[ntp:questions] Loop Filter Gains vs. Polling Interval

Richard B. Gilbert rgilbert88 at comcast.net
Tue May 17 00:32:32 UTC 2011


On 5/14/2011 1:23 PM, Mischanko, Edward T wrote:
> Can anyone tell me, does the sensitivity for frequency adjustment lessen
> as the polling interval increases?  I ask because I'm observing that my
> offset increases and the frequency adjustment decreases to the point I
> fall out of sync at polling intervals above 256.  What am I doing wrong?
>
>
> #    File:       ntp.conf
> #    Purpose:    give the NTP Service its startup parameters and
> #                list of startup files.
> #
> #
> # Miscellaneous stuff
> tinker huffpuff 10240
> tos minclock 5 minsane 3
> #
> driftfile "C:\Program Files\NTP\etc\ntp.drift"
> #
> enable stats
> statsdir "C:\Program Files\NTP\etc\"     # directory for statistics
> files
> statistics loopstats
> filegen loopstats file loopstats type day link enable
> #
> #    Need to set up time sources...
> #
> #
> server 000.000.112.1 burst minpoll 4 maxpoll 8
> server 000.000.120.1 burst minpoll 4 maxpoll 8
> server 000.000.121.1 burst minpoll 4 maxpoll 8
> server 000.000.122.1 burst minpoll 4 maxpoll 8
> server 000.000.123.1 burst minpoll 4 maxpoll 8
> server 000.000.124.1 burst minpoll 4 maxpoll 8
> server 000.000.125.1 burst minpoll 4 maxpoll 8
> server 000.000.126.1 burst minpoll 4 maxpoll 8
> server 000.000.129.1 burst minpoll 4 maxpoll 8
> server 000.000.131.1 burst minpoll 4 maxpoll 8
> server 000.000.134.1 burst minpoll 4 maxpoll 8

Suggest you "lose" the minpoll and maxpoll!  NTPD will pick values 
appropriate for the conditions then obtaining!  If conditions change
NTPD will pick new values.  This is one of those times when your 
computer is smarter than you are!

Then pick four, five, or seven servers that are close to you in "net 
space".  A configuration using four servers can survive the failure of 
one server, five servers will survive the failure of two servers and 
seven will survive the failure of three.  You should use sufficient
geographical diversity that the same power outrage would not affect all 
of your servers.






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