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Re: [dnsop] DNS Anycast revisited (fwd)

  • From: Edward B. Dreger
  • Date: Tue May 03 22:42:45 2005

TV> Date: Tue, 3 May 2005 22:21:45 -0400 (Eastern Daylight Time)
TV> From: Todd Vierling

[ trimming CC list before it grows too long ]


TV> And last time I checked -- on this list, mind you -- it certainly
TV> was not.  Cf. people trying to run and hide, or lash out at me for
TV> complaining, when I pointed out how two anycast routes pointing to
TV> the same dead node made the .ORG anycast implementation unusable.

Akamai's service uses non-coherent DNS by design.  Your post referenced
a failure case in which DNS service was not coherent by virtue of
certain pods not responding; UDNS attempts to provide coherent DNS
service.


TV> I reserve judgment on whether their implementation has been fixed in the

"me too"


TV> meantime; I have no evidence either way at the moment.

One of the challenges of anycast is failure detection and mitigation.

<mumbles>
flooding clusters via source-based routing
tunneling anycast-destined OAM packets via unicast
ns-to-machine affinity within pods
tight coupling of DNS service to anycast route injection
</mumbles>

Anycast implementation _does_ present new operational challenges, but
they're hardly insurmountable.


Eddy
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