Re: [Doh] [Ext] Are we missing an architecture? (was Re: DNS Camel thoughts: TC and message size)

Ben Schwartz <bemasc@google.com> Wed, 13 June 2018 19:43 UTC

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From: Ben Schwartz <bemasc@google.com>
Date: Wed, 13 Jun 2018 15:43:44 -0400
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Subject: Re: [Doh] [Ext] Are we missing an architecture? (was Re: DNS Camel thoughts: TC and message size)
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Snipped to focus on one technical point.

On Wed, Jun 13, 2018 at 3:20 PM Mukund Sivaraman <muks@mukund.org>; wrote:

> Large zone transfers are supported today using TCP continuation messages
> and the same can be encoded by DoH within the 64kB message limit.


This is currently not true, because each DoH query must return at most a
single DNS message in the response.  Therefore, there is no way to make use
of continuation messages in DoH.  I think this is a major reason why we are
having this conversation: lack of continuation messages renders DoH
strictly less expressive than standard DNS, which is a concern for gateway
applications.

Before someone pedantically points out this, AXFRs are sent as DNS QUERY
> but they're not a DNS query in the layman's sense and the charter isn't
> talking about the opcode. :P
>

Without veering into charter interpretation, I agree that supporting AXFR
is distinctly lower priority than typical client-recursive queries.
However, some working group participants believe that it would be valuable,
so it's worth considering if there is a reasonable way to include support
for it, or to leave open the possibility of future support.