To:
Mark.Andrews@isc.org
Cc:
dnsop@cafax.se
From:
Alan Barrett <apb@cequrux.com>
Date:
Thu, 21 Mar 2002 15:57:17 +0200
Content-Disposition:
inline
In-Reply-To:
<200202090148.g191mEs09924@drugs.dv.isc.org>
Sender:
owner-dnsop@cafax.se
Subject:
Re: SRV records - when?
On Sat, 09 Feb 2002, Mark.Andrews@isc.org wrote: > draft-andrews-http-srv-01.txt is available " If the URI does explicitly specify a port to connect to then there " is a potential conflict in the port specification between the URI " and the SRV records, and the SRV record is ignored. In this case " the user agent MUST query for address records for the host name in " the URI (instead of SRV records). It would be possible to prepend a port number to the left hand side of the SRV record: 8080._http._tcp.example.com. SRV 10 1 80 host2.example.com. Also, the text and the examples disagree about what to do if there is an explicit port number, but the explicit port number happens to be "80". This replacement text fixes the problem with port 80, and suggests a different way of handling non-defaulr ports: 2. URIs with a explicit port specification If the URI explicitly specifies a port to connect to, and the explicit port is the same as the default port (that is, port 80), then the user agent MUST behave as if no explicit port had been specified. If the URI explicitly specifies a non-default port to connect to then there is a potential conflict in the port specification between the URI and the SRV records. In this case, the user agent MUST NOT attempt to use SRV records for _http._tcp.<target>. Instead, the user agent MUST follow one of the following two strategies: A) Do not query for SRV records, and instead query for address records for the host name in the URI, and connect to the host address using the port number specified in the URI; or B) Do not query for SRV records for _http._tcp.<target>, but instead query for SRV records for <port>._http._tcp.<target>, where <port> is an ASCII decimal representation of the port number specified in the URI. Apart from the insertion of the port number, follow the logic specified in [RFC2782], including the server selection mechanism provided by the priority and weight fields. If these SRV records do not exist then the client MUST fall back to looking for IP address records. --apb (Alan Barrett)