[ntp:questions] Loopstats updated less frequently than expected

David Mills mills at udel.edu
Sun May 24 03:37:19 UTC 2009


Bill,

Wrong. Please read the description of the clock filter algorithm again 
and we can discuiss ir further.

Dave

Unruh wrote:

>"David J Taylor" <david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid> writes:
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>>Folks,
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>>I have the following entries in ntpd.conf:
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>>server 192.168.0.2  iburst maxpoll 6
>>server 192.168.0.7  maxpoll 6
>>server 0.uk.pool.ntp.org minpoll 10
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>>.. and the following as the most recent loopstats:
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>>54974 37901.029 -0.000209922 13.840 0.000108471 0.007233 6
>>54974 38229.033 0.000346890 13.846 0.000221473 0.007179 6
>>54974 38754.041 -0.000217131 13.840 0.000287548 0.007132 6
>>54974 38954.047 -0.000091306 13.839 0.000272631 0.006682 6
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>>I note that the times between these four entries are:
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>>328s
>>525s
>>200s
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>>As I have maxpoll set to 6, I would have expected entries no more than 64s 
>>apart.  What am I failing to understand here?  The poll values reported in 
>>ntpq -p are 64, 64 and 1024 - as expected.
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>You are forgetting that ntp throws away 7/8 of the stuff it collects.
>(This is in an attempt to counter round trip biases).
>Thus you would expect to have 8 times the max poll interval between
>loopstats. (it is random so it is not always exactly 8 times sometimes
>less, but never more, but it averages out to pretty close to 8 times.)
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>>Thanks,
>>David 
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