Franz, You will need to include an SDP answer (that you would normally include in a 200 OK). The SDP would contain the IP address, a port number on which to receive the media from the caller. It will also contain a CODEC list on the m= line. The Codec List contains a subset of the codecs from the received SDP in the INVITE.
Also, you will need to include a Require:100rel header in the 183 Session Progress. This will make sure that the UAC will act on the SDP in the 183. Nagesh Shekar > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Franz > Edler > Sent: Wednesday, March 30, 2005 12:30 PM > To: [email protected] > Subject: [Sip-implementors] SDP in a 183 Session progress > > > Dear experts, > > I have a question regarding SDP in a 183 Session progress > response in case > of SIP-ISUP interworking (rfc3398). > > rfc3398 states: ... the gateway will generate a 183 message > towards the SIP > node; this contains SDP to establish early media cut-through. > But it is my understanding of offer/answer model that no SDP > in a response > (answer) is necessary to cut-through in backward direction > because the SDP > in INVITE (offer) already contains all information to send > media to the > caller. > > If an SDP is necessary in a 183 message in the above > mentioned case: What > should it contain? > > Thanks for you help. > > Franz > > _______________________________________________ > 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
