[time] variables reported by ntpq

Kiss Gabor kissg
Tue Nov 14 07:52:15 UTC 2006


>> I searched 'frequency' in RFC 1305 but I did not find such a
> variable.
>> I manage 7 ntp servers and this variable may vary from -255.7 to
> 18.57
>> on them.
>
> Frequency is actually the clock frequency error, measured in PPM (parts
> per
> million). Usually not more than a few tens of PPM.

Oh, I see.

>> Another undefined variable is noise. Nor the manual neither the RFC
>> does mention it. (It's value is in the 37-200 range and quite
> unstable.)
>
> Maybe you mean jitter or stability?
>
> I don't see anything called noise from readvars
> in ntpq, if you could cut and paste showing where the phrase occurs I
> think

$ ntpq -c rl localhost
assID=0 status=0644 leap_none, sync_ntp, 4 events, event_peer/strat_chg,
version="ntpd 4.2.0a at 1:4.2.0a+stable-2-r Fri Aug 26 10:30:12 UTC 2005 (1)"?,
processor="i686", system="Linux/2.6.17", leap=00, stratum=2,
precision=-20, rootdelay=0.508, rootdispersion=28.292, peer=9428,
refid=54.70.78.155,
reftime=c903ecee.571ae2da  Tue, Nov 14 2006  8:21:18.340, poll=9,
clock=0xc903ef95.b221ea35, state=4, offset=-0.026, frequency=-255.776,
noise=0.348, jitter=0.340, stability=3.180
^^^^^^^^^^^

> we could help you. 37 to 200 ms might be typical jitters for a
> congested
> network connection. I think different versions of ntpq use different
> units
> for jitter, some using ms and some using seconds.

My jitter above is definitely in ms comparing to to the output of
"ntpdc -c sysinfo localhost":

...
precision:            -20
root distance:        0.00050 s
root dispersion:      0.03027 s
...
jitter:               0.000381 s
stability:            3.180 ppm
broadcastdelay:       0.003998 s
authdelay:            0.000001 s

I've attached a graph of noise. (The measurement unit is just guessed.)

Gabor
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