Subject: Zero Window Probe

From: "Vijay Kumar Choudhary" <[email-masked]>
Date: Fri, 7 Mar 2003 10:14:50 +0530 (India Standard Time)

Hi All,
    This mail is regarding the ZERO WINDOW PROBE. In the SCTP Imp guide
version 7 some new text has been added. 
           It says " Note that zero window probe SHOULD only be sent when
all outstanding DATA chunks have been cumulatively acknowledged and no DATA
chunk(s) are in flight."

    I dont understand one thing how is it possible that all the "outstanding
DATA chunks have been cumulatively acknowledged and no DATA chunk(s) are in
flight" and still the peer receiver window is 0. 

     We also update the Peer Receiver Window at the sending side. If all the
outstanding DATA chunks has been acknowledged and there is no data in  the
flight, we set the Peer Receiver Window to the value which we get at the
time of assciation startup.

Regards,
Vijay

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 6 Mar 2003 22:16:13 -0700

Vijay,

> flight" and still the peer receiver window is 0. 

Because the data has not yet been delivered to the ULP (e.g. the ULP had not
requested to read it yet) although it has been acknowledged to the peer.

> time of assciation startup.

That is not correct.  The peer receive window should be set to the value in
the last SACK that acked something, which is not ever necessarily the initial
value (the receive window could have been changed after association startup)
and takes into consideration how much data is buffered on the receiver
(buffered data is subtracted from the window size).  Also, SWS avoidance
should be considered when setting the peer value received in the SACK so that
the sender will not start sending very small fragments to the overall detriment
of the network.

--brian

-- 
Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
[email-masked]    ¦ world; the unreasonable one persists in  ¦
http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
                        ¦ Therefore  all  progress  depends on the ¦
                        ¦ unreasonable man. -- George Bernard Shaw ¦