On Wed, Jan 7, 2009 at 3:22 PM, Michael Procter <mich...@voip.co.uk> wrote: > Guilherme Balena Versiani wrote: >> 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... > > Easy one. For requests, RFC3261 section 16.6 step 1: > > The proxy MUST NOT add to, modify, > or remove the message body. > > > And for responses, RFC3261 section 16.7 step 9: > > The proxy MUST NOT add to, modify, or > remove the message body. > > > If it breaks these rules, it is no longer acting as a proxy.
When a caller is behind a NAT, rewriting SDP in INVITE to include an RTP relay's address in it is a pretty common practice. Leaving RFC3261 fundamentalism aside-- do we consider it then still legitimate enough to call it a "SIP proxy"? Cheers, -- Victor Pascual Ávila _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
