Hello Paul, Paul Kyzivat wrote: > erol turac wrote: > >> how can proxies edit c line in sdp? which rules can be applied to c line by >> proxies? >> >> I have a sip client behind nat which insert its own private IP at session >> level (c line under m line) >> and NAT adds its own public IP into c line at media level before forwarding >> 200 OK to proxy. >> Here, proxy removes c line at media level and forward 200 OK to ingress side >> with private IP at session level. >> Is it valid behaviour for proxies? >> > > No. Proxies are not permitted to alter the body of a message. > > Paul >
Why? IETF people normally use SHOULD, MUST, etc terms to these affirmatives. I see no reason why a SIP element acting as 'proxy' can't change SDP contents... I think you are trying to match the desired server behavior to some 'documented' or 'prompt' solution, such as the very old discussion about SIP Proxy versus B2BUA. Erol, there is really no reason why you shouldn't try to do this if your SIP server allow it. If you are implementing your own, this surely will be a 'new feature' of your proxy. Anyway you should search for "Session Border Controllers" on Internet (they behave like you want). Indeed, they work normally as 'B2BUA', but don't stay freezed by these terminologies as you go. Best regards, Balena. >> On Thu, Jan 1, 2009 at 1:22 AM, Dale Worley <dwor...@nortel.com> wrote: >> >> >>> On Tue, 2008-12-30 at 22:37 +0800, Serbang, Nabam (Nabam) wrote: >>> >>>> So how u1 knows where to send RTP packet. Usually it will send to >>>> address present in Contact header. >>>> >>> U1 will *never* use the IP address in the Contact header to determine >>> where to send RTP packets, it will use the address in the 'c' line of >>> the SDP it receives. >>> >>> There are problems ensuring that each UA will receive SDP that contains >>> 'c' lines that contain usable addresses for SDP. ICE can be used by the >>> UAs to decide what addresses to use. Alternatively, the proxies >>> involved can edit the SDP to correct the 'c' lines in the presence of >>> NATs. >>> >>> Dale >>> >>> >>> _______________________________________________ >>> Sip-implementors mailing list >>> Sip-implementors@lists.cs.columbia.edu >>> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors >>> >>> >> >> > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > > -- *Guilherme Balena Versiani* /Software Architect/ <http://www.comunip.com.br> Rua Alvarenga Peixoto, 295 / 5º andar Lourdes - CEP 30180-120 - Belo Horizonte, MG (31) 3275-2220 9992-1578 _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
