[dns-operations] dns-operations Digest, Vol 105, Issue 26

Bob Harold rharolde at umich.edu
Thu Oct 23 14:30:11 UTC 2014

> Date: Wed, 22 Oct 2014 15:38:14 -0400
> From: Andrew Sullivan <ajs at anvilwalrusden.com>
> To: dns-operations at dns-oarc.net
> Subject: Re: [dns-operations] resolvers considered harmful
> Message-ID: <20141022193814.GI37494 at mx1.yitter.info>
> Content-Type: text/plain; charset=us-ascii
> On Wed, Oct 22, 2014 at 11:19:45AM -0700, David Conrad wrote:
> >
> > That cost is discussed in the paper (section 5).
> Their model doesn't make it a "large" increase, and I think that's
> because of their unrealistic assumptions about actual use.  The
> problem is that the really popular domains on the Internet (Google is
> one example they do discuss) have completely different patterns than
> everyone else.  The mitigation technique of increasing TTLs imposes a
> cost on the operator of the popular domain (a cost in terms of
> flexibility).  The authors seem to think this is no large cost, and I
> disagree.
> --
> Andrew Sullivan
> I think one of the assumptions that is likely wrong is the cache times.
Many computers are turned off at the end of the day, which clears the
cache, so the numbers should be recalculated with one day max cache time as
a possible worst case.

Also, the two day TTL's on top-level zones are already too long.  If I am
forced to move from one DNS provider to another, being down for two days is
a problem.  Anything longer is even worse.

Bob Harold
University of Michigan
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