[ntp:questions] root vs peer dispersion?

Towli towli at oldboyz.dk
Wed May 6 22:39:32 UTC 2009


I appreciate your time David.
Thank you.

/T
"David Woolley" <david at ex.djwhome.demon.co.uk.invalid> skrev i meddelelsen 
news:49ff2919$0$516$5a6aecb4 at news.aaisp.net.uk...
> Towli wrote:
>
>>
>> why is the root dispertion not "0" when the Dcf77-clock is sitting on 
>> port 20 on the switch? is 5.45 the time the Dcf77-signal takes to travel 
>> from Frankfurt to Denmark where i am located? What then does the peer 
>> dispersion time of 2.84 msec tell me?
>
> Because:
>
> - the DCF 77 time wasn't read immediately before you requested the time 
> from NTP, so the time could have drifted since then.
> - I'm not sure, but I think that the best sample might not be the most 
> recent;
> - there is an uncertainty in reading the clock due to the finite 
> resolution of the clock;
> - I think there may be an element of the historic variability thrown in;
> - using too low a root dispersion means the error band is very small, so 
> it only needs a small error to make it impossible to get overlapping error 
> bands. 




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