[ntp:questions] NTP Performance on WINNT

David J Taylor david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Mon Jul 20 14:36:50 UTC 2009

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.


For comparison, I have the performance of a mixture of Windows systems 
running a mixture of NTP versions plotter here:


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!


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