[ntp:questions] NTP.ORG MEINBERG KEEP TIME ACCURATE to 10MS

David Taylor david-taylor at blueyonder.co.uk.invalid
Wed Nov 14 08:42:01 UTC 2012


On 13/11/2012 21:24, gbusenberg at yahoo.com wrote:
> I am not sure if this is possible.  I have a requirement from a customer that the time must be within 10ms of the parent server which is on the same LAN.  I have tried several different things without an luck.  NTP Time seems to get up to 400ms with defaults.
>
> I have tried to put the following within my ntp.conf file
>
> tinker panic 0 step .3 stepout 60
> driftfile <default>
> server 10.1.126.204 iburst minpoll 5
> server 127.127.1.0
> fudge 127.127.1.0 stratum 12
>
> If it is not possible to do 10ms, then I want to get the time as close as possible.  I really don't know much about NTP.  I have tried my best to search the web as much as possible however most people inclucding myself never use the tinker other than with panic 0.

An example of what Windows PCs can do is shown here:

   http://www.satsignal.eu/mrtg/performance_ntp.php

The top line is a FreeBSD stratum-1 server, to which the other PCs are 
synced (Hydra, Narvik, Puffin, Bergen, Ystad).  Several of the Windows 
PCs have their own GPS/PPS reference clock (Alta, Bacchus, Feenix, 
Stamsund).

The secret has been to make a tight connection between the Windows PCs 
and the "best available" stratum-1 server by fixing the polling at 32 
seconds.  In your case, this may correspond to a line like:

  server 10.1.126.204 iburst minpoll 5 maxpoll 5

On the basis of a test I tried recently, you might try using a FreeBSD 
or Linux-based server to connect to remote server (this could be a 
low-cost Raspberry Pi server, possibly with its own GPS), and sync the 
Windows PCs tightly to that server.  Even using Internet servers I saw 
no more than an 5 ms reported offset with such a simple server:

   http://www.satsignal.eu/ntp/2012-11-10-11-12-raspi1_ntp-b-day.png
   http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

If you can equip that intermediate server with a GPS/PPS source, so much 
the better.  You could also consider equipping one or more PCs with 
GPS/PPS reference clocks.

You may find my Windows information helpful:

   http://www.satsignal.eu/ntp/index.html
-- 
Cheers,
David
Web: http://www.satsignal.eu



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