Re: [DNSOP] [Ext] I-D Action: draft-ietf-dnsop-svcb-https-05.txt

Ben Schwartz <bemasc@google.com> Thu, 13 May 2021 04:33 UTC

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From: Ben Schwartz <bemasc@google.com>
Date: Wed, 12 May 2021 21:33:04 -0700
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To: Brian Dickson <brian.peter.dickson@gmail.com>
Cc: Eric Orth <ericorth=40google.com@dmarc.ietf.org>, dnsop <dnsop@ietf.org>, John Levine <johnl@taugh.com>, Joe Abley <jabley@hopcount.ca>
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Subject: Re: [DNSOP] [Ext] I-D Action: draft-ietf-dnsop-svcb-https-05.txt
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On Wed, May 12, 2021 at 7:14 PM Brian Dickson <brian.peter.dickson@gmail.com>
wrote:

> It is demonstrably more likely that a complex parser will have problems,
> than something that combines data from simple RRs in simple RRsets will
> have problems.
> (The history of SMTP is, I think, a good poster child for this, with MX,
> A, AAAA, plus DNSSEC and TLSA support in the clients, which are email
> transport things, not merely DNS things.)
>

The SVCB parameters' wire format is an extremely simple TLV arrangement; I
don't think "a complex parser" is required.  It's also far from a novel
design for DNS; in fact, it's identical to the widely implemented OPT RR
RDATA format from 1999 [1][2].

What you're describing here, an arrangement in which clients partition
RRSets into subsets and then reassemble bindings from those subsets,
strikes me as highly novel, in contrast, and somewhat more complex.

Perhaps complexity is subjective.  The important thing is that the standard
be reasonably implementable.  I hope that the list of published
implementations [3] will serve as convincing evidence that the current
draft is sufficient in that regard.

--Ben

[1] https://datatracker.ietf.org/doc/html/rfc2671#section-4.4
[2] https://datatracker.ietf.org/doc/html/rfc6891#section-6.1.2
[3]
https://github.com/MikeBishop/dns-alt-svc/blob/master/svcb-implementations.md