Subject: What is "service name" in SRV records?

From: Erik Nordmark <[email-masked]>
Date: Mon, 12 May 2003 16:58:13 +0200 (CEST)

RFC 2782 says
   Currently, the translation from service name to port number happens
   at the client, often using a file such as /etc/services.

I've been assuming that "service name" was the same as "keyword" in
http://www.iana.org/assignments/port-numbers
but the keywords are not unique within the registry.

Somebody else found
http://www.iana.org/assignments/service-names
which has unique service names.

What is the correct answer?

  Erik

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From: Derek Atkins <[email-masked]>
Date: 12 May 2003 11:28:49 -0400

> What is the correct answer?

I think it refers to the former (assignments/port-numbers).  As for
the keyword uniqueness, the only duplicate I saw in a cursory glance
of the file was compressnet, which was asiggned both ports 2 and 3.  I
didn't notice any other duplicates through about 4500 (which is where
I stopped looking).

>   Erik

-derek

-- 
       Derek Atkins
       Computer and Internet Security Consultant
       [email-masked]             www.ihtfp.com

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From: "Eric A. Hall" <[email-masked]>
Date: Mon, 12 May 2003 11:55:17 -0500

> What is the correct answer?

No service name is valid for use with SRV until it has been documented in
a specification which has credible authority over that service. EG,
neither _whois._tcp.domain.dom nor _nicname._tcp.domain.dom are meaningful
until one or the other has been explicitly declared as meaningful within
the context of using SRV RRs to locate the servers associated with a
specific service.

Once an authoritative specification has been written, the service name is
whatever the specification defines it to be. Whether or not that name has
been used anywhere else is simply a matter of convenience.

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/

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From: Paul Vixie <[email-masked]>
Date: Mon, 12 May 2003 17:19:10 +0000

> What is the correct answer?

the authors of that rfc didn't know there was a difference.  certainly the
WKS RR is not used any more, and the second url points to a list which is
very short and out of date.

i think the first url referenced above is a better choice in the modern era.
but, for the record, there was no intent one way or the other at the time
this experimental rfc was submitted.

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From: Paul Vixie <[email-masked]>
Date: Mon, 12 May 2003 17:24:17 +0000

> the context of using SRV RRs to locate the servers associated with a

i'm not sure whether that's true.  at least, that wasn't the authors' intent.

> been used anywhere else is simply a matter of convenience.

i'm sure that that is not true.  there has to be a single authoritative list
of "service names", and the above proposal would cause IANA to have to keep
two such lists, neither of which would be authoritative.

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From: "Eric A. Hall" <[email-masked]>
Date: Mon, 12 May 2003 13:21:26 -0500

on 5/12/2003 12:24 PM Paul Vixie wrote:
>> No service name is valid for use with SRV until it has been
>> documented in a specification which has credible authority over that
>> service. EG, neither _whois._tcp.domain.dom nor
>> _nicname._tcp.domain.dom are meaningful until one or the other has
>> been explicitly declared as meaningful within the context of using
>> SRV RRs to locate the servers associated with a specific service.
> 

I have no doubt that it wasn't your intention but that's the practical
result. Historically, a spec had to detail the usage before a service can
be mapped with SRV in a standardized way, and whatever service name the
spec defined was the service name that got used.

We could argue over whether or not a spec must be written first, and I
won't hold out very long, but that's the way it's shaping up.