Re: [Sipping] Is SDP in an unreliable response "the answer" ???
sipping-bounces@xxxxxxxx 写于 2010-04-21 18:23:39:
> <Dean Willis hat on>
> Offer/answer is a mess. Instead, let's regard media as an
> application on top of SIP, and use an Info Package for negotiating
> the media. There is no connection to the SIP transactions, which
> means we don't need complicated rules on when and where to insert
> SDP, and we don't need to describe how offer/answer works for re-INVITEs
> <Dean Willis hat off>
As SIP is widely deployed, the radical way mentioned
above is not proper. So, I prefer this moderate way.
> 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).
>The important thing is
> not whether the UAS includes the UAS answer in subsequent responses
> or not, because the UAC still has to handle such situation.
IMO, UAC can just ignore any SDP from UAS after the
ANSWER. So, the UAC MAY NOT has to handle it.
> important is that the UAS MUST NOT send a *new* offer.
> > -----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@xxxxxxxxx> Tue, 20
> > 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
> > receives SDP
> > >> (the
> > >> answer) in a reliable response to the INVITE, any SDP
> > subsequent
> > >> responses to the INVITE MUST be ignored.
> > >>
> > >> - Further, if SDP is received in an unreliable response
> > 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
> > >>
> > >[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
> > >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
> > 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
> > >> *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
> > >> subsequent responses to the INVITE.
> > _______________________________________________
> > Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping
> > This list is for NEW development of the application of SIP
> > Use sip-implementors@xxxxxxxxxxxxxxx for questions on current
> > sip Use sip@xxxxxxxx for new developments of core SIP
> Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping
> This list is for NEW development of the application of SIP
> Use sip-implementors@xxxxxxxxxxxxxxx for questions on current sip
> Use sip@xxxxxxxx for new developments of core SIP
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