How to tell if something is anycasted?

Steve Gibbard scg at gibbard.org
Wed May 17 18:11:42 UTC 2006


On Wed, 17 May 2006, Martin Hannigan wrote:

> And there are many, with many TLD's.
> (rough counts)
>
> provider/tld's
>
> UDNS 48
> ISC 19
> PCH 8
> PSG 23
> ICANN 4
> UUNET 61
> RIPE 87
> DEC 10
> NIC.FR 71
>
> Note: There is cross servicing of TLDs counted above.
>
> Some numbers may seem low since there seems to be some bit of
> obfuscation. Or perhaps not and I just haven't confirmed.
>
> Some are anycasted, some appear to be physical separations, and some
> appear to be nested and anycasted i.e. multiple names for the same domain
> anycasted.
>
> I think naming is a bad choice because it's costly to the users and opens
> the root up to custom configuration by customers which I think is bad.
>
> Tagging the route with a community containing the ISO corresponding country
> could be interesting for location purposes, but of course, that's already
> been thought of. :)

Of Marty's list above, only UltraDNS and PCH are anycast (there 
are several other anycast networks hosting TLDs that aren't on Marty's 
list).

The numbers there look odd to me.  My data is a six months old (I really 
need to rerun my script and regenerate it), but my list of /24s and the 
TLDs they host is at:

http://www.gibbard.org/~scg/infrastructure-distribution/ranked-dns-subnets-051110

I assume that in most cases a /24 with multiple DNS server IP addresses 
being authoritative for TLDs is all run by one entity in a common location 
or set of locations.  UUNet is an exception to the location assumption.

-Steve



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