Hi Bert, Thanks for the response.
comment below... > -----Original Message----- > From: Bert Culpepper [mailto:[EMAIL PROTECTED]] > Sent: 21 May 2002 16:34 > To: 'Attila Sipos'; [EMAIL PROTECTED] > Subject: RE: [Sip-implementors] Quick SDP dynamic payload question > > > comment below... > > Attila Sipos wrote: > > > > > > Hi, > > > > If an endpoint A sends SDP containing "m=" and "a=" lines > > like this: > > > > m=audio 10036 RTP/AVP 8 119 > > a=rtpmap:8 PCMA/8000 > > a=rtpmap:119 telephone-event/8000 > > > > I understand this to mean that the sender of this SDP > > wishes to receive DTMF in an RFC2833 RTP stream with > > an RTP payload of 119. > > > > > > If the replying endpoint B, send an SDP with the > > following "m=" and "a=" lines: > > > > m=audio 10022 RTP/AVP 8 97 > > a=rtpmap:8 pcma/8000 > > a=rtpmap:97 telephone-event/8000 > > > > Then I understand this to mean that this person wishes > > to receive an RFC2833 RTP stream with an RTP payload > > of 97. > > > > > > So, if I am right, endpoint A should send RFC2833 RTP > > with an RTP payload of 97. > > > > And endpoint B should send RFC2833 RTP with an > > RTP payload of 119. > > > > Is my understanding correct? > > IMO, this is one main "deficiency" with SDP (RFC 2327) in > SIP. Since there > are no direction attributes in the above, it would seem that neither > endpoint will "communicate" telephone-events to the other. > Neither endpoint > has agreed on the payload type that they will both send and > receive with. > If the endpoints want to use a different payload type for a specific > encoding, they need to be explicit IMHO about which value > they'll use in > each direction. 1. I thought if there were no direction attributes then it is accepted to be "sendrecv". 2. Regarding SDP payloads, it seems to me that SDP descriptions tell other endpoints where to send their media. So if an endpoint specifies port 10000 for a certain media type, then you have to send to port 10000. It seems logical therefore, that if an endpoint specifies payload 99, then you have to send to them using RTP with payload set to 99. Whether or not SDP is the best media descriptor is open to debate. My main point is, given that we do use SDP, is the way I have described above reasonable? Regards, Attila > > Regards, > Bert > > > > > Any help is greatly appreciated. > > > > Thanks, > > > > Attila > > > > > > > > Attila Sipos > > Software Engineer > > > > <mailto:[EMAIL PROTECTED]> > > <http://www.vegastream.com> > > > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
