Merge pull request #7936 from y-zeng/log_test

Add no-logging test
diff --git a/BUILD b/BUILD
index 7dc5b6c..ac1db59 100644
--- a/BUILD
+++ b/BUILD
@@ -312,6 +312,7 @@
     "src/core/ext/census/census_interface.h",
     "src/core/ext/census/census_rpc_stats.h",
     "src/core/ext/census/gen/census.pb.h",
+    "src/core/ext/census/gen/trace_context.pb.h",
     "src/core/ext/census/grpc_filter.h",
     "src/core/ext/census/mlog.h",
     "src/core/ext/census/resource.h",
@@ -493,6 +494,7 @@
     "src/core/ext/census/base_resources.c",
     "src/core/ext/census/context.c",
     "src/core/ext/census/gen/census.pb.c",
+    "src/core/ext/census/gen/trace_context.pb.c",
     "src/core/ext/census/grpc_context.c",
     "src/core/ext/census/grpc_filter.c",
     "src/core/ext/census/grpc_plugin.c",
@@ -1037,6 +1039,7 @@
     "src/core/ext/census/census_interface.h",
     "src/core/ext/census/census_rpc_stats.h",
     "src/core/ext/census/gen/census.pb.h",
+    "src/core/ext/census/gen/trace_context.pb.h",
     "src/core/ext/census/grpc_filter.h",
     "src/core/ext/census/mlog.h",
     "src/core/ext/census/resource.h",
@@ -1189,6 +1192,7 @@
     "src/core/ext/census/base_resources.c",
     "src/core/ext/census/context.c",
     "src/core/ext/census/gen/census.pb.c",
+    "src/core/ext/census/gen/trace_context.pb.c",
     "src/core/ext/census/grpc_context.c",
     "src/core/ext/census/grpc_filter.c",
     "src/core/ext/census/grpc_plugin.c",
@@ -2339,6 +2343,7 @@
     "src/core/ext/census/base_resources.c",
     "src/core/ext/census/context.c",
     "src/core/ext/census/gen/census.pb.c",
+    "src/core/ext/census/gen/trace_context.pb.c",
     "src/core/ext/census/grpc_context.c",
     "src/core/ext/census/grpc_filter.c",
     "src/core/ext/census/grpc_plugin.c",
@@ -2532,6 +2537,7 @@
     "src/core/ext/census/census_interface.h",
     "src/core/ext/census/census_rpc_stats.h",
     "src/core/ext/census/gen/census.pb.h",
+    "src/core/ext/census/gen/trace_context.pb.h",
     "src/core/ext/census/grpc_filter.h",
     "src/core/ext/census/mlog.h",
     "src/core/ext/census/resource.h",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b819465..3e9c44c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -470,6 +470,7 @@
   src/core/ext/census/base_resources.c
   src/core/ext/census/context.c
   src/core/ext/census/gen/census.pb.c
+  src/core/ext/census/gen/trace_context.pb.c
   src/core/ext/census/grpc_context.c
   src/core/ext/census/grpc_filter.c
   src/core/ext/census/grpc_plugin.c
@@ -930,6 +931,7 @@
   src/core/ext/census/base_resources.c
   src/core/ext/census/context.c
   src/core/ext/census/gen/census.pb.c
+  src/core/ext/census/gen/trace_context.pb.c
   src/core/ext/census/grpc_context.c
   src/core/ext/census/grpc_filter.c
   src/core/ext/census/grpc_plugin.c
diff --git a/Makefile b/Makefile
index 2152799..ed326bf 100644
--- a/Makefile
+++ b/Makefile
@@ -2686,6 +2686,7 @@
     src/core/ext/census/base_resources.c \
     src/core/ext/census/context.c \
     src/core/ext/census/gen/census.pb.c \
+    src/core/ext/census/gen/trace_context.pb.c \
     src/core/ext/census/grpc_context.c \
     src/core/ext/census/grpc_filter.c \
     src/core/ext/census/grpc_plugin.c \
@@ -3391,6 +3392,7 @@
     src/core/ext/census/base_resources.c \
     src/core/ext/census/context.c \
     src/core/ext/census/gen/census.pb.c \
+    src/core/ext/census/gen/trace_context.pb.c \
     src/core/ext/census/grpc_context.c \
     src/core/ext/census/grpc_filter.c \
     src/core/ext/census/grpc_plugin.c \
diff --git a/binding.gyp b/binding.gyp
index a29cfda..666547c 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -742,6 +742,7 @@
         'src/core/ext/census/base_resources.c',
         'src/core/ext/census/context.c',
         'src/core/ext/census/gen/census.pb.c',
+        'src/core/ext/census/gen/trace_context.pb.c',
         'src/core/ext/census/grpc_context.c',
         'src/core/ext/census/grpc_filter.c',
         'src/core/ext/census/grpc_plugin.c',
diff --git a/build.yaml b/build.yaml
index 9b182d2..8599d6b 100644
--- a/build.yaml
+++ b/build.yaml
@@ -24,6 +24,7 @@
   - src/core/ext/census/census_interface.h
   - src/core/ext/census/census_rpc_stats.h
   - src/core/ext/census/gen/census.pb.h
+  - src/core/ext/census/gen/trace_context.pb.h
   - src/core/ext/census/grpc_filter.h
   - src/core/ext/census/mlog.h
   - src/core/ext/census/resource.h
@@ -32,6 +33,7 @@
   - src/core/ext/census/base_resources.c
   - src/core/ext/census/context.c
   - src/core/ext/census/gen/census.pb.c
+  - src/core/ext/census/gen/trace_context.pb.c
   - src/core/ext/census/grpc_context.c
   - src/core/ext/census/grpc_filter.c
   - src/core/ext/census/grpc_plugin.c
diff --git a/config.m4 b/config.m4
index 5b47074..1f6abbb 100644
--- a/config.m4
+++ b/config.m4
@@ -261,6 +261,7 @@
     src/core/ext/census/base_resources.c \
     src/core/ext/census/context.c \
     src/core/ext/census/gen/census.pb.c \
+    src/core/ext/census/gen/trace_context.pb.c \
     src/core/ext/census/grpc_context.c \
     src/core/ext/census/grpc_filter.c \
     src/core/ext/census/grpc_plugin.c \
diff --git a/examples/php/run_greeter_client.sh b/examples/php/run_greeter_client.sh
index 1a6e9ee..4d0be4f2 100755
--- a/examples/php/run_greeter_client.sh
+++ b/examples/php/run_greeter_client.sh
@@ -30,5 +30,5 @@
 
 set -e
 cd $(dirname $0)
-php $extension_dir -d extension=grpc.so -d max_execution_time=300 \
+php -d extension=grpc.so -d max_execution_time=300 \
   greeter_client.php $1
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 41ba1b1..900ea41 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -407,6 +407,7 @@
                       'src/core/ext/census/census_interface.h',
                       'src/core/ext/census/census_rpc_stats.h',
                       'src/core/ext/census/gen/census.pb.h',
+                      'src/core/ext/census/gen/trace_context.pb.h',
                       'src/core/ext/census/grpc_filter.h',
                       'src/core/ext/census/mlog.h',
                       'src/core/ext/census/resource.h',
@@ -591,6 +592,7 @@
                       'src/core/ext/census/base_resources.c',
                       'src/core/ext/census/context.c',
                       'src/core/ext/census/gen/census.pb.c',
+                      'src/core/ext/census/gen/trace_context.pb.c',
                       'src/core/ext/census/grpc_context.c',
                       'src/core/ext/census/grpc_filter.c',
                       'src/core/ext/census/grpc_plugin.c',
@@ -768,6 +770,7 @@
                               'src/core/ext/census/census_interface.h',
                               'src/core/ext/census/census_rpc_stats.h',
                               'src/core/ext/census/gen/census.pb.h',
+                              'src/core/ext/census/gen/trace_context.pb.h',
                               'src/core/ext/census/grpc_filter.h',
                               'src/core/ext/census/mlog.h',
                               'src/core/ext/census/resource.h',
diff --git a/grpc.gemspec b/grpc.gemspec
index 95eb28b..2acde40 100755
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -326,6 +326,7 @@
   s.files += %w( src/core/ext/census/census_interface.h )
   s.files += %w( src/core/ext/census/census_rpc_stats.h )
   s.files += %w( src/core/ext/census/gen/census.pb.h )
+  s.files += %w( src/core/ext/census/gen/trace_context.pb.h )
   s.files += %w( src/core/ext/census/grpc_filter.h )
   s.files += %w( src/core/ext/census/mlog.h )
   s.files += %w( src/core/ext/census/resource.h )
@@ -510,6 +511,7 @@
   s.files += %w( src/core/ext/census/base_resources.c )
   s.files += %w( src/core/ext/census/context.c )
   s.files += %w( src/core/ext/census/gen/census.pb.c )
+  s.files += %w( src/core/ext/census/gen/trace_context.pb.c )
   s.files += %w( src/core/ext/census/grpc_context.c )
   s.files += %w( src/core/ext/census/grpc_filter.c )
   s.files += %w( src/core/ext/census/grpc_plugin.c )
diff --git a/include/grpc/impl/codegen/grpc_types.h b/include/grpc/impl/codegen/grpc_types.h
index e5a8288..b3372d7 100644
--- a/include/grpc/impl/codegen/grpc_types.h
+++ b/include/grpc/impl/codegen/grpc_types.h
@@ -222,10 +222,14 @@
 #define GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST (0x00000010u)
 /** Signal that the call should not return UNAVAILABLE before it has started */
 #define GRPC_INITIAL_METADATA_IGNORE_CONNECTIVITY (0x00000020u)
+/** Signal that the call is cacheable. GRPC is free to use GET verb */
+#define GRPC_INITIAL_METADATA_CACHEABLE_REQUEST (0x00000040u)
+
 /** Mask of all valid flags */
-#define GRPC_INITIAL_METADATA_USED_MASK       \
-  (GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST | \
-   GRPC_INITIAL_METADATA_IGNORE_CONNECTIVITY)
+#define GRPC_INITIAL_METADATA_USED_MASK        \
+  (GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST |  \
+   GRPC_INITIAL_METADATA_IGNORE_CONNECTIVITY | \
+   GRPC_INITIAL_METADATA_CACHEABLE_REQUEST)
 
