[80574] in North American Network Operators' Group
Re: [dnsop] DNS Anycast revisited (fwd)
daemon@ATHENA.MIT.EDU (Edward B. Dreger)
Tue May 3 22:42:10 2005
Date: Wed, 4 May 2005 02:41:55 +0000 (GMT)
From: "Edward B. Dreger" <eddy+public+spam@noc.everquick.net>
To: Nanog@merit.edu
In-Reply-To: <Pine.WNT.4.63.0505032219400.3196@tvierling-jvc>
Errors-To: owner-nanog@merit.edu
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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