Subject: [Sigtran] More M2PA 7 questions

From: Andrew Booth <[email-masked]>
Date: Thu, 06 Feb 2003 12:31:41 -0500

Hi All,

A few more questions on M2PA draft 7.

1) Does every User Data received from the peer increases the expected FSN
for the subsequent message, even in cases where the received message is 
later
discarded as part of a Flush Buffers or Changeover procedure?

2) Suppose that an M2PA implementation has received messages from a peer
and that some of the messages are buffered at the M2PA layer (perhaps it is
in processor outage).  Suppose now the link transitions to OOS and the
MTP3 sends a Retrieve BSNT to M2PA.

According to 4.2.6,

   "M2PA determines the Forward Sequence Number of the last User Data
   message received from the peer.  This is the BSNT."

In the M2PA situation it seems more appropriate to respond with the FSN
of the last message which was delivered to MTP3.
Am I missing something?

3) How should T7 be handled when remote processor outage abates?  Should 
we immediately check for excessive ack delay, or reset T7 somehow?

4) In section 5.1 we transition to proving without starting T3 and to 
aligned ready without receiving LS Proving.  Are these omissions 
intentional?

5) In section 5.8 there is some introductory text :

"Note that in this example, the sequence numbers and messages requested
by MTP3 are sent from SCTP to M2PA in the Communication Lost
primitive. In general, the retrieval of sequence numbers and messages
is implementation dependent."

Why are messages retrieved from SCTP?  Is this text indicating that the 
M2PA retransmit buffer is implemented in the SCTP?  Just a little confused.

6) In section 4.2.6, is the following correct or should it be rephrased 
in the context of a circular buffer?
"any transmitted User Data messages beginning with the first
       unacknowledged message with FSN greater than FSNC." 

Thanks for any info,
Andrew

-- 
Andrew Booth, Software Developer
Signaling Systems Group, Performance Technologies
613-237-4344

Visit www.pt.com/mailing.html to subscribe to our Packets & Signals eLetter.

_______________________________________________
Sigtran mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/sigtran