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RE: Above.net problems ??

  • From: Duane Wessels
  • Date: Wed Nov 26 13:35:10 2003 
> You'd think that an unresponsive nameserver would be flagged dead, and such
> information be cached. Does anyone know whether that's actually done in Bind
> 8.3.4? Or perhaps not by default?

This certainly does not happen when all authoritative nameservers
are unresponsive.  See http://www.nanog.org/mtg-0310/wessels.html,
in particular pages 23 and 24 of the slides.

In my simulations with 100% packet loss, DNS caches running BIND8,
dnscache, W2000, and W2003 all amplified the user's query rates.
Only BIND9 attenuated.

The results do depend on the actual query rate, however.  At a
higher query rate, the other caches would/should attenuate as well
(perhaps reaching their hard-coded rate limits), but I don't have
the exact numbers.

It would be interesting to repeat the simulation and take out, say,
half of a set of authoritative nameservers during the middle of the
test.

Duane W.