 /** A single metadata element */
 typedef struct grpc_metadata {
diff --git a/package.xml b/package.xml
index 1df4940..1570735 100644
--- a/package.xml
+++ b/package.xml
@@ -334,6 +334,7 @@
     <file baseinstalldir="/" name="src/core/ext/census/census_interface.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/census_rpc_stats.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/gen/census.pb.h" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/census/gen/trace_context.pb.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/grpc_filter.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/mlog.h" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/resource.h" role="src" />
@@ -518,6 +519,7 @@
     <file baseinstalldir="/" name="src/core/ext/census/base_resources.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/context.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/gen/census.pb.c" role="src" />
+    <file baseinstalldir="/" name="src/core/ext/census/gen/trace_context.pb.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/grpc_context.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/grpc_filter.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/census/grpc_plugin.c" role="src" />
diff --git a/src/core/ext/census/gen/README.md b/src/core/ext/census/gen/README.md
index 72bef65..fdbac10 100644
--- a/src/core/ext/census/gen/README.md
+++ b/src/core/ext/census/gen/README.md
@@ -4,3 +4,7 @@
 * census.pb.{h,c} - Generated from src/core/ext/census/census.proto, using the
   script `tools/codegen/core/gen_nano_proto.sh src/proto/census/census.proto
   $PWD/src/core/ext/census/gen src/core/ext/census/gen`
+* trace_context.pb.{h,c} - Generated from
+  src/core/ext/census/trace_context.proto, using the script
+  `tools/codegen/core/gen_nano_proto.sh src/proto/census/trace_context.proto
+  $PWD/src/core/ext/census/gen src/core/ext/census/gen`
diff --git a/src/core/ext/census/gen/trace_context.pb.c b/src/core/ext/census/gen/trace_context.pb.c
new file mode 100644
index 0000000..c8aea32
--- /dev/null
+++ b/src/core/ext/census/gen/trace_context.pb.c
@@ -0,0 +1,81 @@
+/*
+ *
+ * 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.
+ *
+ */
+/* Automatically generated nanopb constant definitions */
+/* Generated by nanopb-0.3.5-dev */
+
+#include "src/core/ext/census/gen/trace_context.pb.h"
+
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+
+
+const pb_field_t google_trace_TraceId_fields[3] = {
+    PB_FIELD(  1, FIXED64 , OPTIONAL, STATIC  , FIRST, google_trace_TraceId, hi, hi, 0),
+    PB_FIELD(  2, FIXED64 , OPTIONAL, STATIC  , OTHER, google_trace_TraceId, lo, hi, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t google_trace_TraceContext_fields[4] = {
+    PB_FIELD(  1, MESSAGE , OPTIONAL, STATIC  , FIRST, google_trace_TraceContext, trace_id, trace_id, &google_trace_TraceId_fields),
+    PB_FIELD(  2, FIXED64 , OPTIONAL, STATIC  , OTHER, google_trace_TraceContext, span_id, trace_id, 0),
+    PB_FIELD(  3, BOOL    , OPTIONAL, STATIC  , OTHER, google_trace_TraceContext, is_sampled, span_id, 0),
+    PB_LAST_FIELD
+};
+
+
+/* Check that field information fits in pb_field_t */
+#if !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_32BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in 8 or 16 bit
+ * field descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(google_trace_TraceContext, trace_id) < 65536), YOU_MUST_DEFINE_PB_FIELD_32BIT_FOR_MESSAGES_google_trace_TraceId_google_trace_TraceContext)
+#endif
+
+#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
+/* If you get an error here, it means that you need to define PB_FIELD_16BIT
+ * compile-time option. You can do that in pb.h or on compiler command line.
+ * 
+ * The reason you need to do this is that some of your messages contain tag
+ * numbers or field sizes that are larger than what can fit in the default
+ * 8 bit descriptors.
+ */
+PB_STATIC_ASSERT((pb_membersize(google_trace_TraceContext, trace_id) < 256), YOU_MUST_DEFINE_PB_FIELD_16BIT_FOR_MESSAGES_google_trace_TraceId_google_trace_TraceContext)
+#endif
+
+
diff --git a/src/core/ext/census/gen/trace_context.pb.h b/src/core/ext/census/gen/trace_context.pb.h
new file mode 100644
index 0000000..263c4c5
--- /dev/null
+++ b/src/core/ext/census/gen/trace_context.pb.h
@@ -0,0 +1,99 @@
+/*
+ *
+ * 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.
+ *
+ */
+/* Automatically generated nanopb header */
+/* Generated by nanopb-0.3.5-dev */
+
+#ifndef GRPC_CORE_EXT_CENSUS_GEN_TRACE_CONTEXT_PB_H
+#define GRPC_CORE_EXT_CENSUS_GEN_TRACE_CONTEXT_PB_H
+#include "third_party/nanopb/pb.h"
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Struct definitions */
+typedef struct _google_trace_TraceId {
+    bool has_hi;
+    uint64_t hi;
+    bool has_lo;
+    uint64_t lo;
+} google_trace_TraceId;
+
+typedef struct _google_trace_TraceContext {
+    bool has_trace_id;
+    google_trace_TraceId trace_id;
+    bool has_span_id;
+    uint64_t span_id;
+    bool has_is_sampled;
+    bool is_sampled;
+} google_trace_TraceContext;
+
+/* Default values for struct fields */
+
+/* Initializer values for message structs */
+#define google_trace_TraceId_init_default        {false, 0, false, 0}
+#define google_trace_TraceContext_init_default   {false, google_trace_TraceId_init_default, false, 0, false, 0}
+#define google_trace_TraceId_init_zero           {false, 0, false, 0}
+#define google_trace_TraceContext_init_zero      {false, google_trace_TraceId_init_zero, false, 0, false, 0}
+
+/* Field tags (for use in manual encoding/decoding) */
+#define google_trace_TraceId_hi_tag              1
+#define google_trace_TraceId_lo_tag              2
+#define google_trace_TraceContext_trace_id_tag   1
+#define google_trace_TraceContext_span_id_tag    2
+#define google_trace_TraceContext_is_sampled_tag 3
+
+/* Struct field encoding specification for nanopb */
+extern const pb_field_t google_trace_TraceId_fields[3];
+extern const pb_field_t google_trace_TraceContext_fields[4];
+
+/* Maximum encoded size of messages (where known) */
+#define google_trace_TraceId_size                18
+#define google_trace_TraceContext_size           31
+
+/* Message IDs (where set with "msgid" option) */
+#ifdef PB_MSGID
+
+#define TRACE_CONTEXT_MESSAGES \
+
+
+#endif
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
diff --git a/src/core/lib/channel/http_client_filter.c b/src/core/lib/channel/http_client_filter.c
index 9e67df8..ef68cc8 100644
--- a/src/core/lib/channel/http_client_filter.c
+++ b/src/core/lib/channel/http_client_filter.c
@@ -43,6 +43,9 @@
 #define EXPECTED_CONTENT_TYPE "application/grpc"
 #define EXPECTED_CONTENT_TYPE_LENGTH sizeof(EXPECTED_CONTENT_TYPE) - 1
 
