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[DNSOP] Re: RFC 9460 SvcParamValue question - duplicate values

Ben Schwartz <bemasc@meta.com> Thu, 23 October 2025 13:54 UTC

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From: Ben Schwartz <bemasc@meta.com>
To: Petr Špaček <pspacek@isc.org>, dnsop <dnsop@ietf.org>
Thread-Topic: RFC 9460 SvcParamValue question - duplicate values
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Date: Thu, 23 Oct 2025 13:54:22 +0000
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Subject: [DNSOP] Re: RFC 9460 SvcParamValue question - duplicate values
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I'm not sure I understand the question.

Duplicate SvcParamKeys are prohibited, even if the value is the same:

Forbidden: examplekey=examplevalue examplekey=examplevalue

Repeated entries in a list-valued SvcParamValue are permissible, if allowed by the SvcParamKey definition:

Forbidden: mandatory=ech,ech

Ostensibly permitted but very silly and please don't: alpn=h2,h3,h2 ipv6hint=2006:db8::1,2006:db8::1

Possibly useful: example-flags=1,0,0,1

--Ben

________________________________
From: Petr Špaček <pspacek@isc.org>
Sent: Thursday, October 23, 2025 7:45 AM
To: dnsop <dnsop@ietf.org>; Ben Schwartz <bemasc@meta.com>
Subject: RFC 9460 SvcParamValue question - duplicate values

Hi.

RFC 9460 section D.3. Failure Cases figure Figure 16: Multiple Instances
of the Same SvcParamKey in the Mandatory List got me thinking - are
multiple identical values in SvcParamValue generally allowed or disallowed?

I would think they are allowed because there's no requirement to order
them and the check might be expensive.

Am I correct?

--
Petr Špaček
Internet Systems Consortium

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