Christer Holmberg <christer.holmberg@xxxxxxxxxxxx> 写于 2010-04-21 20:09:55:
>
> Hi,
>
> >Yes. As Paul's conclusion of BCP, UAS should not include SDP after
> sending the ANSWER.
> >
> >My talking is , even UAS violate the BCP suggestion, there's no
> normative problem.
>
> Exactly.
>
> So, the important thing is to make clear, that IF the UAS sends SDP
> after sending the answer, it CAN NOT send a new offer.
>
> Personally I have never seen any problems caused if there is SDPs in
> additional responses - since most applications will ignore them.
>
> The problem is when someone claims that the SDP can't be ignored,
> because it contains a new offer. And, again, THAT is what we need to
> clarify: the UAS cannot send a new offer.
Exactly. And I think RFC3261 has such words of the meaning: the UAS cannot send a new offer (in subsequent response):
o Once the UAS has sent or received an answer to the initial
offer, it MUST NOT generate subsequent offers in any responses
to the initial INVITE.
Thanks,
Gao
>
> Regards,
>
> Christer
>
>
>
>
>
> Christer Holmberg <christer.holmberg@xxxxxxxxxxxx>
>
> 2010-04-21 19:44
>
>
> 收件人
> "gao.yang2@xxxxxxxxxx" <gao.yang2@xxxxxxxxxx>
> 抄送
> OKUMURA Shinji <shinji.okumura@xxxxxxxxxxxx>, "sipping@ietf.
> org" <sipping@xxxxxxxx>, "sipping-bounces@xxxxxxxx" <sipping-
> bounces@xxxxxxxx>
> 主题
> RE: [Sipping] Is SDP in an unreliable response "the answer" ???
>
>
>
>
>
>
>
> Hi,
>
> >> I don't disagree with what people are saying, but trying to read it
> >> from a I-am-a-new-implementor-and-I-would-like-to-get-it-right-from-
> >> the-beginning perspective I don't think anything is clarified. Eg.
> >> talking about that an SDP sent after the answer would be
> >> "missunderstood as a new offer" is confusing.
> >
> > I guess "missunderstood as a new offer" issue is clear:
> > If the session-id of o= line is the same the
> ANSWER, UAC can treate it as just COPY of the answer;
> > If the session-id is higher than the ANSWER's
> session-id, the UAC can treate it as *new* offer. As the UAC MUST
> ignore any SDP after ANSWER, it is OK for UAC doing nothing. But if
> UAC checks the SDP and find it is
> > *new* offer and violation of O/A rules then
> terminate the session, I also think it is also OK(UAS do bad
> behavior at first).
>
> I am not talking about the UAC procedure. I fully support saying
> that the UAC ignores the SDP.
>
> My problem is to say that the UAS shall not include SDP, because
> the UAC could "missunderstand it as a new offer". All we need to say
> is that the UAS MUST NOT include a new SDP.
>
> Regards,
>
> Christer
>
>
>
>
>
>
>
>
>
>
>
>
>
> > > -----Original Message-----
> > > From: sipping-bounces@xxxxxxxx
> > > [mailto:sipping-bounces@xxxxxxxx] On Behalf
> Of OKUMURA Shinji
> > > Sent: 21. huhtikuuta 2010 8:45
> > > To: sipping@xxxxxxxx
> > > Subject: Re: [Sipping] Is SDP in an
> unreliable response "the
> > > answer" ???
> > >
> > > Hi,
> > >
> > > Hans Erik van Elburg <ietf.hanserik@gmail.
> com> Tue, 20 Apr
> > > 2010 21:53:17 +0200
> > > >On Tue, Apr 20, 2010 at 3:47 PM, Paul Kyzivat
> > > <pkyzivat@xxxxxxxxx> wrote:
> > > >> Here is my attempt at summarizing the
> discussion conclusions:
> > > >>
> > > >> Normative things (stated or implied in
> existing RFCs):
> > > >>
> > > >> - If the UAC sent an offer in the INVITE,
> then after it
> > > receives SDP
> > > >> (the
> > > >> answer) in a reliable response to the
> INVITE, any SDP in
> > > subsequent
> > > >> responses to the INVITE MUST be ignored.
> > > >>
> > > >> - Further, if SDP is received in an
> unreliable response to
> > > the invite
> > > >> prior to receiving SDP in a reliable
> response, then it MUST be
> > > >> treated as the answer for purposes of
> media processing,
> > > but not for
> > > >> purposes of determining when another offer
> may be sent or received.
> > > >>
> > > >[HE] I miss what the UAC should do in this
> case for subsequent
> > > >responses, does the following hold as well:
> > > >"If the UAC sent an offer in the INVITE,
> then after it receives SDP
> > > >(the answer) in an unreliable response to
> the INVITE, any SDP in
> > > >subsequent responses to the INVITE MUST be
> ignored/granted/... ." ?
> > >
> > > I agree. And it's certainly "ignored".
> > >
> > > >Regardless what the correct behaviour is, it
> is missing in
> > > your summary.
> > > >
> > > >> - if the UAS receives an offer in the
> INVITE, it MUST NOT
> > > include SDP
> > > >> in any response it sends until it has
> determined the
> > > intended answer
> > > >> SDP to the offer.
> > > >>
> > > >> - once the intended answer SDP is
> determined, it MUST be sent in a
> > > >> reliable response to the INVITE. It MAY be
> sent in one or more
> > > >> *preceding* unreliable provisional responses.
> > > >>
> > > >> Non-normative, best practice suggestions:
> > > >>
> > > >> - if the UAS receives an offer in the
> invite, once it has sent the
> > > >> answer in a reliable response, it should
> not send any SDP in
> > > >> subsequent responses to the INVITE.
> > > _______________________________________________
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