North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: Looking for geo-directional DNS service

  • From: Patrick W. Gilmore
  • Date: Tue Jan 15 13:06:17 2008

On Jan 15, 2008, at 12:00 PM, Bill Woodcock wrote:
On Tue, 15 Jan 2008, Hank Nussbacher wrote: 
The Ultradns (now Neustar) Directional DNS service is based on
statically defined IP responses at each of their 14 sites so there
is no proximity checking done.

Yes, and that's how anycast works: it directs traffic to the
_topologically nearest_ server. So as long as there's a DNS server
topologically near your data server, your users will get the topologically
nearest of your servers. Which is why so many content folks _do_ roll
their own: to ensure fate-sharing between the DNS traffic which
effectively selects the data server, and the eventual data traffic.

If you're doing things on the Internet, instead of the physical world,
topological distance is presumably of much greater interest than whatever
geographic proximity may coincidentally obtain.

Except Hank is asking for true topological distance (latency / throughput / packetloss).

Anycast gives you BGP distance, not topological distance.

Say I'm in Ashburn and peer directly with someone in Korea where he has a node (1 AS hop), but I get to his node in Ashburn through my transit provider (2 AS hops), guess which node anycast will pick?

--
TTFN,
patrick