> > You can always lock down a codec by updating the initial offer. Take a > look > at section 10.2 of RFC 3264.
That would be when you have to lock down to a subset of what has been supported in the answer. Lets say if the offer contained A,B,C and the answer contained only B, what would be the need to lockdown specifically by another offer answer? I am trying to understand if there is any particular reason why it has been kept as it has been kept, considering that one more offer answer would mean one more round of signaling overhead. Regards, Ravi. > > Raj > > > > -----Original Message----- > > From: Christer Holmberg [mailto:[EMAIL PROTECTED] > > Sent: Thursday, November 22, 2007 5:34 AM > > To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [email protected] > > Subject: RE: [Sip] SIPit 21 : Topics that attendees argued about > > > > > > Hi, > > > > I agree with Ravi. > > > > Eventhough you in theory is supposed to be able to receive > > what you offer - no matter what you get in the answer - I > > think that in real life the only codecs that participants > > will be prepared to send/receive are the ones sent both in > > the offer and the answer. That is also the reason why the > > answer normally doesn't contain additional codecs - it mostly > > contains a subset of the codecs in the offer. > > > > Regards, > > > > Christer > > > > > > > > >I was surprised to find > > > > > >>* There were implementations that offered an m-line with > > codecs A, B, > > >>and C, got an answer with C, then got upset when they got > > RTP with A > > >>(which is quite legal). > > > > > >On the list (like others who argued about it I think). > > > > > >I had some offline discussions with some of the members on this. > > >While I agree this seems legal, this seems very > > counter-intuitive and > > >may result in wasted resources, would it not? > > > > > >For example, if the offerer is a conference bridge or a > > transcoder, and > > >has a limited number of codecs of each type he offers, why should it > > >hold on to one codec of each type for the duration of the > > session, even > > >though the answerer has not supported it? > > > > > >Any particular reason why this should be continued as a > > legal scenario? > > >Would it not be possible change it to say that the Offerer needs to > > >expect only those codecs which answerer has explicitly > > supported in the > > >answer? > > > > > >Regards, > > >Ravi. > > > > > > -- > > > > > > Ravishankar. G. Shiroor > > > Wipro Technologies, Bangalore. > > > > > > [EMAIL PROTECTED] > > > -- > > > > > > > -----Original Message----- > > > > From: Robert Sparks [mailto:[EMAIL PROTECTED] > > > > Sent: Tuesday, November 20, 2007 2:38 AM > > > > To: sip List > > > > Subject: [Sip] SIPit 21 : Topics that attendees argued about > > > > > > > > Digging through my notes: > > > > > > > > Here are some of the topics where people were arguing. I'm > > > capturing > > > > the smaller topics here. Larger arguments will get their > > > own message. > > > > > > > > * There were arguments about the dynamic payload map from > > > numbers to > > > > codecs (identified in the SDP and sent in the RTP) being > > > the same in > > > > the offer and the answer . The spec says they SHOULD. Some > > > > implementations were insisting they MUST. > > > > * There were arguments around preserving the relative order > > > of codecs > > > > on an m-line between the offer and the answer. The specs > > say SHOULD. > > > > * There were implementations that offered an m-line with > > > codecs A, B, > > > > and C, got an answer with C, then got upset when they got > > > RTP with A > > > > (which is quite legal). > > > > * There were arguments about deleting rejected m-lines on > > > re-invites > > > > (which you cannot do), and on reusing the slot they occupy in re- > > > > invites (which you can do). > > > > * There were implementations that didn't add the > > refresher tag in a > > > > session-refresh message when they were the refresher and > > there were > > > > arguments about whether that meant the other side could > > > take the role. > > > > * Several implementations handled a=sendonly as a session > > > attribute, > > > > but not a media attribute - it can appear in either place. > > > > > > > > > > > > > > > > _______________________________________________ > > > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip > > > > This list is for NEW development of the core SIP Protocol Use > > > > [EMAIL PROTECTED] for questions on current sip Use > > > > [EMAIL PROTECTED] for new developments on the application of sip > > > > > > > > > _______________________________________________ > > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip > > > This list is for NEW development of the core SIP Protocol Use > > > [EMAIL PROTECTED] for questions on current sip Use > > > [EMAIL PROTECTED] for new developments on the application of sip > > > > > > > > > _______________________________________________ > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip > > This list is for NEW development of the core SIP Protocol Use > > [EMAIL PROTECTED] for questions on current sip > > Use [EMAIL PROTECTED] for new developments on the application of sip _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
