Index: firmware/App/Services/MsgQueues.h
===================================================================
diff -u -ra303cd4258157a8fbcbd8af4dd2bbaadec1a736c -rf068446fdb7889d320ddb6ffbd58f347ce0501e7
--- firmware/App/Services/MsgQueues.h	(.../MsgQueues.h)	(revision a303cd4258157a8fbcbd8af4dd2bbaadec1a736c)
+++ firmware/App/Services/MsgQueues.h	(.../MsgQueues.h)	(revision f068446fdb7889d320ddb6ffbd58f347ce0501e7)
@@ -21,7 +21,7 @@
 
 // ********** public definitions **********
 
-#define MAX_MSG_CARGO_SIZE          100         // bytes
+#define MAX_MSG_PAYLOAD_SIZE          100         // bytes
 
 typedef enum Msg_Queues
 {
@@ -32,14 +32,17 @@
 #pragma pack(push,1)
 typedef struct
 {
+#ifndef ACK_NOT_IMPLEMENTED
+    S16 seqNo;                                  // sequence # (and ACK required bit) of message
+#endif
     U16 msgID;                                  // ID of message
-    U08 payloadLen;                               // length of cargo in bytes
+    U08 payloadLen;                             // length of payload in bytes
 } MESSAGE_HEADER_T;
 
 typedef struct
 {
     MESSAGE_HEADER_T hdr;                       // message header
-    U08              payload[MAX_MSG_CARGO_SIZE]; // message cargo
+    U08              payload[ MAX_MSG_PAYLOAD_SIZE ]; // message payload
 } MESSAGE_T;
 
 typedef struct