ntpd flipping between PLL and FLL mode
Michael Proto
mike at jellydonut.org
Tue Dec 19 09:51:44 PST 2006
Jeremy Chadwick wrote:
> On Tue, Dec 19, 2006 at 10:56:22AM -0500, Michael Proto wrote:
>> An alternate workaround I've discovered is to use a maxpoll of 9 in
>> /etc/ntp.conf:
>>
>> server rolex.peachnet.edu maxpoll 9
>>
>> Since implementing this I haven't seen any of the FLL/PLL flips in my logs.
>
> How would decreasing the polling time fix this? I do not understand
> the semantics/behaviour of NTP very well.
>
> Taken from the manpage:
>
> maxpoll maxpoll
> These options specify the minimum and maximum poll intervals for
> NTP messages, in seconds to the power of two. The maximum poll
> interval defaults to 10 (1,024 s), but can be increased by the
> maxpoll option to an upper limit of 17 (36.4 h). The minimum
> poll interval defaults to 6 (64 s), but can be decreased by the
> minpoll option to a lower limit of 4 (16 s).
>
I made the change some time ago after combing newsgroups for this issue,
so my memory is a little hazy, but I seem to remember something about
the FLL/PLL switch being right at about 1024s. Check the Tuning section
here:
http://www.eecis.udel.edu/~ntp/ntpfaq/NTP-s-algo.htm
-Proto
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