Re: [Doh] DNS Camel thoughts: TC and message size

Tony Finch <dot@dotat.at> Wed, 06 June 2018 14:18 UTC

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Date: Wed, 6 Jun 2018 15:18:32 +0100
From: Tony Finch <dot@dotat.at>
To: bert hubert <bert.hubert@powerdns.com>
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Subject: Re: [Doh] DNS Camel thoughts: TC and message size
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bert hubert <bert.hubert@powerdns.com>; wrote:
>
> So, the DNS Camel has a suggestion. Specify that DNS messages carried over
> DOH can be up to 65536 bytes large and note that truncation should be
> handled as if the response was carried over TCP/53.
>
> Effectively this means that a TC response over DOH is almost always useless,
> but this is no loss of functionality since it did not work over TCP/IP
> either. We've not made anything worse here.
>
> And in general this is what I hope that DOH will restrict itself to: provide
> access to the DNS protocol over HTTPS and not change DNS itself.

Full agreement, and with the rest of your message. Thanks for writing it
so that I didn't have to!

I think the semantics of a DNS message transported over HTTPS should be
the same as for DNS-over-TCP, wrt truncation, EDNS buffer sizes, and so
forth.

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>;  http://dotat.at/
Fisher, German Bight: Variable 3 or 4. Moderate at first in west Fisher,
otherwise slight. Fair. Moderate or good, occasionally poor.