[ntp:questions] Is this normal?

Russell, David David.Russell at dowjones.com
Mon May 10 17:45:05 UTC 2010

I am trying to verify the correct implementation of NTP on a device that is configured to poll a GPS based dedicated time server on the local area network.  The round trip times to this stratum 1 vary between 3.3 and 3.4ms.

I have plotted the offset vs drift in the included jpg.  The drift rate varies between -3 and -3.2 us/s and the offset is +/- 200us.  Note that the first part of the graph is when NTP started.

My questions are that given that a device has excellent network access to a good stratum 1 server should the drift rate vary this much?  Can I infer anything from the data regarding proper computations in the code, timestamping of the packets or even the system clock?

Thanks in advance,


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