[dns-operations] EDNS0 client-subnet option from Google Resolvers

Robert Edmonds edmonds at mycre.ws
Fri Oct 23 20:52:23 UTC 2015

Daniel Stirnimann wrote:
> > Is this
> > because the resolver figured out that our authoritative name server is
> > not responding this option, so they don't send it every time but just
> > from time to time to check if we support it now?
> Looks like these are indeed probing requests. Found the following:
> "This is implemented by probing nameservers at a low rate with ECS
> queries and caching the ECS capability for each nameserver. Therefore if
> your nameservers do not support ECS, they may still receive a few ECS
> queries occasionally. And if your nameservers just started to support
> ECS, it may take us several hours to detect the change and start to send
> ECS queries to them."

There's also
which I believe is supposed to be describing the Google implementation.

Robert Edmonds

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