Subject: [DNSOP] ANAME intro text

From: Ray Bellis <[email-masked]>
Date: Tue, 30 Oct 2018 14:58:26 +0000

The introduction of draft-ietf-dnsop-aname-02 includes this text:

   If the web site is hosted by a third-party provider, the ideal way to
   provision its name in the DNS is using a CNAME record, so that the
   third party provider retains control over the mapping from names to
   IP address(es).

I have some issue with the use of the term "ideal" there.  At best it's
merely "expedient", but either way it'ws an abuse of the true original
semanatics of the CNAME record.

AIUI, various protocols have at times required that when a CNAME record
is encountered that the target of that record (the "canonical name") be
the one subsequently used in protocol exchanges.  [e.g. the apparently
obsolete text in §5.2.2 of RFC 1123].

This reinforced the semantic that the RHS of a CNAME is the "one true
name" and that the owner name is just an alias for it [RFC 2181].

Browsers, unfortunately, never did this.  Name-based virtual hosting
actually required the opposite - you have to put the original owner name
in the 'Host:' header.

If we've moved to a world where those original semantics really no
longer apply, I think that needs to be written down in a consensus
document somewhere.

Ray

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From: Tony Finch <[email-masked]>
Date: Tue, 30 Oct 2018 15:38:38 +0000

> obsolete text in §5.2.2 of RFC 1123].

Are there any examples of that other than SMTP? In my experience it was a
terrible idea, but then I'm not a fan of rewriting message headers. It's
also seriously problematic from the authentication point of view
especially in the absence of DNSSEC.

Tony.
-- 
f.anthony.n.finch  <[email-masked]>  http://dotat.at/
Shannon: West or northwest 5 or 6. Rough. Rain or showers. Moderate or good.

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From: "John Levine" <[email-masked]>
Date: 30 Oct 2018 16:38:49 -0000

In article <[email-masked]>,
Tony Finch  <[email-masked]> wrote:
>Are there any examples of that other than SMTP?

Not that I know of, and these days few mail systems do so.

The C in CNAME tells us what its intended application was, but as
we've seen from time to time, here on the Internet what you expect and
what you get are not necessarily the same.

R's,
John

PS: In fairness, I'm not surprised that in 1987 nobody expected
something like the web that would become so popular that there
wouldn't be enough IP addresses to give each site its own IP.  I don't
know whether the other use, to cross admin boundaries, would have been
predictable then.
-- 
Regards,
John Levine, [email-masked], Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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From: Tony Finch <[email-masked]>
Date: Tue, 30 Oct 2018 17:40:20 +0000

Ray Bellis <[email-masked]> wrote:
>
> I have some issue with the use of the term "ideal" there.

Anyway, since this is a value judgment that is probably out of place
[WP:EDITORIAL {{Weasel}} etc.] I've rephrased in a more neutral style.
Thanks for pointing out the weakness; the intro is important for setting
the scene.

Tony.
-- 
f.anthony.n.finch  <[email-masked]>  http://dotat.at/
sovereignty rests with the people and authority
in a democracy derives from the people