Merge branch 'master' of github.com:grpc/grpc into lb_policies_new_interface

40 files changed, 5784 insertions, 0 deletions

diff --git a/src/core/lib/client_config/README.md b/src/core/lib/client_config/README.md
new file mode 100644
index 0000000000..fff7a5af5b
--- /dev/null
+++ b/src/core/lib/client_config/README.md
@@ -0,0 +1,66 @@
+Client Configuration Support for GRPC
+=====================================
+
+This library provides high level configuration machinery to construct client
+channels and load balance between them.
+
+Each grpc_channel is created with a grpc_resolver. It is the resolver's duty
+to resolve a name into configuration data for the channel. Such configuration
+data might include:
+
+- a list of (ip, port) addresses to connect to
+- a load balancing policy to decide which server to send a request to
+- a set of filters to mutate outgoing requests (say, by adding metadata)
+
+The resolver provides this data as a stream of grpc_client_config objects to
+the channel. We represent configuration as a stream so that it can be changed
+by the resolver during execution, by reacting to external events (such as a
+new configuration file being pushed to some store).
+
+
+Load Balancing
+--------------
+
+Load balancing configuration is provided by a grpc_lb_policy object, stored as
+part of grpc_client_config.
+
+The primary job of the load balancing policies is to pick a target server given only the
+initial metadata for a request. It does this by providing a grpc_subchannel
+object to the owning channel.
+
+
+Sub-Channels
+------------
+
+A sub-channel provides a connection to a server for a client channel. It has a
+connectivity state like a regular channel, and so can be connected or
+disconnected. This connectivity state can be used to inform load balancing
+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
+construction arguments for concrete grpc_subchannel instances.
+
+
+Naming for GRPC
+===============
+
+Names in GRPC are represented by a URI (as defined in
+[RFC 3986](https://tools.ietf.org/html/rfc3986)).
+
+The following schemes are currently supported:
+
+dns:///host:port - dns schemes are currently supported so long as authority is
+                   empty (authority based dns resolution is expected in a future
+                   release)
+
+unix:path        - the unix scheme is used to create and connect to unix domain
+                   sockets - the authority must be empty, and the path
+                   represents the absolute or relative path to the desired
+                   socket
+
+ipv4:host:port   - a pre-resolved ipv4 dotted decimal address/port combination
+
+ipv6:[host]:port - a pre-resolved ipv6 address/port combination
diff --git a/src/core/lib/client_config/client_config.c b/src/core/lib/client_config/client_config.c
new file mode 100644
index 0000000000..82c8d68099
--- /dev/null
+++ b/src/core/lib/client_config/client_config.c
@@ -0,0 +1,74 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/client_config.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+
+struct grpc_client_config {
+  gpr_refcount refs;
+  grpc_lb_policy *lb_policy;
+};
+
+grpc_client_config *grpc_client_config_create() {
+  grpc_client_config *c = gpr_malloc(sizeof(*c));
+  memset(c, 0, sizeof(*c));
+  gpr_ref_init(&c->refs, 1);
+  return c;
+}
+
+void grpc_client_config_ref(grpc_client_config *c) { gpr_ref(&c->refs); }
+
+void grpc_client_config_unref(grpc_exec_ctx *exec_ctx, grpc_client_config *c) {
+  if (gpr_unref(&c->refs)) {
+    if (c->lb_policy != NULL) {
+      GRPC_LB_POLICY_UNREF(exec_ctx, c->lb_policy, "client_config");
+    }
+    gpr_free(c);
+  }
+}
+
+void grpc_client_config_set_lb_policy(grpc_client_config *c,
+                                      grpc_lb_policy *lb_policy) {
+  GPR_ASSERT(c->lb_policy == NULL);
+  if (lb_policy) {
+    GRPC_LB_POLICY_REF(lb_policy, "client_config");
+  }
+  c->lb_policy = lb_policy;
+}
+
+grpc_lb_policy *grpc_client_config_get_lb_policy(grpc_client_config *c) {
+  return c->lb_policy;
+}
diff --git a/src/core/lib/client_config/client_config.h b/src/core/lib/client_config/client_config.h
new file mode 100644
index 0000000000..404ec0d3a5
--- /dev/null
+++ b/src/core/lib/client_config/client_config.h
@@ -0,0 +1,53 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_CLIENT_CONFIG_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_CLIENT_CONFIG_H
+
+#include "src/core/lib/client_config/lb_policy.h"
+
+/** Total configuration for a client. Provided, and updated, by
+    grpc_resolver */
+typedef struct grpc_client_config grpc_client_config;
+
+grpc_client_config *grpc_client_config_create();
+void grpc_client_config_ref(grpc_client_config *client_config);
+void grpc_client_config_unref(grpc_exec_ctx *exec_ctx,
+                              grpc_client_config *client_config);
+
+void grpc_client_config_set_lb_policy(grpc_client_config *client_config,
+                                      grpc_lb_policy *lb_policy);
+grpc_lb_policy *grpc_client_config_get_lb_policy(
+    grpc_client_config *client_config);
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_CLIENT_CONFIG_H */
diff --git a/src/core/lib/client_config/connector.c b/src/core/lib/client_config/connector.c
new file mode 100644
index 0000000000..f51d862c6d
--- /dev/null
+++ b/src/core/lib/client_config/connector.c
@@ -0,0 +1,55 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/connector.h"
+
+grpc_connector* grpc_connector_ref(grpc_connector* connector) {
+  connector->vtable->ref(connector);
+  return connector;
+}
+
+void grpc_connector_unref(grpc_exec_ctx* exec_ctx, grpc_connector* connector) {
+  connector->vtable->unref(exec_ctx, connector);
+}
+
+void grpc_connector_connect(grpc_exec_ctx* exec_ctx, grpc_connector* connector,
+                            const grpc_connect_in_args* in_args,
+                            grpc_connect_out_args* out_args,
+                            grpc_closure* notify) {
+  connector->vtable->connect(exec_ctx, connector, in_args, out_args, notify);
+}
+
+void grpc_connector_shutdown(grpc_exec_ctx* exec_ctx,
+                             grpc_connector* connector) {
+  connector->vtable->shutdown(exec_ctx, connector);
+}
diff --git a/src/core/lib/client_config/connector.h b/src/core/lib/client_config/connector.h
new file mode 100644
index 0000000000..21b925aade
--- /dev/null
+++ b/src/core/lib/client_config/connector.h
@@ -0,0 +1,92 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_CONNECTOR_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_CONNECTOR_H
+
+#include "src/core/lib/channel/channel_stack.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+#include "src/core/lib/transport/transport.h"
+
+typedef struct grpc_connector grpc_connector;
+typedef struct grpc_connector_vtable grpc_connector_vtable;
+
+struct grpc_connector {
+  const grpc_connector_vtable *vtable;
+};
+
+typedef struct {
+  /** set of pollsets interested in this connection */
+  grpc_pollset_set *interested_parties;
+  /** address to connect to */
+  const struct sockaddr *addr;
+  size_t addr_len;
+  /** initial connect string to send */
+  gpr_slice initial_connect_string;
+  /** deadline for connection */
+  gpr_timespec deadline;
+  /** channel arguments (to be passed to transport) */
+  const grpc_channel_args *channel_args;
+} grpc_connect_in_args;
+
+typedef struct {
+  /** the connected transport */
+  grpc_transport *transport;
+
+  /** channel arguments (to be passed to the filters) */
+  const grpc_channel_args *channel_args;
+} grpc_connect_out_args;
+
+struct grpc_connector_vtable {
+  void (*ref)(grpc_connector *connector);
+  void (*unref)(grpc_exec_ctx *exec_ctx, grpc_connector *connector);
+  /** Implementation of grpc_connector_shutdown */
+  void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_connector *connector);
+  /** Implementation of grpc_connector_connect */
+  void (*connect)(grpc_exec_ctx *exec_ctx, grpc_connector *connector,
+                  const grpc_connect_in_args *in_args,
+                  grpc_connect_out_args *out_args, grpc_closure *notify);
+};
+
+grpc_connector *grpc_connector_ref(grpc_connector *connector);
+void grpc_connector_unref(grpc_exec_ctx *exec_ctx, grpc_connector *connector);
+/** Connect using the connector: max one outstanding call at a time */
+void grpc_connector_connect(grpc_exec_ctx *exec_ctx, grpc_connector *connector,
+                            const grpc_connect_in_args *in_args,
+                            grpc_connect_out_args *out_args,
+                            grpc_closure *notify);
+/** Cancel any pending connection */
+void grpc_connector_shutdown(grpc_exec_ctx *exec_ctx,
+                             grpc_connector *connector);
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_CONNECTOR_H */
diff --git a/src/core/lib/client_config/default_initial_connect_string.c b/src/core/lib/client_config/default_initial_connect_string.c
new file mode 100644
index 0000000000..86eb37de77
--- /dev/null
+++ b/src/core/lib/client_config/default_initial_connect_string.c
@@ -0,0 +1,39 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include <grpc/support/slice.h>
+#include "src/core/lib/iomgr/sockaddr.h"
+
+void grpc_set_default_initial_connect_string(struct sockaddr **addr,
+                                             size_t *addr_len,
+                                             gpr_slice *initial_str) {}
diff --git a/src/core/lib/client_config/initial_connect_string.c b/src/core/lib/client_config/initial_connect_string.c
new file mode 100644
index 0000000000..95ae728316
--- /dev/null
+++ b/src/core/lib/client_config/initial_connect_string.c
@@ -0,0 +1,53 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/initial_connect_string.h"
+
+#include <stddef.h>
+
+extern void grpc_set_default_initial_connect_string(struct sockaddr **addr,
+                                                    size_t *addr_len,
+                                                    gpr_slice *initial_str);
+
+static grpc_set_initial_connect_string_func g_set_initial_connect_string_func =
+    grpc_set_default_initial_connect_string;
+
+void grpc_test_set_initial_connect_string_function(
+    grpc_set_initial_connect_string_func func) {
+  g_set_initial_connect_string_func = func;
+}
+
+void grpc_set_initial_connect_string(struct sockaddr **addr, size_t *addr_len,
+                                     gpr_slice *initial_str) {
+  g_set_initial_connect_string_func(addr, addr_len, initial_str);
+}
diff --git a/src/core/lib/client_config/initial_connect_string.h b/src/core/lib/client_config/initial_connect_string.h
new file mode 100644
index 0000000000..eec42fa240
--- /dev/null
+++ b/src/core/lib/client_config/initial_connect_string.h
@@ -0,0 +1,50 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_INITIAL_CONNECT_STRING_H
+
+#include <grpc/support/slice.h>
+#include "src/core/lib/iomgr/sockaddr.h"
+
+typedef void (*grpc_set_initial_connect_string_func)(struct sockaddr **addr,
+                                                     size_t *addr_len,
+                                                     gpr_slice *initial_str);
+void grpc_test_set_initial_connect_string_function(
+    grpc_set_initial_connect_string_func func);
+
+/** Set a string to be sent once connected. Optionally reset addr. */
+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 */
diff --git a/src/core/lib/client_config/lb_policies/load_balancer_api.c b/src/core/lib/client_config/lb_policies/load_balancer_api.c
new file mode 100644
index 0000000000..4cbed200df
--- /dev/null
+++ b/src/core/lib/client_config/lb_policies/load_balancer_api.c
@@ -0,0 +1,163 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/lb_policies/load_balancer_api.h"
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+#include <grpc/support/alloc.h>
+
+typedef struct decode_serverlist_arg {
+  int first_pass;
+  int i;
+  size_t num_servers;
+  grpc_grpclb_server **servers;
+} decode_serverlist_arg;
+
+/* invoked once for every Server in ServerList */
+static bool decode_serverlist(pb_istream_t *stream, const pb_field_t *field,
+                              void **arg) {
+  decode_serverlist_arg *dec_arg = *arg;
+  if (dec_arg->first_pass != 0) { /* first pass */
+    grpc_grpclb_server server;
+    if (!pb_decode(stream, grpc_lb_v0_Server_fields, &server)) {
+      return false;
+    }
+    dec_arg->num_servers++;
+  } else { /* second pass */
+    grpc_grpclb_server *server = gpr_malloc(sizeof(grpc_grpclb_server));
+    GPR_ASSERT(dec_arg->num_servers > 0);
+    if (dec_arg->i == 0) { /* first iteration of second pass */
+      dec_arg->servers =
+          gpr_malloc(sizeof(grpc_grpclb_server *) * dec_arg->num_servers);
+    }
+    if (!pb_decode(stream, grpc_lb_v0_Server_fields, server)) {
+      return false;
+    }
+    dec_arg->servers[dec_arg->i++] = server;
+  }
+
+  return true;
+}
+
+grpc_grpclb_request *grpc_grpclb_request_create(const char *lb_service_name) {
+  grpc_grpclb_request *req = gpr_malloc(sizeof(grpc_grpclb_request));
+
+  req->has_client_stats = 0; /* TODO(dgq): add support for stats once defined */
+  req->has_initial_request = 1;
+  req->initial_request.has_name = 1;
+  strncpy(req->initial_request.name, lb_service_name,
+          GRPC_GRPCLB_SERVICE_NAME_MAX_LENGTH);
+  return req;
+}
+
+gpr_slice grpc_grpclb_request_encode(const grpc_grpclb_request *request) {
+  size_t encoded_length;
+  pb_ostream_t sizestream;
+  pb_ostream_t outputstream;
+  gpr_slice slice;
+  memset(&sizestream, 0, sizeof(pb_ostream_t));
+  pb_encode(&sizestream, grpc_lb_v0_LoadBalanceRequest_fields, request);
+  encoded_length = sizestream.bytes_written;
+
+  slice = gpr_slice_malloc(encoded_length);
+  outputstream =
+      pb_ostream_from_buffer(GPR_SLICE_START_PTR(slice), encoded_length);
+  GPR_ASSERT(pb_encode(&outputstream, grpc_lb_v0_LoadBalanceRequest_fields,
+                       request) != 0);
+  return slice;
+}
+
+void grpc_grpclb_request_destroy(grpc_grpclb_request *request) {
+  gpr_free(request);
+}
+
+grpc_grpclb_response *grpc_grpclb_response_parse(gpr_slice encoded_response) {
+  bool status;
+  pb_istream_t stream =
+      pb_istream_from_buffer(GPR_SLICE_START_PTR(encoded_response),
+                             GPR_SLICE_LENGTH(encoded_response));
+  grpc_grpclb_response *res = gpr_malloc(sizeof(grpc_grpclb_response));
+  memset(res, 0, sizeof(*res));
+  status = pb_decode(&stream, grpc_lb_v0_LoadBalanceResponse_fields, res);
+  GPR_ASSERT(status == true);
+  return res;
+}
+
+grpc_grpclb_serverlist *grpc_grpclb_response_parse_serverlist(
+    gpr_slice encoded_response) {
+  grpc_grpclb_serverlist *sl = gpr_malloc(sizeof(grpc_grpclb_serverlist));
+  bool status;
+  decode_serverlist_arg arg;
+  pb_istream_t stream =
+      pb_istream_from_buffer(GPR_SLICE_START_PTR(encoded_response),
+                             GPR_SLICE_LENGTH(encoded_response));
+  pb_istream_t stream_at_start = stream;
+  grpc_grpclb_response *res = gpr_malloc(sizeof(grpc_grpclb_response));
+  memset(res, 0, sizeof(*res));
+  memset(&arg, 0, sizeof(decode_serverlist_arg));
+
+  res->server_list.servers.funcs.decode = decode_serverlist;
+  res->server_list.servers.arg = &arg;
+  arg.first_pass = 1;
+  status = pb_decode(&stream, grpc_lb_v0_LoadBalanceResponse_fields, res);
+  GPR_ASSERT(status == true);
+  GPR_ASSERT(arg.num_servers > 0);
+
+  arg.first_pass = 0;
+  status =
+      pb_decode(&stream_at_start, grpc_lb_v0_LoadBalanceResponse_fields, res);
+  GPR_ASSERT(status == true);
+  GPR_ASSERT(arg.servers != NULL);
+
+  sl->num_servers = arg.num_servers;
+  sl->servers = arg.servers;
+  if (res->server_list.has_expiration_interval) {
+    sl->expiration_interval = res->server_list.expiration_interval;
+  }
+  grpc_grpclb_response_destroy(res);
+  return sl;
+}
+
+void grpc_grpclb_destroy_serverlist(grpc_grpclb_serverlist *serverlist) {
+  size_t i;
+  for (i = 0; i < serverlist->num_servers; i++) {
+    gpr_free(serverlist->servers[i]);
+  }
+  gpr_free(serverlist->servers);
+  gpr_free(serverlist);
+}
+
+void grpc_grpclb_response_destroy(grpc_grpclb_response *response) {
+  gpr_free(response);
+}
diff --git a/src/core/lib/client_config/lb_policies/load_balancer_api.h b/src/core/lib/client_config/lb_policies/load_balancer_api.h
new file mode 100644
index 0000000000..83299adfa9
--- /dev/null
+++ b/src/core/lib/client_config/lb_policies/load_balancer_api.h
@@ -0,0 +1,85 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_LOAD_BALANCER_API_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_LOAD_BALANCER_API_H
+
+#include <grpc/support/slice_buffer.h>
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+#include "src/core/lib/proto/grpc/lb/v0/load_balancer.pb.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define GRPC_GRPCLB_SERVICE_NAME_MAX_LENGTH 128
+
+typedef grpc_lb_v0_LoadBalanceRequest grpc_grpclb_request;
+typedef grpc_lb_v0_LoadBalanceResponse grpc_grpclb_response;
+typedef grpc_lb_v0_Server grpc_grpclb_server;
+typedef grpc_lb_v0_Duration grpc_grpclb_duration;
+typedef struct grpc_grpclb_serverlist {
+  grpc_grpclb_server **servers;
+  size_t num_servers;
+  grpc_grpclb_duration expiration_interval;
+} grpc_grpclb_serverlist;
+
+/** Create a request for a gRPC LB service under \a lb_service_name */
+grpc_grpclb_request *grpc_grpclb_request_create(const char *lb_service_name);
+
+/** Protocol Buffers v3-encode \a request */
+gpr_slice grpc_grpclb_request_encode(const grpc_grpclb_request *request);
+
+/** Destroy \a request */
+void grpc_grpclb_request_destroy(grpc_grpclb_request *request);
+
+/** Parse (ie, decode) the bytes in \a encoded_response as a \a
+ * grpc_grpclb_response */
+grpc_grpclb_response *grpc_grpclb_response_parse(gpr_slice encoded_response);
+
+/** Destroy \a serverlist */
+void grpc_grpclb_destroy_serverlist(grpc_grpclb_serverlist *serverlist);
+
+/** Parse the list of servers from an encoded \a grpc_grpclb_response */
+grpc_grpclb_serverlist *grpc_grpclb_response_parse_serverlist(
+    gpr_slice encoded_response);
+
+/** Destroy \a response */
+void grpc_grpclb_response_destroy(grpc_grpclb_response *response);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_LOAD_BALANCER_API_H */
diff --git a/src/core/lib/client_config/lb_policies/pick_first.c b/src/core/lib/client_config/lb_policies/pick_first.c
new file mode 100644
index 0000000000..9ac550d9e7
--- /dev/null
+++ b/src/core/lib/client_config/lb_policies/pick_first.c
@@ -0,0 +1,444 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/lb_policies/pick_first.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include "src/core/lib/client_config/lb_policy_factory.h"
+#include "src/core/lib/transport/connectivity_state.h"
+
+typedef struct pending_pick {
+  struct pending_pick *next;
+  grpc_pollset *pollset;
+  grpc_connected_subchannel **target;
+  grpc_closure *on_complete;
+} pending_pick;
+
+typedef struct {
+  /** base policy: must be first */
+  grpc_lb_policy base;
+  /** all our subchannels */
+  grpc_subchannel **subchannels;
+  size_t num_subchannels;
+
+  grpc_closure connectivity_changed;
+
+  /** the selected channel (a grpc_connected_subchannel) */
+  gpr_atm selected;
+
+  /** mutex protecting remaining members */
+  gpr_mu mu;
+  /** have we started picking? */
+  int started_picking;
+  /** are we shut down? */
+  int shutdown;
+  /** which subchannel are we watching? */
+  size_t checking_subchannel;
+  /** what is the connectivity of that channel? */
+  grpc_connectivity_state checking_connectivity;
+  /** list of picks that are waiting on connectivity */
+  pending_pick *pending_picks;
+
+  /** our connectivity state tracker */
+  grpc_connectivity_state_tracker state_tracker;
+} pick_first_lb_policy;
+
+#define GET_SELECTED(p) \
+  ((grpc_connected_subchannel *)gpr_atm_acq_load(&(p)->selected))
+
+void pf_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  grpc_connected_subchannel *selected = GET_SELECTED(p);
+  size_t i;
+  GPR_ASSERT(p->pending_picks == NULL);
+  for (i = 0; i < p->num_subchannels; i++) {
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[i], "pick_first");
+  }
+  if (selected != NULL) {
+    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, selected, "picked_first");
+  }
+  grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
+  gpr_free(p->subchannels);
+  gpr_mu_destroy(&p->mu);
+  gpr_free(p);
+}
+
+void pf_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  pending_pick *pp;
+  grpc_connected_subchannel *selected;
+  gpr_mu_lock(&p->mu);
+  selected = GET_SELECTED(p);
+  p->shutdown = 1;
+  pp = p->pending_picks;
+  p->pending_picks = NULL;
+  grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                              GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
+  /* cancel subscription */
+  if (selected != NULL) {
