IMO it would be inappropriate to send a 491 in this case, because it is
not glare, and it is perfectly ok to terminate the dialog. Given that it
has sent the BYE, I *think* it would be ok for S to send a 481 to the
reinvite. (But I haven't scrutinized the state machines regarding this.)
If not 481, it can find some response for the reINVITE. But I think A
should respond 200 to the BYE.
Thanks,
Paul
Vishal Agrawal wrote:
> Hi,
>
> Assume that phone “A” issues a re-INVITE request to the SIP server “S” and
> at the same time “S” issues a BYE request to “A”.
>
> Is it valid for “A” to send a 491 response to this BYE request from “S”?
>
> The SIP INVITE dialog is for a point to point media session.
>
> Here is the quote from the Section 15.1.2 in RFC 3261 –
>
> “A UAS core receiving a BYE request for an existing dialog MUST follow the
> procedures of Section 12.2.2 to process the request. Once done, the UAS
> SHOULD terminate the session (and therefore stop sending and listening for
> media). The only case where it can elect not to are multicast sessions,
> where participation is possible even if the other participant in the dialog
> has terminated its involvement in the session. Whether or not it ends its
> participation on the session, the UAS core MUST generate a 2xx response to
> the BYE, and MUST pass that to the server transaction for transmission.”
>
>>From the above, my understanding is that “A” must send a 200 OK response for
> this BYE request regardless of it terminating the SIP session or not, is
> this understanding correct?
>
>>From reading the sections 14.2 and 21.4.27, it seems RFC 3261 mentions 491
> response for INVITE requests only in glare conditions. Is it valid and a
> good idea to send a 491 response for the BYE request when a re-INVITE client
> transaction is pending?
>
> Lastly – “UAS SHOULD terminate the session” – why is this requirement at
> SHOULD level? If the far-end “S” wants to terminate the session and has sent
> a BYE request, mustn’t “A” terminate the session and expect a 487 from “S”
> for its re-INVITE?
>
> Thanks,
> Vishal
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