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Hi,
I agree that UPDATEs are used outside re-INVITEs, and
we can, and shall, not forbid that.
I guess that the one could say that it is not allowed
to use them as long as the re-INVITE transaction state is still alive. Or
something like that...
Note that I am not proposing to go ahead with that
proposal at this point, and for the fallback solution we did choose the
race condition is not even an issue. But I think it was an interesting idea
:)
Regards,
Christer
Dear Christer Holmberg
I am gaoyang(gao.yang2@xxxxxxxxxx). And it is 23:00
here. :)
Thank you for your explanation for us. And I am glad more people
join in the topic(may be back again for some people).
Your
understanding is correct.
I'd like to point out for Elwell John
that what Christer Holmberg mentioned is the one I called BCP.
And Chapter
4.3.2 is the solution in theory, and it allow UPDATE, which is a new
modification beyond just precondition notification.
I'd like to
have a further talk tomorrow. Good night.
Gaoyang
Date: Tue, 17 Feb 2009 14:59:40 +0100
From:
christer.holmberg@xxxxxxxxxxxx
To: john.elwell@xxxxxxxxxxx;
wang.libo@xxxxxxxxxx
CC: sipping@xxxxxxxx
Subject: Re: [Sipping] About
"rollback of re-Invite"
Hi John,
My understanding of the proposal is that you would only send
UPDATEs if they ARE nested to the re-INVITE transaction. Otherwise you
would send a new re-INVITE. That way you would know that an UPDATE is nested
even if it arrives after the ACK.
That of course means that the ongoing re-INVITE transactions needs
to finish first (either by itself, or by being cancelled).
But, I may have missunderstood, so it's better if the authors
speak for themselves :)
Regards,
Christer
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
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 fo r 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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