+    grpc_connected_subchannel_notify_on_state_change(
+        exec_ctx, selected, NULL, NULL, &p->connectivity_changed);
+  } else {
+    grpc_subchannel_notify_on_state_change(
+        exec_ctx, p->subchannels[p->checking_subchannel], NULL, NULL,
+        &p->connectivity_changed);
+  }
+  gpr_mu_unlock(&p->mu);
+  while (pp != NULL) {
+    pending_pick *next = pp->next;
+    *pp->target = NULL;
+    grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                 pp->pollset);
+    grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+    gpr_free(pp);
+    pp = next;
+  }
+}
+
+static void pf_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                           grpc_connected_subchannel **target) {
+  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->target == target) {
+      grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                   pp->pollset);
+      *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, pick_first_lb_policy *p) {
+  p->started_picking = 1;
+  p->checking_subchannel = 0;
+  p->checking_connectivity = GRPC_CHANNEL_IDLE;
+  GRPC_LB_POLICY_WEAK_REF(&p->base, "pick_first_connectivity");
+  grpc_subchannel_notify_on_state_change(
+      exec_ctx, p->subchannels[p->checking_subchannel],
+      p->base.interested_parties, &p->checking_connectivity,
+      &p->connectivity_changed);
+}
+
+void pf_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  if (!p->started_picking) {
+    start_picking(exec_ctx, p);
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
+            grpc_metadata_batch *initial_metadata,
+            grpc_connected_subchannel **target, grpc_closure *on_complete) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  pending_pick *pp;
+
+  /* Check atomically for a selected channel */
+  grpc_connected_subchannel *selected = GET_SELECTED(p);
+  if (selected != NULL) {
+    *target = selected;
+    return 1;
+  }
+
+  /* No subchannel selected yet, so acquire lock and then attempt again */
+  gpr_mu_lock(&p->mu);
+  selected = GET_SELECTED(p);
+  if (selected) {
+    gpr_mu_unlock(&p->mu);
+    *target = selected;
+    return 1;
+  } else {
+    if (!p->started_picking) {
+      start_picking(exec_ctx, p);
+    }
+    grpc_pollset_set_add_pollset(exec_ctx, p->base.interested_parties, pollset);
+    pp = gpr_malloc(sizeof(*pp));
+    pp->next = p->pending_picks;
+    pp->pollset = pollset;
+    pp->target = target;
+    pp->on_complete = on_complete;
+    p->pending_picks = pp;
+    gpr_mu_unlock(&p->mu);
+    return 0;
+  }
+}
+
+static void destroy_subchannels(grpc_exec_ctx *exec_ctx, void *arg,
+                                bool iomgr_success) {
+  pick_first_lb_policy *p = arg;
+  size_t i;
+  size_t num_subchannels = p->num_subchannels;
+  grpc_subchannel **subchannels;
+
+  gpr_mu_lock(&p->mu);
+  subchannels = p->subchannels;
+  p->num_subchannels = 0;
+  p->subchannels = NULL;
+  gpr_mu_unlock(&p->mu);
+  GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "destroy_subchannels");
+
+  for (i = 0; i < num_subchannels; i++) {
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannels[i], "pick_first");
+  }
+
+  gpr_free(subchannels);
+}
+
+static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
+                                    bool iomgr_success) {
+  pick_first_lb_policy *p = arg;
+  grpc_subchannel *selected_subchannel;
+  pending_pick *pp;
+  grpc_connected_subchannel *selected;
+
+  gpr_mu_lock(&p->mu);
+
+  selected = GET_SELECTED(p);
+
+  if (p->shutdown) {
+    gpr_mu_unlock(&p->mu);
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+    return;
+  } else if (selected != NULL) {
+    if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+      /* if the selected channel goes bad, we're done */
+      p->checking_connectivity = GRPC_CHANNEL_FATAL_FAILURE;
+    }
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                p->checking_connectivity, "selected_changed");
+    if (p->checking_connectivity != GRPC_CHANNEL_FATAL_FAILURE) {
+      grpc_connected_subchannel_notify_on_state_change(
+          exec_ctx, selected, p->base.interested_parties,
+          &p->checking_connectivity, &p->connectivity_changed);
+    } else {
+      GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+    }
+  } else {
+  loop:
+    switch (p->checking_connectivity) {
+      case GRPC_CHANNEL_READY:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_READY, "connecting_ready");
+        selected_subchannel = p->subchannels[p->checking_subchannel];
+        selected =
+            grpc_subchannel_get_connected_subchannel(selected_subchannel);
+        GPR_ASSERT(selected != NULL);
+        GRPC_CONNECTED_SUBCHANNEL_REF(selected, "picked_first");
+        /* drop the pick list: we are connected now */
+        GRPC_LB_POLICY_WEAK_REF(&p->base, "destroy_subchannels");
+        gpr_atm_rel_store(&p->selected, (gpr_atm)selected);
+        grpc_exec_ctx_enqueue(
+            exec_ctx, grpc_closure_create(destroy_subchannels, p), true, NULL);
+        /* update any calls that were waiting for a pick */
+        while ((pp = p->pending_picks)) {
+          p->pending_picks = pp->next;
+          *pp->target = selected;
+          grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                       pp->pollset);
+          grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+          gpr_free(pp);
+        }
+        grpc_connected_subchannel_notify_on_state_change(
+            exec_ctx, selected, p->base.interested_parties,
+            &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;
+        p->checking_connectivity = grpc_subchannel_check_connectivity(
+            p->subchannels[p->checking_subchannel]);
+        if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+          grpc_subchannel_notify_on_state_change(
+              exec_ctx, p->subchannels[p->checking_subchannel],
+              p->base.interested_parties, &p->checking_connectivity,
+              &p->connectivity_changed);
+        } else {
+          goto loop;
+        }
+        break;
+      case GRPC_CHANNEL_CONNECTING:
+      case GRPC_CHANNEL_IDLE:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_CONNECTING,
+                                    "connecting_changed");
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, p->subchannels[p->checking_subchannel],
+            p->base.interested_parties, &p->checking_connectivity,
+            &p->connectivity_changed);
+        break;
+      case GRPC_CHANNEL_FATAL_FAILURE:
+        p->num_subchannels--;
+        GPR_SWAP(grpc_subchannel *, p->subchannels[p->checking_subchannel],
+                 p->subchannels[p->num_subchannels]);
+        GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[p->num_subchannels],
+                              "pick_first");
+        if (p->num_subchannels == 0) {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_FATAL_FAILURE,
+                                      "no_more_channels");
+          while ((pp = p->pending_picks)) {
+            p->pending_picks = pp->next;
+            *pp->target = NULL;
+            grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+            gpr_free(pp);
+          }
+          GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base,
+                                    "pick_first_connectivity");
+        } else {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                      "subchannel_failed");
+          p->checking_subchannel %= p->num_subchannels;
+          p->checking_connectivity = grpc_subchannel_check_connectivity(
+              p->subchannels[p->checking_subchannel]);
+          goto loop;
+        }
+    }
+  }
+
+  gpr_mu_unlock(&p->mu);
+}
+
+static grpc_connectivity_state pf_check_connectivity(grpc_exec_ctx *exec_ctx,
+                                                     grpc_lb_policy *pol) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  grpc_connectivity_state st;
+  gpr_mu_lock(&p->mu);
+  st = grpc_connectivity_state_check(&p->state_tracker);
+  gpr_mu_unlock(&p->mu);
+  return st;
+}
+
+void pf_notify_on_state_change(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                               grpc_connectivity_state *current,
+                               grpc_closure *notify) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  grpc_connectivity_state_notify_on_state_change(exec_ctx, &p->state_tracker,
+                                                 current, notify);
+  gpr_mu_unlock(&p->mu);
+}
+
+void pf_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                 grpc_closure *closure) {
+  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+  grpc_connected_subchannel *selected = GET_SELECTED(p);
+  if (selected) {
+    grpc_connected_subchannel_ping(exec_ctx, selected, closure);
+  } else {
+    grpc_exec_ctx_enqueue(exec_ctx, closure, false, NULL);
+  }
+}
+
+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};
+
+static void pick_first_factory_ref(grpc_lb_policy_factory *factory) {}
+
+static void pick_first_factory_unref(grpc_lb_policy_factory *factory) {}
+
+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);
+
+  if (args->addresses->naddrs == 0) return NULL;
+
+  pick_first_lb_policy *p = gpr_malloc(sizeof(*p));
+  memset(p, 0, sizeof(*p));
+
+  p->subchannels =
+      gpr_malloc(sizeof(grpc_subchannel *) * args->addresses->naddrs);
+  memset(p->subchannels, 0, sizeof(*p->subchannels) * args->addresses->naddrs);
+  grpc_subchannel_args sc_args;
+  size_t subchannel_idx = 0;
+  for (size_t i = 0; i < args->addresses->naddrs; i++) {
+    memset(&sc_args, 0, sizeof(grpc_subchannel_args));
+    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);
+
+    if (subchannel != NULL) {
+      p->subchannels[subchannel_idx++] = subchannel;
+    }
+  }
+  if (subchannel_idx == 0) {
+    gpr_free(p->subchannels);
+    gpr_free(p);
+    return NULL;
+  }
+  p->num_subchannels = subchannel_idx;
+
+  grpc_lb_policy_init(&p->base, &pick_first_lb_policy_vtable);
+  grpc_closure_init(&p->connectivity_changed, pf_connectivity_changed, p);
+  gpr_mu_init(&p->mu);
+  return &p->base;
+}
+
+static const grpc_lb_policy_factory_vtable pick_first_factory_vtable = {
+    pick_first_factory_ref, pick_first_factory_unref, create_pick_first,
+    "pick_first"};
+
+static grpc_lb_policy_factory pick_first_lb_policy_factory = {
+    &pick_first_factory_vtable};
+
+grpc_lb_policy_factory *grpc_pick_first_lb_factory_create() {
+  return &pick_first_lb_policy_factory;
+}
diff --git a/src/core/lib/client_config/lb_policies/pick_first.h b/src/core/lib/client_config/lb_policies/pick_first.h
new file mode 100644
index 0000000000..dba86ea7ad
--- /dev/null
+++ b/src/core/lib/client_config/lb_policies/pick_first.h
@@ -0,0 +1,43 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_PICK_FIRST_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_PICK_FIRST_H
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+
+/** Returns a load balancing factory for the pick first policy, which picks up
+ * the first subchannel from \a subchannels to succesfully connect */
+grpc_lb_policy_factory *grpc_pick_first_lb_factory_create();
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_PICK_FIRST_H */
diff --git a/src/core/lib/client_config/lb_policies/round_robin.c b/src/core/lib/client_config/lb_policies/round_robin.c
new file mode 100644
index 0000000000..a4bc2c4786
--- /dev/null
+++ b/src/core/lib/client_config/lb_policies/round_robin.c
@@ -0,0 +1,563 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/lb_policies/round_robin.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include "src/core/lib/transport/connectivity_state.h"
+
+typedef struct round_robin_lb_policy round_robin_lb_policy;
+
+int grpc_lb_round_robin_trace = 0;
+
+/** List of entities waiting for a pick.
+ *
+ * Once a pick is available, \a target is updated and \a on_complete called. */
+typedef struct pending_pick {
+  struct pending_pick *next;
+  grpc_pollset *pollset;
+  grpc_connected_subchannel **target;
+  grpc_closure *on_complete;
+} pending_pick;
+
+/** List of subchannels in a connectivity READY state */
+typedef struct ready_list {
+  grpc_subchannel *subchannel;
+  struct ready_list *next;
+  struct ready_list *prev;
+} ready_list;
+
+typedef struct {
+  /** index within policy->subchannels */
+  size_t index;
+  /** backpointer to owning policy */
+  round_robin_lb_policy *policy;
+  /** subchannel itself */
+  grpc_subchannel *subchannel;
+  /** notification that connectivity has changed on subchannel */
+  grpc_closure connectivity_changed_closure;
+  /** this subchannels current position in subchannel->ready_list */
+  ready_list *ready_list_node;
+  /** last observed connectivity */
+  grpc_connectivity_state connectivity_state;
+} subchannel_data;
+
+struct round_robin_lb_policy {
+  /** base policy: must be first */
+  grpc_lb_policy base;
+
+  /** all our subchannels */
+  size_t num_subchannels;
+  subchannel_data **subchannels;
+
+  /** mutex protecting remaining members */
+  gpr_mu mu;
+  /** have we started picking? */
+  int started_picking;
+  /** are we shutting down? */
+  int shutdown;
+  /** List of picks that are waiting on connectivity */
+  pending_pick *pending_picks;
+
+  /** our connectivity state tracker */
+  grpc_connectivity_state_tracker state_tracker;
+
+  /** (Dummy) root of the doubly linked list containing READY subchannels */
+  ready_list ready_list;
+  /** Last pick from the ready list. */
+  ready_list *ready_list_last_pick;
+};
+
+/** Returns the next subchannel from the connected list or NULL if the list is
+ * empty.
+ *
+ * Note that this function does *not* advance p->ready_list_last_pick. Use \a
+ * advance_last_picked_locked() for that. */
+static ready_list *peek_next_connected_locked(const round_robin_lb_policy *p) {
+  ready_list *selected;
+  selected = p->ready_list_last_pick->next;
+
+  while (selected != NULL) {
+    if (selected == &p->ready_list) {
+      GPR_ASSERT(selected->subchannel == NULL);
+      /* skip dummy root */
+      selected = selected->next;
+    } else {
+      GPR_ASSERT(selected->subchannel != NULL);
+      return selected;
+    }
+  }
+  return NULL;
+}
+
+/** Advance the \a ready_list picking head. */
+static void advance_last_picked_locked(round_robin_lb_policy *p) {
+  if (p->ready_list_last_pick->next != NULL) { /* non-empty list */
+    p->ready_list_last_pick = p->ready_list_last_pick->next;
+    if (p->ready_list_last_pick == &p->ready_list) {
+      /* skip dummy root */
+      p->ready_list_last_pick = p->ready_list_last_pick->next;
+    }
+  } else { /* should be an empty list */
+    GPR_ASSERT(p->ready_list_last_pick == &p->ready_list);
+  }
+
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "[READYLIST] ADVANCED LAST PICK. NOW AT NODE %p (SC %p)",
+            p->ready_list_last_pick, p->ready_list_last_pick->subchannel);
+  }
+}
+
+/** Prepends (relative to the root at p->ready_list) the connected subchannel \a
+ * csc to the list of ready subchannels. */
+static ready_list *add_connected_sc_locked(round_robin_lb_policy *p,
+                                           grpc_subchannel *sc) {
+  ready_list *new_elem = gpr_malloc(sizeof(ready_list));
+  new_elem->subchannel = sc;
+  if (p->ready_list.prev == NULL) {
+    /* first element */
+    new_elem->next = &p->ready_list;
+    new_elem->prev = &p->ready_list;
+    p->ready_list.next = new_elem;
+    p->ready_list.prev = new_elem;
+  } else {
+    new_elem->next = &p->ready_list;
+    new_elem->prev = p->ready_list.prev;
+    p->ready_list.prev->next = new_elem;
+    p->ready_list.prev = new_elem;
+  }
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "[READYLIST] ADDING NODE %p (SC %p)", new_elem, sc);
+  }
+  return new_elem;
+}
+
+/** Removes \a node from the list of connected subchannels */
+static void remove_disconnected_sc_locked(round_robin_lb_policy *p,
+                                          ready_list *node) {
+  if (node == NULL) {
+    return;
+  }
+  if (node == p->ready_list_last_pick) {
+    /* If removing the lastly picked node, reset the last pick pointer to the
+     * dummy root of the list */
+    p->ready_list_last_pick = &p->ready_list;
+  }
+
+  /* removing last item */
+  if (node->next == &p->ready_list && node->prev == &p->ready_list) {
+    GPR_ASSERT(p->ready_list.next == node);
+    GPR_ASSERT(p->ready_list.prev == node);
+    p->ready_list.next = NULL;
+    p->ready_list.prev = NULL;
+  } else {
+    node->prev->next = node->next;
+    node->next->prev = node->prev;
+  }
+
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "[READYLIST] REMOVED NODE %p (SC %p)", node,
+            node->subchannel);
+  }
+
+  node->next = NULL;
+  node->prev = NULL;
+  node->subchannel = NULL;
+
+  gpr_free(node);
+}
+
+void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  size_t i;
+  ready_list *elem;
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
+    gpr_free(sd);
+  }
+
+  grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
+  gpr_free(p->subchannels);
+  gpr_mu_destroy(&p->mu);
+
+  elem = p->ready_list.next;
+  while (elem != NULL && elem != &p->ready_list) {
+    ready_list *tmp;
+    tmp = elem->next;
+    elem->next = NULL;
+    elem->prev = NULL;
+    elem->subchannel = NULL;
+    gpr_free(elem);
+    elem = tmp;
+  }
+  gpr_free(p);
+}
+
+void rr_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  pending_pick *pp;
+  size_t i;
+
+  gpr_mu_lock(&p->mu);
+
+  p->shutdown = 1;
+  while ((pp = p->pending_picks)) {
+    p->pending_picks = pp->next;
+    *pp->target = NULL;
+    grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, false, NULL);
+    gpr_free(pp);
+  }
+  grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                              GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    grpc_subchannel_notify_on_state_change(exec_ctx, sd->subchannel, NULL, NULL,
+                                           &sd->connectivity_changed_closure);
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+static void rr_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                           grpc_connected_subchannel **target) {
+  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->target == target) {
+      grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                   pp->pollset);
+      *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;
+
+  gpr_log(GPR_DEBUG, "LB_POLICY: p=%p num_subchannels=%d", p,
+          p->num_subchannels);
+
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    sd->connectivity_state = GRPC_CHANNEL_IDLE;
+    grpc_subchannel_notify_on_state_change(
+        exec_ctx, sd->subchannel, p->base.interested_parties,
+        &sd->connectivity_state, &sd->connectivity_changed_closure);
+    GRPC_LB_POLICY_WEAK_REF(&p->base, "round_robin_connectivity");
+  }
+}
+
+void rr_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  if (!p->started_picking) {
+    start_picking(exec_ctx, p);
+  }
+  gpr_mu_unlock(&p->mu);
+}
+
+int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
+            grpc_metadata_batch *initial_metadata,
+            grpc_connected_subchannel **target, grpc_closure *on_complete) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  pending_pick *pp;
+  ready_list *selected;
+  gpr_mu_lock(&p->mu);
+  if ((selected = peek_next_connected_locked(p))) {
+    gpr_mu_unlock(&p->mu);
+    *target = grpc_subchannel_get_connected_subchannel(selected->subchannel);
+    if (grpc_lb_round_robin_trace) {
+      gpr_log(GPR_DEBUG,
+              "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)",
+              selected->subchannel, selected);
+    }
+    /* only advance the last picked pointer if the selection was used */
+    advance_last_picked_locked(p);
+    return 1;
+  } else {
+    if (!p->started_picking) {
+      start_picking(exec_ctx, p);
+    }
+    grpc_pollset_set_add_pollset(exec_ctx, p->base.interested_parties, pollset);
+    pp = gpr_malloc(sizeof(*pp));
+    pp->next = p->pending_picks;
+    pp->pollset = pollset;
+    pp->target = target;
+    pp->on_complete = on_complete;
+    p->pending_picks = pp;
+    gpr_mu_unlock(&p->mu);
+    return 0;
+  }
+}
+
+static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
+                                    bool iomgr_success) {
+  subchannel_data *sd = arg;
+  round_robin_lb_policy *p = sd->policy;
+  pending_pick *pp;
+  ready_list *selected;
+
+  int unref = 0;
+
+  gpr_mu_lock(&p->mu);
+
+  if (p->shutdown) {
+    unref = 1;
+  } else {
+    switch (sd->connectivity_state) {
+      case GRPC_CHANNEL_READY:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_READY, "connecting_ready");
+        /* add the newly connected subchannel to the list of connected ones.
