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

Tue Apr 15 11:15:53 UTC 2008

Update can be used for early and confirmed dialogs as per 3311. Re-invite can only be used on confirmed dialog

Thnx

-----Original Message-----
From: rajesh <rajeshkumar.r at imimobile.com>
To: Manpreet Singh; pkyzivat at cisco.com <pkyzivat at cisco.com>
CC: sip-implementors at lists.cs.columbia.edu <sip-implementors at lists.cs.columbia.edu>; discussion at sipforum.org <discussion at sipforum.org>; brett at broadsoft.com <brett at broadsoft.com>
Sent: Tue Apr 15 00:26:03 2008
Subject: Re: [SIPForum-discussion] [Sip-implementors] Offer/Answer question

Hi All,

As per rfc 3311 , update is used for early media (early dialog) .
As per my understanding , early dialog means the 200 OK has been not recvd for the INVITE.
Please tell me whether ReInvite cannot be used for this Particular case.

Thanks and Regards
Rajesh Kumar
Sr. Software Engineer
R & D - Network Group 
+91 40 23555945 - 235
+91 99084 00027
www.imimobile.com 

	----- Original Message ----- 
	From: Manpreet Singh <mailto:msingh at ibasis.net>  
	To: pkyzivat at cisco.com 
	Cc: sip-implementors at lists.cs.columbia.edu ; discussion at sipforum.org ; brett at broadsoft.com 
	Sent: Monday, April 14, 2008 7:11 PM
	Subject: Re: [SIPForum-discussion] [Sip-implementors] Offer/Answer question

	Agree with session refresh(without o/a in specific). Makes call flow simplistic and in lots of cases avoids interoperability issues caused due to o/a wth re-invites

	Thnx

	-----Original Message-----
	From: Paul Kyzivat <pkyzivat at cisco.com>
	To: Manpreet Singh
	CC: brett at broadsoft.com <brett at broadsoft.com>; 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 09:30:57 2008
	Subject: Re: [Sip-implementors] Offer/Answer question

	Manpreet Singh wrote:
	> 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 :-)

	Sometimes the call flow won't work right if a human delay is inserted in
	it. In that case UPDATE is ideal because it prevents that eventuality.

	The 3pcc call flow RFC (I forget the number) is getting a bit long in
	the tooth now, but it it talks about some cases with that kind of
	constraint.

	UPDATE is also useful without o/a for session timer refresh.

	        Paul

	> 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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	> Sip-implementors at lists.cs.columbia.edu
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	>

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