXHAUSTED
             end
           end
         end