The now-expired draft http://tools.ietf.org/html/draft-jennings-sipping-multipart-02 explored multipart/alternative. One difficulty, however, is what does it mean to say "can understand a part".
This is easy if one part is SDP and another part is SDPng. If you understand SDPng, you process it; if you don't, you process the SDP. However, it's really hard if one part is SDP and another part is also SDP -- in some cases we would like the answerer to "pick the better SDP". At the time, we were considering multipart/alternative as a way to offer RTP (RTP/AVP) and SRTP (RTP/SAVP), but we found it doesn't work well at all. Since then, draft-ietf-mmusic-sdp-capability-negotiation is a superior solution to sending an offer containing RTP and SRTP. I suppose we could avoid the difficulty by prohibiting identical Content-Types in the alternatives. -d > -----Original Message----- > From: Christer Holmberg (JO/LMF) > [mailto:[EMAIL PROTECTED] > Sent: Thursday, May 03, 2007 3:50 AM > To: [EMAIL PROTECTED]; [email protected] > Subject: RE: [Sip] Support for Multipart/MIME > > > Hi, > > Multipart/alternative is interesting. I guess that, for SDP, > it could be > used to provide different "offer alternatives". I think it > would be good > to compare it against some of the other grouping/alternative > mechanisms > we have defined for that purpose. > > Regards, > > Christer > > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > > Sent: 30. huhtikuuta 2007 19:13 > > To: [email protected] > > Subject: Re: [Sip] Support for Multipart/MIME > > > > From: Cullen Jennings <[EMAIL PROTECTED]> > > > > I think the WG should consider an update to 3261 (likely > > done through > > the process Keith has proposed) that makes this multipart/MIME > > mandatory to implement. > > > > I assume that the requirement is that if a message has a > > multipart/alternative body, and the UA is capable of > > understanding one part of the body, then it must be able to > > extract that part and use it to process the message. > > > > Dale > > > > > > _______________________________________________ > > 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
