Comment #11 on issue 2 by imo...@gmail.com: GenericAcknowledgmentType http://code.google.com/p/ogf-nsi-project/issues/detail?id=2 This was re-discussed on the Wed. call, with the following results: 1. Message transport layer takes care of ack retransmission in case of a packet loss. 2. Confirm/Fail message responses should be sent out without waiting on the receipt of the message ack. [comment on error recovery: if message transport layer is broken, say unidirectionally, the ack sending will eventually timeout and generate a message transport error that the NSA will need to handle] 3. From the receiving state machine perspective, receiving a confirm/fail message from a particular NSA should cancel out the need to receive an ACK. So the state machine should not only continue to process the confirm/fail message, but not gate on or wait for the ACK message. Hope this resolves this issue