[ntp:questions] Varying Offset Values

David Russell drussell at thrupoint.net
Sat Aug 19 19:16:50 UTC 2006



I have been observing the values that a stratum 2 server has for its clock
offset from multiple stratum 1 GPS based time servers using ntpq -p.


Two of the three time servers show an offset agreement in the 50-200
microsecond range.  But the offset for third, which is at the same site as
one of the first two, has been off as much as 10 milliseconds from the other
two but now is down to 800 microseconds. 


The first two timer servers are installed at different sites and the third
is installed on an adjacent subnet to one of the servers in the first group.
I am showing a consistent offset for two stratum 1 servers at different
sites but a significant difference between two stratum 1 servers that have a
nearly identical path to/from the stratum 2 server.


It seems to me that the data is telling me that the third stratum 1 server
is drifting all over the place and should be taken out of service and fixed.


My question is: if I had three stratum 1 servers installed side by side that
were perfect time keepers, shouldn't my stratum 2's clock offset from the
each of stratum 1 servers be nearly the same? 








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