Subject: Re: [Sipping] Expert review for draft-burger-sipping-netann-04.txt

From: William Marshall <[email-masked]>
Date: Fri, 14 Feb 2003 10:41:41 -0500 (EST)

There is one issue in dealing with announcements and announcement
servers that doesn't arise with normal sessions - the timing of the
session termination.

In a normal media session, the media is being generated in real time
and transmitted via RTP to the UAC.  When the source of the media
stops, the session is terminated with a BYE, and the UAC closes
both the signaling and media paths.  While there is potential for
a race, it is not significant.

However, when the media is an announcement, contained likely within
a single (possibly large) file, it is conceivable that the server
will send the (large) RTP packets to the UAC, and then send a BYE
while the UAC has most of the announcement still unplayed.

The basic architectural question is whether it is the responsibility
of the UAC to drain any pending media before closing a session.  I
do not know of any such requirement in RFC3261.  Is it considered
a common implementation practice to do so?

Alternatively, it could be the responsibility of the announcement
server to delay sending the BYE (or 4xx response) based on the 
expected playout time, though it is not clear how that would be
calculated.

One choice or the other needs to be stated, and required, in order
to achieve interoperability.

I also have concerns about the use of 487 to terminate early media
sessions.  This has been raised by others.

Bill Marshall
[email-masked]

-----original message-----
Date: Mon, 10 Feb 2003 12:39:56 +0200
From: Gonzalo Camarillo <[email-masked]>
To: sipping <[email-masked]>
Subject: [Sipping] Expert review for draft-burger-sipping-netann-04.txt

Folks,

We would like the SIPPING working group to provide expert review of:

http://www.ietf.org/internet-drafts/draft-burger-sipping-netann-04.txt

The authors have requested individual publication of this document. 
Expert Review will close on March 10th, 2003

Thanks,

Gonzalo
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---

From: "David R. Oran" <[email-masked]>
Date: Mon, 17 Feb 2003 14:23:15 -0500

> a common implementation practice to do so?
In the real world, don't announcment servers just replay the message over 
and over until the user hangs up? Or, if they don't hang up for a longish 
time, they just time out and send a BYE to conserve resources or avoid the 
"John Clayton memorial PBX bug".

> expected playout time, though it is not clear how that would be
Well, you could be conservative.

> Expert Review will close on March 10th, 2003

------------------------
David R. Oran
Cisco Systems
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Acton, MA 01720
Office: +1 978 264 2048
VoIP: +1 408 571 4576
Email: [email-masked]