[ntp:questions] Jitter versus polling interval

Unruh unruh-spam at physics.ubc.ca
Fri Mar 6 05:48:14 UTC 2009


mayer at ntp.org (Danny Mayer) writes:

>David J Taylor wrote:
>> I know it's probably one of those "how long is a piece of string" 
>> questions but....
>> 
>> Does anyone know an approximate relationship between polling interval and 
>> peak-to-peak jitter for a non-ref-clock system?  I.e would the jitter 
>> offset) go up linearly with polling interval, or as the square, or what?

>Increased polling frequency increases jitter.

>Think about it.

Yes, and I do not understand your claim. If the averaging interval is the
same, then increased polling will decrease the jitter. If the averaging
interval is a multiple of the polling interval, than the jitter would be
roughly the same, assuming that you are dominated by network measurement
noise. If you are dominated by changes in rate of your clock, then
increasing the polling interval will decrease the jitter. 



>Danny


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