Subject: SRV continued

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Tue, 19 Jul 2005 19:39:26 -0700

While we are on the subject of SRV, port numbers etc:

Why not define SRV prefixes for POP3, IMAP4 and SUBMIT so that email
applications can auto-configure from the email address alone.

I recognize that this would be much more satisfactory with better DNS
security. But even without DNSSEC it would make network management a lot
more flexible and make it much harder for attackers to bamboozle end
users into compromizing themselves with bogus administrative messages
'redirect your email client to use this bogo-server'.

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From: John C Klensin <[email-masked]>
Date: Wed, 20 Jul 2005 03:51:19 -0400

--On Tuesday, 19 July, 2005 19:39 -0700 "Hallam-Baker, Phillip"
<[email-masked]> wrote:

> Why not define SRV prefixes for POP3, IMAP4 and SUBMIT so that
> email applications can auto-configure from the email address
> alone.

Because it raises some very "interesting" issues about just
which server a particular client should be bound to.  The
network-nearest available one or  the one associated with the
same organization as the client are typical possibilities (along
with the somewhat vague "email address") and, if the wrong one
is chosen, it may be inaccessible.  

These issues are discussed in part in draft-hall-email-srv (the
most recent version of which is, I think, expired, partially
because of debates about  the issue raised above.

  john

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From: Jeroen Massar <[email-masked]>
Date: Wed, 20 Jul 2005 13:12:43 +0200

> applications can auto-configure from the email address alone.

Actually...... there is, at least in draft form:
http://www.ietf.org/internet-drafts/draft-massar-dnsop-service-00.txt

8<-------
   This document defines a new domain, _service., which can be used for
   automatic service configuration and discovery.  The associated
   anycast prefixes can be used to configure a default DNS server, which
   provides lookups for a local _service. domain but also acts as a
   (caching) recursive DNS server, thus allowing DNS clients to use this
   well-known address as their default DNS server as well as to use it
   to find various well known services, thus avoiding manual
   configuration.
------->8

Applied to automatically setting up IPv6 tunnels:
http://www.ietf.org/internet-drafts/draft-massar-v6ops-tunneldiscovery-00.txt

Greets,
 Jeroen