[dns-operations] Who Ignores TTLs ?

Patrick W. Gilmore patrick at ianai.net
Tue Feb 22 10:01:18 UTC 2011

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.

I'll check internally to verify my data.


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