Re: Looking for geo-directional DNS service

[Paul Vixie <vixie () isc org>]

[patrick () ianai net ("Patrick W.Gilmore")]
> And even if you do define topology to be equivalent to BGP, that is not
> what is of the greatest interest.  "Goodput" (latency, packet loss,
> throughput) is far more important.  IMHO.

in my less humble justified true belief, this is 100% truth.

> This in no way means anycast sux.  It just means anycast is not, by a
> long shot, guaranteed to give you the "closest" node by any reasonable
> definition.  (Sorry, I don't think "node BGP picks" is "reasonable".  ...

i also second this notion.

in our (ISC's) current use of anycase (for f-root and other dns servers),
anycast is a crutch for not having a global backbone, but wanting f-root to
have global representation and extreme replication.  informal studies don't
show as much locality as we'd like -- but by peering aggressively everywhere
and by setting no-export on our route almost everywhere, we've been able to
localize and isolate ddos effects, which is all we were trying to accomplish.

but note, f-root is a normal dns server, it has an absolute mapping between
<qname,qtype,qclass,time> and <answer>.  i don't believe in stupid dns tricks
(where that mapping is relativized for TE purposes), and one of the reasons
for my disbelief is that many ISP's in f-root's ~40 IXP locations do not
peer with us, and their traffic is therefore answered in remote (to them)
places where TE can't be predicted.  in other words, people doing "stupid dns
tricks" are probably counting on anycast to do something f-root doesn't care
about (and which i think BGP won't do even on its best day.)
-- 
Paul Vixie