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 <[EMAIL PROTECTED]>
> To: Manpreet Singh
> CC: [EMAIL PROTECTED] <[EMAIL PROTECTED]>;
> [email protected]
> <[email protected]>
> 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: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] On
>> Behalf Of Paul Kyzivat
>> Sent: Monday, April 14, 2008 12:34 AM
>> To: Manpreet Singh
>> Cc: Bob Penfield; [EMAIL PROTECTED];
>> [email protected]
>> 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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