+/* default maximum size of payload eligable for GET request */
+static const size_t kMaxPayloadSizeForGet = 2048;
+
 typedef struct call_data {
   grpc_linked_mdelem method;
   grpc_linked_mdelem scheme;
@@ -50,20 +53,39 @@
   grpc_linked_mdelem te_trailers;
   grpc_linked_mdelem content_type;
   grpc_linked_mdelem user_agent;
+  grpc_linked_mdelem payload_bin;
 
   grpc_metadata_batch *recv_initial_metadata;
+  uint8_t *payload_bytes;
+
+  /* Vars to read data off of send_message */
+  grpc_transport_stream_op send_op;
+  uint32_t send_length;
+  uint32_t send_flags;
+  gpr_slice incoming_slice;
+  grpc_slice_buffer_stream replacement_stream;
+  gpr_slice_buffer slices;
+  /* flag that indicates that all slices of send_messages aren't availble */
+  bool send_message_blocked;
 
   /** Closure to call when finished with the hc_on_recv hook */
   grpc_closure *on_done_recv;
+  grpc_closure *on_complete;
+  grpc_closure *post_send;
+
   /** Receive closures are chained: we inject this closure as the on_done_recv
       up-call on transport_op, and remember to call our on_done_recv member
       after handling it. */
   grpc_closure hc_on_recv;
+  grpc_closure hc_on_complete;
+  grpc_closure got_slice;
+  grpc_closure send_done;
 } call_data;
 
 typedef struct channel_data {
   grpc_mdelem *static_scheme;
   grpc_mdelem *user_agent;
+  size_t max_payload_size_for_get;
 } channel_data;
 
 typedef struct {
@@ -119,6 +141,24 @@
   calld->on_done_recv->cb(exec_ctx, calld->on_done_recv->cb_arg, error);
 }
 
+static void hc_on_complete(grpc_exec_ctx *exec_ctx, void *user_data,
+                           grpc_error *error) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+  if (calld->payload_bytes) {
+    gpr_free(calld->payload_bytes);
+    calld->payload_bytes = NULL;
+  }
+  calld->on_complete->cb(exec_ctx, calld->on_complete->cb_arg, error);
+}
+
+static void send_done(grpc_exec_ctx *exec_ctx, void *elemp, grpc_error *error) {
+  grpc_call_element *elem = elemp;
+  call_data *calld = elem->call_data;
+  gpr_slice_buffer_reset_and_unref(&calld->slices);
+  calld->post_send->cb(exec_ctx, calld->post_send->cb_arg, error);
+}
+
 static grpc_mdelem *client_strip_filter(void *user_data, grpc_mdelem *md) {
   /* eat the things we'd like to set ourselves */
   if (md->key == GRPC_MDSTR_METHOD) return NULL;
@@ -129,22 +169,105 @@
   return md;
 }
 
-static void hc_mutate_op(grpc_call_element *elem,
+static void continue_send_message(grpc_exec_ctx *exec_ctx,
+                                  grpc_call_element *elem) {
+  call_data *calld = elem->call_data;
+  uint8_t *wrptr = calld->payload_bytes;
+  while (grpc_byte_stream_next(exec_ctx, calld->send_op.send_message,
+                               &calld->incoming_slice, ~(size_t)0,
+                               &calld->got_slice)) {
+    memcpy(wrptr, GPR_SLICE_START_PTR(calld->incoming_slice),
+           GPR_SLICE_LENGTH(calld->incoming_slice));
+    wrptr += GPR_SLICE_LENGTH(calld->incoming_slice);
+    gpr_slice_buffer_add(&calld->slices, calld->incoming_slice);
+    if (calld->send_length == calld->slices.length) {
+      calld->send_message_blocked = false;
+      break;
+    }
+  }
+}
+
+static void got_slice(grpc_exec_ctx *exec_ctx, void *elemp, grpc_error *error) {
+  grpc_call_element *elem = elemp;
+  call_data *calld = elem->call_data;
+  calld->send_message_blocked = false;
+  gpr_slice_buffer_add(&calld->slices, calld->incoming_slice);
+  if (calld->send_length == calld->slices.length) {
+    /* Pass down the original send_message op that was blocked.*/
+    grpc_slice_buffer_stream_init(&calld->replacement_stream, &calld->slices,
+                                  calld->send_flags);
+    calld->send_op.send_message = &calld->replacement_stream.base;
+    calld->post_send = calld->send_op.on_complete;
+    calld->send_op.on_complete = &calld->send_done;
+    grpc_call_next_op(exec_ctx, elem, &calld->send_op);
+  } else {
+    continue_send_message(exec_ctx, elem);
+  }
+}
+
+static void hc_mutate_op(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                          grpc_transport_stream_op *op) {
   /* grab pointers to our data from the call element */
   call_data *calld = elem->call_data;
   channel_data *channeld = elem->channel_data;
+
   if (op->send_initial_metadata != NULL) {
+    /* Decide which HTTP VERB to use. We use GET if the request is marked
+    cacheable, and the operation contains both initial metadata and send
+    message, and the payload is below the size threshold, and all the data
+    for this request is immediately available. */
+    grpc_mdelem *method = GRPC_MDELEM_METHOD_POST;
+    calld->send_message_blocked = false;
+    if ((op->send_initial_metadata_flags &
+         GRPC_INITIAL_METADATA_CACHEABLE_REQUEST) &&
+        op->send_message != NULL &&
+        op->send_message->length < channeld->max_payload_size_for_get) {
+      method = GRPC_MDELEM_METHOD_GET;
+      calld->send_message_blocked = true;
+    } else if (op->send_initial_metadata_flags &
+               GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) {
+      method = GRPC_MDELEM_METHOD_PUT;
+    }
+
+    /* Attempt to read the data from send_message and create a header field. */
+    if (method == GRPC_MDELEM_METHOD_GET) {
+      /* allocate memory to hold the entire payload */
+      calld->payload_bytes = gpr_malloc(op->send_message->length);
+      GPR_ASSERT(calld->payload_bytes);
+
+      /* read slices of send_message and copy into payload_bytes */
+      calld->send_op = *op;
+      calld->send_length = op->send_message->length;
+      calld->send_flags = op->send_message->flags;
+      continue_send_message(exec_ctx, elem);
+
+      if (calld->send_message_blocked == false) {
+        /* when all the send_message data is available, then create a MDELEM and
+        append to headers */
+        grpc_mdelem *payload_bin = grpc_mdelem_from_metadata_strings(
+            GRPC_MDSTR_GRPC_PAYLOAD_BIN,
+            grpc_mdstr_from_buffer(calld->payload_bytes,
+                                   op->send_message->length));
+        grpc_metadata_batch_add_tail(op->send_initial_metadata,
+                                     &calld->payload_bin, payload_bin);
+        calld->on_complete = op->on_complete;
+        op->on_complete = &calld->hc_on_complete;
+        op->send_message = NULL;
+      } else {
+        /* Not all data is available. Fall back to POST. */
+        gpr_log(GPR_DEBUG,
+                "Request is marked Cacheable but not all data is available.\
+                            Falling back to POST");
+        method = GRPC_MDELEM_METHOD_POST;
+      }
+    }
+
     grpc_metadata_batch_filter(op->send_initial_metadata, client_strip_filter,
                                elem);
     /* Send : prefixed headers, which have to be before any application
        layer headers. */
-    grpc_metadata_batch_add_head(
-        op->send_initial_metadata, &calld->method,
-        op->send_initial_metadata_flags &
-                GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST
-            ? GRPC_MDELEM_METHOD_PUT
-            : GRPC_MDELEM_METHOD_POST);
+    grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->method,
+                                 method);
     grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->scheme,
                                  channeld->static_scheme);
     grpc_metadata_batch_add_tail(op->send_initial_metadata, &calld->te_trailers,
@@ -169,9 +292,16 @@
                                   grpc_transport_stream_op *op) {
   GPR_TIMER_BEGIN("hc_start_transport_op", 0);
   GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
-  hc_mutate_op(elem, op);
+  hc_mutate_op(exec_ctx, elem, op);
   GPR_TIMER_END("hc_start_transport_op", 0);
-  grpc_call_next_op(exec_ctx, elem, op);
+  call_data *calld = elem->call_data;
+  if (op->send_message != NULL && calld->send_message_blocked) {
+    /* Don't forward the op. send_message contains slices that aren't ready
+    yet. The call will be forwarded by the op_complete of slice read call.
+    */
+  } else {
+    grpc_call_next_op(exec_ctx, elem, op);
+  }
 }
 
