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

["Christer Holmberg" <[e-mail]>]

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.

Regards,

Christer

 

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