I am surprised why you think it is problem of interprettion.
This standard doc do use B2BUA way, the there are only two choice about INVITE to C:
1. With SDP.
2. Without SDP.
Using no-precondition, the standard doc chooses 1.
Then what about precondition? This standard doc did not talk this intensively.
And if it choose 1, it would have the problem memtioned.
Gao.
| Hans Erik van Elburg <ietf.hanserik@xxxxxxxxx>
2009-04-10 21:41 |
|
Discussing 3GPP/TISPAN specs seems little off topic here. I'd just like to say that the 3GPP/TISPAN specification does not imply this. It seems merely a problem with your interpretation of that specification.
BR,
/Hans Erik van Elburg
2009/4/10 <gao.yang2@xxxxxxxxxx>
Yes, I think so too.
We has decided to propose this problem to 3GPP and TISPAN in next meeting. And we want to know is there any other corporations or individuals want to consider this probelm. We can talk it in the coming meeting.
Thanks
Gao
| Paul Kyzivat <pkyzivat@xxxxxxxxx>
2009-04-10 21:02 |
|
OK. Then I guess TISPAN will have to figure out how to deal with the
difficulties that their choices bring.
Thanks,
Palu
gao.yang2@xxxxxxxxxx wrote:
>
> To Paul
>
> Yes.
>
> But there has been the emergence of the practical problem while
> interworking of equipment from different corporation.
>
> To solve the call forwarding problem, we has two base choice: Forking
> and no Forking.
>
> Currently, TISPAN using no Forking way(in fact, B2BUA way).
>
> Then, if 3GPP want to using Forking way to replace the current no
> Forking way, it should rewrite "3GPP TS 24.404".
>
> Or if 3GPP want to along the no Forking way, then it should resolve the
> interworking problem arosed by "INVITE with/without SDP problem".
>
> Thanks
>
> Gao
>
>
> To Christer
>
> As you are the rustler of 3GPP, can you talk about this topic too.
>
> Thanks
>
> Gao
>
>
> Paul Kyzivat <pkyzivat@xxxxxxxxx> 写于 2009-04-10 12:59:59:
>
> >
> >
> > gao.yang2@xxxxxxxxxx wrote:
> > >
> > > Hi,
> > >
> > > Thanks for your answer.
> > >
> > > Using forking, Offer/Answer would be in two different dialogs. So, it
> > > has no such problem. But the TISPAN's standard using B2BUA mode for
> Call
> > > Forwarding.
> >
> > Oh. Then the game may be different.
> >
> > > As:
> > >
> > > if A-C's negotiate still in the original dialog(having done A-B's
> > > negotiate), then it is B2BUA mode:
> > >
> > > 1. if the INVITE to C has Offer, there would be using C's Answer as
> > > Offer send to A, usually using UPDATE.
> > >
> > >
> > > |---->Offer(1)
> > > |<----Answer(2)
> > > Offer(3) <----|
> > > Answer(4) ---->|
> > >
> > > Then we would have to judge whether the Answer(4) should be
> intercept or
> > > transfer. If it should be transfered, then its the begin of next
> loop as
> > > the current one.
> > >
> > > 2. if the INVITE to C has no Offer, then C's Offer would has different
> > > stream as A's original desire. It is also a well known problem.
> > >
> > >
> > > So. I want to know how you considering the problems. Thanks.
> >
> > I think it is very difficult to make this work. There are often
> > problems, even without preconditions. Preconditions don't make it any
> > simpler.
> >
> > IMO the answer is: if it hurts, don't do it.
> > Even if the AS wants to act as a B2BUA, the AS can still establish
> > multiple dialogs back to A, so the issue of sorting this out is left to
> > A. Unless you are trying to deal with UAs that are unable to do that.
> >
> > Unless the B2BUA also terminates the media it may be impossible to
> > resolve all the problems.
> >
> > Paul
> >
> > > Gao
> > >
> > >
> > >
> > >
> > > *Paul Kyzivat <pkyzivat@xxxxxxxxx>*
> > >
> > > 2009-04-09 21:32
> > >
> > >
> > > 收件人
> > > gao.yang2@xxxxxxxxxx
> > > 抄送
> > > sipping@xxxxxxxx
> > > 主题
> > > Re: [Sipping] Question about Call Forwarding Busy(CFB)
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > gao.yang2@xxxxxxxxxx wrote:
> > > >
> > > > Use case: A call B(Busy), AS forward the call to C.
> > > >
> > > > By TISPAN standard(current 3GPP 24.404), AS would send INVITE to
> C. And
> > > > this INVITE contain A's initial Offer.
> > > >
> > > > But if considering precondition, B would has Offer/Answer with A.
> > > > Now, should the INVITE(by AS) contain A's initial Offer or not?
> Or is
> > > > there standard define it?
> > >
> > > Are you assuming that the AS is acting as a proxy? Or as a B2BUA?
> > >
> > > Assuming its a proxy:
> > >
> > > If B is busy, then I would expect that there was no answer from B.
> > > Rather just an immediate 486 response. This would never reach A and so
> > > there is no issue.
> > >
> > > If for some reason B did send an answer in a provisional response
> before
> > > signaling busy, then that would establish an early dialog with
> to-tag B.
> > > Then later there will be a 486 response, intercepted by the AS, and not
> > > forwarded to A.
> > >
> > > And then a copy of the original INVITE will be sent by the AS to C.
> When
> > > C responds with an answer, it will be with to-tag C. Hence A will see
> > > this as a new early (or final) dialog.
> > >
> > > A must negotiate the preconditions independently in the two dialogs.
> > >
> > > Thanks,
> > > Paul
> > >
> > >
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