________________________________________ From: [email protected] [[email protected]] On Behalf Of goutam kumar [[email protected]]
In case we receive an INVITE without an SDP body, as per rfc 3261, it is mentioned that the 200 OK from our side should contain the offer-SDP and the ACK from the calling party will contain the answer-SDP. But, in such case, how do we alert the user agent at the receiving end and then generate a 200 OK response?? Because, now we have no idea on what codec to start our media on. When should we open the media streams( and for which codec) in this situation?? Also, if the calling party rejects the offer in the 200 OK then how do we handle this?? Does the calling party send a BYE instead of an ACK or does he send a 405 (Media not supported)?? _______________________________________________ You alert the user the same way you would always, since the alerting does not depend on the codecs. In regard to "what codec to start our media on", you need to be prepared to receive all codecs that you list in the SDP. It is a common desire to send a list of codecs but restrict the other end to utilize only one, but SDP does not directly support that. In general in this situation, you cannot get the codecs configured correctly until the ACK is received. But the ACK will be received shortly after the 200 is sent, which will happen shortly after the user answers the call, and by definition, that is soon enough. The caller cannot reject the SDP sent in the 200. If it wants to achieve that effect, it must use some trick. One trick is to send the ACK and then immediately terminate the dialog with BYE. Another is to send the ACK and then renegotiate the SDP by sending a re-INVITE. Dale _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
