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

[Robert Edmonds]

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
https://tools.ietf.org/html/draft-ietf-dnsop-edns-client-subnet-04#section-12.1,
which I believe is supposed to be describing the Google implementation.

-- 
Robert Edmonds