[62486] in North American Network Operators' Group
Re: .ORG problems this evening
daemon@ATHENA.MIT.EDU (E.B. Dreger)
Thu Sep 18 13:25:01 2003
Date: Thu, 18 Sep 2003 17:15:46 +0000 (GMT)
From: "E.B. Dreger" <eddy+public+spam@noc.everquick.net>
To: nanog@merit.edu
In-Reply-To: <Pine.NEB.4.58.0309181250260.8936@server.duh.org>
Errors-To: owner-nanog-outgoing@merit.edu
TV> Date: Thu, 18 Sep 2003 12:52:29 -0400 (EDT)
TV> From: Todd Vierling
TV> I couldn't know for sure from some sites, but traceroutes
TV> sure got there. That would imply that (at their end) the
TV> advertisements were still up.
Which would be an implementation flaw, not something inherently
wrong with anycast.
TV> (Sure, you could run zebra on the cluster. But what about if
TV> the name server SEGVs? There's a lot of possible
TV> scenarios....)
That's why the routing daemon must be aware if the service is up
or not. It requires custom or modified routing software.
Having zebra stat(2) a file that the DNS daemon periodically
touches is a quick way to verify that the DNS server software is
still running. Easy enough. Gross, but effective, and easy
enough.
A proper implementation has the routing daemon monitor the
service in question -- in this case DNS. If a series of test
queries provide the correct response, all is well; if not, it's
time to yank the route.
Again, perhaps there are implementation flaws... I don't know
anything about UltraDNS's internal network. But these can be
fixed, and do not make anycast inherently unreliable. If one
understands, thinks about, and approaches the problem, it can be
solved.
Eddy
--
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