[ntp:questions] What level of timesynch error is typical on Win XP?

Joseph Gwinn joegwinn at comcast.net
Thu Oct 21 12:34:38 UTC 2010


In article <i9njj8$eae$1 at news.eternal-september.org>,
 David Woolley <david at ex.djwhome.demon.invalid> wrote:

> Joseph Gwinn wrote:
> > I have a small network of Windows XP (64 bit) running simulations, with 
> > NTPv4 running on all the boxes and using a GPS-based timeserver on the 
> > company network.  The ping time to the server is 2 milliseconds from my 
> > desk, but I'm seeing random time errors of order plus/minus 5 to 10 
> > milliseconds, based on loopstats data.
> 
> Loopstats data cannot give you an accurate measure of error when ntpd is 
> locked on.  It will give a value that is distinctly pessimistic.  If 
> ntpd could measure the actual error, it ought to be possible for it to 
> remove that error.

This is certainly true, but loopstats and peerstats data is nonetheless 
useful as a proxy for the unmeasured actual clock offset.  In other 
words, if loopstats data shows adequate stability for my application, 
true offset error will also be adequate.   Unless the transport delay is 
asymmetric, which is not the case here.

Nor do I have the hardware to make better offset measurements than those 
provided by loopstats and peerstats.


Joe Gwinn




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