+         * Note that it goes to the "end of the line". */
+        sd->ready_list_node = add_connected_sc_locked(p, sd->subchannel);
+        /* at this point we know there's at least one suitable subchannel. Go
+         * ahead and pick one and notify the pending suitors in
+         * p->pending_picks. This preemtively replicates rr_pick()'s actions. */
+        selected = peek_next_connected_locked(p);
+        if (p->pending_picks != NULL) {
+          /* if the selected subchannel is going to be used for the pending
+           * picks, update the last picked pointer */
+          advance_last_picked_locked(p);
+        }
+        while ((pp = p->pending_picks)) {
+          p->pending_picks = pp->next;
+          *pp->target =
+              grpc_subchannel_get_connected_subchannel(selected->subchannel);
+          if (grpc_lb_round_robin_trace) {
+            gpr_log(GPR_DEBUG,
+                    "[RR CONN CHANGED] TARGET <-- SUBCHANNEL %p (NODE %p)",
+                    selected->subchannel, selected);
+          }
+          grpc_pollset_set_del_pollset(exec_ctx, p->base.interested_parties,
+                                       pp->pollset);
+          grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+          gpr_free(pp);
+        }
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, sd->subchannel, p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
+        break;
+      case GRPC_CHANNEL_CONNECTING:
+      case GRPC_CHANNEL_IDLE:
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    sd->connectivity_state,
+                                    "connecting_changed");
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, sd->subchannel, p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
+        break;
+      case GRPC_CHANNEL_TRANSIENT_FAILURE:
+        /* renew state notification */
+        grpc_subchannel_notify_on_state_change(
+            exec_ctx, sd->subchannel, p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
+
+        /* remove from ready list if still present */
+        if (sd->ready_list_node != NULL) {
+          remove_disconnected_sc_locked(p, sd->ready_list_node);
+          sd->ready_list_node = NULL;
+        }
+        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                    GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                    "connecting_transient_failure");
+        break;
+      case GRPC_CHANNEL_FATAL_FAILURE:
+        if (sd->ready_list_node != NULL) {
+          remove_disconnected_sc_locked(p, sd->ready_list_node);
+          sd->ready_list_node = NULL;
+        }
+
+        p->num_subchannels--;
+        GPR_SWAP(subchannel_data *, p->subchannels[sd->index],
+                 p->subchannels[p->num_subchannels]);
+        GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
+        p->subchannels[sd->index]->index = sd->index;
+        gpr_free(sd);
+
+        unref = 1;
+        if (p->num_subchannels == 0) {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_FATAL_FAILURE,
+                                      "no_more_channels");
+          while ((pp = p->pending_picks)) {
+            p->pending_picks = pp->next;
+            *pp->target = NULL;
+            grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, true, NULL);
+            gpr_free(pp);
+          }
+        } else {
+          grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                      GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                      "subchannel_failed");
+        }
+    } /* switch */
+  }   /* !unref */
+
+  gpr_mu_unlock(&p->mu);
+
+  if (unref) {
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "round_robin_connectivity");
+  }
+}
+
+static grpc_connectivity_state rr_check_connectivity(grpc_exec_ctx *exec_ctx,
+                                                     grpc_lb_policy *pol) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  grpc_connectivity_state st;
+  gpr_mu_lock(&p->mu);
+  st = grpc_connectivity_state_check(&p->state_tracker);
+  gpr_mu_unlock(&p->mu);
+  return st;
+}
+
+static void rr_notify_on_state_change(grpc_exec_ctx *exec_ctx,
+                                      grpc_lb_policy *pol,
+                                      grpc_connectivity_state *current,
+                                      grpc_closure *notify) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  gpr_mu_lock(&p->mu);
+  grpc_connectivity_state_notify_on_state_change(exec_ctx, &p->state_tracker,
+                                                 current, notify);
+  gpr_mu_unlock(&p->mu);
+}
+
+static void rr_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
+                        grpc_closure *closure) {
+  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
+  ready_list *selected;
+  grpc_connected_subchannel *target;
+  gpr_mu_lock(&p->mu);
+  if ((selected = peek_next_connected_locked(p))) {
+    gpr_mu_unlock(&p->mu);
+    target = grpc_subchannel_get_connected_subchannel(selected->subchannel);
+    grpc_connected_subchannel_ping(exec_ctx, target, closure);
+  } else {
+    gpr_mu_unlock(&p->mu);
+    grpc_exec_ctx_enqueue(exec_ctx, closure, false, NULL);
+  }
+}
+
+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};
+
+static void round_robin_factory_ref(grpc_lb_policy_factory *factory) {}
+
+static void round_robin_factory_unref(grpc_lb_policy_factory *factory) {}
+
+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);
+
+  round_robin_lb_policy *p = gpr_malloc(sizeof(*p));
+  memset(p, 0, sizeof(*p));
+
+  p->subchannels =
+      gpr_malloc(sizeof(*p->subchannels) * args->addresses->naddrs);
+  memset(p->subchannels, 0, sizeof(*p->subchannels) * args->addresses->naddrs);
+
+  grpc_subchannel_args sc_args;
+  size_t subchannel_idx = 0;
+  for (size_t i = 0; i < args->addresses->naddrs; i++) {
+    memset(&sc_args, 0, sizeof(grpc_subchannel_args));
+    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);
+
+    if (subchannel != NULL) {
+      subchannel_data *sd = gpr_malloc(sizeof(*sd));
+      memset(sd, 0, sizeof(*sd));
+      p->subchannels[subchannel_idx] = sd;
+      sd->policy = p;
+      sd->index = subchannel_idx;
+      sd->subchannel = subchannel;
+      ++subchannel_idx;
+      grpc_closure_init(&sd->connectivity_changed_closure,
+                        rr_connectivity_changed, sd);
+    }
+  }
+  if (subchannel_idx == 0) {
+    gpr_free(p->subchannels);
+    gpr_free(p);
+    return NULL;
+  }
+  p->num_subchannels = subchannel_idx;
+
+  /* The (dummy node) root of the ready list */
+  p->ready_list.subchannel = NULL;
+  p->ready_list.prev = NULL;
+  p->ready_list.next = NULL;
+  p->ready_list_last_pick = &p->ready_list;
+
+  grpc_lb_policy_init(&p->base, &round_robin_lb_policy_vtable);
+  grpc_connectivity_state_init(&p->state_tracker, GRPC_CHANNEL_IDLE,
+                               "round_robin");
+  gpr_mu_init(&p->mu);
+  return &p->base;
+}
+
+static const grpc_lb_policy_factory_vtable round_robin_factory_vtable = {
+    round_robin_factory_ref, round_robin_factory_unref, create_round_robin,
+    "round_robin"};
+
+static grpc_lb_policy_factory round_robin_lb_policy_factory = {
+    &round_robin_factory_vtable};
+
+grpc_lb_policy_factory *grpc_round_robin_lb_factory_create() {
+  return &round_robin_lb_policy_factory;
+}
diff --git a/src/core/lib/client_config/lb_policies/round_robin.h b/src/core/lib/client_config/lb_policies/round_robin.h
new file mode 100644
index 0000000000..52db1caa0c
--- /dev/null
+++ b/src/core/lib/client_config/lb_policies/round_robin.h
@@ -0,0 +1,46 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_ROUND_ROBIN_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_ROUND_ROBIN_H
+
+#include "src/core/lib/client_config/lb_policy.h"
+
+extern int grpc_lb_round_robin_trace;
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+
+/** Returns a load balancing factory for the round robin policy */
+grpc_lb_policy_factory *grpc_round_robin_lb_factory_create();
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICIES_ROUND_ROBIN_H */
diff --git a/src/core/lib/client_config/lb_policy.c b/src/core/lib/client_config/lb_policy.c
new file mode 100644
index 0000000000..ee20ccd76a
--- /dev/null
+++ b/src/core/lib/client_config/lb_policy.c
@@ -0,0 +1,134 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/lb_policy.h"
+
+#define WEAK_REF_BITS 16
+
+void grpc_lb_policy_init(grpc_lb_policy *policy,
+                         const grpc_lb_policy_vtable *vtable) {
+  policy->vtable = vtable;
+  gpr_atm_no_barrier_store(&policy->ref_pair, 1 << WEAK_REF_BITS);
+  policy->interested_parties = grpc_pollset_set_create();
+}
+
+#ifdef GRPC_LB_POLICY_REFCOUNT_DEBUG
+#define REF_FUNC_EXTRA_ARGS , const char *file, int line, const char *reason
+#define REF_MUTATE_EXTRA_ARGS REF_FUNC_EXTRA_ARGS, const char *purpose
+#define REF_FUNC_PASS_ARGS(new_reason) , file, line, new_reason
+#define REF_MUTATE_PASS_ARGS(purpose) , file, line, reason, purpose
+#else
+#define REF_FUNC_EXTRA_ARGS
+#define REF_MUTATE_EXTRA_ARGS
+#define REF_FUNC_PASS_ARGS(new_reason)
+#define REF_MUTATE_PASS_ARGS(x)
+#endif
+
+static gpr_atm ref_mutate(grpc_lb_policy *c, gpr_atm delta,
+                          int barrier REF_MUTATE_EXTRA_ARGS) {
+  gpr_atm old_val = barrier ? gpr_atm_full_fetch_add(&c->ref_pair, delta)
+                            : gpr_atm_no_barrier_fetch_add(&c->ref_pair, delta);
+#ifdef GRPC_LB_POLICY_REFCOUNT_DEBUG
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+          "LB_POLICY: %p % 12s 0x%08x -> 0x%08x [%s]", c, purpose, old_val,
+          old_val + delta, reason);
+#endif
+  return old_val;
+}
+
+void grpc_lb_policy_ref(grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  ref_mutate(policy, 1 << WEAK_REF_BITS, 0 REF_MUTATE_PASS_ARGS("STRONG_REF"));
+}
+
+void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx,
+                          grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  gpr_atm old_val =
+      ref_mutate(policy, (gpr_atm)1 - (gpr_atm)(1 << WEAK_REF_BITS),
+                 1 REF_MUTATE_PASS_ARGS("STRONG_UNREF"));
+  gpr_atm mask = ~(gpr_atm)((1 << WEAK_REF_BITS) - 1);
+  gpr_atm check = 1 << WEAK_REF_BITS;
+  if ((old_val & mask) == check) {
+    policy->vtable->shutdown(exec_ctx, policy);
+  }
+  grpc_lb_policy_weak_unref(exec_ctx,
+                            policy REF_FUNC_PASS_ARGS("strong-unref"));
+}
+
+void grpc_lb_policy_weak_ref(grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  ref_mutate(policy, 1, 0 REF_MUTATE_PASS_ARGS("WEAK_REF"));
+}
+
+void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx,
+                               grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  gpr_atm old_val =
+      ref_mutate(policy, -(gpr_atm)1, 1 REF_MUTATE_PASS_ARGS("WEAK_UNREF"));
+  if (old_val == 1) {
+    grpc_pollset_set_destroy(policy->interested_parties);
+    policy->vtable->destroy(exec_ctx, policy);
+  }
+}
+
+int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                        grpc_pollset *pollset,
+                        grpc_metadata_batch *initial_metadata,
+                        grpc_connected_subchannel **target,
+                        grpc_closure *on_complete) {
+  return policy->vtable->pick(exec_ctx, policy, pollset, initial_metadata,
+                              target, on_complete);
+}
+
+void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                                grpc_connected_subchannel **target) {
+  policy->vtable->cancel_pick(exec_ctx, policy, target);
+}
+
+void grpc_lb_policy_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy) {
+  policy->vtable->exit_idle(exec_ctx, policy);
+}
+
+void grpc_lb_policy_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                             grpc_closure *closure) {
+  policy->vtable->ping_one(exec_ctx, policy, closure);
+}
+
+void grpc_lb_policy_notify_on_state_change(grpc_exec_ctx *exec_ctx,
+                                           grpc_lb_policy *policy,
+                                           grpc_connectivity_state *state,
+                                           grpc_closure *closure) {
+  policy->vtable->notify_on_state_change(exec_ctx, policy, state, closure);
+}
+
+grpc_connectivity_state grpc_lb_policy_check_connectivity(
+    grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy) {
+  return policy->vtable->check_connectivity(exec_ctx, policy);
+}
diff --git a/src/core/lib/client_config/lb_policy.h b/src/core/lib/client_config/lb_policy.h
new file mode 100644
index 0000000000..58a0a04d85
--- /dev/null
+++ b/src/core/lib/client_config/lb_policy.h
@@ -0,0 +1,144 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_H
+
+#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/lib/transport/connectivity_state.h"
+
+/** A load balancing policy: specified by a vtable and a struct (which
+    is expected to be extended to contain some parameters) */
+typedef struct grpc_lb_policy grpc_lb_policy;
+typedef struct grpc_lb_policy_vtable grpc_lb_policy_vtable;
+
+typedef void (*grpc_lb_completion)(void *cb_arg, grpc_subchannel *subchannel,
+                                   grpc_status_code status, const char *errmsg);
+
+struct grpc_lb_policy {
+  const grpc_lb_policy_vtable *vtable;
+  gpr_atm ref_pair;
+  /* owned pointer to interested parties in load balancing decisions */
+  grpc_pollset_set *interested_parties;
+};
+
+struct grpc_lb_policy_vtable {
+  void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
+
+  void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
+
+  /** implement grpc_lb_policy_pick */
+  int (*pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+              grpc_pollset *pollset, grpc_metadata_batch *initial_metadata,
+              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 (*ping_one)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                   grpc_closure *closure);
+
+  /** try to enter a READY connectivity state */
+  void (*exit_idle)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
+
+  /** check the current connectivity of the lb_policy */
+  grpc_connectivity_state (*check_connectivity)(grpc_exec_ctx *exec_ctx,
+                                                grpc_lb_policy *policy);
+
+  /** call notify when the connectivity state of a channel changes from *state.
+      Updates *state with the new state of the policy */
+  void (*notify_on_state_change)(grpc_exec_ctx *exec_ctx,
+                                 grpc_lb_policy *policy,
+                                 grpc_connectivity_state *state,
+                                 grpc_closure *closure);
+};
+
+/*#define GRPC_LB_POLICY_REFCOUNT_DEBUG*/
+#ifdef GRPC_LB_POLICY_REFCOUNT_DEBUG
+#define GRPC_LB_POLICY_REF(p, r) \
+  grpc_lb_policy_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_LB_POLICY_UNREF(exec_ctx, p, r) \
+  grpc_lb_policy_unref((exec_ctx), (p), __FILE__, __LINE__, (r))
+#define GRPC_LB_POLICY_WEAK_REF(p, r) \
+  grpc_lb_policy_weak_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, p, r) \
+  grpc_lb_policy_weak_unref((exec_ctx), (p), __FILE__, __LINE__, (r))
+void grpc_lb_policy_ref(grpc_lb_policy *policy, const char *file, int line,
+                        const char *reason);
+void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                          const char *file, int line, const char *reason);
+void grpc_lb_policy_weak_ref(grpc_lb_policy *policy, const char *file, int line,
+                             const char *reason);
+void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                               const char *file, int line, const char *reason);
+#else
+#define GRPC_LB_POLICY_REF(p, r) grpc_lb_policy_ref((p))
+#define GRPC_LB_POLICY_UNREF(cl, p, r) grpc_lb_policy_unref((cl), (p))
+#define GRPC_LB_POLICY_WEAK_REF(p, r) grpc_lb_policy_weak_ref((p))
+#define GRPC_LB_POLICY_WEAK_UNREF(cl, p, r) grpc_lb_policy_weak_unref((cl), (p))
+void grpc_lb_policy_ref(grpc_lb_policy *policy);
+void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
+void grpc_lb_policy_weak_ref(grpc_lb_policy *policy);
+void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
+#endif
+
+/** called by concrete implementations to initialize the base struct */
+void grpc_lb_policy_init(grpc_lb_policy *policy,
+                         const grpc_lb_policy_vtable *vtable);
+
+/** Given initial metadata in \a initial_metadata, find an appropriate
+    target for this rpc, and 'return' it by calling \a on_complete after setting
+    \a target.
+    Picking can be asynchronous. Any IO should be done under \a pollset. */
+int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                        grpc_pollset *pollset,
+                        grpc_metadata_batch *initial_metadata,
+                        grpc_connected_subchannel **target,
+                        grpc_closure *on_complete);
+
+void grpc_lb_policy_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                             grpc_closure *closure);
+
+void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                                grpc_connected_subchannel **target);
+
+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,
+                                           grpc_lb_policy *policy,
+                                           grpc_connectivity_state *state,
+                                           grpc_closure *closure);
+
+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 */
diff --git a/src/core/lib/client_config/lb_policy_factory.c b/src/core/lib/client_config/lb_policy_factory.c
new file mode 100644
index 0000000000..ede1d624af
--- /dev/null
+++ b/src/core/lib/client_config/lb_policy_factory.c
@@ -0,0 +1,49 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/lb_policy_factory.h"
+
+void grpc_lb_policy_factory_ref(grpc_lb_policy_factory* factory) {
+  factory->vtable->ref(factory);
+}
+
+void grpc_lb_policy_factory_unref(grpc_lb_policy_factory* factory) {
+  factory->vtable->unref(factory);
+}
+
+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) {
+  if (factory == NULL) return NULL;
+  return factory->vtable->create_lb_policy(exec_ctx, factory, args);
+}
diff --git a/src/core/lib/client_config/lb_policy_factory.h b/src/core/lib/client_config/lb_policy_factory.h
new file mode 100644
index 0000000000..9a93a8ca3f
--- /dev/null
+++ b/src/core/lib/client_config/lb_policy_factory.h
@@ -0,0 +1,78 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_FACTORY_H
+#define GRPC_CORE_LIB_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/lib/iomgr/resolve_address.h"
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+
+typedef struct grpc_lb_policy_factory grpc_lb_policy_factory;
+typedef struct grpc_lb_policy_factory_vtable grpc_lb_policy_factory_vtable;
+
+/** grpc_lb_policy provides grpc_client_config objects to grpc_channel
+    objects */
+struct grpc_lb_policy_factory {
+  const grpc_lb_policy_factory_vtable *vtable;
+};
+
+typedef struct grpc_lb_policy_args {
+  grpc_resolved_addresses *addresses;
+  grpc_subchannel_factory *subchannel_factory;
+} grpc_lb_policy_args;
+
+struct grpc_lb_policy_factory_vtable {
+  void (*ref)(grpc_lb_policy_factory *factory);
+  void (*unref)(grpc_lb_policy_factory *factory);
+
+  /** Implementation of grpc_lb_policy_factory_create_lb_policy */
+  grpc_lb_policy *(*create_lb_policy)(grpc_exec_ctx *exec_ctx,
+                                      grpc_lb_policy_factory *factory,
+                                      grpc_lb_policy_args *args);
+
+  /** Name for the LB policy this factory implements */
+  const char *name;
+};
+
+void grpc_lb_policy_factory_ref(grpc_lb_policy_factory *factory);
+void grpc_lb_policy_factory_unref(grpc_lb_policy_factory *factory);
+
+/** Create a lb_policy instance. */
+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 */
diff --git a/src/core/lib/client_config/lb_policy_registry.c b/src/core/lib/client_config/lb_policy_registry.c
new file mode 100644
index 0000000000..f703e630a0
--- /dev/null
+++ b/src/core/lib/client_config/lb_policy_registry.c
@@ -0,0 +1,88 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/lb_policy_registry.h"
+
+#include <string.h>
+
+#define MAX_POLICIES 10
+
+static grpc_lb_policy_factory *g_all_of_the_lb_policies[MAX_POLICIES];
+static int g_number_of_lb_policies = 0;
+
+static grpc_lb_policy_factory *g_default_lb_policy_factory;
+
+void grpc_lb_policy_registry_init(grpc_lb_policy_factory *default_factory) {
+  g_number_of_lb_policies = 0;
+  g_default_lb_policy_factory = default_factory;
+}
+
+void grpc_lb_policy_registry_shutdown(void) {
+  int i;
+  for (i = 0; i < g_number_of_lb_policies; i++) {
+    grpc_lb_policy_factory_unref(g_all_of_the_lb_policies[i]);
+  }
+}
+
+void grpc_register_lb_policy(grpc_lb_policy_factory *factory) {
+  int i;
+  for (i = 0; i < g_number_of_lb_policies; i++) {
+    GPR_ASSERT(0 != strcmp(factory->vtable->name,
+                           g_all_of_the_lb_policies[i]->vtable->name));
+  }
+  GPR_ASSERT(g_number_of_lb_policies != MAX_POLICIES);
+  grpc_lb_policy_factory_ref(factory);
+  g_all_of_the_lb_policies[g_number_of_lb_policies++] = factory;
+}
+
+static grpc_lb_policy_factory *lookup_factory(const char *name) {
+  int i;
+
+  if (name == NULL) return NULL;
+
+  for (i = 0; i < g_number_of_lb_policies; i++) {
+    if (0 == strcmp(name, g_all_of_the_lb_policies[i]->vtable->name)) {
+      return g_all_of_the_lb_policies[i];
+    }
+  }
+
+  return NULL;
+}
+
+grpc_lb_policy *grpc_lb_policy_create(grpc_exec_ctx *exec_ctx, const char *name,
+                                      grpc_lb_policy_args *args) {
+  grpc_lb_policy_factory *factory = lookup_factory(name);
+  grpc_lb_policy *lb_policy =
+      grpc_lb_policy_factory_create_lb_policy(exec_ctx, factory, args);
+  return lb_policy;
+}
diff --git a/src/core/lib/client_config/lb_policy_registry.h b/src/core/lib/client_config/lb_policy_registry.h
new file mode 100644
index 0000000000..789854bd20
--- /dev/null
+++ b/src/core/lib/client_config/lb_policy_registry.h
@@ -0,0 +1,55 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_REGISTRY_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_LB_POLICY_REGISTRY_H
+
+#include "src/core/lib/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
+ * returned when no name is provided in a lookup */
+void grpc_lb_policy_registry_init(grpc_lb_policy_factory *default_factory);
+void grpc_lb_policy_registry_shutdown(void);
+
+/** Register a LB policy factory. */
+void grpc_register_lb_policy(grpc_lb_policy_factory *factory);
+
+/** Create a \a grpc_lb_policy instance.
