[ntp:questions] Reg: NTP accuracy

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Mon Dec 3 16:17:49 UTC 2007


In article <a64f67eb0712020844y6ff010fej38dfabf651da5d68 at mail.gmail.com>,
 linux.newbie79 at gmail.com (linux newbie) writes:
>HI,
>Need following clarification.
>
>Our Application needs to have two individual hardware (with DSP processor)
>to have same crystal clock freqency. Though individual boards are alike, due
>to environmental factors there might be drift after long run.
>
>As the two boards are connected to local LAN through ethernet, we feel by
>comparing time at regular intervals can determine any drift in clock.
>(assuming one board as server and another as client).

>We run 'ntpd' in server and ntpdate in the client and after every 5 seconds,
>if we query the client (ntpdate -q) we find there is millisecond difference.
>As both of them are connected through the same LAN and both are running the
>same time( ofcourse same clock freq) we are suppose to get 'zero' time
>difference.

>Can anyone explain why there is millisecond delay and how to reduce it?

1 ms is a small number.  Try waiting longer.

ntpd tries to keep your local clock in sync with UTC.
One of the important things it does is figure out how
far off your local crystal is.  Look in your drift file.

If you run ntpd (rather than ntpdate) on the client side,
it will also figure out the drift on that machine.

-- 
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