El Domingo, 28 de Septiembre de 2008, Attila Sipos escribió: > For a UA, the rport just declares that "I can receive UDP on the same port > I transmitted". A UA not supoprting rport could, in theory, be transmitting > on one UDP port but be listening on another. So sending back to the port > you received on would not work - you have to send back to the port in the > sent-by. > > Having said that the asymetric usage of UDP SIP signalling is very rare - I > saw it in UA many years ago. > > Most (today I would say (I hope) 100% of) UAs will send using a UDP source > port which matches their UDP listening port. And using rport declares this > "symmetric" behaviour. Of course a UA won't directly use the rport > information - it just allows upstream proxies to know that they can send > UDP responses back to the source. > > In fact, since the UDP symmetry is so common these some SIP proxies (or B2B > UAs) add an rport header even if one wasn't included. So some people are > already doing what you suggested (at the very small risk that the > request-sending-UA doesn't have UDP SIP signalling symmetry)
Thanks a lot. IMHO is good to make SIP more simple (for example by replying always to incoming IP:port in UDP) even if it breaks annoying backaward compatibility with old and extrange implementations. Let's move on! ;) -- Iñaki Baz Castillo _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