 /* Constructor for call_data */
@@ -180,14 +310,23 @@
                                   grpc_call_element_args *args) {
   call_data *calld = elem->call_data;
   calld->on_done_recv = NULL;
+  calld->on_complete = NULL;
+  calld->payload_bytes = NULL;
+  gpr_slice_buffer_init(&calld->slices);
   grpc_closure_init(&calld->hc_on_recv, hc_on_recv, elem);
+  grpc_closure_init(&calld->hc_on_complete, hc_on_complete, elem);
+  grpc_closure_init(&calld->got_slice, got_slice, elem);
+  grpc_closure_init(&calld->send_done, send_done, elem);
   return GRPC_ERROR_NONE;
 }
 
 /* Destructor for call_data */
 static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                               const grpc_call_final_info *final_info,
-                              void *ignored) {}
+                              void *ignored) {
+  call_data *calld = elem->call_data;
+  gpr_slice_buffer_destroy(&calld->slices);
+}
 
 static grpc_mdelem *scheme_from_args(const grpc_channel_args *args) {
   unsigned i;
@@ -210,6 +349,22 @@
   return GRPC_MDELEM_SCHEME_HTTP;
 }
 
+static size_t max_payload_size_from_args(const grpc_channel_args *args) {
+  if (args != NULL) {
+    for (size_t i = 0; i < args->num_args; ++i) {
+      if (0 == strcmp(args->args[i].key, GRPC_ARG_MAX_PAYLOAD_SIZE_FOR_GET)) {
+        if (args->args[i].type != GRPC_ARG_INTEGER) {
+          gpr_log(GPR_ERROR, "%s: must be an integer",
+                  GRPC_ARG_MAX_PAYLOAD_SIZE_FOR_GET);
+        } else {
+          return (size_t)args->args[i].value.integer;
+        }
+      }
+    }
+  }
+  return kMaxPayloadSizeForGet;
+}
+
 static grpc_mdstr *user_agent_from_args(const grpc_channel_args *args,
                                         const char *transport_name) {
   gpr_strvec v;
@@ -268,6 +423,8 @@
   GPR_ASSERT(!args->is_last);
   GPR_ASSERT(args->optional_transport != NULL);
   chand->static_scheme = scheme_from_args(args->channel_args);
+  chand->max_payload_size_for_get =
+      max_payload_size_from_args(args->channel_args);
   chand->user_agent = grpc_mdelem_from_metadata_strings(
       GRPC_MDSTR_USER_AGENT,
       user_agent_from_args(args->channel_args,
diff --git a/src/core/lib/channel/http_client_filter.h b/src/core/lib/channel/http_client_filter.h
index 4708117..9e6e106 100644
--- a/src/core/lib/channel/http_client_filter.h
+++ b/src/core/lib/channel/http_client_filter.h
@@ -41,4 +41,7 @@
 /* Channel arg to override the http2 :scheme header */
 #define GRPC_ARG_HTTP2_SCHEME "grpc.http2_scheme"
 
+/* Channel arg to determine maximum size of payload eligable for GET request */
+#define GRPC_ARG_MAX_PAYLOAD_SIZE_FOR_GET "grpc.max_payload_size_for_get"
+
 #endif /* GRPC_CORE_LIB_CHANNEL_HTTP_CLIENT_FILTER_H */
diff --git a/src/core/lib/channel/http_server_filter.c b/src/core/lib/channel/http_server_filter.c
index 5ce51f9..0f2bf97 100644
--- a/src/core/lib/channel/http_server_filter.c
+++ b/src/core/lib/channel/http_server_filter.c
@@ -49,17 +49,32 @@
   uint8_t seen_scheme;
   uint8_t seen_te_trailers;
   uint8_t seen_authority;
+  uint8_t seen_payload_bin;
   grpc_linked_mdelem status;
   grpc_linked_mdelem content_type;
 
+  /* flag to ensure payload_bin is delivered only once */
+  uint8_t payload_bin_delivered;
+
   grpc_metadata_batch *recv_initial_metadata;
   bool *recv_idempotent_request;
+  bool *recv_cacheable_request;
   /** Closure to call when finished with the hs_on_recv hook */
   grpc_closure *on_done_recv;
+  /** Closure to call when we retrieve read message from the payload-bin header
+   */
+  grpc_closure *recv_message_ready;
+  grpc_closure *on_complete;
+  grpc_byte_stream **pp_recv_message;
+  gpr_slice_buffer read_slice_buffer;
+  grpc_slice_buffer_stream read_stream;
+
   /** Receive closures are chained: we inject this closure as the on_done_recv
       up-call on transport_op, and remember to call our on_done_recv member
       after handling it. */
   grpc_closure hs_on_recv;
+  grpc_closure hs_on_complete;
+  grpc_closure hs_recv_message_ready;
 } call_data;
 
 typedef struct channel_data { uint8_t unused; } channel_data;
@@ -76,16 +91,20 @@
 
   /* Check if it is one of the headers we care about. */
   if (md == GRPC_MDELEM_TE_TRAILERS || md == GRPC_MDELEM_METHOD_POST ||
-      md == GRPC_MDELEM_METHOD_PUT || md == GRPC_MDELEM_SCHEME_HTTP ||
-      md == GRPC_MDELEM_SCHEME_HTTPS ||
+      md == GRPC_MDELEM_METHOD_PUT || md == GRPC_MDELEM_METHOD_GET ||
+      md == GRPC_MDELEM_SCHEME_HTTP || md == GRPC_MDELEM_SCHEME_HTTPS ||
       md == GRPC_MDELEM_CONTENT_TYPE_APPLICATION_SLASH_GRPC) {
     /* swallow it */
     if (md == GRPC_MDELEM_METHOD_POST) {
       calld->seen_method = 1;
       *calld->recv_idempotent_request = false;
+      *calld->recv_cacheable_request = false;
     } else if (md == GRPC_MDELEM_METHOD_PUT) {
       calld->seen_method = 1;
       *calld->recv_idempotent_request = true;
+    } else if (md == GRPC_MDELEM_METHOD_GET) {
+      calld->seen_method = 1;
+      *calld->recv_cacheable_request = true;
     } else if (md->key == GRPC_MDSTR_SCHEME) {
       calld->seen_scheme = 1;
     } else if (md == GRPC_MDELEM_TE_TRAILERS) {
@@ -137,6 +156,16 @@
         GRPC_MDSTR_AUTHORITY, GRPC_MDSTR_REF(md->value));
     calld->seen_authority = 1;
     return authority;
+  } else if (md->key == GRPC_MDSTR_GRPC_PAYLOAD_BIN) {
+    /* Retrieve the payload from the value of the 'grpc-internal-payload-bin'
+       header field */
+    calld->seen_payload_bin = 1;
+    gpr_slice_buffer_init(&calld->read_slice_buffer);
+    gpr_slice_buffer_add(&calld->read_slice_buffer,
+                         gpr_slice_ref(md->value->slice));
+    grpc_slice_buffer_stream_init(&calld->read_stream,
+                                  &calld->read_slice_buffer, 0);
+    return NULL;
   } else {
     return md;
   }
@@ -189,6 +218,36 @@
   GRPC_ERROR_UNREF(err);
 }
 
+static void hs_on_complete(grpc_exec_ctx *exec_ctx, void *user_data,
+                           grpc_error *err) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+  /* Call recv_message_ready if we got the payload via the header field */
+  if (calld->seen_payload_bin && calld->recv_message_ready != NULL) {
+    *calld->pp_recv_message = calld->payload_bin_delivered
+                                  ? NULL
+                                  : (grpc_byte_stream *)&calld->read_stream;
+    calld->recv_message_ready->cb(exec_ctx, calld->recv_message_ready->cb_arg,
+                                  err);
+    calld->recv_message_ready = NULL;
+    calld->payload_bin_delivered = true;
+  }
+  calld->on_complete->cb(exec_ctx, calld->on_complete->cb_arg, err);
+}
+
+static void hs_recv_message_ready(grpc_exec_ctx *exec_ctx, void *user_data,
+                                  grpc_error *err) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+  if (calld->seen_payload_bin) {
+    /* do nothing. This is probably a GET request, and payload will be returned
+    in hs_on_complete callback. */
+  } else {
+    calld->recv_message_ready->cb(exec_ctx, calld->recv_message_ready->cb_arg,
+                                  err);
+  }
+}
+
 static void hs_mutate_op(grpc_call_element *elem,
                          grpc_transport_stream_op *op) {
   /* grab pointers to our data from the call element */
@@ -206,11 +265,25 @@
   if (op->recv_initial_metadata) {
     /* substitute our callback for the higher callback */
     GPR_ASSERT(op->recv_idempotent_request != NULL);
+    GPR_ASSERT(op->recv_cacheable_request != NULL);
     calld->recv_initial_metadata = op->recv_initial_metadata;
     calld->recv_idempotent_request = op->recv_idempotent_request;
+    calld->recv_cacheable_request = op->recv_cacheable_request;
     calld->on_done_recv = op->recv_initial_metadata_ready;
     op->recv_initial_metadata_ready = &calld->hs_on_recv;
   }
+
+  if (op->recv_message) {
+    calld->recv_message_ready = op->recv_message_ready;
+    calld->pp_recv_message = op->recv_message;
+    if (op->recv_message_ready) {
+      op->recv_message_ready = &calld->hs_recv_message_ready;
+    }
+    if (op->on_complete) {
+      calld->on_complete = op->on_complete;
+      op->on_complete = &calld->hs_on_complete;
+    }
+  }
 }
 
