I haven't been following all of this discussion, but there is
nothing explicitly to bind an UPDATE transaction to a parent INVITE or re-INVITE
transaction. It is implicit in the vast majority of cases, but timing issues
break this, particularly where unreliable transport is concerned. For example,
if UPDATE arrives while awaiting ACK, is it because UPDATE was sent before the
ACK, or because the ACK was lost? If UPDATE arrives before sending a final
response to re-INVITE, is it because UPDATE is nested within the re-INVITE
transaction, or has there been a CANCEL request that has been lost and will be
repeated later? Without explicit binding, the only consistent thing to do is to
treat each transaction separately, and not roll back. If this means
pre-conditions are broken, the focus should be on fixing pre-conditions
somehow.
John
From: sipping-bounces@xxxxxxxx [mailto:sipping-bounces@xxxxxxxx] On Behalf Of Christer Holmberg
Sent: 16 February 2009 18:00
To: wang.libo@xxxxxxxxxx
Cc: sipping@xxxxxxxx
Subject: Re: About "rollback of re-Invite"Hi,
>The key point of this discussion is how to find out the proper state of the rollback.
>I think ,Some rules of using re-invite may be helpful.Such as, we restrict only
>one offer/answer pair in a re-invite,I don't think we can do that, because at least some pre-condition scenarios require more offer/answer pairs.And, even if you would only allow e.g. a single UPDATE within the re-INVITE, you would still have the same question: if the UPDATE suceeds, but the re-INVITE then fails, what is the state?Regards,Christer
"Christer Holmberg" <christer.holmberg@xxxxxxxxxxxx> 写于 2009-02-16 21:41:59:
>
> Hi,
>
>
> >>I also pay high attention to the topic of "rollback of re-Invite".
> >>As lots of service is implemented on the network using SIP, and
> >>different ways may be carried out by different corporations, it's
> necessary to define
> >>a complete and clear method to solve the failure when the unsuccessful
> re-Invite
> >>happens.
> >
> >I agree, and we thought that having a generic rule, not related to
> >specific use-cases, would be the most clear, clean and complete
> >solution.
> >
> >[gaoyang] It is simple and clear. But it disregard nature property of
> nested transaction. I concluded incorrectness and drawback of such way.
> More details in
> http://www.ietf.org/internet-drafts/draft-gaoyang-sipping-session-state-
> analysis-01.txt.
>
> I agree it's not the most "beautiful" solution - that's why we spent a
> long time discussing it.
>
> >>And the problems "Commit any session parameters that have been
> sucessfully changed"
> >>metioned in "draft-gaoyang-sipping-session-state-analysis-01.txt" need
> further discuss,
> >>I think.
> >
> >The draft does not define a generic rule. It more or less says that
> >every time there is a new use-case, the offer/answer rollback aspects
> >needs to be documented for that use-case. I think that is something we
> >wanted to avoid.
> >
> >[gaoyang] It is not use-case oriented, but rules/definition oriented.
> >And the definition of how o/a pairs form nested transaction should be
> open for future.
> >Such as "a=chain" and so on extension can form more o/a pairs as nested
> transaction. It is not use-case.
> >We can have a further talk.
> >
> >If I understand chapter 4.3.3 correct, it says that if you have a
> >pending re-INVITE transaction, a NEW modification must be sent in a
> >re-INVITE request. That way we would get rid of the race condition
> >problem. That is an interesting point. I guess the question is whether
> >it's too lake to make such a rule.
> >
> >[gaoyang] Is the "lake" late? I think it can be BCP, not rules :).
>
> Perhaps, yes.
>
> Regards,
>
> Christer
>
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