Hi, >I understand that this is a very rare case, > > A B > | | > |INVITE (offer) | > |================================>| > | 1xx-rel(answer)| > |<===========\ /=================| > | \/ | > | /\ 18x-norel(answer)| > |<===========/ \=================| > |PRACK | > |-------------------------------->| > | | > >IIUC, if 18x-norel has a SDP(answer), UAC(A) can not insert >new offer into PRACK. You now seem to be suggesting that an SDP answer can be transported unreliably. I strongly disagree to such statement. A copy of the SDP answer can be sent unreliably, and the UAC can use it, but the "real" SDP answer must still be sent reliably. Maybe "ignore" is the wrong wording. The UAC cannot ignore the fact that the reliable response contains the SDP answer, because THAT SDP finishes the offer/answer transaction, but it does not need to parse it. Regards, Christer > > To avoid this situation UAS should not ... > > Regards, > Shinji > > Christer Holmberg <christer.holmberg@xxxxxxxxxxxx> Wed, 21 > Apr 2010 12:23:39 +0200 > >Hi, > > > ><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 etc. > > > ><Dean Willis hat off> > > > >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. 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. > >What is important is that the UAS MUST NOT send a *new* offer. > > > >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@xxxxxxxxx> 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. > _______________________________________________ > 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