 static void hs_start_transport_op(grpc_exec_ctx *exec_ctx,
@@ -232,6 +305,8 @@
   /* initialize members */
   memset(calld, 0, sizeof(*calld));
   grpc_closure_init(&calld->hs_on_recv, hs_on_recv, elem);
+  grpc_closure_init(&calld->hs_on_complete, hs_on_complete, elem);
+  grpc_closure_init(&calld->hs_recv_message_ready, hs_recv_message_ready, elem);
   return GRPC_ERROR_NONE;
 }
 
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 64afcec..55e6d99 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -149,6 +149,7 @@
 
   grpc_metadata_batch *recv_initial_metadata;
   bool recv_idempotent_request;
+  bool recv_cacheable_request;
   grpc_metadata_array initial_metadata;
 
   request_matcher *request_matcher;
@@ -497,9 +498,12 @@
             &rc->data.batch.details->method_capacity, calld->path);
       rc->data.batch.details->deadline = calld->deadline;
       rc->data.batch.details->flags =
-          0 | (calld->recv_idempotent_request
-                   ? GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST
-                   : 0);
+          (calld->recv_idempotent_request
+               ? GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST
+               : 0) |
+          (calld->recv_cacheable_request
+               ? GRPC_INITIAL_METADATA_CACHEABLE_REQUEST
+               : 0);
       break;
     case REGISTERED_CALL:
       *rc->data.registered.deadline = calld->deadline;
@@ -779,6 +783,7 @@
     calld->on_done_recv_initial_metadata = op->recv_initial_metadata_ready;
     op->recv_initial_metadata_ready = &calld->server_on_recv_initial_metadata;
     op->recv_idempotent_request = &calld->recv_idempotent_request;
+    op->recv_cacheable_request = &calld->recv_cacheable_request;
   }
 }
 
diff --git a/src/core/lib/transport/static_metadata.c b/src/core/lib/transport/static_metadata.c
index 8f3e5b5..fce591f 100644
--- a/src/core/lib/transport/static_metadata.c
+++ b/src/core/lib/transport/static_metadata.c
@@ -51,15 +51,15 @@
     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
 
 const uint8_t grpc_static_metadata_elem_indices[GRPC_STATIC_MDELEM_COUNT * 2] =
-    {11, 33, 10, 33, 12, 33, 12, 49, 13, 33, 14, 33, 15, 33, 16, 33, 17, 33,
+    {11, 33, 10, 33, 12, 33, 12, 50, 13, 33, 14, 33, 15, 33, 16, 33, 17, 33,
      19, 33, 20, 33, 21, 33, 22, 33, 23, 33, 24, 33, 25, 33, 26, 33, 27, 33,
      28, 18, 28, 33, 29, 33, 30, 33, 34, 33, 35, 33, 36, 33, 37, 33, 40, 31,
-     40, 32, 40, 48, 40, 53, 40, 54, 40, 55, 40, 56, 42, 31, 42, 48, 42, 53,
-     45, 0,  45, 1,  45, 2,  50, 33, 57, 33, 58, 33, 59, 33, 60, 33, 61, 33,
-     62, 33, 63, 33, 64, 33, 65, 33, 66, 33, 67, 33, 68, 38, 68, 70, 68, 73,
-     69, 81, 69, 82, 71, 33, 72, 33, 74, 33, 75, 33, 76, 33, 77, 33, 78, 39,
-     78, 51, 78, 52, 79, 33, 80, 33, 83, 3,  83, 4,  83, 5,  83, 6,  83, 7,
-     83, 8,  83, 9,  84, 33, 85, 86, 87, 33, 88, 33, 89, 33, 90, 33, 91, 33};
+     40, 32, 40, 49, 40, 54, 40, 55, 40, 56, 40, 57, 42, 31, 42, 49, 42, 54,
+     46, 0,  46, 1,  46, 2,  51, 33, 58, 33, 59, 33, 60, 33, 61, 33, 62, 33,
+     63, 33, 64, 33, 65, 33, 66, 33, 67, 33, 68, 33, 69, 38, 69, 71, 69, 74,
+     70, 82, 70, 83, 72, 33, 73, 33, 75, 33, 76, 33, 77, 33, 78, 33, 79, 39,
+     79, 52, 79, 53, 80, 33, 81, 33, 84, 3,  84, 4,  84, 5,  84, 6,  84, 7,
+     84, 8,  84, 9,  85, 33, 86, 87, 88, 33, 89, 33, 90, 33, 91, 33, 92, 33};
 
 const char *const grpc_static_metadata_strings[GRPC_STATIC_MDSTR_COUNT] = {
     "0",
@@ -107,6 +107,7 @@
     "grpc-encoding",
     "grpc-internal-encoding-request",
     "grpc-message",
+    "grpc-payload-bin",
     "grpc-status",
     "grpc-timeout",
     "grpc-tracing-bin",
diff --git a/src/core/lib/transport/static_metadata.h b/src/core/lib/transport/static_metadata.h
index b51baca..54b6f38 100644
--- a/src/core/lib/transport/static_metadata.h
+++ b/src/core/lib/transport/static_metadata.h
@@ -44,7 +44,7 @@
 
 #include "src/core/lib/transport/metadata.h"
 
