[ntp:questions] Re: What modulates polling interval?

David L. Mills mills at udel.edu
Sat Jan 29 01:16:48 UTC 2005


Chris,

Did you open a window? An engineers description of the poll-adjust 
algorthm would drive the non-engineer to tears, although the flow 
diagrams are on the NTP project page. A non-engineers description is 
that the poll interval is pushed up by increasing time jitter and pushed 
down by increasing frequency wander (temperature change). The pushes 
reach equillibrium at something called the Allan intercept, which 
determines the poll interval. See the papers on the NTP ptroject page.

Dave

Chris Richmond - MD6-FDC ~ wrote:

> Hi Folks,
> 
>    So, the poll time was out to 1024 earlier today.  Now it 64.  What
> causes this to modulate?
> 
> Also, what units are offset and jitter?  Is is ms or us?  In any case,
> this is a home network, so no big deal.
> 
> CMD: [/usr/local/bin/ntpq -p -n]
>      remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> +216.27.190.202  140.142.16.34    2 u   59   64  377   22.290   -0.767   1.800
> *63.192.96.2     63.192.96.10     2 u   96   64  377   28.060   -1.166   0.600
> -192.83.249.28   207.126.98.204   2 u   48   64  377   18.010    3.338   0.470
> +204.87.183.6    128.9.176.30     2 u   59   64  377   27.080    2.489   8.180
> 
> Chris
> 



More information about the questions mailing list