diff --git a/shared/protos/tunnelbroker.proto b/shared/protos/tunnelbroker.proto
index 40c023407..19df906d8 100644
--- a/shared/protos/tunnelbroker.proto
+++ b/shared/protos/tunnelbroker.proto
@@ -1,168 +1,169 @@
 syntax = "proto3";
 
 package tunnelbroker;
 
 import "google/protobuf/empty.proto";
 
 service TunnelbrokerService {
 
   // The old API service methods
   // to support the native client build
   // until we switch to the new one
   
   rpc CheckIfPrimaryDeviceOnline(CheckRequest) returns (CheckResponse) {}
   rpc BecomeNewPrimaryDevice(NewPrimaryRequest) returns (NewPrimaryResponse) {}
   rpc SendPong (PongRequest) returns (google.protobuf.Empty) {}
 
   // New API service methods
 
   rpc SessionSignature(SessionSignatureRequest) returns (SessionSignatureResponse) {}
   rpc NewSession(NewSessionRequest) returns (NewSessionResponse) {}
   rpc Send(SendRequest) returns (google.protobuf.Empty) {}
   rpc Get(GetRequest) returns (stream GetResponse) {}
 
   // Replacing Send and Get with a single bidirectional streaming RPC
+  // The client should provide the valid `sessionID` identifier 
+  // from the `NewSession` in the stream request metadata
   rpc MessagesStream(stream MessageToTunnelbroker) returns (stream MessageToClient) {}
 }
 
 // Session
 
 message SessionSignatureRequest {
   string deviceID = 1;
 }
 
 message SessionSignatureResponse {
   string toSign = 1;
 }
 
 message NewSessionRequest {
   string deviceID = 1;
   string publicKey = 2;
   string signature = 3;
   optional string notifyToken = 4;
   DeviceTypes deviceType = 5;
   string deviceAppVersion = 6;
   string deviceOS = 7;
   // Nested enum devices type
   enum DeviceTypes {
     MOBILE = 0;
     WEB = 1;
     KEYSERVER = 2;
   }
 }
 
 message NewSessionResponse {
   string sessionID = 1;
 }
 
 // Send payload to device
 
 message SendRequest {
   string sessionID = 1;
   string toDeviceID = 2;
   bytes payload = 3;
   repeated string blobHashes = 4;
 }
 
 // Get messages from devices
 
 message GetRequest {
   string sessionID = 1;
   optional string newNotifyToken = 2;
 }
 
 message GetResponseMessage {
   string fromDeviceID = 1;
   bytes payload = 2;
   repeated string blobHashes = 3;
 }
 
 message GetResponse {
   oneof data {
     GetResponseMessage responseMessage = 1;
     google.protobuf.Empty ping = 2;
     google.protobuf.Empty newNotifyTokenRequired = 3;
   }
 }
 
 // Common messages structures for the MessagesStream
 
 message ProcessedMessages {
   repeated string messageID = 1;
 }
 
 // The messages from the Client to the Tunnelbroker
 
 message MessageToTunnelbrokerStruct {
   string messageID = 1;
   string toDeviceID = 2;
   string payload = 3;
   repeated string blobHashes = 4;
 }
 
 message MessagesToSend {
   repeated MessageToTunnelbrokerStruct messages = 1;
 }
 
 message MessageToTunnelbroker {
-  string sessionID = 1;
   oneof data {
-    MessagesToSend messagesToSend = 2;
-    ProcessedMessages processedMessages = 3;
-    string newNotifyToken = 4;
+    MessagesToSend messagesToSend = 1;
+    ProcessedMessages processedMessages = 2;
+    string newNotifyToken = 3;
   }
 }
 
 // The messages from the Tunnelbroker to the Client
 
 message MessageToClientStruct {
   string messageID = 1;
   string fromDeviceID = 2;
   string payload = 3;
   repeated string blobHashes = 4;
 }
 
 message MessagesToDeliver {
   repeated MessageToClientStruct messages = 1;
 }
 
 message MessageToClient {
   oneof data {
     MessagesToDeliver messagesToDeliver = 1;
     ProcessedMessages processedMessages = 2;
     google.protobuf.Empty newNotifyTokenRequired = 3;
     google.protobuf.Empty ping = 4;
   }
 }
 
 // Old API structures
 
 enum CheckResponseType {
   PRIMARY_DOESNT_EXIST = 0;
   PRIMARY_ONLINE = 1;
   PRIMARY_OFFLINE = 2;
   CURRENT_IS_PRIMARY = 3;
 }
 
 message CheckRequest {
   string userId = 1;
   string deviceToken = 2;
 }
 
 message CheckResponse {
   CheckResponseType checkResponseType = 1;
 }
 
 message NewPrimaryRequest {
   string userId = 1;
   string deviceToken = 2;
 }
 
 message NewPrimaryResponse {
   bool success = 1;
 }
 
 message PongRequest {
   string userId = 1;
   string deviceToken = 2;
 }