Following up on Sumanth's and Dale's responses: >From my point of view, the original URI structure (as copied from RFC 2396) probably assumes the hostname portion will be used directly for A/AAAA record lookup, and in that case, "_" is illegal in DNS. But we are actually expecting to perform more of a service lookup on that hostname portion, getting to an A/AAAA is the last resort. The A/AAAA lookp for this name, if the client gets that far, will simply fail (because "_" is illegal in hostnames in DNS, which mostly means illegal for A/AAAA records). But the NAPTR and/or SRV lookups will have no problem. I'm not sure how to get around the URI syntax issue, other than to redefine the syntax. I note that while RFC 3261 is based on the URI syntax of RFC 2396, RFC 3986 (which obsoletes it) is less restrictive about "host" syntax, and treats this component as a registered name rather than purely a hostname. So I imagine the SIP URI syntax could be extended to fix this at the expense of allowing more illegal A/AAAA lookups to be generated from SIP URIs with "_". -josh Dale Worley wrote: > On Tue, 2008-12-02 at 16:32 +0100, Geir Arne Sandbakken wrote: > >> The Local-Network profile in the framework requires "_sipuaconfig" >> concatenated with the local network domain to be used as the host part >> of the Request URI. >> >> Our SIP stack does not view this as valid SIP URI, and rejects the >> message. AFAICC RFC 3261 seems to agree with our parser. >> >> IMHO, using underscores in DNS host for finding services related names >> in DNS queries is one thing. Changing the grammar of a SIP URI >> potentially breaking parsers is quite another matter. >> > > Yes, that seems to be a problem. > > There was a discussion starting at > http://www.ietf.org/mail-archive/web/sip/current/msg00966.html regarding > adding "_" and other characters to the allowed set of characters in > host-parts of SIP URIs, but it was inconclusive. > > It seems that the use of "_sipuaconfig" prefixing a domain name was > introduced in regard to looking up DNS A records. (This is a valid > extension of current practice.) But at some point, this was > transitioned into being the request-URI of a SUBSCRIBE. And as you say, > that's not syntactically valid. > > Interestingly, "_" has no reserved uses in RFC 3261 section 25.1, so we > could extend the grammar to allow it in host names with no ill effects. > > Dale > > > _______________________________________________ > Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping > This list is for NEW development of the application of SIP > Use sip-implementors@xxxxxxxxxxxxxxx for questions on current sip > Use sip@xxxxxxxx for new developments of core SIP > -- ===================================================================== Josh Littlefield Cisco Systems, Inc. joshl@xxxxxxxxx 1414 Massachusetts Avenue tel: 978-936-1379 fax: 978-936-2226 Boxborough, MA 01719-2205 _______________________________________________ Sipping mailing list https://www.ietf.org/mailman/listinfo/sipping This list is for NEW development of the application of SIP Use sip-implementors@xxxxxxxxxxxxxxx for questions on current sip Use sip@xxxxxxxx for new developments of core SIP
