[time-nuts] NTP, PPS and < 10 us offsets

Miguel Barbosa Gonçalves m at mbg.pt
Tue May 14 20:30:56 EDT 2013


I am trying to figure out why NTP takes so long to react to oscillator
changes... I want it to track the PPS from a Trimble Acutime as closely
as possible.

When checking ntptime on startup I see that the NTP daemon is using
PLL and starts the adjustment interval at 8 s. It then increases to
16, 32, 64, 128 and stops at 256.

I read in the documentation that this limit should be 128 but is now 256.

--- start from http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm ---
intervals 57 says that there were 57 calibration intervals. When PPS
pulses are arriving, this number should increase. Each frequency
adjustment requires a good calibration interval. The length of the
current calibration interval can be found as interval 128 s (128
seconds is the default maximum length). Remaining numbers count
abnormal conditions as explained below.
--- end ---

How can I make it stop earlier? At 64 s for example?

Any ideas?


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