[ntp:questions] Single best NTP status indicator of clock accuracy?
kjans
kert.jans at gmail.com
Thu Dec 10 20:16:24 UTC 2009
Hi,
I am looking for the best single indicator that can be used to
determine/monitor the current clock accuracy.
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)
- precision (from ntpq -crl)
- ?
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
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