[SIPForum-discussion] [Sip-implementors] Offer/Answer question

[Manpreet Singh]

That's one reason why I have seen most implementations use re-invites instead of updates for mid call changes. Why leave a possibility of 2 transactions when one can live with 1. But then its implementation specific :-)

Thnx

-----Original Message-----
From: Brett Tate <brett at broadsoft.com>
To: Manpreet Singh
CC: discussion at sipforum.org <discussion at sipforum.org>; sip-implementors at lists.cs.columbia.edu <sip-implementors at lists.cs.columbia.edu>
Sent: Mon Apr 14 09:04:10 2008
Subject: RE: [Sip-implementors] Offer/Answer question

I agree with Paul; however I'll highlight the rfc3311 section 5.2 text
concerning UPDATE with SDP potentially triggering a 504.  Thus UAC
receiving 504 for UPDATE with SDP should be aware that a re-INVITE might
be needed to perform the SDP modification.

"If the UAS cannot change the session parameters without prompting the
user, it SHOULD reject the request with a 504 response."


> -----Original Message-----
> From: sip-implementors-bounces at lists.cs.columbia.edu 
> [mailto:sip-implementors-bounces at lists.cs.columbia.edu] On 
> Behalf Of Paul Kyzivat
> Sent: Monday, April 14, 2008 12:34 AM
> To: Manpreet Singh
> Cc: Bob Penfield; discussion at sipforum.org; 
> sip-implementors at lists.cs.columbia.edu
> Subject: Re: [Sip-implementors] Offer/Answer question
> 
> 
> 
> Manpreet Singh wrote:
> > Wasn't denying the use of update on confirmed dialog, just 
> saying the 
> > recommended use of UPDATE is for early dialog and not for confirmed 
> > based on the spec.
> > 
> > ""Although UPDATE can be used on confirmed dialogs, it is 
> RECOMMENDED 
> > that a re-INVITE be used instead. This is because an UPDATE 
> needs to 
> > be answered immediately, ruling out the possibility of user 
> approval. 
> > Such approval will frequently be needed, and is possible with a 
> > re-INVITE.""
> 
> IMO the "denial" is a bit overstated. It is only pointing out 
> that its inappropriate if the offer it carries will require 
> an extended time for approval before being answered. If that 
> isn't to be the case then there isn't any issue with using UPDATE.
> 
> Note that the issue with immediate response also applies to 
> an UPDATE used during an early dialog.
> 
> 	Paul

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