diff --git a/src/proto/grpc/testing/messages.proto b/src/proto/grpc/testing/messages.proto
index 70e34277607..689c6217360 100644
--- a/src/proto/grpc/testing/messages.proto
+++ b/src/proto/grpc/testing/messages.proto
@@ -212,3 +212,40 @@ message LoadBalancerStatsResponse {
   int32 num_failures = 2;
   map<string, RpcsByPeer> rpcs_by_method = 3;
 }
+
+// Request for retrieving a test client's accumulated stats.
+message LoadBalancerAccumulatedStatsRequest {}
+
+// Accumulated stats for RPCs sent by a test client.
+message LoadBalancerAccumulatedStatsResponse {
+  // The total number of RPCs have ever issued.
+  int32 num_rpcs_started = 1;
+  // The total number of RPCs have ever completed successfully for each peer.
+  map<string, int32> num_rpcs_succeeded_by_peer = 2;
+  // The total number of RPCs have ever failed.
+  int32 num_rpcs_failed = 3;
+}
+
+// Configurations for a test client.
+message ClientConfigureRequest {
+  // Type of RPCs to send.
+  enum RpcType {
+    EMPTY_CALL = 0;
+    UNARY_CALL = 1;
+  }
+
+  // Metadata to be attached for the given type of RPCs.
+  message Metadata {
+    RpcType type = 1;
+    string key = 2;
+    string value = 3;
+  }
+
+  // The types of RPCs the client sends.
+  repeated RpcType types = 1;
+  // The collection of custom metadata to be attached to RPCs sent by the client.
+  repeated Metadata metadata = 2;
+}
+
+// Response for updating a test client's configuration.
+message ClientConfigureResponse {}
diff --git a/src/proto/grpc/testing/test.proto b/src/proto/grpc/testing/test.proto
index 1da43f48989..5805a41da99 100644
--- a/src/proto/grpc/testing/test.proto
+++ b/src/proto/grpc/testing/test.proto
@@ -83,6 +83,10 @@ service LoadBalancerStatsService {
   // Gets the backend distribution for RPCs sent by a test client.
   rpc GetClientStats(LoadBalancerStatsRequest)
       returns (LoadBalancerStatsResponse) {}
+
+  // Gets the accumulated stats for RPCs sent by a test client.
+  rpc GetClientAccumulatedStats(LoadBalancerAccumulatedStatsRequest)
+      returns (LoadBalancerAccumulatedStatsResponse) {}
 }
 
 // A service to remotely control health status of an xDS test server.
@@ -90,3 +94,9 @@ service XdsUpdateHealthService {
   rpc SetServing(grpc.testing.Empty) returns (grpc.testing.Empty);
   rpc SetNotServing(grpc.testing.Empty) returns (grpc.testing.Empty);
 }
+
+// A service to dynamically update the configuration of an xDS test client.
+service XdsUpdateClientConfigureService {
+  // Update the tes client's configuration.
+  rpc Configure(ClientConfigureRequest) returns (ClientConfigureResponse);
+}