[dns-operations] Who Ignores TTLs ?

Florian Weimer fweimer at bfk.de
Tue Feb 22 13:07:49 UTC 2011

* Patrick W. Gilmore:

> On Feb 22, 2011, at 4:44 AM, Florian Weimer wrote:
>> * Roy Arends:
>>> The bulk of caching resolvers will adhere to TTL, but not the exact
>>> value. Mostly, we see resolvers come back slightly before TTL
>>> expires. Don't know the exact error rate yet, will have to
>>> investigate.
>> I expect that more resolvers will be deployed which implement
>> prefetching of frequently queried names, so you'll see more resolvers
>> which come back before the TTL expires.
> I believe this is in contradiction to our data.  There are notable
> exceptions (e.g. 8.8.[8|4].[8|4]), but by-and-large, we do not see
> recursive NSes come back before the TTL.

This was meant as a prediction, not as something which describes
current traffic patterns.

Several implementers are considering some form of prefetch
(particularly for delegations, so it might not be visible across the
board), but it will take some time until this materializes in actual
running code.

Florian Weimer                <fweimer at bfk.de>
BFK edv-consulting GmbH       http://www.bfk.de/
Kriegsstraße 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99

More information about the dns-operations mailing list