[ntp:questions] NTP Performance on WINNT

paul chaofu.chen at gmail.com
Mon Jul 20 15:22:38 UTC 2009

On Jul 20, 10:36 pm, "David J Taylor" <david-tay... at blueyonder.not-
this-part.nor-this.co.uk.invalid> wrote:
> paul wrote:
> > Hi All, I'm new to NTP, glad to meet you here.
> > I did some experiments to test NTP performance on WINNT. In an
> > isolated network, two machines are inter connnected with a switcher.
> > Machine A is configure as a stratum 12 NTP server, using lcl as
> > reference clock; machine B is sychronized to machine A. Then, 'ntpq -
> > p' is performed on machine B every 16 seconds. The output of ntpq is
> > cooked by a python script and offset field is recorded to log file.
> > After about 2 hours, I check the log file and found the offset value
> > is 4 ~ 8 ms. Is this normal? I mean if things are properly done, how
> > small the offset I can expect? Thanks.
> > The OS is Windows XP Pro SP3 and NTP software is 4.2.4-p7 from
> > mainberg.
> Paul,
> For comparison, I have the performance of a mixture of Windows systems
> running a mixture of NTP versions plotter here:
>  http://www.satsignal.eu/mrtg/daily_ntp.html
> The Windows XP system synced to a local stratum-1 clock is Narvik, showing
> an offset of within 1.5ms, but that is with a poll interval clamped to
> 64s.  The best is the system Feenix with a local GPS serial and PPS
> reference clock (but no temperature control) where the offset is within
> about 0.2ms, and the worst the Windows Vista system Gemini which has a
> DVB/USB data reception system capturing about 20GB/day, but clobbering the
> offset with transient peaks of at least 50ms.
> "How long is a piece of string...." comes to mind!
> Cheers,
> David

Thank you, David.

In my situation, no GPS is availiable. So can I expect better
performance when GPS is used as reference clock, or when a stratum-1
NTP server is added to the network?

And, I noticed the offset for Narvik is more stable than that for
Hydra, is it due the PPS feeded to Narvik? But Bacchus is doing good
too without PPS, Why?

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