+ *
+ * If \a name is NULL, the default factory from \a grpc_lb_policy_registry_init
+ * will be returned. */
+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 */
diff --git a/src/core/lib/client_config/resolver.c b/src/core/lib/client_config/resolver.c
new file mode 100644
index 0000000000..32f0643adb
--- /dev/null
+++ b/src/core/lib/client_config/resolver.c
@@ -0,0 +1,82 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/resolver.h"
+
+void grpc_resolver_init(grpc_resolver *resolver,
+                        const grpc_resolver_vtable *vtable) {
+  resolver->vtable = vtable;
+  gpr_ref_init(&resolver->refs, 1);
+}
+
+#ifdef GRPC_RESOLVER_REFCOUNT_DEBUG
+void grpc_resolver_ref(grpc_resolver *resolver, grpc_closure_list *closure_list,
+                       const char *file, int line, const char *reason) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "RESOLVER:%p   ref %d -> %d %s",
+          resolver, (int)resolver->refs.count, (int)resolver->refs.count + 1,
+          reason);
+#else
+void grpc_resolver_ref(grpc_resolver *resolver) {
+#endif
+  gpr_ref(&resolver->refs);
+}
+
+#ifdef GRPC_RESOLVER_REFCOUNT_DEBUG
+void grpc_resolver_unref(grpc_resolver *resolver,
+                         grpc_closure_list *closure_list, const char *file,
+                         int line, const char *reason) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "RESOLVER:%p unref %d -> %d %s",
+          resolver, (int)resolver->refs.count, (int)resolver->refs.count - 1,
+          reason);
+#else
+void grpc_resolver_unref(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver) {
+#endif
+  if (gpr_unref(&resolver->refs)) {
+    resolver->vtable->destroy(exec_ctx, resolver);
+  }
+}
+
+void grpc_resolver_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver) {
+  resolver->vtable->shutdown(exec_ctx, resolver);
+}
+
+void grpc_resolver_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                     grpc_resolver *resolver) {
+  resolver->vtable->channel_saw_error(exec_ctx, resolver);
+}
+
+void grpc_resolver_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
+                        grpc_client_config **target_config,
+                        grpc_closure *on_complete) {
+  resolver->vtable->next(exec_ctx, resolver, target_config, on_complete);
+}
diff --git a/src/core/lib/client_config/resolver.h b/src/core/lib/client_config/resolver.h
new file mode 100644
index 0000000000..1ee879293a
--- /dev/null
+++ b/src/core/lib/client_config/resolver.h
@@ -0,0 +1,94 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_H
+
+#include "src/core/lib/client_config/client_config.h"
+#include "src/core/lib/client_config/subchannel.h"
+#include "src/core/lib/iomgr/iomgr.h"
+
+typedef struct grpc_resolver grpc_resolver;
+typedef struct grpc_resolver_vtable grpc_resolver_vtable;
+
+/** grpc_resolver provides grpc_client_config objects to grpc_channel
+    objects */
+struct grpc_resolver {
+  const grpc_resolver_vtable *vtable;
+  gpr_refcount refs;
+};
+
+struct grpc_resolver_vtable {
+  void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
+  void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
+  void (*channel_saw_error)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
+  void (*next)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
+               grpc_client_config **target_config, grpc_closure *on_complete);
+};
+
+#ifdef GRPC_RESOLVER_REFCOUNT_DEBUG
+#define GRPC_RESOLVER_REF(p, r) grpc_resolver_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_RESOLVER_UNREF(cl, p, r) \
+  grpc_resolver_unref((cl), (p), __FILE__, __LINE__, (r))
+void grpc_resolver_ref(grpc_resolver *policy, const char *file, int line,
+                       const char *reason);
+void grpc_resolver_unref(grpc_resolver *policy, grpc_closure_list *closure_list,
+                         const char *file, int line, const char *reason);
+#else
+#define GRPC_RESOLVER_REF(p, r) grpc_resolver_ref((p))
+#define GRPC_RESOLVER_UNREF(cl, p, r) grpc_resolver_unref((cl), (p))
+void grpc_resolver_ref(grpc_resolver *policy);
+void grpc_resolver_unref(grpc_exec_ctx *exec_ctx, grpc_resolver *policy);
+#endif
+
+void grpc_resolver_init(grpc_resolver *resolver,
+                        const grpc_resolver_vtable *vtable);
+
+void grpc_resolver_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
+
+/** Notification that the channel has seen an error on some address.
+    Can be used as a hint that re-resolution is desirable soon. */
+void grpc_resolver_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                     grpc_resolver *resolver);
+
+/** Get the next client config. Called by the channel to fetch a new
+    configuration. Expected to set *target_config with a new configuration,
+    and then schedule on_complete for execution.
+
+    If resolution is fatally broken, set *target_config to NULL and
+    schedule on_complete. */
+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 */
diff --git a/src/core/lib/client_config/resolver_factory.c b/src/core/lib/client_config/resolver_factory.c
new file mode 100644
index 0000000000..0f76c664fa
--- /dev/null
+++ b/src/core/lib/client_config/resolver_factory.c
@@ -0,0 +1,55 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/resolver_factory.h"
+
+void grpc_resolver_factory_ref(grpc_resolver_factory* factory) {
+  factory->vtable->ref(factory);
+}
+
+void grpc_resolver_factory_unref(grpc_resolver_factory* factory) {
+  factory->vtable->unref(factory);
+}
+
+/** Create a resolver instance for a name */
+grpc_resolver* grpc_resolver_factory_create_resolver(
+    grpc_resolver_factory* factory, grpc_resolver_args* args) {
+  if (factory == NULL) return NULL;
+  return factory->vtable->create_resolver(factory, args);
+}
+
+char* grpc_resolver_factory_get_default_authority(
+    grpc_resolver_factory* factory, grpc_uri* uri) {
+  if (factory == NULL) return NULL;
+  return factory->vtable->get_default_authority(factory, uri);
+}
diff --git a/src/core/lib/client_config/resolver_factory.h b/src/core/lib/client_config/resolver_factory.h
new file mode 100644
index 0000000000..7765c3c844
--- /dev/null
+++ b/src/core/lib/client_config/resolver_factory.h
@@ -0,0 +1,82 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_FACTORY_H
+#define GRPC_CORE_LIB_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"
+
+typedef struct grpc_resolver_factory grpc_resolver_factory;
+typedef struct grpc_resolver_factory_vtable grpc_resolver_factory_vtable;
+
+/** grpc_resolver provides grpc_client_config objects to grpc_channel
+    objects */
+struct grpc_resolver_factory {
+  const grpc_resolver_factory_vtable *vtable;
+};
+
+typedef struct grpc_resolver_args {
+  grpc_uri *uri;
+  grpc_subchannel_factory *subchannel_factory;
+} grpc_resolver_args;
+
+struct grpc_resolver_factory_vtable {
+  void (*ref)(grpc_resolver_factory *factory);
+  void (*unref)(grpc_resolver_factory *factory);
+
+  /** Implementation of grpc_resolver_factory_create_resolver */
+  grpc_resolver *(*create_resolver)(grpc_resolver_factory *factory,
+                                    grpc_resolver_args *args);
+
+  /** Implementation of grpc_resolver_factory_get_default_authority */
+  char *(*get_default_authority)(grpc_resolver_factory *factory, grpc_uri *uri);
+
+  /** URI scheme that this factory implements */
+  const char *scheme;
+};
+
+void grpc_resolver_factory_ref(grpc_resolver_factory *resolver);
+void grpc_resolver_factory_unref(grpc_resolver_factory *resolver);
+
+/** Create a resolver instance for a name */
+grpc_resolver *grpc_resolver_factory_create_resolver(
+    grpc_resolver_factory *factory, grpc_resolver_args *args);
+
+/** Return a (freshly allocated with gpr_malloc) string representing
+    the default authority to use for this scheme. */
+char *grpc_resolver_factory_get_default_authority(
+    grpc_resolver_factory *factory, grpc_uri *uri);
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_FACTORY_H */
diff --git a/src/core/lib/client_config/resolver_registry.c b/src/core/lib/client_config/resolver_registry.c
new file mode 100644
index 0000000000..29bd00c284
--- /dev/null
+++ b/src/core/lib/client_config/resolver_registry.c
@@ -0,0 +1,137 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/resolver_registry.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+
+#define MAX_RESOLVERS 10
+
+static grpc_resolver_factory *g_all_of_the_resolvers[MAX_RESOLVERS];
+static int g_number_of_resolvers = 0;
+
+static char *g_default_resolver_prefix;
+
+void grpc_resolver_registry_init(const char *default_resolver_prefix) {
+  g_number_of_resolvers = 0;
+  g_default_resolver_prefix = gpr_strdup(default_resolver_prefix);
+}
+
+void grpc_resolver_registry_shutdown(void) {
+  int i;
+  for (i = 0; i < g_number_of_resolvers; i++) {
+    grpc_resolver_factory_unref(g_all_of_the_resolvers[i]);
+  }
+  gpr_free(g_default_resolver_prefix);
+}
+
+void grpc_register_resolver_type(grpc_resolver_factory *factory) {
+  int i;
+  for (i = 0; i < g_number_of_resolvers; i++) {
+    GPR_ASSERT(0 != strcmp(factory->vtable->scheme,
+                           g_all_of_the_resolvers[i]->vtable->scheme));
+  }
+  GPR_ASSERT(g_number_of_resolvers != MAX_RESOLVERS);
+  grpc_resolver_factory_ref(factory);
+  g_all_of_the_resolvers[g_number_of_resolvers++] = factory;
+}
+
+static grpc_resolver_factory *lookup_factory(grpc_uri *uri) {
+  int i;
+
+  /* handling NULL uri's here simplifies grpc_resolver_create */
+  if (!uri) return NULL;
+
+  for (i = 0; i < g_number_of_resolvers; i++) {
+    if (0 == strcmp(uri->scheme, g_all_of_the_resolvers[i]->vtable->scheme)) {
+      return g_all_of_the_resolvers[i];
+    }
+  }
+
+  return NULL;
+}
+
+static grpc_resolver_factory *resolve_factory(const char *target,
+                                              grpc_uri **uri) {
+  char *tmp;
+  grpc_resolver_factory *factory = NULL;
+
+  GPR_ASSERT(uri != NULL);
+  *uri = grpc_uri_parse(target, 1);
+  factory = lookup_factory(*uri);
+  if (factory == NULL) {
+    if (g_default_resolver_prefix != NULL) {
+      grpc_uri_destroy(*uri);
+      gpr_asprintf(&tmp, "%s%s", g_default_resolver_prefix, target);
+      *uri = grpc_uri_parse(tmp, 1);
+      factory = lookup_factory(*uri);
+      if (factory == NULL) {
+        grpc_uri_destroy(grpc_uri_parse(target, 0));
+        grpc_uri_destroy(grpc_uri_parse(tmp, 0));
+        gpr_log(GPR_ERROR, "don't know how to resolve '%s' or '%s'", target,
+                tmp);
+      }
+      gpr_free(tmp);
+    } else {
+      grpc_uri_destroy(grpc_uri_parse(target, 0));
+      gpr_log(GPR_ERROR, "don't know how to resolve '%s'", target);
+    }
+  }
+  return factory;
+}
+
+grpc_resolver *grpc_resolver_create(
+    const char *target, grpc_subchannel_factory *subchannel_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;
+  resolver = grpc_resolver_factory_create_resolver(factory, &args);
+  grpc_uri_destroy(uri);
+  return resolver;
+}
+
+char *grpc_get_default_authority(const char *target) {
+  grpc_uri *uri = NULL;
+  grpc_resolver_factory *factory = resolve_factory(target, &uri);
+  char *authority = grpc_resolver_factory_get_default_authority(factory, uri);
+  grpc_uri_destroy(uri);
+  return authority;
+}
diff --git a/src/core/lib/client_config/resolver_registry.h b/src/core/lib/client_config/resolver_registry.h
new file mode 100644
index 0000000000..22289ca6bd
--- /dev/null
+++ b/src/core/lib/client_config/resolver_registry.h
@@ -0,0 +1,65 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_REGISTRY_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVER_REGISTRY_H
+
+#include "src/core/lib/client_config/resolver_factory.h"
+
+void grpc_resolver_registry_init(const char *default_prefix);
+void grpc_resolver_registry_shutdown(void);
+
+/** Register a resolver type.
+    URI's of \a scheme will be resolved with the given resolver.
+    If \a priority is greater than zero, then the resolver will be eligible
+    to resolve names that are passed in with no scheme. Higher priority
+    resolvers will be tried before lower priority schemes. */
+void grpc_register_resolver_type(grpc_resolver_factory *factory);
+
+/** Create a resolver given \a target.
+    First tries to parse \a target as a URI. If this succeeds, tries
+    to locate a registered resolver factory based on the URI scheme.
+    If parsing or location fails, prefixes default_prefix from
+    grpc_resolver_registry_init to target, and tries again (if default_prefix
+    was not NULL).
+    If a resolver factory was found, use it to instantiate a resolver and
+    return it.
