[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





More information about the questions mailing list