Dear, I have a question regarding how to deliver ringback rtp to a SIP station if it is located under a broadband router, assuming the broadband router acts as a dummy line sharer. As you may know, rtp port number recorded in the dummy router can be different the rtp port number stated in SDP body sent by the SIP station, and this annoys the INVITE answerer about how to guarantee its own rtp packets to be delivered to the SIP station, the call initiater. In case of answering back with 200 OK message, the answerer can figure out the destination rtp port number after checking where the received rtp packets are coming from. No matter what rtp port is used in the dummy router, the answerer simply use the port number as a destination rtp port and the router is supposed to deliver the packets to the SIP station.
As to 183 response, however, it may get more complicated. When sending 183 response back to the call initiater, the answerer(or a media server) is supposed to send rtp packets first, and there may be no way to know where to send. We may think of setting 183 response's session attribute to 'sendrecv' expecting to receive rtp packets, but what if the initiater ignores it and does not send any rtp packets? Any comment will be welcomed. Thanks. Lee, Sungwoo _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
