Hi Paul,
I still think UAS MUST NOT send the copy of SDP in any response after the ini-O/A.
By RFC3262:
The UAS MAY send a final response to the initial request before
having received PRACKs for all unacknowledged reliable provisional
responses, unless the final response is 2xx and any of the
unacknowledged reliable provisional responses contained a session
description. In that case, it MUST NOT send a final response until
those provisional responses are acknowledged.
If the 1xx REL has SDP and the final response is 2xx, UAS MUST wait it get the PRACK, that is the UAC MUST has gotten the 1xx REL.
Thanks,
Gao
sipping-bounces@xxxxxxxx 写于 2010-04-20 22:04:45:
>
>
> DRAGE, Keith (Keith) wrote:
> > Do remember that there are certain cases where the UAC will not
> ignore it. These are the cases where the message containing original
> answer has not yet arrived or been lost, and the protocol has not
> yet recovered from that.
>
> Hmm. Can you say more?
>
> Are you thinking of a case where the answer has been sent in a reliable
> provisional, but the PRACK has not yet been received? And then that
> *some* SDP is included in a subsequent unreliable provisional, or 2xx?
>
> That is an interesting case. The one that would be least wierd is:
>
> UAC UAS
> | INVITE (SDP1) |
> |----------------->|
> | 1xx REL (SDP2) |
> | X--------------|
> | 2xx (no SDP) |
> |<-----------------|
>
> I think that implies a different best practice:
>
> If the UAS has sent an answer in a reliable provisional, if it sends a
> 2xx before receiving a prack of the answer, it should include the answer
> in the 2xx as well.
>
> (If the UAS intends to initiate another o/a it MUST await the prack, so
> if the 1xx is lost it will be retransmitted.)
>
> Thanks,
> Paul
>
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