Subject: RE: [SIP] First cut review of Session Timer draft.

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 14 Jun 2001 17:16:48 -0400

> -----Original Message-----
> From: Steve Donovan 
> Sent: Wednesday, May 09, 2001 10:11 AM
> To: 'Adam Roach (EUS)'; Ben Campbell; Steve Donovan; Jonathan 
> Rosenberg
> Cc: Rakesh Shah; [email-masked]'
> Subject: RE: [SIP] First cut review of Session Timer draft.
> 
> 
> > 10:2 - How can a proxy know that it is the closes proxy to 
> > the UAC that 
> > cares about the timer? Except in the trivial case where the 
> > proxy is the 
> > closest to the UAC period, this seems problematic. 
> 
> Because the *first* proxy that cares will *add* a "Session-Expires" 
> header. Other proxies will merely notice (and occasionally 
> adjust) it. So, if you see no "Session-Expires," you're the 
> first node 
> that cares. If you don't, you aren't. 
> 
> A clarification to this effect would probably be useful... 
> 
> SRD> It's already there, in 10:2 - "...For the proxy closest 
> to the UAS, the final response to the \INVITE does not 
> contain a Session-Expires header..."

I've further clarified the text on this subject. It now reads:

When the UAS sends the response, it will not contain a
\header{Session-Expires} or \header{Require} header. This response is
forwarded upstream, and it will eventually arrive at a proxy which
inserted the \header{Session-Expires} header into the request. Because
there is no \header{Session-Expires} or \header{Require} in the
response, the proxy knows it is the first session-timer-aware proxy to
receive the response. This proxy \MUST insert a
\header{Session-Expires} header into the response with the value it
remembered from the forwarded request. The proxy \MUST also
insert the \header{Require} header into the response, with the value
``timer'', before forwarding it upstream. The value of the
\header{Session-Expires} in the forwarded response represents the
expiration time of the session. For other proxies, the response will
already contain the \header{Session-Expires} and \header{Require}
header, so that this cae is indistinguishable from CASE IV.

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

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