[DNSOP] Re: Definition of DNS latency

[Warren Kumari <[e-mail]>]

Depends what you mean by "defining DNS query/response latency".

If you are meaning "The latency from a stub to a recursive MUST be less
than 100ms. The latency from a recursive to an auth MUST be less then
123.4ms", then no, I don't think that there is anything like that (modulo
timeouts and similar).

There are, however, many RFCs about the desire to minimize latency,
including things like:
RFC9824 - "Compact Denial of Existence in DNSSEC"
<https://datatracker.ietf.org/doc/rfc9824/> - saves small bits of time by
not having to fetch from a DB style setup.
RFC9715 - "IP Fragmentation Avoidance in DNS over UDP"
<https://datatracker.ietf.org/doc/rfc9715/> - by not failing over to TCP,
you can save quite a few RTT.
RFC9520 - "Negative Caching of DNS Resolution Failures"
<https://datatracker.ietf.org/doc/rfc9520/> - if you cache non-response
answers you can immediately return these to clients.
RFC9276 - "Guidance for NSEC3 Parameter Settings"
<https://datatracker.ietf.org/doc/rfc9276/> - a bit of a stretch, but not
doing iterations saves, um, many microseconds.
RFC9210 - "DNS Transport over TCP - Operational Requirements"
<https://datatracker.ietf.org/doc/rfc9210/> - if you *do* have to fail over
to TCP, making sure it actually works means clients get an answer, and
don't just hang.
RFC9156 - "DNS Query Name Minimisation to Improve Privacy"
<https://datatracker.ietf.org/doc/rfc9156/> - trades some latency to
improve privacy
RFC8906 - "A Common Operational Problem in DNS Servers: Failure to
Communicate" <https://datatracker.ietf.org/doc/rfc8906/> - if you don't
answer, or answer incorrectly, some queries take much longer.
RFC8806 - "Running a Root Server Local to a Resolver"
<https://datatracker.ietf.org/doc/rfc8806/> - by having zones locally you
don't need to do a lookup.
RFC8198 - "Aggressive Use of DNSSEC-Validated Cache"
<https://datatracker.ietf.org/doc/rfc8198/> - if you know (through e.g
NSEC) that a name doesn't exist, you can immediately send back a negative
answer.
RFC8020 - "NXDOMAIN: There Really Is Nothing Underneath"
<https://datatracker.ietf.org/doc/rfc8020/> - same. If you get an NXD for
foo.example, you know that bar.foo.example doesn't exist
RFC7706 - "Decreasing Access Time to Root Servers by Running One on
Loopback" <https://datatracker.ietf.org/doc/rfc7706/> - same as RFC8806.
RFC4472 - "Operational Considerations and Issues with IPv6 DNS"
<https://datatracker.ietf.org/doc/rfc4472/>, RFC3901 - "DNS IPv6 Transport
Operational Guidelines" <https://datatracker.ietf.org/doc/rfc3901/> - Make
DNS fast by making sure IPv6 works too….
RFC3258 - "Distributing Authoritative Name Servers via Shared Unicast
Addresses" <https://datatracker.ietf.org/doc/rfc3258/> - A  big one. Any
cast FTW!

W



On Mon, Jan 26, 2026 at 11:19 PM, Cathy Zhang <[e-mail]> wrote:

> Hello everyone,
>
> Are there any RFCs or drafts defining DNS query/response latency?
>
> Regards,
> Cathy
>
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