According to that section of RFC3263, the SRV procedures for resolution of the sent-by field are to be followed only upon a "failure" to send the initial response to the source address of the packet using the port in the sent-by field.
Quoting from Section 5, paragraph 2 of RFC3263 ... "A server, according to RFC 3261 [1], will send a response on the connection it arrived on (in the case of reliable transport protocols), and for unreliable transport protocols, to the source address of the request, and the port in the Via header field. The procedures here are invoked when a server attempts to send to that location and that response fails (the specific conditions are detailed in RFC 3261)." thanks, -Sachin -----Original Message----- From: Scott Lawrence [mailto:[EMAIL PROTECTED] Sent: Thursday, October 12, 2006 10:48 AM To: Sachin Danait (sdanait) Cc: [email protected] Subject: Re: [Sip] RFC3263 - Server Usage query On Wed, 2006-10-11 at 08:34 -0700, Sachin Danait (sdanait) wrote: [reply limited to sip-implemntors] > I have a question regarding Section 5 (Server Usage) of RFC3263 that I > am requesting your opinion on. > IMHO, there appears to be an issue with server-side Via header > processing rules as currently specified in RFC 3263, when a Via header > of the received request sent-by address field has an SRV name (a port > is not specified on the header) and the SRV name resolves to > non-default SIP ports. > Section 5 of RFC3263 references section 18.2.2 of RFC3261, and states > that for unreliable transports, the initial response transmission sent > by a UAS should be attempted towards the source address of the > received request and the default destination port (5060) if none is > specified in the Via header. If this initial response encounters a > failure and there wasn't any port specified in the Via, the UAS should > resolve the domain name in the sent-by field using SRV procedures, and > the response should be sent to the address and port selected based on > that SRV query. > My question is regarding the first step of the above response > processing logic. > Since SRV lookups are performed on a domain-name only when no port is > specified, this obligates the sender of a request to not encode a port > in its Via header if that sender wishes to be reachable using SRV > resolution. Consequently, this appears to imply that the sender needs > to be listening for responses on the default SIP port in addition to > any of the ports resolved from the SRV query, since the first > transmission of any incoming response will always be directed towards > the default port as per section 18.2.2 of RFC3261. I don't think so. If the name in the Via is resolvable as an SRV name, then the SRV record _does_ specify the port, so section 18.2.2 does not apply. Only if the name in the Via must be resolved as a host address lookup without SRV should the port be considered unspecified and be sent to the default well known port. -- Scott Lawrence tel:+1-781-938-5306;ext=162 or sip:[EMAIL PROTECTED] sipXpbx project coordinator - SIPfoundry http://www.sipfoundry.org/sipX Chief Architect - Pingtel Corp. http://www.pingtel.com/ _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
