[Pool] DNS queries per second

Chuck Swiger cswiger at mac.com
Wed Mar 23 00:06:43 UTC 2011


On Mar 22, 2011, at 4:59 PM, Ask Bjørn Hansen wrote:
> I don't have any ideas for how to avoid this; but basically a crazy amount of the SNTP clients sync just at the top of the hour; or close to it. 
> 
> Below is a second by second query count on one of the busier DNS servers for pool.ntp.org.   The normal load is as it is just before the top of the hour and it drops most of the way back to that after a few minutes (and all the way after ~15 minutes it looks like).

Yes, it seems to be common for people to set up cron jobs sync'ing once an hour, rather than once an hour + random(300) or so seconds.

A tenfold increase in query rate doesn't strike me as surprising.  Even a T1 or 1.5Mbs symmetric DSL/cable link should be able to handle 1000 NTP queries per second and still have most of its bandwidth left over.

Regards,
-- 
-Chuck



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