Re: [Sipping] Liaison Statement on offer/answer procedures

[Paul Kyzivat <[e-mail]>]

Christer Holmberg wrote:
> Hi,
>  
>>>>> - If an UPDATE (inside or outside of a reINVITE) fails, any o/a in
>>>>> the UPDATE has no effect on the media session state.
>>>>> [Ian Elz ] OK, but how will we determine if an UPDATE is inside or
>>>>> outside a re-INVITE?
>>>> [Christer] I assume that any stateful entity must know whether it has
>>>> a pending re-INVITE transaction for a specific call or not.
>>> That's not actually enough. A UAS (or dialog stateful proxy) cannot know
>>> whether an UPDATE received shortly after a 2xx is sent upstream was sent
>>> before or after the 2xx was received by the UAC. We could add an
>>> explicit indication to that effect, I suppose...
>> Yes. Taking this approach to the current problem requires that we find a
>> solution to knowing whether the update was sent inside the reinvite or not.
> 
> If the UAS sends a 2xx response to the re-INVITE I guess it really doesn't matter when the UPDATE was sent.
> 
> But, if the UAS sends a non-2xx response to the re-INVITE I guess it would need to know when the UPDATE was sent: was it sent still assuming that the re-INVITE will succeed, OR was it sent bacause the re-INVITE did NOT succeed?
> 
> If we would go for the non-rollback alternative we wouldn't have this problem since the re-INVITE failure response doesn't affect UPDATE/PRACK offer/answers, and then it doesn't matter when the UPDATE was sent.

Exactly! That is an advantage of the non-rollback solution.
But the rollback solution has the advantage of providing a solution to 
the precondition rollback problem.

We need to pick our poison.

	Paul

> Regards,
> 
> Christer
> 
>  
> 
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