Re: [DNSOP] Alias mode processing in auths for draft-ietf-dnsop-svcb-https-01

Tony Finch <> Mon, 10 August 2020 22:17 UTC

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Date: Mon, 10 Aug 2020 23:17:00 +0100
From: Tony Finch <>
To: Brian Dickson <>
cc: Ben Schwartz <>, dnsop <>, Pieter Lexis <>
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Subject: Re: [DNSOP] Alias mode processing in auths for draft-ietf-dnsop-svcb-https-01
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Brian Dickson <> wrote:
> What I would suggest is the following, paraphrased (i.e. please clean it up
> before using in the I-D, if you agree it's the right semantics):
>    - In-bailiwick CNAME, SVCB, A, and AAAA records SHOULD be added (and for
>    CNAME and SVCB, in-bailiwick RDATA for those SHOULD also be iteratively
>    processed for inclusion)
>    - CNAME and SVCB records MUST be placed in the Answer section (because
>    of existing CNAME rules and because of RRTYPE match to the query)
>    - A and AAAA records MUST be placed in the Additional section (since
>    those would not match the query RRTYPE of SVCB)

I've only skimmed this thread, so I might be repeating something that's
already agreed... but I want to emphasize that a new RR type specification
will have impossible interop problems if it tries to put records in the
ANSWER section that aren't expected by existing DNS software.

"Unexpected" means anything that isn't part of a CNAME or DNAME chain on
the way from the original query name to an RRset of the query type.

If a resolver queries for the owner of SVCB record (or a CNAME pointing at
one) then anything related to the RDATA of the SVCB record(s) has to go in
the ADDITIONAL section, or there will be sadness.

It was a very long time before DNAME was usable and even within the last
10 years there was software that would choke on DNAME records in the
ANSWER section that it didn't expect.

f.anthony.n.finch  <>
Shannon, Rockall: Variable 2 to 4. Moderate, occasionally slight. Drizzle.
Moderate or poor.