[ntp:questions] Polling time backoff

Bill Unruh unruh at physics.ubc.ca
Mon Nov 30 04:59:45 UTC 2009


On Sun, 29 Nov 2009, Richard B. Gilbert wrote:
>> 
> A much oversimplified explanation is that short poll intervals are used to 
> correct large errors quickly and long intervals are to correct small errors 
> very accurately.

That is true if you are refering to rate errors, it is not for offset
errors. For offset errors you are probably better off always with a
short poll interval-- it catches all errors more rapidly. For rate
errors there is the balance between white noise ( the independent errors
from measuements of the offset due to delays, etc,) which become less as
the baseline is increased, and fluctuations in the rate itself. But most
people want their clock to minimize offset not to minimize rate errors,
unless you expect there to be long periods of time in which the clock is
offline.

>
>

-- 




More information about the questions mailing list