-#define GRPC_STATIC_MDSTR_COUNT 92
+#define GRPC_STATIC_MDSTR_COUNT 93
 extern grpc_mdstr grpc_static_mdstr_table[GRPC_STATIC_MDSTR_COUNT];
 /* "0" */
 #define GRPC_MDSTR_0 (&grpc_static_mdstr_table[0])
@@ -136,101 +136,103 @@
 #define GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST (&grpc_static_mdstr_table[43])
 /* "grpc-message" */
 #define GRPC_MDSTR_GRPC_MESSAGE (&grpc_static_mdstr_table[44])
+/* "grpc-payload-bin" */
+#define GRPC_MDSTR_GRPC_PAYLOAD_BIN (&grpc_static_mdstr_table[45])
 /* "grpc-status" */
-#define GRPC_MDSTR_GRPC_STATUS (&grpc_static_mdstr_table[45])
+#define GRPC_MDSTR_GRPC_STATUS (&grpc_static_mdstr_table[46])
 /* "grpc-timeout" */
-#define GRPC_MDSTR_GRPC_TIMEOUT (&grpc_static_mdstr_table[46])
+#define GRPC_MDSTR_GRPC_TIMEOUT (&grpc_static_mdstr_table[47])
 /* "grpc-tracing-bin" */
-#define GRPC_MDSTR_GRPC_TRACING_BIN (&grpc_static_mdstr_table[47])
+#define GRPC_MDSTR_GRPC_TRACING_BIN (&grpc_static_mdstr_table[48])
 /* "gzip" */
-#define GRPC_MDSTR_GZIP (&grpc_static_mdstr_table[48])
+#define GRPC_MDSTR_GZIP (&grpc_static_mdstr_table[49])
 /* "gzip, deflate" */
-#define GRPC_MDSTR_GZIP_COMMA_DEFLATE (&grpc_static_mdstr_table[49])
+#define GRPC_MDSTR_GZIP_COMMA_DEFLATE (&grpc_static_mdstr_table[50])
 /* "host" */
-#define GRPC_MDSTR_HOST (&grpc_static_mdstr_table[50])
+#define GRPC_MDSTR_HOST (&grpc_static_mdstr_table[51])
 /* "http" */
-#define GRPC_MDSTR_HTTP (&grpc_static_mdstr_table[51])
+#define GRPC_MDSTR_HTTP (&grpc_static_mdstr_table[52])
 /* "https" */
-#define GRPC_MDSTR_HTTPS (&grpc_static_mdstr_table[52])
+#define GRPC_MDSTR_HTTPS (&grpc_static_mdstr_table[53])
 /* "identity" */
-#define GRPC_MDSTR_IDENTITY (&grpc_static_mdstr_table[53])
+#define GRPC_MDSTR_IDENTITY (&grpc_static_mdstr_table[54])
 /* "identity,deflate" */
-#define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE (&grpc_static_mdstr_table[54])
+#define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE (&grpc_static_mdstr_table[55])
 /* "identity,deflate,gzip" */
 #define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE_COMMA_GZIP \
-  (&grpc_static_mdstr_table[55])
+  (&grpc_static_mdstr_table[56])
 /* "identity,gzip" */
-#define GRPC_MDSTR_IDENTITY_COMMA_GZIP (&grpc_static_mdstr_table[56])
+#define GRPC_MDSTR_IDENTITY_COMMA_GZIP (&grpc_static_mdstr_table[57])
 /* "if-match" */
-#define GRPC_MDSTR_IF_MATCH (&grpc_static_mdstr_table[57])
+#define GRPC_MDSTR_IF_MATCH (&grpc_static_mdstr_table[58])
 /* "if-modified-since" */
-#define GRPC_MDSTR_IF_MODIFIED_SINCE (&grpc_static_mdstr_table[58])
+#define GRPC_MDSTR_IF_MODIFIED_SINCE (&grpc_static_mdstr_table[59])
 /* "if-none-match" */
-#define GRPC_MDSTR_IF_NONE_MATCH (&grpc_static_mdstr_table[59])
+#define GRPC_MDSTR_IF_NONE_MATCH (&grpc_static_mdstr_table[60])
 /* "if-range" */
-#define GRPC_MDSTR_IF_RANGE (&grpc_static_mdstr_table[60])
+#define GRPC_MDSTR_IF_RANGE (&grpc_static_mdstr_table[61])
 /* "if-unmodified-since" */
-#define GRPC_MDSTR_IF_UNMODIFIED_SINCE (&grpc_static_mdstr_table[61])
+#define GRPC_MDSTR_IF_UNMODIFIED_SINCE (&grpc_static_mdstr_table[62])
 /* "last-modified" */
-#define GRPC_MDSTR_LAST_MODIFIED (&grpc_static_mdstr_table[62])
+#define GRPC_MDSTR_LAST_MODIFIED (&grpc_static_mdstr_table[63])
 /* "link" */
-#define GRPC_MDSTR_LINK (&grpc_static_mdstr_table[63])
+#define GRPC_MDSTR_LINK (&grpc_static_mdstr_table[64])
 /* "load-reporting-initial" */
-#define GRPC_MDSTR_LOAD_REPORTING_INITIAL (&grpc_static_mdstr_table[64])
+#define GRPC_MDSTR_LOAD_REPORTING_INITIAL (&grpc_static_mdstr_table[65])
 /* "load-reporting-trailing" */
-#define GRPC_MDSTR_LOAD_REPORTING_TRAILING (&grpc_static_mdstr_table[65])
+#define GRPC_MDSTR_LOAD_REPORTING_TRAILING (&grpc_static_mdstr_table[66])
 /* "location" */
-#define GRPC_MDSTR_LOCATION (&grpc_static_mdstr_table[66])
+#define GRPC_MDSTR_LOCATION (&grpc_static_mdstr_table[67])
 /* "max-forwards" */
-#define GRPC_MDSTR_MAX_FORWARDS (&grpc_static_mdstr_table[67])
+#define GRPC_MDSTR_MAX_FORWARDS (&grpc_static_mdstr_table[68])
 /* ":method" */
-#define GRPC_MDSTR_METHOD (&grpc_static_mdstr_table[68])
+#define GRPC_MDSTR_METHOD (&grpc_static_mdstr_table[69])
 /* ":path" */
-#define GRPC_MDSTR_PATH (&grpc_static_mdstr_table[69])
+#define GRPC_MDSTR_PATH (&grpc_static_mdstr_table[70])
 /* "POST" */
-#define GRPC_MDSTR_POST (&grpc_static_mdstr_table[70])
+#define GRPC_MDSTR_POST (&grpc_static_mdstr_table[71])
 /* "proxy-authenticate" */
-#define GRPC_MDSTR_PROXY_AUTHENTICATE (&grpc_static_mdstr_table[71])
+#define GRPC_MDSTR_PROXY_AUTHENTICATE (&grpc_static_mdstr_table[72])
 /* "proxy-authorization" */
-#define GRPC_MDSTR_PROXY_AUTHORIZATION (&grpc_static_mdstr_table[72])
+#define GRPC_MDSTR_PROXY_AUTHORIZATION (&grpc_static_mdstr_table[73])
 /* "PUT" */
-#define GRPC_MDSTR_PUT (&grpc_static_mdstr_table[73])
+#define GRPC_MDSTR_PUT (&grpc_static_mdstr_table[74])
 /* "range" */
-#define GRPC_MDSTR_RANGE (&grpc_static_mdstr_table[74])
+#define GRPC_MDSTR_RANGE (&grpc_static_mdstr_table[75])
 /* "referer" */
-#define GRPC_MDSTR_REFERER (&grpc_static_mdstr_table[75])
+#define GRPC_MDSTR_REFERER (&grpc_static_mdstr_table[76])
 /* "refresh" */
-#define GRPC_MDSTR_REFRESH (&grpc_static_mdstr_table[76])
+#define GRPC_MDSTR_REFRESH (&grpc_static_mdstr_table[77])
 /* "retry-after" */
-#define GRPC_MDSTR_RETRY_AFTER (&grpc_static_mdstr_table[77])
+#define GRPC_MDSTR_RETRY_AFTER (&grpc_static_mdstr_table[78])
 /* ":scheme" */
-#define GRPC_MDSTR_SCHEME (&grpc_static_mdstr_table[78])
+#define GRPC_MDSTR_SCHEME (&grpc_static_mdstr_table[79])
 /* "server" */
-#define GRPC_MDSTR_SERVER (&grpc_static_mdstr_table[79])
+#define GRPC_MDSTR_SERVER (&grpc_static_mdstr_table[80])
 /* "set-cookie" */
-#define GRPC_MDSTR_SET_COOKIE (&grpc_static_mdstr_table[80])
+#define GRPC_MDSTR_SET_COOKIE (&grpc_static_mdstr_table[81])
 /* "/" */
-#define GRPC_MDSTR_SLASH (&grpc_static_mdstr_table[81])
+#define GRPC_MDSTR_SLASH (&grpc_static_mdstr_table[82])
 /* "/index.html" */
-#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (&grpc_static_mdstr_table[82])
+#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (&grpc_static_mdstr_table[83])
 /* ":status" */
-#define GRPC_MDSTR_STATUS (&grpc_static_mdstr_table[83])
+#define GRPC_MDSTR_STATUS (&grpc_static_mdstr_table[84])
 /* "strict-transport-security" */
-#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (&grpc_static_mdstr_table[84])
+#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (&grpc_static_mdstr_table[85])
 /* "te" */
-#define GRPC_MDSTR_TE (&grpc_static_mdstr_table[85])
+#define GRPC_MDSTR_TE (&grpc_static_mdstr_table[86])
 /* "trailers" */
-#define GRPC_MDSTR_TRAILERS (&grpc_static_mdstr_table[86])
+#define GRPC_MDSTR_TRAILERS (&grpc_static_mdstr_table[87])
 /* "transfer-encoding" */
-#define GRPC_MDSTR_TRANSFER_ENCODING (&grpc_static_mdstr_table[87])
+#define GRPC_MDSTR_TRANSFER_ENCODING (&grpc_static_mdstr_table[88])
 /* "user-agent" */
-#define GRPC_MDSTR_USER_AGENT (&grpc_static_mdstr_table[88])
+#define GRPC_MDSTR_USER_AGENT (&grpc_static_mdstr_table[89])
 /* "vary" */
-#define GRPC_MDSTR_VARY (&grpc_static_mdstr_table[89])
+#define GRPC_MDSTR_VARY (&grpc_static_mdstr_table[90])
 /* "via" */
-#define GRPC_MDSTR_VIA (&grpc_static_mdstr_table[90])
+#define GRPC_MDSTR_VIA (&grpc_static_mdstr_table[91])
 /* "www-authenticate" */
-#define GRPC_MDSTR_WWW_AUTHENTICATE (&grpc_static_mdstr_table[91])
+#define GRPC_MDSTR_WWW_AUTHENTICATE (&grpc_static_mdstr_table[92])
 
