+
+ If the receiver of a message is a backlevel RMR, and it uses RTS to
+ return a message, it will only update the old size, but when the
+ message is received back at a new RMR application it will appear that
+ the message came from a new instance. Therefore, we must compare
+ the old and new sizes and if they are different we must use the old
+ size assuming that this is the case.