Trying to understand SRV records

Kevin Darcy kcd at daimlerchrysler.com
Wed Jul 11 22:04:14 UTC 2001


Cricket Liu wrote:

> > The first problem I have is that Cricket shows an example (p517 4th ed):
> >      _http._tcp.www.movie.edu.     IN SRV  ..........
> > Now RFC 2782 says this about the service name:
> >      If Assigned Numbers names the service indicated, that name is the
> only
> > name which is legal for SRV lookups.
> > But RFC1700 says:
> >      www-http         80/tcp    World Wide Web HTTP
> >      www-http         80/udp    World Wide Web HTTP
> > Has Cricket got his example wrong?
>
> Arguably.  However, what's important is the label the client
> prepends when looking up the relevant SRV records, and no
> SRV-smart web clients yet exist, to my knowledge.
>
> The discussion I remember from previous IETFs suggests that
> the use of SRV records in conjunction with a particular service
> should be specified in an RFC.  That RFC, presumably, would
> define the appropriate label to use.
>
> RFC 2782 says that Levon is working on some document to
> specify how to use SRV records to locate LDAP servers; I
> don't know of any such document for web servers.
>
> I'll certainly adjust the example to follow whatever the IETF
> comes up with.  Until then, though, it's just an example.

RFC 1700 is not the definitive source for port number assignments any more.
According to http://www.iana.org/assignments/port-numbers, port 80 can be
referred to as "www-http", "www" or "http". Obviously, the last mnemonic is
the one which is most consistent with URL syntax.Also, in terms of Internet
Drafts, Mark Andrews and Thor Kottelin put out a draft (now expired) on the
subject of using SRV records for HTTP access. See
http://www.ietf.org/internet-drafts/draft-andrews-http-srv-00.txt


- Kevin





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