 #define GRPC_STATIC_MDELEM_COUNT 81
 extern grpc_mdelem grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index 1705e6e..26ed6cb 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -124,6 +124,7 @@
   /** Receive initial metadata from the stream, into provided metadata batch. */
   grpc_metadata_batch *recv_initial_metadata;
   bool *recv_idempotent_request;
+  bool *recv_cacheable_request;
   /** Should be enqueued when initial metadata is ready to be processed. */
   grpc_closure *recv_initial_metadata_ready;
 
diff --git a/src/cpp/server/server_builder.cc b/src/cpp/server/server_builder.cc
index 45bb858..87a526f 100644
--- a/src/cpp/server/server_builder.cc
+++ b/src/cpp/server/server_builder.cc
@@ -35,10 +35,9 @@
 
 #include <grpc++/impl/service_type.h>
 #include <grpc++/server.h>
-#include <grpc/support/cpu.h>
 #include <grpc/support/log.h>
+#include <grpc/support/useful.h>
 
-#include "include/grpc/support/useful.h"
 #include "src/cpp/server/thread_pool_interface.h"
 
 namespace grpc {
diff --git a/src/php/lib/Grpc/AbstractCall.php b/src/php/lib/Grpc/AbstractCall.php
index c86d298..c58ee56 100644
--- a/src/php/lib/Grpc/AbstractCall.php
+++ b/src/php/lib/Grpc/AbstractCall.php
@@ -34,8 +34,15 @@
 
 namespace Grpc;
 
+/**
+ * Class AbstractCall
+ * @package Grpc
+ */
 abstract class AbstractCall
 {
+    /**
+     * @var Call
+     */
     protected $call;
     protected $deserialize;
     protected $metadata;
@@ -51,13 +58,15 @@
      *                              the response
      * @param array    $options     Call options (optional)
      */
-    public function __construct(Channel $channel,
-                                $method,
-                                $deserialize,
-                                $options = [])
-    {
-        if (isset($options['timeout']) &&
-            is_numeric($timeout = $options['timeout'])) {
+    public function __construct(
+        Channel $channel,
+        $method,
+        $deserialize,
+        $options = []
+    ) {
+        if (array_key_exists('timeout', $options) &&
+            is_numeric($timeout = $options['timeout'])
+        ) {
             $now = Timeval::now();
             $delta = new Timeval($timeout);
             $deadline = $now->add($delta);
@@ -68,17 +77,19 @@
         $this->deserialize = $deserialize;
         $this->metadata = null;
         $this->trailing_metadata = null;
-        if (isset($options['call_credentials_callback']) &&
+        if (array_key_exists('call_credentials_callback', $options) &&
             is_callable($call_credentials_callback =
-                        $options['call_credentials_callback'])) {
+                $options['call_credentials_callback'])
+        ) {
             $call_credentials = CallCredentials::createFromPlugin(
-                $call_credentials_callback);
+                $call_credentials_callback
+            );
             $this->call->setCredentials($call_credentials);
         }
     }
 
     /**
-     * @return The metadata sent by the server.
+     * @return mixed The metadata sent by the server.
      */
     public function getMetadata()
     {
@@ -86,7 +97,7 @@
     }
 
     /**
-     * @return The trailing metadata sent by the server.
+     * @return mixed The trailing metadata sent by the server.
      */
     public function getTrailingMetadata()
     {
@@ -114,7 +125,7 @@
      *
      * @param string $value The binary value to deserialize
      *
-     * @return The deserialized value
+     * @return mixed The deserialized value
      */
     protected function deserializeResponse($value)
     {
diff --git a/src/php/lib/Grpc/BidiStreamingCall.php b/src/php/lib/Grpc/BidiStreamingCall.php
index c2fdb94..5d6ecfb 100644
--- a/src/php/lib/Grpc/BidiStreamingCall.php
+++ b/src/php/lib/Grpc/BidiStreamingCall.php
@@ -45,7 +45,7 @@
      *
      * @param array $metadata Metadata to send with the call, if applicable
      */
-    public function start($metadata = [])
+    public function start(array $metadata = [])
     {
         $this->call->startBatch([
             OP_SEND_INITIAL_METADATA => $metadata,
@@ -55,7 +55,7 @@
     /**
      * Reads the next value from the server.
      *
-     * @return The next value from the server, or null if there is none
+     * @return mixed The next value from the server, or null if there is none
      */
     public function read()
     {
@@ -82,7 +82,7 @@
     public function write($data, $options = [])
     {
         $message_array = ['message' => $data->serialize()];
-        if (isset($options['flags'])) {
+        if (array_key_exists('flags', $options)) {
             $message_array['flags'] = $options['flags'];
         }
         $this->call->startBatch([
@@ -103,8 +103,8 @@
     /**
      * Wait for the server to send the status, and return it.
      *
-     * @return object The status object, with integer $code, string $details,
-     *                and array $metadata members
+     * @return \stdClass The status object, with integer $code, string $details,
+     *                   and array $metadata members
      */
     public function getStatus()
     {
diff --git a/src/php/lib/Grpc/ClientStreamingCall.php b/src/php/lib/Grpc/ClientStreamingCall.php
index 4050f7e..c96e26d 100644
--- a/src/php/lib/Grpc/ClientStreamingCall.php
+++ b/src/php/lib/Grpc/ClientStreamingCall.php
@@ -60,10 +60,10 @@
      * @param array      $options an array of options, possible keys:
      *                            'flags' => a number
      */
-    public function write($data, $options = [])
+    public function write($data, array $options = [])
     {
         $message_array = ['message' => $data->serialize()];
-        if (isset($options['flags'])) {
+        if (array_key_exists('flags', $options)) {
             $message_array['flags'] = $options['flags'];
         }
         $this->call->startBatch([
@@ -74,7 +74,7 @@
     /**
      * Wait for the server to respond with data and a status.
      *
-     * @return [response data, status]
+     * @return array [response data, status]
      */
     public function wait()
     {
diff --git a/src/php/lib/Grpc/ServerStreamingCall.php b/src/php/lib/Grpc/ServerStreamingCall.php
index ba89d9f..5f0d42c 100644
--- a/src/php/lib/Grpc/ServerStreamingCall.php
+++ b/src/php/lib/Grpc/ServerStreamingCall.php
@@ -36,14 +36,14 @@
 
 /**
  * Represents an active call that sends a single message and then gets a stream
- * of reponses.
+ * of responses.
  */
 class ServerStreamingCall extends AbstractCall
 {
     /**
      * Start the call.
      *
-     * @param $data The data to send
+     * @param mixed $data     The data to send
      * @param array $metadata Metadata to send with the call, if applicable
      * @param array $options  an array of options, possible keys:
      *                        'flags' => a number
@@ -51,7 +51,7 @@
     public function start($data, $metadata = [], $options = [])
     {
         $message_array = ['message' => $data->serialize()];
-        if (isset($options['flags'])) {
+        if (array_key_exists('flags', $options)) {
             $message_array['flags'] = $options['flags'];
         }
         $event = $this->call->startBatch([
@@ -64,7 +64,7 @@
     }
 
