On 2010-05-10, Russell, David <[email protected]> wrote: > --_004_C430DA47D51D0C4B940F6928BAE21F4626A3F15C21SBKMXSMB06win_ > Content-Type: text/plain; charset="us-ascii" > > 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.
Wow. that is a looooong time. If it is really on the same local network, it should be much shorter than that. What is causing the delays-- bad router/switch, or is the local network a modem controlled network? > > 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? Sorry, that can in no way be called excellent network access. It is very poor network access. With the huge variablility of the offset, one would expect variability of the rate. What poll interval are you using on the ntp? Did you write the implimentation of ntp that you are asking whether it works correctly? And what is this "device"? > _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
