Re: [Sip] Should early dialogs be dropped when 2xx is received???

[Bob Penfield <BPenfield at acmepacket.com>]

I would say no, since 3261 has a specific guidance for this case:

   The UAC core considers the INVITE transaction completed 64*T1 seconds
   after the reception of the first 2xx response.  At this point all the
   early dialogs that have not transitioned to established dialogs are
   terminated.  Once the INVITE transaction is considered completed by
   the UAC core, no more new 2xx responses are expected to arrive.

Thus the other early dialogs will linger for 64*T1 seconds.

If the UAC does destroy all the other early dialogs, then it would need to be able to handle any additional 2xx responses for unknown dialogs, presumably by sending an ACK immediately followed by a BYE. This is really the same case as an additional 2xx response arriving for a brand new dialog (i.e. the UAC never received a 1xx).

cheers,
(-:bob

-----Original Message-----
From: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On Behalf Of Paul Kyzivat
Sent: Tuesday, August 05, 2008 10:16 AM
To: Christer Holmberg
Cc: SIP IETF
Subject: [Sip] Should early dialogs be dropped when 2xx is received???

The following in the discussion of 199 issues reminded me of a question
I have had for a long time. I'm changing the subject because it isn't
directly pertinent to the 199 discussion.

Christer Holmberg wrote:

> What I mean to say is that when the UAC receives a final response for an
> early dialog it normally releases all other early dialogs (the UAC
> should of course still be ready to accept 200 OK responses for other
> dialogs).

This has always been a fuzzy area to me. If the UAC is prepared to
retain multiple final dialogs if they happen, is it still expected to
release early dialog state for other dialogs when it receives the first
2xx? That could mean that subsequent 2xx responses can't be turned into
viable dialogs because state has been lost. (E.g. if preconditions were
being negotiated during the early dialog.)

Shouldn't the rule be that *if* the UAC is only intending to retain the
first final dialog then it should/may abandon all other early dialogs
when it receives a 2xx, but if it might want to keep additional dialogs
if additional 2xx responses are received, then it ought not drop the
early dialogs?

        Thanks,
        Paul

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