[ntp:questions] step and stepout
david at ex.djwhome.demon.invalid
Sun Jun 30 11:49:12 UTC 2013
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Orna Sumszyk wrote:
> My last question is how can I monitor the time offset from my ntp server
> during the running of ntpd to make sure this happens?
Use a PCI parallel port, or possibly a modem control signal on a PCI
serial port. Output a pulse on that port and also record the
interpolated system time at that time. Use a hardware counter to
measure the the time difference between the pulses form the two machines
and combine that with the information they output about their view of
the time when they output the pulses.
Although loopstats will give you the "offset" used as input to the ntpd
clock discipline algorithm, this includes various random and systematic
errors that cannot be measured without special instrumentation, like
that described above. If they could be accurately measured in real
time, ntpd would be using them to correct the time to a level at which
the errors could no longer be corrected in that way.
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