Re: [v6ops] New draft at dnsop a bis for DNS IPv6 Transport Operational Guidelines

David Farmer <> Sun, 12 November 2023 06:23 UTC

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From: David Farmer <>
Date: Sun, 12 Nov 2023 00:22:45 -0600
Message-ID: <>
To: Geoff Huston <>
Cc: Owen DeLong <>, list <>
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Subject: Re: [v6ops] New draft at dnsop a bis for DNS IPv6 Transport Operational Guidelines
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I think Owen is referring to the behavior of DNS clients communicating with
a recursive DNS resolver specified in Section 3.1 of RFC 8305, Happy
Eyeballs v2;

3.1.  Handling Multiple DNS Server Addresses

   If multiple DNS server addresses are configured for the current
   network, the client may have the option of sending its DNS queries
   over IPv4 or IPv6.  In keeping with the Happy Eyeballs approach,
   queries SHOULD be sent over IPv6 first (note that this is not
   referring to the sending of AAAA or A queries, but rather the address
   of the DNS server itself and IP version used to transport DNS
   messages).  If DNS queries sent to the IPv6 address do not receive
   responses, that address may be marked as penalized and queries can be
   sent to other DNS server addresses.

   As native IPv6 deployments become more prevalent and IPv4 addresses
   are exhausted, it is expected that IPv6 connectivity will have
   preferential treatment within networks.  If a DNS server is
   configured to be accessible over IPv6, IPv6 should be assumed to be
   the preferred address family.

On the other hand, Geoff is referring to the behavior of a recursive DNS
resolver communicating with an authoritative DNS server. And I think he is
correct that there isn't any Happy Eyeballs type behavior there.


On Sat, Nov 11, 2023 at 10:18 PM Geoff Huston <> wrote:

> >>>
> >>> It may not be in the HE RFCs, but I’ve noticed MANY implementations
> will ask over v4 and v6 for the same resolver query on the first shot, or
> in some cases a few seconds later, so there is, in fact, happy eyeballs
> like implementation in the wild even if it isn’t official.
> >>>
> >>> Owen
> >>>
> >>
> >
> Don’t forget that all this started with the 3901bis draft so we are
> talking about DNS queries made from recursive to authoritative servers.
> So the question is do recursive resolvers perform back-to-back queries in
> V4 and V6 for the same query name and query type?
> I’ll go look
> g
> _______________________________________________
> v6ops mailing list

David Farmer     
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