David Taylor david-taylor at blueyonder.co.uk.invalid
Thu Nov 15 06:54:20 UTC 2012

On 14/11/2012 21:40, gbusenberg at yahoo.com wrote:
> Below ntpq -p from my server which gets time from  I see there is a lot of Jitter.  Is the offset of 259ms.
>       remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> *       3 u 1006 1024   77    0.043  -259.69 165.850
> driftfile "C:\Program Files (x86)\NTP\etc\ntp.drift"
> server iburst minpoll 4

In which case, there must be something grossly wrong.  The jitter I see 
with LAN servers to LAN clients is usually well under a millisecond, and 
on Windows Vista 0.977 milliseconds.  Even WAN servers only show 2 - 10 
milliseconds (typically the low end of that range).  Offsets are in the 
order of 0.5 milliseconds for LAN servers, and less than 10 milliseconds 
for WAN servers.

So for a LAN connection to show 259 milliseconds offset and 165 
milliseconds of jitter suggests a problem.  Perhaps is 
really not very stable at all?  Perhaps, as was suggested, you are tying 
too closely to the off-site server?  Perhaps the LAN is saturated?  I do 
suggest that you consider a GPS/PPS for one of your local servers (or 
even the PC if one is on 24 x 7 and has a serial port).  You could even 
use a box as simple as the Raspberry Pi computer coupled with a GPS with 
the total solution coming to around US $100 and providing within 50 
microseconds accuracy.


Stick it somewhere on your LAN where there is a view through a window!
Web: http://www.satsignal.eu

More information about the questions mailing list