An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing
dynamicsoft
dynamicsoft
Columbia U.
The Session Initiation Protocol (SIP) operates over UDP and TCP. When used with UDP, responses to requests are returned to the source address the request came from, but from the port written into the topmost Via header of the request. This behavior is not desirable in many cases, most notably, when the client is behind a NAT. This extension defines a new parameter for the Via header, called rport, that allows a client to request that the server send the response back to the source IP address and port where the request came from.