Work on ROS2.

communication.md

@@ -9,7 +9,9 @@ Lossy communication. Protocols to detect and handle.
 Some service calls return a list of com-uuid which can be checked for
 if the message they correspons to arrived properly.
 
-QUERY: Is it one per message or one per message-unit?
+there is one uuid per "data". So one node distributed to 5 agents will
+give on com-uuid.  There is a service call to check that this com-uuid
+have received confirmation from all 5 agents then.
 
 ## DistributeTree