Re: [DNSOP] Anycast and DNS questions

[Joe Abley <[e-mail]>]

On 6 August 2014 at 8:10:25, Patrick W. Gilmore ([e-mail]) wrote:

> Composed on a virtual keyboard, please forgive typos.
> 
> On Aug 6, 2014, at 7:47, Toerless Eckert wrote:
> >
> > Sorry, haven't been following this group for a long time, so
> > please excuse if answers to these questions have been discussed in before:
> >
> > a) What documents beside RFC3258 are describing any uses/procedures
> > for having DNS servers use an anycast address to receive and respond to
> > requests ?
> 
> Dunno, but something tells me a quick BING search would return millions of answers.

I've written some stuff:

RFC 4786 has some general advice
ISC-TN-2003-1 and ISC-TN-2004-1 were mainly written with F-Root in mind
https://www.usenix.org/legacy/publications/login/2008-02/openpdfs/abley.pdf
https://www.nanog.org/meetings/nanog34/presentations/abley.nameservers.pdf

> > b) How common are deployments in which the information returned by different
> > anycast member DNS servers for the same query would be different,
> > aka: to "localize" lookup results, such as pointing to
> > local CDN caches or the like ? What would be the most well known examples
> > of such deployed instances ? Any IETF documents describing this ? Any
> > rules to follow ?
> 
> Common? Ridiculously so, for at least 20 years.
> 
> Well known examples? CDNs, as you already mentioned. E.g. LLNW.

Various commercial DNS services do this (e.g. Dyn does this). I'm not aware of any documentation produced in the IETF beyond the base DNS specification (which doesn't talk about anycast, but does talk about the loose coherence between sibling authority servers and between caching resolvers and authority servers).

It's not obvious to me whether pool.ntp.org does this. I think the geo focus there is pulled in the QNAME, and the RRSets in the response are near-consistent across the authority set at query time (but the response sets vary with time, according to performance of the target NTP servers). But you could ask Ask. I bet he never gets tired of people saying that.

> > c) Any example in which the DNS servers utilizing a single shared
> > IP address (anycast address) are run by different operators ? Any
> > documents describing this ? (RFC3258 seems to focus on single operator
> > anycast group of DNS servers.
> 
> How about the root servers?

Root servers are not an example of that: each letter is run by a single organisation and each letter has a set of service addresses that are unique to that letter.

AS112 is a better example (see RFC 6304, http://www.as112.net/)


Joe