Re: [DNSOP] new ANAME draft: draft-hunt-dnsop-aname-00.txt

Evan Hunt <each@isc.org> Fri, 07 April 2017 22:47 UTC

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Date: Fri, 7 Apr 2017 22:47:16 +0000
From: Evan Hunt <each@isc.org>
To: Paul Wouters <paul@nohats.ca>
Cc: dnsop@ietf.org
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Subject: Re: [DNSOP] new ANAME draft: draft-hunt-dnsop-aname-00.txt
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Hi Paul,

On Fri, Apr 07, 2017 at 05:16:14PM -0400, Paul Wouters wrote:
>     When a recursive resolver sends a query of type A or AAAA and
>     receives a response with an ANAME RRset in the answer section, it
>     MUST re-query for the ANAME <target>.  This is necessary because, in
>     some cases, the address received will be dependent on network
>     topology and other considerations, and the resolver may find a
>     different answer than the authoritative server did.
> 
> That opens up a whole can of worms :P We start with the problem of
> "we need addresses at the APEX be non-static, but then you add logic
> to support that and then it is not good enough for the job. AUTH servers
> already know how to return split view answers with various
> implementations based on geolocation, edns-subnet or what not.

The hope here is that, in the long run, ANAME resolution would be the job
of the resolver, which in in a position to get the best answer for its
clients, given geolocation and topology considerations.

Expansion of ANAME on the authoritative end is a workaround for the
fact that we can't go back in time and put ANAME support into all
the resolvers.

> But really, what it comes down to for me is that if you are adding logic
> to the AUTH nameservers to synthesize ANAME into A/AAAA records, why bother
> ever sending ANAME over the wire? Just let clients send A/AAAA and never
> ask for ANAME.

Resolvers don't ask for ANAME. They ask for A/AAAA, and get an A/AAAA
answer, along with an ANAME record so they can go directly to the source
and get a better answer if they support that.

-- 
Evan Hunt -- each@isc.org
Internet Systems Consortium, Inc.