     /**
-     * @return An iterator of response values
+     * @return mixed An iterator of response values
      */
     public function responses()
     {
@@ -82,8 +82,8 @@
     /**
      * Wait for the server to send the status, and return it.
      *
-     * @return object The status object, with integer $code, string $details,
-     *                and array $metadata members
+     * @return \stdClass The status object, with integer $code, string $details,
+     *                   and array $metadata members
      */
     public function getStatus()
     {
diff --git a/src/php/lib/Grpc/UnaryCall.php b/src/php/lib/Grpc/UnaryCall.php
index a71b05d..487b89e 100644
--- a/src/php/lib/Grpc/UnaryCall.php
+++ b/src/php/lib/Grpc/UnaryCall.php
@@ -43,7 +43,7 @@
     /**
      * Start the call.
      *
-     * @param $data The data to send
+     * @param mixed $data     The data to send
      * @param array $metadata Metadata to send with the call, if applicable
      * @param array $options  an array of options, possible keys:
      *                        'flags' => a number
@@ -66,7 +66,7 @@
     /**
      * Wait for the server to respond with data and a status.
      *
-     * @return [response data, status]
+     * @return array [response data, status]
      */
     public function wait()
     {
diff --git a/src/proto/census/trace_context.options b/src/proto/census/trace_context.options
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/proto/census/trace_context.options
diff --git a/src/proto/census/trace_context.proto b/src/proto/census/trace_context.proto
new file mode 100644
index 0000000..a5d5a95
--- /dev/null
+++ b/src/proto/census/trace_context.proto
@@ -0,0 +1,48 @@
+// 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.
+
+syntax = "proto3";
+
+package google.trace;
+
+// A TraceId uniquely represents a single Trace. It is a 128-bit nonce.
+message TraceId {
+  fixed64 hi = 1;
+  fixed64 lo = 2;
+}
+
+// Tracing information that is propagated with RPC's.
+message TraceContext {
+  // Trace identifer. Must be present.
+  TraceId trace_id = 1;
+  // ID of parent (client) span. Must be present.
+  fixed64 span_id = 2;
+  // true if this trace is sampled.
+  bool is_sampled = 3;
+}
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 660e34d..c3db2f9 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -255,6 +255,7 @@
   'src/core/ext/census/base_resources.c',
   'src/core/ext/census/context.c',
   'src/core/ext/census/gen/census.pb.c',
+  'src/core/ext/census/gen/trace_context.pb.c',
   'src/core/ext/census/grpc_context.c',
   'src/core/ext/census/grpc_filter.c',
   'src/core/ext/census/grpc_plugin.c',
diff --git a/test/core/end2end/fuzzers/hpack.dictionary b/test/core/end2end/fuzzers/hpack.dictionary
index 3157dfc..e5a73d5 100644
--- a/test/core/end2end/fuzzers/hpack.dictionary
+++ b/test/core/end2end/fuzzers/hpack.dictionary
@@ -44,6 +44,7 @@
 "\x0Dgrpc-encoding"
 "\x1Egrpc-internal-encoding-request"
 "\x0Cgrpc-message"
+"\x10grpc-payload-bin"
 "\x0Bgrpc-status"
 "\x0Cgrpc-timeout"
 "\x10grpc-tracing-bin"
diff --git a/tools/codegen/core/gen_static_metadata.py b/tools/codegen/core/gen_static_metadata.py
index 859adcb..2a16baa 100755
--- a/tools/codegen/core/gen_static_metadata.py
+++ b/tools/codegen/core/gen_static_metadata.py
@@ -42,6 +42,7 @@
 CONFIG = [
     'grpc-timeout',
     'grpc-internal-encoding-request',
+    'grpc-payload-bin',
     ':path',
     'grpc-encoding',
     'grpc-accept-encoding',
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index 77f951a..cc07b93 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -945,6 +945,7 @@
 src/core/ext/census/census_interface.h \
 src/core/ext/census/census_rpc_stats.h \
 src/core/ext/census/gen/census.pb.h \
+src/core/ext/census/gen/trace_context.pb.h \
 src/core/ext/census/grpc_filter.h \
 src/core/ext/census/mlog.h \
 src/core/ext/census/resource.h \
@@ -1129,6 +1130,7 @@
 src/core/ext/census/base_resources.c \
 src/core/ext/census/context.c \
 src/core/ext/census/gen/census.pb.c \
+src/core/ext/census/gen/trace_context.pb.c \
 src/core/ext/census/grpc_context.c \
 src/core/ext/census/grpc_filter.c \
 src/core/ext/census/grpc_plugin.c \
diff --git a/tools/jenkins/run_full_interop.sh b/tools/jenkins/run_full_cloud_prod.sh
old mode 100755
new mode 100644
similarity index 87%
rename from tools/jenkins/run_full_interop.sh
rename to tools/jenkins/run_full_cloud_prod.sh
index a82da1c..ea51b50
--- a/tools/jenkins/run_full_interop.sh
+++ b/tools/jenkins/run_full_cloud_prod.sh
@@ -31,7 +31,14 @@
 # This script is invoked by Jenkins and runs interop test suite.
 set -ex
 
+export LANG=en_US.UTF-8
+
 # Enter the gRPC repo root
 cd $(dirname $0)/../..
 
-tools/run_tests/run_interop_tests.py -l all -s all --cloud_to_prod --cloud_to_prod_auth --prod_servers default cloud_gateway gateway_v2 cloud_gateway_v2 gateway_v4 cloud_gateway_v4 --use_docker --http2_interop -t -j 12 $@ || true
+tools/run_tests/run_interop_tests.py \
+    -l all \
+    --cloud_to_prod \
+    --cloud_to_prod_auth \
+    --prod_servers default cloud_gateway gateway_v4 cloud_gateway_v4 \
+    --use_docker -t -j 12 $@ || true
diff --git a/tools/run_tests/run_interop_tests.py b/tools/run_tests/run_interop_tests.py
index 0d402d6..5feda65 100755
--- a/tools/run_tests/run_interop_tests.py
+++ b/tools/run_tests/run_interop_tests.py
@@ -623,15 +623,15 @@
 # TODO(adelez): implement logic for errors_allowed where if the indicated tests
 # fail, they don't impact the overall test result.
 prod_servers = {
-    'default': ('grpc-test.sandbox.googleapis.com',
+    'default': ('216.239.32.254',
                 'grpc-test.sandbox.googleapis.com', False),
-    'gateway_v2': ('grpc-test2.sandbox.googleapis.com',
+    'gateway_v2': ('216.239.32.254',
                    'grpc-test2.sandbox.googleapis.com', True),
     'cloud_gateway': ('216.239.32.255', 'grpc-test.sandbox.googleapis.com',
                       False),
     'cloud_gateway_v2': ('216.239.32.255', 'grpc-test2.sandbox.googleapis.com',
                          True),
-    'gateway_v4': ('grpc-test4.sandbox.googleapis.com',
+    'gateway_v4': ('216.239.32.254',
                    'grpc-test4.sandbox.googleapis.com', True),
     'cloud_gateway_v4': ('216.239.32.255', 'grpc-test4.sandbox.googleapis.com',
                          True),
diff --git a/tools/run_tests/sources_and_headers.json b/tools/run_tests/sources_and_headers.json
index 7b91937..dced425 100644
--- a/tools/run_tests/sources_and_headers.json
+++ b/tools/run_tests/sources_and_headers.json
@@ -5597,6 +5597,7 @@
       "src/core/ext/census/census_interface.h", 
       "src/core/ext/census/census_rpc_stats.h", 
       "src/core/ext/census/gen/census.pb.h", 
+      "src/core/ext/census/gen/trace_context.pb.h", 
       "src/core/ext/census/grpc_filter.h", 
       "src/core/ext/census/mlog.h", 
       "src/core/ext/census/resource.h", 
@@ -5614,6 +5615,8 @@
       "src/core/ext/census/context.c", 
       "src/core/ext/census/gen/census.pb.c", 
       "src/core/ext/census/gen/census.pb.h", 
+      "src/core/ext/census/gen/trace_context.pb.c", 
+      "src/core/ext/census/gen/trace_context.pb.h", 
       "src/core/ext/census/grpc_context.c", 
       "src/core/ext/census/grpc_filter.c", 
       "src/core/ext/census/grpc_filter.h", 
diff --git a/vsprojects/vcxproj/grpc/grpc.vcxproj b/vsprojects/vcxproj/grpc/grpc.vcxproj
index d805fdf..6cceb17 100644
--- a/vsprojects/vcxproj/grpc/grpc.vcxproj
+++ b/vsprojects/vcxproj/grpc/grpc.vcxproj
@@ -454,6 +454,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\census_interface.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\census_rpc_stats.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\grpc_filter.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\mlog.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\resource.h" />
@@ -820,6 +821,8 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\grpc_context.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\grpc_filter.c">
diff --git a/vsprojects/vcxproj/grpc/grpc.vcxproj.filters b/vsprojects/vcxproj/grpc/grpc.vcxproj.filters
index 991bbec..16b2ed86 100644
--- a/vsprojects/vcxproj/grpc/grpc.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc/grpc.vcxproj.filters
@@ -541,6 +541,9 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.c">
       <Filter>src\core\ext\census\gen</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.c">
+      <Filter>src\core\ext\census\gen</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\grpc_context.c">
       <Filter>src\core\ext\census</Filter>
     </ClCompile>
@@ -1130,6 +1133,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.h">
       <Filter>src\core\ext\census\gen</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.h">
+      <Filter>src\core\ext\census\gen</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\grpc_filter.h">
       <Filter>src\core\ext\census</Filter>
     </ClInclude>
diff --git a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj
index 66ec41d..0af0497 100644
--- a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj
+++ b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj
@@ -420,6 +420,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\census_interface.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\census_rpc_stats.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\grpc_filter.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\mlog.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\resource.h" />
@@ -728,6 +729,8 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\grpc_context.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\grpc_filter.c">
diff --git a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters
index 6f2dc35..9f8727f 100644
--- a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters
@@ -454,6 +454,9 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.c">
       <Filter>src\core\ext\census\gen</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.c">
+      <Filter>src\core\ext\census\gen</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\ext\census\grpc_context.c">
       <Filter>src\core\ext\census</Filter>
     </ClCompile>
@@ -968,6 +971,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\census.pb.h">
       <Filter>src\core\ext\census\gen</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\gen\trace_context.pb.h">
+      <Filter>src\core\ext\census\gen</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\ext\census\grpc_filter.h">
       <Filter>src\core\ext\census</Filter>
     </ClInclude>