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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