[dnsdist] Latency of the DNS resolver

[Stephane Bortzmeyer]

On Sat, Jan 30, 2021 at 06:11:01PM +0000,
 SAMI RAHAL via dnsdist <dnsdist at mailman.powerdns.com> wrote 
 a message of 228 lines which said:

> I want to know the normal response from a dns resolver server in
> general (the value in ms)

For an authoritative server, it is *sometimes* possible to discuss
"typical" or "expected" response times, but it is impossible for a
resolver.

If the data is in the cache, the resolver replies in one or two
milliseconds or less, if it's "local".

If it is not in the cache, all bets are off since the response time
depends on the authoritative name servers of the queried domain. Huge
latencies are possible if they are far away or slow.

That's why it is very difficult to benchmark resolvers.