[ntp:questions] Question about min/max poll and an interesting plot showing maxpoll's effect

John Ackermann N8UR jra at febo.com
Thu Apr 20 18:48:43 UTC 2006


I am running a stratum 2 server that syncs to my pile o' stratum 1s.  In
addition, just in case my lab explodes, I have a couple of external
clocks.  I've set maxpoll to 6 on the server lines for the internal
machines, to hold the poll interval at 64 seconds.

However, doing so seems to cause the polling interval for the other
servers -- even though they don't specify a shorter maxpoll than the
default, they continue to poll at 64 seconds.  Is that normal?

By the way -- if you want to see the effect of more tightly controlling
ntpd through shorter polling, take a look at
http://www.febo.com/time-freq/ntp/stats/clients.  These plots update
every hour, so may look different by the time you see them, but at least
for now they show a dramatic improvement in stability when switching
from normal polling (which ran out to 1024 seconds) down to maxpoll 6.
The level 2 server is holding within about +/- 4 microseconds to about a
4 microsecond offset from the server (a stratum 1) that is monitoring
it.  Looking at the 7 day plot shows the dramatic change when I made the
maxpoll adjustment.  (Of course "dramatic" is a relative word -- even
polling at 1024 seconds, the server stayed within about a millisecond).

John



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