+    If a resolver factory was not found, return NULL. */
+grpc_resolver *grpc_resolver_create(
+    const char *target, grpc_subchannel_factory *subchannel_factory);
+
+/** Given a target, return a (freshly allocated with gpr_malloc) string
+    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 */
diff --git a/src/core/lib/client_config/resolvers/dns_resolver.c b/src/core/lib/client_config/resolvers/dns_resolver.c
new file mode 100644
index 0000000000..62bccdd045
--- /dev/null
+++ b/src/core/lib/client_config/resolvers/dns_resolver.c
@@ -0,0 +1,294 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/resolvers/dns_resolver.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#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/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/timer.h"
+#include "src/core/lib/support/backoff.h"
+#include "src/core/lib/support/string.h"
+
+#define BACKOFF_MULTIPLIER 1.6
+#define BACKOFF_JITTER 0.2
+#define BACKOFF_MIN_SECONDS 1
+#define BACKOFF_MAX_SECONDS 120
+
+typedef struct {
+  /** base class: must be first */
+  grpc_resolver base;
+  /** refcount */
+  gpr_refcount refs;
+  /** name to resolve */
+  char *name;
+  /** default port to use */
+  char *default_port;
+  /** subchannel factory */
+  grpc_subchannel_factory *subchannel_factory;
+  /** load balancing policy name */
+  char *lb_policy_name;
+
+  /** mutex guarding the rest of the state */
+  gpr_mu mu;
+  /** are we currently resolving? */
+  int resolving;
+  /** which version of resolved_config have we published? */
+  int published_version;
+  /** which version of resolved_config is current? */
+  int resolved_version;
+  /** pending next completion, or NULL */
+  grpc_closure *next_completion;
+  /** target config address for next completion */
+  grpc_client_config **target_config;
+  /** current (fully resolved) config */
+  grpc_client_config *resolved_config;
+  /** retry timer */
+  bool have_retry_timer;
+  grpc_timer retry_timer;
+  /** retry backoff state */
+  gpr_backoff backoff_state;
+} dns_resolver;
+
+static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+
+static void dns_start_resolving_locked(dns_resolver *r);
+static void dns_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                         dns_resolver *r);
+
+static void dns_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+static void dns_next(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
+                     grpc_client_config **target_config,
+                     grpc_closure *on_complete);
+
+static const grpc_resolver_vtable dns_resolver_vtable = {
+    dns_destroy, dns_shutdown, dns_channel_saw_error, dns_next};
+
+static void dns_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver) {
+  dns_resolver *r = (dns_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  if (r->have_retry_timer) {
+    grpc_timer_cancel(exec_ctx, &r->retry_timer);
+  }
+  if (r->next_completion != NULL) {
+    *r->target_config = NULL;
+    grpc_exec_ctx_enqueue(exec_ctx, r->next_completion, true, NULL);
+    r->next_completion = NULL;
+  }
+  gpr_mu_unlock(&r->mu);
+}
+
+static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                  grpc_resolver *resolver) {
+  dns_resolver *r = (dns_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  if (!r->resolving) {
+    gpr_backoff_reset(&r->backoff_state);
+    dns_start_resolving_locked(r);
+  }
+  gpr_mu_unlock(&r->mu);
+}
+
+static void dns_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
+                     grpc_client_config **target_config,
+                     grpc_closure *on_complete) {
+  dns_resolver *r = (dns_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  GPR_ASSERT(!r->next_completion);
+  r->next_completion = on_complete;
+  r->target_config = target_config;
+  if (r->resolved_version == 0 && !r->resolving) {
+    gpr_backoff_reset(&r->backoff_state);
+    dns_start_resolving_locked(r);
+  } else {
+    dns_maybe_finish_next_locked(exec_ctx, r);
+  }
+  gpr_mu_unlock(&r->mu);
+}
+
+static void dns_on_retry_timer(grpc_exec_ctx *exec_ctx, void *arg,
+                               bool success) {
+  dns_resolver *r = arg;
+
+  gpr_mu_lock(&r->mu);
+  r->have_retry_timer = false;
+  if (success) {
+    if (!r->resolving) {
+      dns_start_resolving_locked(r);
+    }
+  }
+  gpr_mu_unlock(&r->mu);
+
+  GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "retry-timer");
+}
+
+static void dns_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
+                            grpc_resolved_addresses *addresses) {
+  dns_resolver *r = arg;
+  grpc_client_config *config = NULL;
+  grpc_lb_policy *lb_policy;
+  gpr_mu_lock(&r->mu);
+  GPR_ASSERT(r->resolving);
+  r->resolving = 0;
+  if (addresses != NULL) {
+    grpc_lb_policy_args lb_policy_args;
+    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 =
+        grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
+    if (lb_policy != NULL) {
+      grpc_client_config_set_lb_policy(config, lb_policy);
+      GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "construction");
+    }
+    grpc_resolved_addresses_destroy(addresses);
+  } else {
+    gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
+    gpr_timespec next_try = gpr_backoff_step(&r->backoff_state, now);
+    gpr_timespec timeout = gpr_time_sub(next_try, now);
+    gpr_log(GPR_DEBUG, "dns resolution failed: retrying in %d.%09d seconds",
+            timeout.tv_sec, timeout.tv_nsec);
+    GPR_ASSERT(!r->have_retry_timer);
+    r->have_retry_timer = true;
+    GRPC_RESOLVER_REF(&r->base, "retry-timer");
+    grpc_timer_init(exec_ctx, &r->retry_timer, next_try, dns_on_retry_timer, r,
+                    now);
+  }
+  if (r->resolved_config) {
+    grpc_client_config_unref(exec_ctx, r->resolved_config);
+  }
+  r->resolved_config = config;
+  r->resolved_version++;
+  dns_maybe_finish_next_locked(exec_ctx, r);
+  gpr_mu_unlock(&r->mu);
+
+  GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "dns-resolving");
+}
+
+static void dns_start_resolving_locked(dns_resolver *r) {
+  GRPC_RESOLVER_REF(&r->base, "dns-resolving");
+  GPR_ASSERT(!r->resolving);
+  r->resolving = 1;
+  grpc_resolve_address(r->name, r->default_port, dns_on_resolved, r);
+}
+
+static void dns_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                         dns_resolver *r) {
+  if (r->next_completion != NULL &&
+      r->resolved_version != r->published_version) {
+    *r->target_config = r->resolved_config;
+    if (r->resolved_config) {
+      grpc_client_config_ref(r->resolved_config);
+    }
+    grpc_exec_ctx_enqueue(exec_ctx, r->next_completion, true, NULL);
+    r->next_completion = NULL;
+    r->published_version = r->resolved_version;
+  }
+}
+
+static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
+  dns_resolver *r = (dns_resolver *)gr;
+  gpr_mu_destroy(&r->mu);
+  if (r->resolved_config) {
+    grpc_client_config_unref(exec_ctx, r->resolved_config);
+  }
+  grpc_subchannel_factory_unref(exec_ctx, r->subchannel_factory);
+  gpr_free(r->name);
+  gpr_free(r->default_port);
+  gpr_free(r->lb_policy_name);
+  gpr_free(r);
+}
+
+static grpc_resolver *dns_create(grpc_resolver_args *args,
+                                 const char *default_port,
+                                 const char *lb_policy_name) {
+  dns_resolver *r;
+  const char *path = args->uri->path;
+
+  if (0 != strcmp(args->uri->authority, "")) {
+    gpr_log(GPR_ERROR, "authority based dns uri's not supported");
+    return NULL;
+  }
+
+  if (path[0] == '/') ++path;
+
+  r = gpr_malloc(sizeof(dns_resolver));
+  memset(r, 0, sizeof(*r));
+  gpr_ref_init(&r->refs, 1);
+  gpr_mu_init(&r->mu);
+  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;
+  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);
+  r->lb_policy_name = gpr_strdup(lb_policy_name);
+  return &r->base;
+}
+
+/*
+ * FACTORY
+ */
+
+static void dns_factory_ref(grpc_resolver_factory *factory) {}
+
+static void dns_factory_unref(grpc_resolver_factory *factory) {}
+
+static grpc_resolver *dns_factory_create_resolver(
+    grpc_resolver_factory *factory, grpc_resolver_args *args) {
+  return dns_create(args, "https", "pick_first");
+}
+
+char *dns_factory_get_default_host_name(grpc_resolver_factory *factory,
+                                        grpc_uri *uri) {
+  const char *path = uri->path;
+  if (path[0] == '/') ++path;
+  return gpr_strdup(path);
+}
+
+static const grpc_resolver_factory_vtable dns_factory_vtable = {
+    dns_factory_ref, dns_factory_unref, dns_factory_create_resolver,
+    dns_factory_get_default_host_name, "dns"};
+static grpc_resolver_factory dns_resolver_factory = {&dns_factory_vtable};
+
+grpc_resolver_factory *grpc_dns_resolver_factory_create() {
+  return &dns_resolver_factory;
+}
diff --git a/src/core/lib/client_config/resolvers/dns_resolver.h b/src/core/lib/client_config/resolvers/dns_resolver.h
new file mode 100644
index 0000000000..eb46e41c77
--- /dev/null
+++ b/src/core/lib/client_config/resolvers/dns_resolver.h
@@ -0,0 +1,42 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_DNS_RESOLVER_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_DNS_RESOLVER_H
+
+#include "src/core/lib/client_config/resolver_factory.h"
+
+/** Create a dns resolver factory */
+grpc_resolver_factory *grpc_dns_resolver_factory_create(void);
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_DNS_RESOLVER_H */
diff --git a/src/core/lib/client_config/resolvers/sockaddr_resolver.c b/src/core/lib/client_config/resolvers/sockaddr_resolver.c
new file mode 100644
index 0000000000..c787bd57d6
--- /dev/null
+++ b/src/core/lib/client_config/resolvers/sockaddr_resolver.c
@@ -0,0 +1,354 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/client_config/resolvers/sockaddr_resolver.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#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/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/unix_sockets_posix.h"
+#include "src/core/lib/support/string.h"
+
+typedef struct {
+  /** base class: must be first */
+  grpc_resolver base;
+  /** refcount */
+  gpr_refcount refs;
+  /** subchannel factory */
+  grpc_subchannel_factory *subchannel_factory;
+  /** load balancing policy name */
+  char *lb_policy_name;
+
+  /** the addresses that we've 'resolved' */
+  grpc_resolved_addresses *addresses;
+
+  /** mutex guarding the rest of the state */
+  gpr_mu mu;
+  /** have we published? */
+  int published;
+  /** pending next completion, or NULL */
+  grpc_closure *next_completion;
+  /** target config address for next completion */
+  grpc_client_config **target_config;
+} sockaddr_resolver;
+
+static void sockaddr_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+
+static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                              sockaddr_resolver *r);
+
+static void sockaddr_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+static void sockaddr_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                       grpc_resolver *r);
+static void sockaddr_next(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
+                          grpc_client_config **target_config,
+                          grpc_closure *on_complete);
+
+static const grpc_resolver_vtable sockaddr_resolver_vtable = {
+    sockaddr_destroy, sockaddr_shutdown, sockaddr_channel_saw_error,
+    sockaddr_next};
+
+static void sockaddr_shutdown(grpc_exec_ctx *exec_ctx,
+                              grpc_resolver *resolver) {
+  sockaddr_resolver *r = (sockaddr_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  if (r->next_completion != NULL) {
+    *r->target_config = NULL;
+    grpc_exec_ctx_enqueue(exec_ctx, r->next_completion, true, NULL);
+    r->next_completion = NULL;
+  }
+  gpr_mu_unlock(&r->mu);
+}
+
+static void sockaddr_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                       grpc_resolver *resolver) {
+  sockaddr_resolver *r = (sockaddr_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  r->published = 0;
+  sockaddr_maybe_finish_next_locked(exec_ctx, r);
+  gpr_mu_unlock(&r->mu);
+}
+
+static void sockaddr_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
+                          grpc_client_config **target_config,
+                          grpc_closure *on_complete) {
+  sockaddr_resolver *r = (sockaddr_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  GPR_ASSERT(!r->next_completion);
+  r->next_completion = on_complete;
+  r->target_config = target_config;
+  sockaddr_maybe_finish_next_locked(exec_ctx, r);
+  gpr_mu_unlock(&r->mu);
+}
+
+static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                              sockaddr_resolver *r) {
+  if (r->next_completion != NULL && !r->published) {
+    grpc_client_config *cfg = grpc_client_config_create();
+    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;
+    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);
+    GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "sockaddr");
+    r->published = 1;
+    *r->target_config = cfg;
+    grpc_exec_ctx_enqueue(exec_ctx, r->next_completion, true, NULL);
+    r->next_completion = NULL;
+  }
+}
+
+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_resolved_addresses_destroy(r->addresses);
+  gpr_free(r->lb_policy_name);
+  gpr_free(r);
+}
+
+static char *ip_get_default_authority(grpc_uri *uri) {
+  const char *path = uri->path;
+  if (path[0] == '/') ++path;
+  return gpr_strdup(path);
+}
+
+static char *ipv4_get_default_authority(grpc_resolver_factory *factory,
+                                        grpc_uri *uri) {
+  return ip_get_default_authority(uri);
+}
+
+static char *ipv6_get_default_authority(grpc_resolver_factory *factory,
+                                        grpc_uri *uri) {
+  return ip_get_default_authority(uri);
+}
+
+static int parse_ipv4(grpc_uri *uri, struct sockaddr_storage *addr,
+                      size_t *len) {
+  const char *host_port = uri->path;
+  char *host;
+  char *port;
+  int port_num;
+  int result = 0;
+  struct sockaddr_in *in = (struct sockaddr_in *)addr;
+
+  if (*host_port == '/') ++host_port;
+  if (!gpr_split_host_port(host_port, &host, &port)) {
+    return 0;
+  }
+
+  memset(in, 0, sizeof(*in));
+  *len = sizeof(*in);
+  in->sin_family = AF_INET;
+  if (inet_pton(AF_INET, host, &in->sin_addr) == 0) {
+    gpr_log(GPR_ERROR, "invalid ipv4 address: '%s'", host);
+    goto done;
+  }
+
+  if (port != NULL) {
+    if (sscanf(port, "%d", &port_num) != 1 || port_num < 0 ||
+        port_num > 65535) {
+      gpr_log(GPR_ERROR, "invalid ipv4 port: '%s'", port);
+      goto done;
+    }
+    in->sin_port = htons((uint16_t)port_num);
+  } else {
+    gpr_log(GPR_ERROR, "no port given for ipv4 scheme");
+    goto done;
+  }
+
+  result = 1;
+done:
+  gpr_free(host);
+  gpr_free(port);
+  return result;
+}
+
+static int parse_ipv6(grpc_uri *uri, struct sockaddr_storage *addr,
+                      size_t *len) {
+  const char *host_port = uri->path;
+  char *host;
+  char *port;
+  int port_num;
+  int result = 0;
+  struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)addr;
+
+  if (*host_port == '/') ++host_port;
+  if (!gpr_split_host_port(host_port, &host, &port)) {
+    return 0;
+  }
+
+  memset(in6, 0, sizeof(*in6));
+  *len = sizeof(*in6);
+  in6->sin6_family = AF_INET6;
+  if (inet_pton(AF_INET6, host, &in6->sin6_addr) == 0) {
+    gpr_log(GPR_ERROR, "invalid ipv6 address: '%s'", host);
+    goto done;
+  }
+
+  if (port != NULL) {
+    if (sscanf(port, "%d", &port_num) != 1 || port_num < 0 ||
+        port_num > 65535) {
+      gpr_log(GPR_ERROR, "invalid ipv6 port: '%s'", port);
+      goto done;
+    }
+    in6->sin6_port = htons((uint16_t)port_num);
+  } else {
+    gpr_log(GPR_ERROR, "no port given for ipv6 scheme");
+    goto done;
+  }
+
+  result = 1;
+done:
+  gpr_free(host);
+  gpr_free(port);
+  return result;
+}
+
+static void do_nothing(void *ignored) {}
+
+static grpc_resolver *sockaddr_create(
+    grpc_resolver_args *args, const char *default_lb_policy_name,
+    int parse(grpc_uri *uri, struct sockaddr_storage *dst, size_t *len)) {
+  int errors_found = 0; /* GPR_FALSE */
+  sockaddr_resolver *r;
+  gpr_slice path_slice;
+  gpr_slice_buffer path_parts;
+
+  if (0 != strcmp(args->uri->authority, "")) {
+    gpr_log(GPR_ERROR, "authority based uri's not supported by the %s scheme",
+            args->uri->scheme);
+    return NULL;
+  }
+
+  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);
+  }
+  if (r->lb_policy_name == NULL) {
+    r->lb_policy_name = gpr_strdup(default_lb_policy_name);
+  }
+
+  path_slice =
+      gpr_slice_new(args->uri->path, strlen(args->uri->path), do_nothing);
+  gpr_slice_buffer_init(&path_parts);
+
+  gpr_slice_split(path_slice, ",", &path_parts);
+  r->addresses = gpr_malloc(sizeof(grpc_resolved_addresses));
+  r->addresses->naddrs = path_parts.count;
+  r->addresses->addrs =
+      gpr_malloc(sizeof(grpc_resolved_address) * r->addresses->naddrs);
+
+  for (size_t i = 0; i < r->addresses->naddrs; i++) {
+    grpc_uri ith_uri = *args->uri;
+    char *part_str = gpr_dump_slice(path_parts.slices[i], GPR_DUMP_ASCII);
+    ith_uri.path = part_str;
+    if (!parse(&ith_uri,
+               (struct sockaddr_storage *)(&r->addresses->addrs[i].addr),
+               &r->addresses->addrs[i].len)) {
+      errors_found = 1; /* GPR_TRUE */
+    }
+    gpr_free(part_str);
+    if (errors_found) break;
+  }
+
+  gpr_slice_buffer_destroy(&path_parts);
+  gpr_slice_unref(path_slice);
+  if (errors_found) {
+    gpr_free(r->lb_policy_name);
+    grpc_resolved_addresses_destroy(r->addresses);
+    gpr_free(r);
+    return NULL;
+  }
+
+  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);
+
+  return &r->base;
+}
+
+/*
+ * FACTORY
+ */
+
+static void sockaddr_factory_ref(grpc_resolver_factory *factory) {}
+
+static void sockaddr_factory_unref(grpc_resolver_factory *factory) {}
+
+#define DECL_FACTORY(name, prefix)                                          \
+  static grpc_resolver *name##_factory_create_resolver(                     \
+      grpc_resolver_factory *factory, grpc_resolver_args *args) {           \
+    return sockaddr_create(args, "pick_first", prefix##parse_##name);       \
+  }                                                                         \
+  static const grpc_resolver_factory_vtable name##_factory_vtable = {       \
+      sockaddr_factory_ref, sockaddr_factory_unref,                         \
+      name##_factory_create_resolver, prefix##name##_get_default_authority, \
+      #name};                                                               \
+  static grpc_resolver_factory name##_resolver_factory = {                  \
+      &name##_factory_vtable};                                              \
+  grpc_resolver_factory *grpc_##name##_resolver_factory_create() {          \
+    return &name##_resolver_factory;                                        \
+  }
+
+#ifdef GPR_HAVE_UNIX_SOCKET
+DECL_FACTORY(unix, grpc_)
+#endif
+DECL_FACTORY(ipv4, ) DECL_FACTORY(ipv6, )
diff --git a/src/core/lib/client_config/resolvers/sockaddr_resolver.h b/src/core/lib/client_config/resolvers/sockaddr_resolver.h
new file mode 100644
index 0000000000..45c55bd160
--- /dev/null
+++ b/src/core/lib/client_config/resolvers/sockaddr_resolver.h
@@ -0,0 +1,50 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_SOCKADDR_RESOLVER_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_SOCKADDR_RESOLVER_H
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/client_config/resolver_factory.h"
+
+grpc_resolver_factory *grpc_ipv4_resolver_factory_create(void);
+
+grpc_resolver_factory *grpc_ipv6_resolver_factory_create(void);
+
+#ifdef GPR_POSIX_SOCKET
+/** Create a unix resolver factory */
+grpc_resolver_factory *grpc_unix_resolver_factory_create(void);
+#endif
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_SOCKADDR_RESOLVER_H */
diff --git a/src/core/lib/client_config/resolvers/zookeeper_resolver.c b/src/core/lib/client_config/resolvers/zookeeper_resolver.c
new file mode 100644
index 0000000000..404dfcd423
--- /dev/null
+++ b/src/core/lib/client_config/resolvers/zookeeper_resolver.c
@@ -0,0 +1,514 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/resolvers/zookeeper_resolver.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
+
+#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/lib/iomgr/resolve_address.h"
+#include "src/core/lib/json/json.h"
+#include "src/core/lib/support/string.h"
+#include "src/core/lib/surface/api_trace.h"
+
+/** Zookeeper session expiration time in milliseconds */
+#define GRPC_ZOOKEEPER_SESSION_TIMEOUT 15000
+
+typedef struct {
+  /** base class: must be first */
+  grpc_resolver base;
+  /** refcount */
+  gpr_refcount refs;
+  /** name to resolve */
+  char *name;
+  /** subchannel factory */
+  grpc_subchannel_factory *subchannel_factory;
+  /** load balancing policy name */
+  char *lb_policy_name;
+
+  /** mutex guarding the rest of the state */
+  gpr_mu mu;
+  /** are we currently resolving? */
+  int resolving;
+  /** which version of resolved_config have we published? */
+  int published_version;
+  /** which version of resolved_config is current? */
+  int resolved_version;
+  /** pending next completion, or NULL */
+  grpc_closure *next_completion;
+  /** target config address for next completion */
+  grpc_client_config **target_config;
