Subject: Shutdown-Peer Rwnd

From: "Vijay Kumar Choudhary" <[email-masked]>
Date: Thu, 27 Feb 2003 17:35:45 +0530 (India Standard Time)

Hi All,
   In the SCTP imp guide version 7, the following line is written ...

---------
   New text: (Section 9.2)
   ---------
   If there are still outstanding DATA chunks left, the SHUTDOWN
   receiver shall continue to follow normal data transmission procedures
   defined in Section 6 until all outstanding DATA chunks are acknowledged;
however, the SHUTDOWN receiver MUST NOT accept new data  from its       SCTP
user.

   While in SHUTDOWN-SENT state, the SHUTDOWN sender MUST immediately  
respond to each received packet containing one or more DATA chunk(s)   with
a SHUTDOWN chunk, and restart the T2-shutdown timer. If a
   SHUTDOWN chunk by itself cannot acknowledge all of the received DATA
   chunks (i.e. there are TSN's that can be acknowledged that are larger
   than the cumulative TSN and thus gaps exist in the TSN sequence) or
   if duplicate TSN's have been recieved then a SACK chunk MUST also be sent

From statements it means that, whenever we will receive DATA chunk in 
SHUTDOWN-SENT state, we will reponse with the SHUTDOWN chunk and not with
the SACK chunk.(except in case of gap or duplicate TSN). The SHUTDOWN chunk
will contain the updated cumulative TSN. When the SHUTDOWN chunk will be
received, we need to delete the data from the queue upto the cumulative TSN
and update Flight size and Peer Rwnd.
Since in the SHUTDOWN chunk Peer Rwnd field is not there .... We may end up
with the wrong value of Peer Rwnd. 
   How to calculate the Peer Rwnd in this case ??

Regards,
Vijay

---

From: "Randall Stewart (cisco)" <[email-masked]>
Date: Thu, 27 Feb 2003 08:33:06 -0600

>   How to calculate the Peer Rwnd in this case ??
Vijay:

You MUST respond with a SHUTDOWN.. but I also always bundle a
SACK with the SHUTDOWN... this way it is not a problem...

Another thing to remember is that you are at the end of the
association at this point... I don't think large volumes of data transfer
would be a concern..

R

-- 
Randall R. Stewart
ITD
Cisco Systems Inc.
[email-masked] 815-342-5222(cell) or 815-477-2127(office)