Hi, Just to point out that media may still flow if you consider IM using the MESSAGE method as media. Roni Even
> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:sip-implementors- > [EMAIL PROTECTED] On Behalf Of Paul Kyzivat > Sent: Monday, October 09, 2006 9:11 PM > To: Retesh Chadha > Cc: [email protected] > Subject: Re: [Sip-implementors] regarding SDP > > First, IMO it is entirely valid to send an offer where all media lines > have the port set to zero. It is however somewhat of a strain to find a > good reason why someone would do this. (But I expect we can come up with > something.) > > Its also quite ok to send an answer with all the ports set to zero, and > if the offer had them that way then the answer must. > > While an answer may want to refuse an INVITE if all media have been > rejected, I don't believe it is required to do so. Its quite all right > to have a call with no media. I don't see why it should matter how you > get into that state: > - an initial offer with no m-lines > - because the answerer rejected all the m-lines in the offer > - because the offerer started out with port=0 in all the > m-lines of the initial offer > - because the offerer in a re-INVITE sets the port=0 in > all the m-lines. > > Some of these may make more sense than others, but they all seem ok, and > likely to eventually find a use. > > Retesh Chadha wrote: > > RFC doesnt put any restriction regarding this. > > > > It doesnt make much sense apart from the following scenario i can think > of. > > While the following is possible, it might make more sense to achieve the > intended results by using a non-zero port number and c=0.0.0.0 (a "black > holed" media address.) > > Paul > > > Say, UAC just wants to check if the UAS is available or not, and then > > when UAS responds with 200 ok, UAC negotiates the capabilities; ie UAC > > doesnt want to negotiate media unless it knows for sure UAS is > > available. Here we may think that INVITE without sdp may do the same > > but not actually because, then UAS may send sdp in 200 ok which will > > force UAC to negotiate. > > > > Dont know if the above is a practical scenario. > > > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