+  /** current (fully resolved) config */
+  grpc_client_config *resolved_config;
+
+  /** zookeeper handle */
+  zhandle_t *zookeeper_handle;
+  /** zookeeper resolved addresses */
+  grpc_resolved_addresses *resolved_addrs;
+  /** total number of addresses to be resolved */
+  int resolved_total;
+  /** number of addresses resolved */
+  int resolved_num;
+} zookeeper_resolver;
+
+static void zookeeper_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+
+static void zookeeper_start_resolving_locked(zookeeper_resolver *r);
+static void zookeeper_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                               zookeeper_resolver *r);
+
+static void zookeeper_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+static void zookeeper_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                        grpc_resolver *r);
+static void zookeeper_next(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
+                           grpc_client_config **target_config,
+                           grpc_closure *on_complete);
+
+static const grpc_resolver_vtable zookeeper_resolver_vtable = {
+    zookeeper_destroy, zookeeper_shutdown, zookeeper_channel_saw_error,
+    zookeeper_next};
+
+static void zookeeper_shutdown(grpc_exec_ctx *exec_ctx,
+                               grpc_resolver *resolver) {
+  zookeeper_resolver *r = (zookeeper_resolver *)resolver;
+  grpc_closure *call = NULL;
+  gpr_mu_lock(&r->mu);
+  if (r->next_completion != NULL) {
+    *r->target_config = NULL;
+    call = r->next_completion;
+    r->next_completion = NULL;
+  }
+  zookeeper_close(r->zookeeper_handle);
+  gpr_mu_unlock(&r->mu);
+  if (call != NULL) {
+    call->cb(exec_ctx, call->cb_arg, 1);
+  }
+}
+
+static void zookeeper_channel_saw_error(grpc_exec_ctx *exec_ctx,
+                                        grpc_resolver *resolver) {
+  zookeeper_resolver *r = (zookeeper_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  if (r->resolving == 0) {
+    zookeeper_start_resolving_locked(r);
+  }
+  gpr_mu_unlock(&r->mu);
+}
+
+static void zookeeper_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
+                           grpc_client_config **target_config,
+                           grpc_closure *on_complete) {
+  zookeeper_resolver *r = (zookeeper_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  GPR_ASSERT(r->next_completion == NULL);
+  r->next_completion = on_complete;
+  r->target_config = target_config;
+  if (r->resolved_version == 0 && r->resolving == 0) {
+    zookeeper_start_resolving_locked(r);
+  } else {
+    zookeeper_maybe_finish_next_locked(exec_ctx, r);
+  }
+  gpr_mu_unlock(&r->mu);
+}
+
+/** Zookeeper global watcher for connection management
+    TODO: better connection management besides logs */
+static void zookeeper_global_watcher(zhandle_t *zookeeper_handle, int type,
+                                     int state, const char *path,
+                                     void *watcher_ctx) {
+  if (type == ZOO_SESSION_EVENT) {
+    if (state == ZOO_EXPIRED_SESSION_STATE) {
+      gpr_log(GPR_ERROR, "Zookeeper session expired");
+    } else if (state == ZOO_AUTH_FAILED_STATE) {
+      gpr_log(GPR_ERROR, "Zookeeper authentication failed");
+    }
+  }
+}
+
+/** Zookeeper watcher triggered by changes to watched nodes
+    Once triggered, it tries to resolve again to get updated addresses */
+static void zookeeper_watcher(zhandle_t *zookeeper_handle, int type, int state,
+                              const char *path, void *watcher_ctx) {
+  if (watcher_ctx != NULL) {
+    zookeeper_resolver *r = (zookeeper_resolver *)watcher_ctx;
+    if (state == ZOO_CONNECTED_STATE) {
+      gpr_mu_lock(&r->mu);
+      if (r->resolving == 0) {
+        zookeeper_start_resolving_locked(r);
+      }
+      gpr_mu_unlock(&r->mu);
+    }
+  }
+}
+
+/** Callback function after getting all resolved addresses
+    Creates a subchannel for each address */
+static void zookeeper_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
+                                  grpc_resolved_addresses *addresses) {
+  zookeeper_resolver *r = arg;
+  grpc_client_config *config = NULL;
+  grpc_lb_policy *lb_policy;
+
+  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 =
+        grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
+
+    if (lb_policy != NULL) {
+      grpc_client_config_set_lb_policy(config, lb_policy);
+      GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "construction");
+    }
+    grpc_resolved_addresses_destroy(addresses);
+  }
+  gpr_mu_lock(&r->mu);
+  GPR_ASSERT(r->resolving == 1);
+  r->resolving = 0;
+  if (r->resolved_config != NULL) {
+    grpc_client_config_unref(exec_ctx, r->resolved_config);
+  }
+  r->resolved_config = config;
+  r->resolved_version++;
+  zookeeper_maybe_finish_next_locked(exec_ctx, r);
+  gpr_mu_unlock(&r->mu);
+
+  GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "zookeeper-resolving");
+}
+
+/** Callback function for each DNS resolved address */
+static void zookeeper_dns_resolved(grpc_exec_ctx *exec_ctx, void *arg,
+                                   grpc_resolved_addresses *addresses) {
+  size_t i;
+  zookeeper_resolver *r = arg;
+  int resolve_done = 0;
+
+  gpr_mu_lock(&r->mu);
+  r->resolved_num++;
+  r->resolved_addrs->addrs =
+      gpr_realloc(r->resolved_addrs->addrs,
+                  sizeof(grpc_resolved_address) *
+                      (r->resolved_addrs->naddrs + addresses->naddrs));
+  for (i = 0; i < addresses->naddrs; i++) {
+    memcpy(r->resolved_addrs->addrs[i + r->resolved_addrs->naddrs].addr,
+           addresses->addrs[i].addr, addresses->addrs[i].len);
+    r->resolved_addrs->addrs[i + r->resolved_addrs->naddrs].len =
+        addresses->addrs[i].len;
+  }
+
+  r->resolved_addrs->naddrs += addresses->naddrs;
+  grpc_resolved_addresses_destroy(addresses);
+
+  /** Wait for all addresses to be resolved */
+  resolve_done = (r->resolved_num == r->resolved_total);
+  gpr_mu_unlock(&r->mu);
+  if (resolve_done) {
+    zookeeper_on_resolved(exec_ctx, r, r->resolved_addrs);
+  }
+}
+
+/** Parses JSON format address of a zookeeper node */
+static char *zookeeper_parse_address(const char *value, size_t value_len) {
+  grpc_json *json;
+  grpc_json *cur;
+  const char *host;
+  const char *port;
+  char *buffer;
+  char *address = NULL;
+
+  buffer = gpr_malloc(value_len);
+  memcpy(buffer, value, value_len);
+  json = grpc_json_parse_string_with_len(buffer, value_len);
+  if (json != NULL) {
+    host = NULL;
+    port = NULL;
+    for (cur = json->child; cur != NULL; cur = cur->next) {
+      if (!strcmp(cur->key, "host")) {
+        host = cur->value;
+        if (port != NULL) {
+          break;
+        }
+      } else if (!strcmp(cur->key, "port")) {
+        port = cur->value;
+        if (host != NULL) {
+          break;
+        }
+      }
+    }
+    if (host != NULL && port != NULL) {
+      gpr_asprintf(&address, "%s:%s", host, port);
+    }
+    grpc_json_destroy(json);
+  }
+  gpr_free(buffer);
+
+  return address;
+}
+
+static void zookeeper_get_children_node_completion(int rc, const char *value,
+                                                   int value_len,
+                                                   const struct Stat *stat,
+                                                   const void *arg) {
+  char *address = NULL;
+  zookeeper_resolver *r = (zookeeper_resolver *)arg;
+  int resolve_done = 0;
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+
+  if (rc != 0) {
+    gpr_log(GPR_ERROR, "Error in getting a child node of %s", r->name);
+    grpc_exec_ctx_finish(&exec_ctx);
+    return;
+  }
+
+  address = zookeeper_parse_address(value, (size_t)value_len);
+  if (address != NULL) {
+    /** Further resolves address by DNS */
+    grpc_resolve_address(address, NULL, zookeeper_dns_resolved, r);
+    gpr_free(address);
+  } else {
+    gpr_log(GPR_ERROR, "Error in resolving a child node of %s", r->name);
+    gpr_mu_lock(&r->mu);
+    r->resolved_total--;
+    resolve_done = (r->resolved_num == r->resolved_total);
+    gpr_mu_unlock(&r->mu);
+    if (resolve_done) {
+      zookeeper_on_resolved(&exec_ctx, r, r->resolved_addrs);
+    }
+  }
+
+  grpc_exec_ctx_finish(&exec_ctx);
+}
+
+static void zookeeper_get_children_completion(
+    int rc, const struct String_vector *children, const void *arg) {
+  char *path;
+  int status;
+  int i;
+  zookeeper_resolver *r = (zookeeper_resolver *)arg;
+
+  if (rc != 0) {
+    gpr_log(GPR_ERROR, "Error in getting zookeeper children of %s", r->name);
+    return;
+  }
+
+  if (children->count == 0) {
+    gpr_log(GPR_ERROR, "Error in resolving zookeeper address %s", r->name);
+    return;
+  }
+
+  r->resolved_addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
+  r->resolved_addrs->addrs = NULL;
+  r->resolved_addrs->naddrs = 0;
+  r->resolved_total = children->count;
+
+  /** TODO: Replace expensive heap allocation with stack
+      if we can get maximum length of zookeeper path */
+  for (i = 0; i < children->count; i++) {
+    gpr_asprintf(&path, "%s/%s", r->name, children->data[i]);
+    status = zoo_awget(r->zookeeper_handle, path, zookeeper_watcher, r,
+                       zookeeper_get_children_node_completion, r);
+    gpr_free(path);
+    if (status != 0) {
+      gpr_log(GPR_ERROR, "Error in getting zookeeper node %s", path);
+    }
+  }
+}
+
+static void zookeeper_get_node_completion(int rc, const char *value,
+                                          int value_len,
+                                          const struct Stat *stat,
+                                          const void *arg) {
+  int status;
+  char *address = NULL;
+  zookeeper_resolver *r = (zookeeper_resolver *)arg;
+  r->resolved_addrs = NULL;
+  r->resolved_total = 0;
+  r->resolved_num = 0;
+
+  if (rc != 0) {
+    gpr_log(GPR_ERROR, "Error in getting zookeeper node %s", r->name);
+    return;
+  }
+
+  /** If zookeeper node of path r->name does not have address
+      (i.e. service node), get its children */
+  address = zookeeper_parse_address(value, (size_t)value_len);
+  if (address != NULL) {
+    r->resolved_addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
+    r->resolved_addrs->addrs = NULL;
+    r->resolved_addrs->naddrs = 0;
+    r->resolved_total = 1;
+    /** Further resolves address by DNS */
+    grpc_resolve_address(address, NULL, zookeeper_dns_resolved, r);
+    gpr_free(address);
+    return;
+  }
+
+  status = zoo_awget_children(r->zookeeper_handle, r->name, zookeeper_watcher,
+                              r, zookeeper_get_children_completion, r);
+  if (status != 0) {
+    gpr_log(GPR_ERROR, "Error in getting zookeeper children of %s", r->name);
+  }
+}
+
+static void zookeeper_resolve_address(zookeeper_resolver *r) {
+  int status;
+  status = zoo_awget(r->zookeeper_handle, r->name, zookeeper_watcher, r,
+                     zookeeper_get_node_completion, r);
+  if (status != 0) {
+    gpr_log(GPR_ERROR, "Error in getting zookeeper node %s", r->name);
+  }
+}
+
+static void zookeeper_start_resolving_locked(zookeeper_resolver *r) {
+  GRPC_RESOLVER_REF(&r->base, "zookeeper-resolving");
+  GPR_ASSERT(r->resolving == 0);
+  r->resolving = 1;
+  zookeeper_resolve_address(r);
+}
+
+static void zookeeper_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                               zookeeper_resolver *r) {
+  if (r->next_completion != NULL &&
+      r->resolved_version != r->published_version) {
+    *r->target_config = r->resolved_config;
+    if (r->resolved_config != NULL) {
+      grpc_client_config_ref(r->resolved_config);
+    }
+    grpc_exec_ctx_enqueue(exec_ctx, r->next_completion, true, NULL);
+    r->next_completion = NULL;
+    r->published_version = r->resolved_version;
+  }
+}
+
+static void zookeeper_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
+  zookeeper_resolver *r = (zookeeper_resolver *)gr;
+  gpr_mu_destroy(&r->mu);
+  if (r->resolved_config != NULL) {
+    grpc_client_config_unref(exec_ctx, r->resolved_config);
+  }
+  grpc_subchannel_factory_unref(exec_ctx, r->subchannel_factory);
+  gpr_free(r->name);
+  gpr_free(r->lb_policy_name);
+  gpr_free(r);
+}
+
+static grpc_resolver *zookeeper_create(grpc_resolver_args *args,
+                                       const char *lb_policy_name) {
+  zookeeper_resolver *r;
+  size_t length;
+  char *path = args->uri->path;
+
+  if (0 == strcmp(args->uri->authority, "")) {
+    gpr_log(GPR_ERROR, "No authority specified in zookeeper uri");
+    return NULL;
+  }
+
+  /** Removes the trailing slash if exists */
+  length = strlen(path);
+  if (length > 1 && path[length - 1] == '/') {
+    path[length - 1] = 0;
+  }
+
+  r = gpr_malloc(sizeof(zookeeper_resolver));
+  memset(r, 0, sizeof(*r));
+  gpr_ref_init(&r->refs, 1);
+  gpr_mu_init(&r->mu);
+  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->lb_policy_name = gpr_strdup(lb_policy_name);
+
+  /** Initializes zookeeper client */
+  zoo_set_debug_level(ZOO_LOG_LEVEL_WARN);
+  r->zookeeper_handle =
+      zookeeper_init(args->uri->authority, zookeeper_global_watcher,
+                     GRPC_ZOOKEEPER_SESSION_TIMEOUT, 0, 0, 0);
+  if (r->zookeeper_handle == NULL) {
+    gpr_log(GPR_ERROR, "Unable to connect to zookeeper server");
+    return NULL;
+  }
+
+  return &r->base;
+}
+
+static void zookeeper_plugin_init() {
+  grpc_register_resolver_type(grpc_zookeeper_resolver_factory_create());
+}
+
+void grpc_zookeeper_register() {
+  GRPC_API_TRACE("grpc_zookeeper_register(void)", 0, ());
+  grpc_register_plugin(zookeeper_plugin_init, NULL);
+}
+
+/*
+ * FACTORY
+ */
+
+static void zookeeper_factory_ref(grpc_resolver_factory *factory) {}
+
+static void zookeeper_factory_unref(grpc_resolver_factory *factory) {}
+
+static char *zookeeper_factory_get_default_hostname(
+    grpc_resolver_factory *factory, grpc_uri *uri) {
+  return NULL;
+}
+
+static grpc_resolver *zookeeper_factory_create_resolver(
+    grpc_resolver_factory *factory, grpc_resolver_args *args) {
+  return zookeeper_create(args, "pick_first");
+}
+
+static const grpc_resolver_factory_vtable zookeeper_factory_vtable = {
+    zookeeper_factory_ref, zookeeper_factory_unref,
+    zookeeper_factory_create_resolver, zookeeper_factory_get_default_hostname,
+    "zookeeper"};
+
+static grpc_resolver_factory zookeeper_resolver_factory = {
+    &zookeeper_factory_vtable};
+
+grpc_resolver_factory *grpc_zookeeper_resolver_factory_create() {
+  return &zookeeper_resolver_factory;
+}
diff --git a/src/core/lib/client_config/resolvers/zookeeper_resolver.h b/src/core/lib/client_config/resolvers/zookeeper_resolver.h
new file mode 100644
index 0000000000..7ee7604360
--- /dev/null
+++ b/src/core/lib/client_config/resolvers/zookeeper_resolver.h
@@ -0,0 +1,42 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_ZOOKEEPER_RESOLVER_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_ZOOKEEPER_RESOLVER_H
+
+#include "src/core/lib/client_config/resolver_factory.h"
+
+/** Create a zookeeper resolver factory */
+grpc_resolver_factory *grpc_zookeeper_resolver_factory_create(void);
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_RESOLVERS_ZOOKEEPER_RESOLVER_H */
diff --git a/src/core/lib/client_config/subchannel.c b/src/core/lib/client_config/subchannel.c
new file mode 100644
index 0000000000..41242f0dd7
--- /dev/null
+++ b/src/core/lib/client_config/subchannel.c
@@ -0,0 +1,678 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/subchannel.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/avl.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"
+#include "src/core/lib/surface/channel.h"
+#include "src/core/lib/surface/channel_init.h"
+#include "src/core/lib/transport/connectivity_state.h"
+
+#define INTERNAL_REF_BITS 16
+#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_RECONNECT_BACKOFF_MULTIPLIER 1.6
+#define GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS 120
+#define GRPC_SUBCHANNEL_RECONNECT_JITTER 0.2
+
+#define GET_CONNECTED_SUBCHANNEL(subchannel, barrier)      \
+  ((grpc_connected_subchannel *)(gpr_atm_##barrier##_load( \
+      &(subchannel)->connected_subchannel)))
+
+typedef struct {
+  grpc_closure closure;
+  grpc_subchannel *subchannel;
+  grpc_connectivity_state connectivity_state;
+} state_watcher;
+
+typedef struct external_state_watcher {
+  grpc_subchannel *subchannel;
+  grpc_pollset_set *pollset_set;
+  grpc_closure *notify;
+  grpc_closure closure;
+  struct external_state_watcher *next;
+  struct external_state_watcher *prev;
+} external_state_watcher;
+
+struct grpc_subchannel {
+  grpc_connector *connector;
+
+  /** refcount
+      - lower INTERNAL_REF_BITS bits are for internal references:
+        these do not keep the subchannel open.
+      - upper remaining bits are for public references: these do
+        keep the subchannel open */
+  gpr_atm ref_pair;
+
+  /** non-transport related channel filters */
+  const grpc_channel_filter **filters;
+  size_t num_filters;
+  /** channel arguments */
+  grpc_channel_args *args;
+  /** address to connect to */
+  struct sockaddr *addr;
+  size_t addr_len;
+
+  grpc_subchannel_key *key;
+
+  /** initial string to send to peer */
+  gpr_slice initial_connect_string;
+
+  /** set during connection */
+  grpc_connect_out_args connecting_result;
+
+  /** callback for connection finishing */
+  grpc_closure connected;
+
+  /** pollset_set tracking who's interested in a connection
+      being setup */
+  grpc_pollset_set *pollset_set;
+
+  /** active connection, or null; of type grpc_connected_subchannel */
+  gpr_atm connected_subchannel;
+
+  /** mutex protecting remaining elements */
+  gpr_mu mu;
+
+  /** have we seen a disconnection? */
+  int disconnected;
+  /** are we connecting */
+  int connecting;
+  /** connectivity state tracking */
+  grpc_connectivity_state_tracker state_tracker;
+
+  external_state_watcher root_external_state_watcher;
+
+  /** next connect attempt time */
+  gpr_timespec next_attempt;
+  /** backoff state */
+  gpr_backoff backoff_state;
+  /** do we have an active alarm? */
+  int have_alarm;
+  /** our alarm */
+  grpc_timer alarm;
+  /** current random value */
+  uint32_t random;
+};
+
+struct grpc_subchannel_call {
+  grpc_connected_subchannel *connection;
+};
+
+#define SUBCHANNEL_CALL_TO_CALL_STACK(call) ((grpc_call_stack *)((call) + 1))
+#define CHANNEL_STACK_FROM_CONNECTION(con) ((grpc_channel_stack *)(con))
+#define CALLSTACK_TO_SUBCHANNEL_CALL(callstack) \
+  (((grpc_subchannel_call *)(callstack)) - 1)
+
+static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *subchannel,
+                                 bool iomgr_success);
+
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+#define REF_REASON reason
+#define REF_LOG(name, p)                                                  \
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "%s: %p   ref %d -> %d %s", \
+          (name), (p), (p)->refs.count, (p)->refs.count + 1, reason)
+#define UNREF_LOG(name, p)                                                \
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "%s: %p unref %d -> %d %s", \
+          (name), (p), (p)->refs.count, (p)->refs.count - 1, reason)
+#define REF_MUTATE_EXTRA_ARGS \
+  GRPC_SUBCHANNEL_REF_EXTRA_ARGS, const char *purpose
+#define REF_MUTATE_PURPOSE(x) , file, line, reason, x
+#else
+#define REF_REASON ""
+#define REF_LOG(name, p) \
+  do {                   \
+  } while (0)
+#define UNREF_LOG(name, p) \
+  do {                     \
+  } while (0)
+#define REF_MUTATE_EXTRA_ARGS
+#define REF_MUTATE_PURPOSE(x)
+#endif
+
+/*
+ * connection implementation
+ */
+
+static void connection_destroy(grpc_exec_ctx *exec_ctx, void *arg,
+                               bool success) {
+  grpc_connected_subchannel *c = arg;
+  grpc_channel_stack_destroy(exec_ctx, CHANNEL_STACK_FROM_CONNECTION(c));
+  gpr_free(c);
+}
+
+void grpc_connected_subchannel_ref(
+    grpc_connected_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  GRPC_CHANNEL_STACK_REF(CHANNEL_STACK_FROM_CONNECTION(c), REF_REASON);
+}
+
+void grpc_connected_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                                     grpc_connected_subchannel *c
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, CHANNEL_STACK_FROM_CONNECTION(c),
+                           REF_REASON);
+}
+
+/*
+ * grpc_subchannel implementation
+ */
+
+static void subchannel_destroy(grpc_exec_ctx *exec_ctx, void *arg,
+                               bool success) {
+  grpc_subchannel *c = arg;
+  gpr_free((void *)c->filters);
+  grpc_channel_args_destroy(c->args);
+  gpr_free(c->addr);
+  gpr_slice_unref(c->initial_connect_string);
+  grpc_connectivity_state_destroy(exec_ctx, &c->state_tracker);
+  grpc_connector_unref(exec_ctx, c->connector);
+  grpc_pollset_set_destroy(c->pollset_set);
+  grpc_subchannel_key_destroy(exec_ctx, c->key);
+  gpr_free(c);
+}
+
+static gpr_atm ref_mutate(grpc_subchannel *c, gpr_atm delta,
+                          int barrier REF_MUTATE_EXTRA_ARGS) {
+  gpr_atm old_val = barrier ? gpr_atm_full_fetch_add(&c->ref_pair, delta)
+                            : gpr_atm_no_barrier_fetch_add(&c->ref_pair, delta);
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+          "SUBCHANNEL: %p % 12s 0x%08x -> 0x%08x [%s]", c, purpose, old_val,
+          old_val + delta, reason);
+#endif
+  return old_val;
+}
+
+grpc_subchannel *grpc_subchannel_ref(
