Hi Manoj Here I have put the example in detail how Record-Route, Route plays a role in message routing and how it affects Req-URI. Also a small description on Via.
Endpoint A sends a request say INVITE to proxy1, proxy1 forwards it to proxy2 and proxy2 gives that INVITE to endpoint B. Each proxy adds its Record-route at the start of the record-route header, when called party gets request, last proxies record-route token is the at the start of record route header. Unlike Via, the record route is not deleted by respective proxies in return path. At calling party, whole record route is received. Now lets see how route set is prepared. When the request is arrived at UAS, the route set is prepared from record-route header taken in order. If record-route is absent, route set is set to NULL. When the response received at UAS, route set is prepared at UAS by taking RR in reverse order. In next transactions because of Route set request URI may be affected. If route set is empty, the UAC must place remote target URI into the Request-URI. If first route URI in route set contains lr parameter (loose routing), then request-URI is not affected.. However if first route URI does not contain lr parameter, then UA should put the first route to request-URI, then put the route set in order, and finally adds remote target to Route header at the end. 2. Via Via is used by UAS to to determine target to send immediate response. All proxies in path adds corresponding Via at the start of Via header. Say there are N proxies. So Via at called party looks at proxy(n).via;proxy(n-1).via.... Calling-phone-via So when UAS responds back, it sends all Via without any modification. Now each proxy deletes its corresponding via, finally when response is received at endpoint , endpoint sees its own via only. Regards, Kamal Cisco, Bangalore India -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Rajani Sent: Wednesday, December 09, 2009 11:52 PM To: 'Manoj Priyankara [TG]'; [email protected] Subject: Re: [Sip-implementors] differences between Via,Record-Route and Route headers Refer the below link for a detailed explanation of the header fields. (Thanks to Jan) http://www.openser.org/pipermail/users/2005-September/000839.html Thanks & Regards, Rajani -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Manoj Priyankara [TG] Sent: Wednesday, December 09, 2009 10:51 PM To: [email protected] Subject: [Sip-implementors] differences between Via, Record-Route and Route headers Dear All, Can anyone explain the differences between Via, Record-Route and Route headers? Further, are there any other routing related Headers associated with SIP? Thanks! BR, Manoj _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
