Subject: [Sip] Some thoughts about sip-reconstitute-state and session timers.

From: "Venkatesh Venkataramanan" <[email-masked]>
Date: Tue, 5 Feb 2002 22:04:14 -0800

Hi,

The sip-reconstitue-state favours failure detection by means of RTCP/RTP
failures by the far end which triggers re-INVITEs that could be used to
reconstruct state by servers that crashed. This model works well for servers
where the media originates from the device that is also generating RTP. More
specifically, this model doesn't help reconstitution of sessions in cases
where applications (such as B2B UA's) enable non-SIP devices to communicate
with SIP end devices, since in this scenario, no RTP/RTCP failures are
detected due to the application crash.

I was wondering if we could enhance sip-session-timer-08.txt to make the UA
that is waiting for 'session refreshes' to send a re-INVITE before it tears
the call down by sending a BYE on session-timer expiry (rather a few seconds
before the expiry). This would assist such applications to reconstitute
state of sessions as well if they persist exactly the same information that
is indicated in the sip-reconstitute-state draft and keep such dialogs
active.

Regards.
Venkatesh

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 08 Feb 2002 00:30:00 -0500

Venkatesh Venkataramanan wrote:

> is indicated in the sip-reconstitute-state draft and keep such dialogs

Well, I don't see anything wrong with doing that per se, but there are
two issues:

1. session-timer has already gone to IESG, so it is a bit late for
addition of features to the draft,

2. Its not clear to me what the scope of applicability of this would be.
Specifically, the amount of time it takes to discover failures with
session timer is really, really long. More than likely if you
application crashed for 20m before that was reconstitiuted by session
timer, its been gone too long to be useful. Session timer is really
meant as a state cleanup mechanism, i.e., a long term garbage collector,
not for failure recovery. The ICMP approach in the reconstitute draft is
very rapid because it uses the media stream.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
Chief Scientist                         First Floor
dynamicsoft                             East Hanover, NJ 07936
[email-masked]                 FAX: (973) 952-5050
http://www.jdrosen.net                  PH:  (973) 952-5000
http://www.dynamicsoft.com