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, (1 << INTERNAL_REF_BITS),
+                        0 REF_MUTATE_PURPOSE("STRONG_REF"));
+  GPR_ASSERT((old_refs & STRONG_REF_MASK) != 0);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_weak_ref(
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, 1, 0 REF_MUTATE_PURPOSE("WEAK_REF"));
+  GPR_ASSERT(old_refs != 0);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_ref_from_weak_ref(
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  if (!c) return NULL;
+  for (;;) {
+    gpr_atm old_refs = gpr_atm_acq_load(&c->ref_pair);
+    if (old_refs >= (1 << INTERNAL_REF_BITS)) {
+      gpr_atm new_refs = old_refs + (1 << INTERNAL_REF_BITS);
+      if (gpr_atm_rel_cas(&c->ref_pair, old_refs, new_refs)) {
+        return c;
+      }
+    } else {
+      return NULL;
+    }
+  }
+}
+
+static void disconnect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
+  grpc_connected_subchannel *con;
+  grpc_subchannel_index_unregister(exec_ctx, c->key, c);
+  gpr_mu_lock(&c->mu);
+  GPR_ASSERT(!c->disconnected);
+  c->disconnected = 1;
+  grpc_connector_shutdown(exec_ctx, c->connector);
+  con = GET_CONNECTED_SUBCHANNEL(c, no_barrier);
+  if (con != NULL) {
+    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, con, "connection");
+    gpr_atm_no_barrier_store(&c->connected_subchannel, 0xdeadbeef);
+  }
+  gpr_mu_unlock(&c->mu);
+}
+
+void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                           grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, (gpr_atm)1 - (gpr_atm)(1 << INTERNAL_REF_BITS),
+                        1 REF_MUTATE_PURPOSE("STRONG_UNREF"));
+  if ((old_refs & STRONG_REF_MASK) == (1 << INTERNAL_REF_BITS)) {
+    disconnect(exec_ctx, c);
+  }
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "strong-unref");
+}
+
+void grpc_subchannel_weak_unref(grpc_exec_ctx *exec_ctx,
+                                grpc_subchannel *c
+                                    GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, -(gpr_atm)1, 1 REF_MUTATE_PURPOSE("WEAK_UNREF"));
+  if (old_refs == 1) {
+    grpc_exec_ctx_enqueue(exec_ctx, grpc_closure_create(subchannel_destroy, c),
+                          true, NULL);
+  }
+}
+
+static uint32_t random_seed() {
+  return (uint32_t)(gpr_time_to_millis(gpr_now(GPR_CLOCK_MONOTONIC)));
+}
+
+grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
+                                        grpc_connector *connector,
+                                        grpc_subchannel_args *args) {
+  grpc_subchannel_key *key = grpc_subchannel_key_create(connector, args);
+  grpc_subchannel *c = grpc_subchannel_index_find(exec_ctx, key);
+  if (c) {
+    grpc_subchannel_key_destroy(exec_ctx, key);
+    return c;
+  }
+
+  c = gpr_malloc(sizeof(*c));
+  memset(c, 0, sizeof(*c));
+  c->key = key;
+  gpr_atm_no_barrier_store(&c->ref_pair, 1 << INTERNAL_REF_BITS);
+  c->connector = connector;
+  grpc_connector_ref(c->connector);
+  c->num_filters = args->filter_count;
+  if (c->num_filters > 0) {
+    c->filters = gpr_malloc(sizeof(grpc_channel_filter *) * c->num_filters);
+    memcpy((void *)c->filters, args->filters,
+           sizeof(grpc_channel_filter *) * c->num_filters);
+  } else {
+    c->filters = NULL;
+  }
+  c->addr = gpr_malloc(args->addr_len);
+  memcpy(c->addr, args->addr, args->addr_len);
+  c->pollset_set = grpc_pollset_set_create();
+  c->addr_len = args->addr_len;
+  grpc_set_initial_connect_string(&c->addr, &c->addr_len,
+                                  &c->initial_connect_string);
+  c->args = grpc_channel_args_copy(args->args);
+  c->random = random_seed();
+  c->root_external_state_watcher.next = c->root_external_state_watcher.prev =
+      &c->root_external_state_watcher;
+  grpc_closure_init(&c->connected, subchannel_connected, c);
+  grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
+                               "subchannel");
+  gpr_backoff_init(&c->backoff_state,
+                   GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
+                   GRPC_SUBCHANNEL_RECONNECT_JITTER,
+                   GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000,
+                   GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  if (c->args) {
+    for (size_t i = 0; i < c->args->num_args; i++) {
+      if (0 == strcmp(c->args->args[i].key,
+                      "grpc.testing.fixed_reconnect_backoff")) {
+        GPR_ASSERT(c->args->args[i].type == GRPC_ARG_INTEGER);
+        gpr_backoff_init(&c->backoff_state, 1.0, 0.0,
+                         c->args->args[i].value.integer,
+                         c->args->args[i].value.integer);
+      }
+    }
+  }
+  gpr_mu_init(&c->mu);
+
+  return grpc_subchannel_index_register(exec_ctx, key, c);
+}
+
+static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
+  grpc_connect_in_args args;
+
+  args.interested_parties = c->pollset_set;
+  args.addr = c->addr;
+  args.addr_len = c->addr_len;
+  args.deadline = c->next_attempt;
+  args.channel_args = c->args;
+  args.initial_connect_string = c->initial_connect_string;
+
+  grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
+                              GRPC_CHANNEL_CONNECTING, "state_change");
+  grpc_connector_connect(exec_ctx, c->connector, &args, &c->connecting_result,
+                         &c->connected);
+}
+
+static void start_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
+  c->next_attempt =
+      gpr_backoff_begin(&c->backoff_state, gpr_now(GPR_CLOCK_MONOTONIC));
+  continue_connect(exec_ctx, c);
+}
+
+grpc_connectivity_state grpc_subchannel_check_connectivity(grpc_subchannel *c) {
+  grpc_connectivity_state state;
+  gpr_mu_lock(&c->mu);
+  state = grpc_connectivity_state_check(&c->state_tracker);
+  gpr_mu_unlock(&c->mu);
+  return state;
+}
+
+static void on_external_state_watcher_done(grpc_exec_ctx *exec_ctx, void *arg,
+                                           bool success) {
+  external_state_watcher *w = arg;
+  grpc_closure *follow_up = w->notify;
+  if (w->pollset_set != NULL) {
+    grpc_pollset_set_del_pollset_set(exec_ctx, w->subchannel->pollset_set,
+                                     w->pollset_set);
+  }
+  gpr_mu_lock(&w->subchannel->mu);
+  w->next->prev = w->prev;
+  w->prev->next = w->next;
+  gpr_mu_unlock(&w->subchannel->mu);
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, w->subchannel, "external_state_watcher");
+  gpr_free(w);
+  follow_up->cb(exec_ctx, follow_up->cb_arg, success);
+}
+
+void grpc_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel *c,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *notify) {
+  external_state_watcher *w;
+
+  if (state == NULL) {
+    gpr_mu_lock(&c->mu);
+    for (w = c->root_external_state_watcher.next;
+         w != &c->root_external_state_watcher; w = w->next) {
+      if (w->notify == notify) {
+        grpc_connectivity_state_notify_on_state_change(
+            exec_ctx, &c->state_tracker, NULL, &w->closure);
+      }
+    }
+    gpr_mu_unlock(&c->mu);
+  } else {
+    w = gpr_malloc(sizeof(*w));
+    w->subchannel = c;
+    w->pollset_set = interested_parties;
+    w->notify = notify;
+    grpc_closure_init(&w->closure, on_external_state_watcher_done, w);
+    if (interested_parties != NULL) {
+      grpc_pollset_set_add_pollset_set(exec_ctx, c->pollset_set,
+                                       interested_parties);
+    }
+    GRPC_SUBCHANNEL_WEAK_REF(c, "external_state_watcher");
+    gpr_mu_lock(&c->mu);
+    w->next = &c->root_external_state_watcher;
+    w->prev = w->next->prev;
+    w->next->prev = w->prev->next = w;
+    if (grpc_connectivity_state_notify_on_state_change(
+            exec_ctx, &c->state_tracker, state, &w->closure)) {
+      c->connecting = 1;
+      /* released by connection */
+      GRPC_SUBCHANNEL_WEAK_REF(c, "connecting");
+      start_connect(exec_ctx, c);
+    }
+    gpr_mu_unlock(&c->mu);
+  }
+}
+
+void grpc_connected_subchannel_process_transport_op(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
+    grpc_transport_op *op) {
+  grpc_channel_stack *channel_stack = CHANNEL_STACK_FROM_CONNECTION(con);
+  grpc_channel_element *top_elem = grpc_channel_stack_element(channel_stack, 0);
+  top_elem->filter->start_transport_op(exec_ctx, top_elem, op);
+}
+
+static void subchannel_on_child_state_changed(grpc_exec_ctx *exec_ctx, void *p,
+                                              bool iomgr_success) {
+  state_watcher *sw = p;
+  grpc_subchannel *c = sw->subchannel;
+  gpr_mu *mu = &c->mu;
+
+  gpr_mu_lock(mu);
+
+  /* if we failed just leave this closure */
+  if (iomgr_success) {
+    if (sw->connectivity_state == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+      /* any errors on a subchannel ==> we're done, create a new one */
+      sw->connectivity_state = GRPC_CHANNEL_FATAL_FAILURE;
+    }
+    grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
+                                sw->connectivity_state, "reflect_child");
+    if (sw->connectivity_state != GRPC_CHANNEL_FATAL_FAILURE) {
+      grpc_connected_subchannel_notify_on_state_change(
+          exec_ctx, GET_CONNECTED_SUBCHANNEL(c, no_barrier), NULL,
+          &sw->connectivity_state, &sw->closure);
+      GRPC_SUBCHANNEL_WEAK_REF(c, "state_watcher");
+      sw = NULL;
+    }
+  }
+
+  gpr_mu_unlock(mu);
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "state_watcher");
+  gpr_free(sw);
+}
+
+static void connected_subchannel_state_op(grpc_exec_ctx *exec_ctx,
+                                          grpc_connected_subchannel *con,
+                                          grpc_pollset_set *interested_parties,
+                                          grpc_connectivity_state *state,
+                                          grpc_closure *closure) {
+  grpc_transport_op op;
+  grpc_channel_element *elem;
+  memset(&op, 0, sizeof(op));
+  op.connectivity_state = state;
+  op.on_connectivity_state_change = closure;
+  op.bind_pollset_set = interested_parties;
+  elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(con), 0);
+  elem->filter->start_transport_op(exec_ctx, elem, &op);
+}
+
+void grpc_connected_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *closure) {
+  connected_subchannel_state_op(exec_ctx, con, interested_parties, state,
+                                closure);
+}
+
+void grpc_connected_subchannel_ping(grpc_exec_ctx *exec_ctx,
+                                    grpc_connected_subchannel *con,
+                                    grpc_closure *closure) {
+  grpc_transport_op op;
+  grpc_channel_element *elem;
+  memset(&op, 0, sizeof(op));
+  op.send_ping = closure;
+  elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(con), 0);
+  elem->filter->start_transport_op(exec_ctx, elem, &op);
+}
+
+static void publish_transport_locked(grpc_exec_ctx *exec_ctx,
+                                     grpc_subchannel *c) {
+  grpc_connected_subchannel *con;
+  grpc_channel_stack *stk;
+  state_watcher *sw_subchannel;
+
+  /* construct channel stack */
+  con = grpc_channel_init_create_stack(
+      exec_ctx, GRPC_CLIENT_SUBCHANNEL, 0, c->connecting_result.channel_args, 1,
+      connection_destroy, NULL, c->connecting_result.transport);
+  stk = CHANNEL_STACK_FROM_CONNECTION(con);
+  memset(&c->connecting_result, 0, sizeof(c->connecting_result));
+
+  /* initialize state watcher */
+  sw_subchannel = gpr_malloc(sizeof(*sw_subchannel));
+  sw_subchannel->subchannel = c;
+  sw_subchannel->connectivity_state = GRPC_CHANNEL_READY;
+  grpc_closure_init(&sw_subchannel->closure, subchannel_on_child_state_changed,
+                    sw_subchannel);
+
+  if (c->disconnected) {
+    gpr_free(sw_subchannel);
+    grpc_channel_stack_destroy(exec_ctx, stk);
+    gpr_free(con);
+    GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
+    return;
+  }
+
+  /* publish */
+  /* TODO(ctiller): this full barrier seems to clear up a TSAN failure.
+                    I'd have expected the rel_cas below to be enough, but
+                    seemingly it's not.
+                    Re-evaluate if we really need this. */
+  gpr_atm_full_barrier();
+  GPR_ASSERT(gpr_atm_rel_cas(&c->connected_subchannel, 0, (gpr_atm)con));
+  c->connecting = 0;
+
+  /* setup subchannel watching connected subchannel for changes; subchannel ref
+     for connecting is donated
+     to the state watcher */
+  GRPC_SUBCHANNEL_WEAK_REF(c, "state_watcher");
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
+  grpc_connected_subchannel_notify_on_state_change(
+      exec_ctx, con, c->pollset_set, &sw_subchannel->connectivity_state,
+      &sw_subchannel->closure);
+
+  /* signal completion */
+  grpc_connectivity_state_set(exec_ctx, &c->state_tracker, GRPC_CHANNEL_READY,
+                              "connected");
+}
+
+static void on_alarm(grpc_exec_ctx *exec_ctx, void *arg, bool iomgr_success) {
+  grpc_subchannel *c = arg;
+  gpr_mu_lock(&c->mu);
+  c->have_alarm = 0;
+  if (c->disconnected) {
+    iomgr_success = 0;
+  }
+  if (iomgr_success) {
+    c->next_attempt =
+        gpr_backoff_step(&c->backoff_state, gpr_now(GPR_CLOCK_MONOTONIC));
+    continue_connect(exec_ctx, c);
+    gpr_mu_unlock(&c->mu);
+  } else {
+    gpr_mu_unlock(&c->mu);
+    GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
+  }
+}
+
+static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *arg,
+                                 bool iomgr_success) {
+  grpc_subchannel *c = arg;
+
+  GRPC_SUBCHANNEL_WEAK_REF(c, "connected");
+  gpr_mu_lock(&c->mu);
+  if (c->connecting_result.transport != NULL) {
+    publish_transport_locked(exec_ctx, c);
+  } else if (c->disconnected) {
+    GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
+  } else {
+    gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
+    GPR_ASSERT(!c->have_alarm);
+    c->have_alarm = 1;
+    grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
+                                GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                "connect_failed");
+    grpc_timer_init(exec_ctx, &c->alarm, c->next_attempt, on_alarm, c, now);
+  }
+  gpr_mu_unlock(&c->mu);
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
+}
+
+/*
+ * grpc_subchannel_call implementation
+ */
+
+static void subchannel_call_destroy(grpc_exec_ctx *exec_ctx, void *call,
+                                    bool success) {
+  grpc_subchannel_call *c = call;
+  GPR_TIMER_BEGIN("grpc_subchannel_call_unref.destroy", 0);
+  grpc_call_stack_destroy(exec_ctx, SUBCHANNEL_CALL_TO_CALL_STACK(c));
+  GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, c->connection, "subchannel_call");
+  gpr_free(c);
+  GPR_TIMER_END("grpc_subchannel_call_unref.destroy", 0);
+}
+
+void grpc_subchannel_call_ref(
+    grpc_subchannel_call *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  GRPC_CALL_STACK_REF(SUBCHANNEL_CALL_TO_CALL_STACK(c), REF_REASON);
+}
+
+void grpc_subchannel_call_unref(grpc_exec_ctx *exec_ctx,
+                                grpc_subchannel_call *c
+                                    GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  GRPC_CALL_STACK_UNREF(exec_ctx, SUBCHANNEL_CALL_TO_CALL_STACK(c), REF_REASON);
+}
+
+char *grpc_subchannel_call_get_peer(grpc_exec_ctx *exec_ctx,
+                                    grpc_subchannel_call *call) {
+  grpc_call_stack *call_stack = SUBCHANNEL_CALL_TO_CALL_STACK(call);
+  grpc_call_element *top_elem = grpc_call_stack_element(call_stack, 0);
+  return top_elem->filter->get_peer(exec_ctx, top_elem);
+}
+
+void grpc_subchannel_call_process_op(grpc_exec_ctx *exec_ctx,
+                                     grpc_subchannel_call *call,
+                                     grpc_transport_stream_op *op) {
+  grpc_call_stack *call_stack = SUBCHANNEL_CALL_TO_CALL_STACK(call);
+  grpc_call_element *top_elem = grpc_call_stack_element(call_stack, 0);
+  top_elem->filter->start_transport_stream_op(exec_ctx, top_elem, op);
+}
+
+grpc_connected_subchannel *grpc_subchannel_get_connected_subchannel(
+    grpc_subchannel *c) {
+  return GET_CONNECTED_SUBCHANNEL(c, acq);
+}
+
+grpc_subchannel_call *grpc_connected_subchannel_create_call(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
+    grpc_pollset *pollset) {
+  grpc_channel_stack *chanstk = CHANNEL_STACK_FROM_CONNECTION(con);
+  grpc_subchannel_call *call =
+      gpr_malloc(sizeof(grpc_subchannel_call) + chanstk->call_stack_size);
+  grpc_call_stack *callstk = SUBCHANNEL_CALL_TO_CALL_STACK(call);
+  call->connection = con;
+  GRPC_CONNECTED_SUBCHANNEL_REF(con, "subchannel_call");
+  grpc_call_stack_init(exec_ctx, chanstk, 1, subchannel_call_destroy, call,
+                       NULL, NULL, callstk);
+  grpc_call_stack_set_pollset(exec_ctx, callstk, pollset);
+  return call;
+}
+
+grpc_call_stack *grpc_subchannel_call_get_call_stack(
+    grpc_subchannel_call *subchannel_call) {
+  return SUBCHANNEL_CALL_TO_CALL_STACK(subchannel_call);
+}
diff --git a/src/core/lib/client_config/subchannel.h b/src/core/lib/client_config/subchannel.h
new file mode 100644
index 0000000000..b4f545be52
--- /dev/null
+++ b/src/core/lib/client_config/subchannel.h
@@ -0,0 +1,174 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_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
+    address. Provides a target for load balancing. */
+typedef struct grpc_subchannel grpc_subchannel;
+typedef struct grpc_connected_subchannel grpc_connected_subchannel;
+typedef struct grpc_subchannel_call grpc_subchannel_call;
+typedef struct grpc_subchannel_args grpc_subchannel_args;
+
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+#define GRPC_SUBCHANNEL_REF(p, r) \
+  grpc_subchannel_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(p, r) \
+  grpc_subchannel_ref_from_weak_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_UNREF(cl, p, r) \
+  grpc_subchannel_unref((cl), (p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_WEAK_REF(p, r) \
+  grpc_subchannel_weak_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_WEAK_UNREF(cl, p, r) \
+  grpc_subchannel_weak_unref((cl), (p), __FILE__, __LINE__, (r))
+#define GRPC_CONNECTED_SUBCHANNEL_REF(p, r) \
+  grpc_connected_subchannel_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_CONNECTED_SUBCHANNEL_UNREF(cl, p, r) \
+  grpc_connected_subchannel_unref((cl), (p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_CALL_REF(p, r) \
+  grpc_subchannel_call_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_CALL_UNREF(cl, p, r) \
+  grpc_subchannel_call_unref((cl), (p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_REF_EXTRA_ARGS \
+  , const char *file, int line, const char *reason
+#else
+#define GRPC_SUBCHANNEL_REF(p, r) grpc_subchannel_ref((p))
+#define GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(p, r) \
+  grpc_subchannel_ref_from_weak_ref((p))
+#define GRPC_SUBCHANNEL_UNREF(cl, p, r) grpc_subchannel_unref((cl), (p))
+#define GRPC_SUBCHANNEL_WEAK_REF(p, r) grpc_subchannel_weak_ref((p))
+#define GRPC_SUBCHANNEL_WEAK_UNREF(cl, p, r) \
+  grpc_subchannel_weak_unref((cl), (p))
+#define GRPC_CONNECTED_SUBCHANNEL_REF(p, r) grpc_connected_subchannel_ref((p))
+#define GRPC_CONNECTED_SUBCHANNEL_UNREF(cl, p, r) \
+  grpc_connected_subchannel_unref((cl), (p))
+#define GRPC_SUBCHANNEL_CALL_REF(p, r) grpc_subchannel_call_ref((p))
+#define GRPC_SUBCHANNEL_CALL_UNREF(cl, p, r) \
+  grpc_subchannel_call_unref((cl), (p))
+#define GRPC_SUBCHANNEL_REF_EXTRA_ARGS
+#endif
+
+grpc_subchannel *grpc_subchannel_ref(
+    grpc_subchannel *channel GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+grpc_subchannel *grpc_subchannel_ref_from_weak_ref(
+    grpc_subchannel *channel GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                           grpc_subchannel *channel
+                               GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+grpc_subchannel *grpc_subchannel_weak_ref(
+    grpc_subchannel *channel GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_subchannel_weak_unref(grpc_exec_ctx *exec_ctx,
+                                grpc_subchannel *channel
+                                    GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_connected_subchannel_ref(
+    grpc_connected_subchannel *channel GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_connected_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                                     grpc_connected_subchannel *channel
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_subchannel_call_ref(
+    grpc_subchannel_call *call GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_subchannel_call_unref(grpc_exec_ctx *exec_ctx,
+                                grpc_subchannel_call *call
+                                    GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+
+/** construct a subchannel call */
+grpc_subchannel_call *grpc_connected_subchannel_create_call(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *connected_subchannel,
+    grpc_pollset *pollset);
+
+/** process a transport level op */
+void grpc_connected_subchannel_process_transport_op(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *subchannel,
+    grpc_transport_op *op);
+
+/** poll the current connectivity state of a channel */
+grpc_connectivity_state grpc_subchannel_check_connectivity(
+    grpc_subchannel *channel);
+
+/** call notify when the connectivity state of a channel changes from *state.
