[ntp:questions] Single best NTP status indicator of clock accuracy?
Ulrich Windl
Ulrich.Windl at RZ.Uni-Regensburg.DE
Fri Jul 16 06:05:29 UTC 2010
kjans <kert.jans at gmail.com> writes:
> Hi,
>
> I am looking for the best single indicator that can be used to
> determine/monitor the current clock accuracy.
"Best and single" seem to contradict. What about "root dispersion"? ;-)
>
> I have several remote/embedded Linux devices that I am monitoring
> via SNMP and want to monitor a single variable to know how accurate
> the device thinks its time is.
>
> There seems to be several possibilities:
> - delay or offset or jitter (from ntpq -clpeers)
> - sync distance (from ntptrace)
> - maximum error (from ntpdc)
estimated error, maybe.
> - precision (from ntpq -crl)
That's a constant.
> - ?
>
> Below is the output of several NTP status monitoring commands...
>
>
> # ntpq -clpeers
> remote refid st t when poll reach delay
> offset jitter
> ==============================================================================
> LOCAL(0) .LOCL. 10 l 43 64 377 0.000
> 0.000 0.015
> *GPS_NMEA(0) .MAL. 0 l 4 16 377 0.000
> 0.156 0.015
> +ntp-2.gw.uiuc.e 128.118.25.5 2 u 41 64 377 71.652
> 2.432 0.528
> +ntp-1.gw.uiuc.e 128.174.38.133 2 u 21 64 377 72.009
> 2.373 1.389
>
>
> # ntptrace
> localhost: stratum 1, offset 0.000159, synch distance 0.000539, refid
> 'MAL'
>
>
> # ntpdc -c kerninfo 127.0.0.1
> pll offset: 0.000151 s
> pll frequency: -27.934 ppm
> maximum error: 0.007856 s
> estimated error: 1.5e-05 s
> status: 0001 pll
> pll time constant: 4
> precision: 1e-06 s
> frequency tolerance: 512 ppm
>
> # ntpq -crl
> assID=0 status=04f4 leap_none, sync_uhf_clock, 15 events, event_peer/
> strat_chg,
> version="ntpd 4.2.2p4 at 1.1585-o Fri Jun 15 10:17:41 UTC 2007 (1)",
> processor="i486", system="Linux/2.6.21-tinytgb5-pc", leap=00,
> stratum=1,
> precision=-16, rootdelay=0.000, rootdispersion=0.393, peer=56438,
> refid=MAL, reftime=cecbd50a.91b1b70c Thu, Dec 10 2009 12:14:02.569,
> poll=10, clock=cecbd50f.302c13d6 Thu, Dec 10 2009 12:14:07.188,
> state=4, offset=0.057, frequency=-27.993, jitter=0.015, noise=0.015,
> stability=0.000, tai=0
>
>
> Thanks,
> Kert
More information about the questions
mailing list