deploying DNS in large ISP

ray at doubleclick.net ray at doubleclick.net
Thu Jul 5 20:04:39 UTC 2001


On Thu, 5 Jul 2001, Barry Margolin wrote:

> But if you think [pointing users to an "anycast" IP] is a problem,
> imagine putting multiple servers were behind load balancing
> hardware. Then the same client could get different answers from
> one minute to the next.

By anycast, you mean having a single netblock, advertised to multiple
sites via BGP4 routes, and at each site your nameserver(s) would use
the same IP(s); such that US clients would contact the closest
(route-wise) nameserver, and clients in China would contact the
closest nameserver (again, in terms of BGP4 routes)?

We are considering using this exact strategy for our auth DNS, but the
difficulty with troubleshooting you raised (need to gather forensics
from the client-side) is definitely a concern. We would combine the
BGP4 anycast setup with clustering at each site (using a L4 switch).
Anyone (other than the new-defunct UltraDNS) set this up w/ success?

--
Ray



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