+    Updates *state with the new state of the channel */
+void grpc_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel *channel,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *notify);
+void grpc_connected_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *channel,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *notify);
+void grpc_connected_subchannel_ping(grpc_exec_ctx *exec_ctx,
+                                    grpc_connected_subchannel *channel,
+                                    grpc_closure *notify);
+
+/** retrieve the grpc_connected_subchannel - or NULL if called before
+    the subchannel becomes connected */
+grpc_connected_subchannel *grpc_subchannel_get_connected_subchannel(
+    grpc_subchannel *subchannel);
+
+/** continue processing a transport op */
+void grpc_subchannel_call_process_op(grpc_exec_ctx *exec_ctx,
+                                     grpc_subchannel_call *subchannel_call,
+                                     grpc_transport_stream_op *op);
+
+/** continue querying for peer */
+char *grpc_subchannel_call_get_peer(grpc_exec_ctx *exec_ctx,
+                                    grpc_subchannel_call *subchannel_call);
+
+grpc_call_stack *grpc_subchannel_call_get_call_stack(
+    grpc_subchannel_call *subchannel_call);
+
+struct grpc_subchannel_args {
+  /* When updating this struct, also update subchannel_index.c */
+
+  /** Channel filters for this channel - wrapped factories will likely
+      want to mutate this */
+  const grpc_channel_filter **filters;
+  /** The number of filters in the above array */
+  size_t filter_count;
+  /** Channel arguments to be supplied to the newly created channel */
+  const grpc_channel_args *args;
+  /** Address to connect to */
+  struct sockaddr *addr;
+  size_t addr_len;
+};
+
+/** create a subchannel given a connector */
+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 */
diff --git a/src/core/lib/client_config/subchannel_factory.c b/src/core/lib/client_config/subchannel_factory.c
new file mode 100644
index 0000000000..727a48a6c8
--- /dev/null
+++ b/src/core/lib/client_config/subchannel_factory.c
@@ -0,0 +1,49 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/subchannel_factory.h"
+
+void grpc_subchannel_factory_ref(grpc_subchannel_factory* factory) {
+  factory->vtable->ref(factory);
+}
+
+void grpc_subchannel_factory_unref(grpc_exec_ctx* exec_ctx,
+                                   grpc_subchannel_factory* factory) {
+  factory->vtable->unref(exec_ctx, factory);
+}
+
+grpc_subchannel* grpc_subchannel_factory_create_subchannel(
+    grpc_exec_ctx* exec_ctx, grpc_subchannel_factory* factory,
+    grpc_subchannel_args* args) {
+  return factory->vtable->create_subchannel(exec_ctx, factory, args);
+}
diff --git a/src/core/lib/client_config/subchannel_factory.h b/src/core/lib/client_config/subchannel_factory.h
new file mode 100644
index 0000000000..3ba2f860fe
--- /dev/null
+++ b/src/core/lib/client_config/subchannel_factory.h
@@ -0,0 +1,66 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_FACTORY_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_FACTORY_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;
+
+/** Constructor for new configured channels.
+    Creating decorators around this type is encouraged to adapt behavior. */
+struct grpc_subchannel_factory {
+  const grpc_subchannel_factory_vtable *vtable;
+};
+
+struct grpc_subchannel_factory_vtable {
+  void (*ref)(grpc_subchannel_factory *factory);
+  void (*unref)(grpc_exec_ctx *exec_ctx, grpc_subchannel_factory *factory);
+  grpc_subchannel *(*create_subchannel)(grpc_exec_ctx *exec_ctx,
+                                        grpc_subchannel_factory *factory,
+                                        grpc_subchannel_args *args);
+};
+
+void grpc_subchannel_factory_ref(grpc_subchannel_factory *factory);
+void grpc_subchannel_factory_unref(grpc_exec_ctx *exec_ctx,
+                                   grpc_subchannel_factory *factory);
+
+/** Create a new grpc_subchannel */
+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 */
diff --git a/src/core/lib/client_config/subchannel_index.c b/src/core/lib/client_config/subchannel_index.c
new file mode 100644
index 0000000000..2c545002a2
--- /dev/null
+++ b/src/core/lib/client_config/subchannel_index.c
@@ -0,0 +1,262 @@
+//
+//
+// 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.
+//
+//
+
+#include "src/core/lib/client_config/subchannel_index.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
+#include <grpc/support/tls.h>
+
+#include "src/core/lib/channel/channel_args.h"
+
+// a map of subchannel_key --> subchannel, used for detecting connections
+// to the same destination in order to share them
+static gpr_avl g_subchannel_index;
+
+static gpr_mu g_mu;
+
+struct grpc_subchannel_key {
+  grpc_connector *connector;
+  grpc_subchannel_args args;
+};
+
+GPR_TLS_DECL(subchannel_index_exec_ctx);
+
+static void enter_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == 0);
+  gpr_tls_set(&subchannel_index_exec_ctx, (intptr_t)exec_ctx);
+}
+
+static void leave_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == (intptr_t)exec_ctx);
+  gpr_tls_set(&subchannel_index_exec_ctx, 0);
+}
+
+static grpc_exec_ctx *current_ctx() {
+  grpc_exec_ctx *c = (grpc_exec_ctx *)gpr_tls_get(&subchannel_index_exec_ctx);
+  GPR_ASSERT(c != NULL);
+  return c;
+}
+
+static grpc_subchannel_key *create_key(
+    grpc_connector *connector, grpc_subchannel_args *args,
+    grpc_channel_args *(*copy_channel_args)(const grpc_channel_args *args)) {
+  grpc_subchannel_key *k = gpr_malloc(sizeof(*k));
+  k->connector = grpc_connector_ref(connector);
+  k->args.filter_count = args->filter_count;
+  k->args.filters = gpr_malloc(sizeof(*k->args.filters) * k->args.filter_count);
+  memcpy((grpc_channel_filter *)k->args.filters, args->filters,
+         sizeof(*k->args.filters) * k->args.filter_count);
+  k->args.addr_len = args->addr_len;
+  k->args.addr = gpr_malloc(args->addr_len);
+  memcpy(k->args.addr, args->addr, k->args.addr_len);
+  k->args.args = copy_channel_args(args->args);
+  return k;
+}
+
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *connector,
+                                                grpc_subchannel_args *args) {
+  return create_key(connector, args, grpc_channel_args_normalize);
+}
+
+static grpc_subchannel_key *subchannel_key_copy(grpc_subchannel_key *k) {
+  return create_key(k->connector, &k->args, grpc_channel_args_copy);
+}
+
+static int subchannel_key_compare(grpc_subchannel_key *a,
+                                  grpc_subchannel_key *b) {
+  int c = GPR_ICMP(a->connector, b->connector);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.addr_len, b->args.addr_len);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.filter_count, b->args.filter_count);
+  if (c != 0) return c;
+  c = memcmp(a->args.addr, b->args.addr, a->args.addr_len);
+  if (c != 0) return c;
+  c = memcmp(a->args.filters, b->args.filters,
+             a->args.filter_count * sizeof(*a->args.filters));
+  if (c != 0) return c;
+  return grpc_channel_args_compare(a->args.args, b->args.args);
+}
+
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *k) {
+  grpc_connector_unref(exec_ctx, k->connector);
+  gpr_free(k->args.addr);
+  gpr_free((grpc_channel_args *)k->args.filters);
+  grpc_channel_args_destroy((grpc_channel_args *)k->args.args);
+  gpr_free(k);
+}
+
+static void sck_avl_destroy(void *p) {
+  grpc_subchannel_key_destroy(current_ctx(), p);
+}
+
+static void *sck_avl_copy(void *p) { return subchannel_key_copy(p); }
+
+static long sck_avl_compare(void *a, void *b) {
+  return subchannel_key_compare(a, b);
+}
+
+static void scv_avl_destroy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_UNREF(current_ctx(), p, "subchannel_index");
+}
+
+static void *scv_avl_copy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_REF(p, "subchannel_index");
+  return p;
+}
+
+static const gpr_avl_vtable subchannel_avl_vtable = {
+    .destroy_key = sck_avl_destroy,
+    .copy_key = sck_avl_copy,
+    .compare_keys = sck_avl_compare,
+    .destroy_value = scv_avl_destroy,
+    .copy_value = scv_avl_copy};
+
+void grpc_subchannel_index_init(void) {
+  g_subchannel_index = gpr_avl_create(&subchannel_avl_vtable);
+  gpr_mu_init(&g_mu);
+  gpr_tls_init(&subchannel_index_exec_ctx);
+}
+
+void grpc_subchannel_index_shutdown(void) {
+  gpr_mu_destroy(&g_mu);
+  gpr_avl_unref(g_subchannel_index);
+  gpr_tls_destroy(&subchannel_index_exec_ctx);
+}
+
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key) {
+  enter_ctx(exec_ctx);
+
+  // Lock, and take a reference to the subchannel index.
+  // We don't need to do the search under a lock as avl's are immutable.
+  gpr_mu_lock(&g_mu);
+  gpr_avl index = gpr_avl_ref(g_subchannel_index);
+  gpr_mu_unlock(&g_mu);
+
+  grpc_subchannel *c =
+      GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(gpr_avl_get(index, key), "index_find");
+  gpr_avl_unref(index);
+
+  leave_ctx(exec_ctx);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  grpc_subchannel *c = NULL;
+
+  while (c == NULL) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // - Check to see if a subchannel already exists
+    c = gpr_avl_get(index, key);
+    if (c != NULL) {
+      // yes -> we're done
+      GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, constructed, "index_register");
+    } else {
+      // no -> update the avl and compare/swap
+      gpr_avl updated =
+          gpr_avl_add(gpr_avl_ref(index), subchannel_key_copy(key),
+                      GRPC_SUBCHANNEL_WEAK_REF(constructed, "index_register"));
+
+      // it may happen (but it's expected to be unlikely)
+      // that some other thread has changed the index:
+      // compare/swap here to check that, and retry as necessary
+      gpr_mu_lock(&g_mu);
+      if (index.root == g_subchannel_index.root) {
+        GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+        c = constructed;
+      }
+      gpr_mu_unlock(&g_mu);
+
+      gpr_avl_unref(updated);
+    }
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+
+  return c;
+}
+
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  bool done = false;
+  while (!done) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // Check to see if this key still refers to the previously
+    // registered subchannel
+    grpc_subchannel *c = gpr_avl_get(index, key);
+    if (c != constructed) {
+      gpr_avl_unref(index);
+      break;
+    }
+
+    // compare and swap the update (some other thread may have
+    // mutated the index behind us)
+    gpr_avl updated = gpr_avl_remove(gpr_avl_ref(index), key);
+
+    gpr_mu_lock(&g_mu);
+    if (index.root == g_subchannel_index.root) {
+      GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+      done = true;
+    }
+    gpr_mu_unlock(&g_mu);
+
+    gpr_avl_unref(updated);
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+}
diff --git a/src/core/lib/client_config/subchannel_index.h b/src/core/lib/client_config/subchannel_index.h
new file mode 100644
index 0000000000..bc5f03beb4
--- /dev/null
+++ b/src/core/lib/client_config/subchannel_index.h
@@ -0,0 +1,77 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+
+#include "src/core/lib/client_config/connector.h"
+#include "src/core/lib/client_config/subchannel.h"
+
+/** \file Provides an index of active subchannels so that they can be
+    shared amongst channels */
+
+typedef struct grpc_subchannel_key grpc_subchannel_key;
+
+/** Create a key that can be used to uniquely identify a subchannel */
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *con,
+                                                grpc_subchannel_args *args);
+
+/** Destroy a subchannel key */
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *key);
+
+/** Given a subchannel key, find the subchannel registered for it.
+    Returns NULL if no such channel exists.
+    Thread-safe. */
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key);
+
+/** Register a subchannel against a key.
+    Takes ownership of \a constructed.
+    Returns the registered subchannel. This may be different from
+    \a constructed in the case of a registration race. */
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed);
+
+/** Remove \a constructed as the registered subchannel for \a key. */
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed);
+
+/** Initialize the subchannel index (global) */
+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 */
diff --git a/src/core/lib/client_config/uri_parser.c b/src/core/lib/client_config/uri_parser.c
new file mode 100644
index 0000000000..d3228dec5f
--- /dev/null
+++ b/src/core/lib/client_config/uri_parser.c
@@ -0,0 +1,242 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#include "src/core/lib/client_config/uri_parser.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/port_platform.h>
+#include <grpc/support/string_util.h>
+
+/** a size_t default value... maps to all 1's */
+#define NOT_SET (~(size_t)0)
+
+static grpc_uri *bad_uri(const char *uri_text, size_t pos, const char *section,
+                         int suppress_errors) {
+  char *line_prefix;
+  size_t pfx_len;
+
+  if (!suppress_errors) {
+    gpr_asprintf(&line_prefix, "bad uri.%s: '", section);
+    pfx_len = strlen(line_prefix) + pos;
+    gpr_log(GPR_ERROR, "%s%s'", line_prefix, uri_text);
+    gpr_free(line_prefix);
+
+    line_prefix = gpr_malloc(pfx_len + 1);
+    memset(line_prefix, ' ', pfx_len);
+    line_prefix[pfx_len] = 0;
+    gpr_log(GPR_ERROR, "%s^ here", line_prefix);
+    gpr_free(line_prefix);
+  }
+
+  return NULL;
+}
+
+/** Returns a copy of \a src[begin, end) */
+static char *copy_component(const char *src, size_t begin, size_t end) {
+  char *out = gpr_malloc(end - begin + 1);
+  memcpy(out, src + begin, end - begin);
+  out[end - begin] = 0;
+  return out;
+}
+
+/** Returns how many chars to advance if \a uri_text[i] begins a valid \a pchar
+ * production. If \a uri_text[i] introduces an invalid \a pchar (such as percent
+ * sign not followed by two hex digits), NOT_SET is returned. */
+static size_t parse_pchar(const char *uri_text, size_t i) {
+  /* pchar = unreserved / pct-encoded / sub-delims / ":" / "@"
+   * unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
+   * pct-encoded = "%" HEXDIG HEXDIG
+   * sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
+   / "*" / "+" / "," / ";" / "=" */
+  char c = uri_text[i];
+  if (((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z')) ||
+      ((c >= '0') && (c <= '9')) ||
+      (c == '-' || c == '.' || c == '_' || c == '~') || /* unreserved */
+      (c == '!' || c == '$' || c == '&' || c == '\'' || c == '$' || c == '&' ||
+       c == '(' || c == ')' || c == '*' || c == '+' || c == ',' || c == ';' ||
+       c == '=') /* sub-delims */) {
+    return 1;
+  }
+  if (c == '%') { /* pct-encoded */
+    size_t j;
+    if (uri_text[i + 1] == 0 || uri_text[i + 2] == 0) {
+      return NOT_SET;
+    }
+    for (j = i + 1; j < 2; j++) {
+      c = uri_text[j];
+      if (!(((c >= '0') && (c <= '9')) || ((c >= 'a') && (c <= 'f')) ||
+            ((c >= 'A') && (c <= 'F')))) {
+        return NOT_SET;
+      }
+    }
+    return 2;
+  }
+  return 0;
+}
+
+/* *( pchar / "?" / "/" ) */
+static int parse_fragment_or_query(const char *uri_text, size_t *i) {
+  char c;
+  while ((c = uri_text[*i]) != 0) {
+    const size_t advance = parse_pchar(uri_text, *i); /* pchar */
+    switch (advance) {
+      case 0: /* uri_text[i] isn't in pchar */
+        /* maybe it's ? or / */
+        if (uri_text[*i] == '?' || uri_text[*i] == '/') {
+          (*i)++;
+          break;
+        } else {
+          return 1;
+        }
+        GPR_UNREACHABLE_CODE(return 0);
+      default:
+        (*i) += advance;
+        break;
+      case NOT_SET: /* uri_text[i] introduces an invalid URI */
+        return 0;
+    }
+  }
+  /* *i is the first uri_text position past the \a query production, maybe \0 */
+  return 1;
+}
+
+grpc_uri *grpc_uri_parse(const char *uri_text, int suppress_errors) {
+  grpc_uri *uri;
+  size_t scheme_begin = 0;
+  size_t scheme_end = NOT_SET;
+  size_t authority_begin = NOT_SET;
+  size_t authority_end = NOT_SET;
+  size_t path_begin = NOT_SET;
+  size_t path_end = NOT_SET;
+  size_t query_begin = NOT_SET;
+  size_t query_end = NOT_SET;
+  size_t fragment_begin = NOT_SET;
+  size_t fragment_end = NOT_SET;
+  size_t i;
+
+  for (i = scheme_begin; uri_text[i] != 0; i++) {
+    if (uri_text[i] == ':') {
+      scheme_end = i;
+      break;
+    }
+    if (uri_text[i] >= 'a' && uri_text[i] <= 'z') continue;
+    if (uri_text[i] >= 'A' && uri_text[i] <= 'Z') continue;
+    if (i != scheme_begin) {
+      if (uri_text[i] >= '0' && uri_text[i] <= '9') continue;
+      if (uri_text[i] == '+') continue;
+      if (uri_text[i] == '-') continue;
+      if (uri_text[i] == '.') continue;
+    }
+    break;
+  }
+  if (scheme_end == NOT_SET) {
+    return bad_uri(uri_text, i, "scheme", suppress_errors);
+  }
+
+  if (uri_text[scheme_end + 1] == '/' && uri_text[scheme_end + 2] == '/') {
+    authority_begin = scheme_end + 3;
+    for (i = authority_begin; uri_text[i] != 0 && authority_end == NOT_SET;
+         i++) {
+      if (uri_text[i] == '/' || uri_text[i] == '?' || uri_text[i] == '#') {
+        authority_end = i;
+      }
+    }
+    if (authority_end == NOT_SET && uri_text[i] == 0) {
+      authority_end = i;
+    }
+    if (authority_end == NOT_SET) {
+      return bad_uri(uri_text, i, "authority", suppress_errors);
+    }
+    /* TODO(ctiller): parse the authority correctly */
+    path_begin = authority_end;
+  } else {
+    path_begin = scheme_end + 1;
+  }
+
+  for (i = path_begin; uri_text[i] != 0; i++) {
+    if (uri_text[i] == '?' || uri_text[i] == '#') {
+      path_end = i;
+      break;
+    }
+  }
+  if (path_end == NOT_SET && uri_text[i] == 0) {
+    path_end = i;
+  }
+  if (path_end == NOT_SET) {
+    return bad_uri(uri_text, i, "path", suppress_errors);
+  }
+
+  if (uri_text[i] == '?') {
+    query_begin = ++i;
+    if (!parse_fragment_or_query(uri_text, &i)) {
+      return bad_uri(uri_text, i, "query", suppress_errors);
+    } else if (uri_text[i] != 0 && uri_text[i] != '#') {
+      /* We must be at the end or at the beginning of a fragment */
+      return bad_uri(uri_text, i, "query", suppress_errors);
+    }
+    query_end = i;
+  }
+  if (uri_text[i] == '#') {
+    fragment_begin = ++i;
+    if (!parse_fragment_or_query(uri_text, &i)) {
+      return bad_uri(uri_text, i - fragment_end, "fragment", suppress_errors);
+    } else if (uri_text[i] != 0) {
+      /* We must be at the end */
+      return bad_uri(uri_text, i, "fragment", suppress_errors);
+    }
+    fragment_end = i;
+  }
+
+  uri = gpr_malloc(sizeof(*uri));
+  memset(uri, 0, sizeof(*uri));
+  uri->scheme = copy_component(uri_text, scheme_begin, scheme_end);
+  uri->authority = copy_component(uri_text, authority_begin, authority_end);
+  uri->path = copy_component(uri_text, path_begin, path_end);
+  uri->query = copy_component(uri_text, query_begin, query_end);
+  uri->fragment = copy_component(uri_text, fragment_begin, fragment_end);
+
+  return uri;
+}
+
+void grpc_uri_destroy(grpc_uri *uri) {
+  if (!uri) return;
+  gpr_free(uri->scheme);
+  gpr_free(uri->authority);
+  gpr_free(uri->path);
+  gpr_free(uri->query);
+  gpr_free(uri->fragment);
+  gpr_free(uri);
+}
diff --git a/src/core/lib/client_config/uri_parser.h b/src/core/lib/client_config/uri_parser.h
new file mode 100644
index 0000000000..d70d451e60
--- /dev/null
+++ b/src/core/lib/client_config/uri_parser.h
@@ -0,0 +1,51 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_CLIENT_CONFIG_URI_PARSER_H
+#define GRPC_CORE_LIB_CLIENT_CONFIG_URI_PARSER_H
+
+typedef struct {
+  char *scheme;
+  char *authority;
+  char *path;
+  char *query;
+  char *fragment;
+} grpc_uri;
+
+/** parse a uri, return NULL on failure */
+grpc_uri *grpc_uri_parse(const char *uri_text, int suppress_errors);
+
+/** destroy a uri */
+void grpc_uri_destroy(grpc_uri *uri);
+
+#endif /* GRPC_CORE_LIB_CLIENT_CONFIG_URI_PARSER_H */