readme.stats

Network time protocol source study

Statistics file formats (README.stats)

The xntp3 daemon can produce a variety of statistics files which are
useful for maintenance, evaluation and retrospective calibration
purposes. See the xntpd.8 man page for instructions on how to configure
this feature. Since these files can become rather large and cumbersome,
they are ordinarily reduced to summary form by running the summary.sh
shell script once per day, week or month, as appropriate. There are
three file collections presently defined: peerstats, loopstats and
clockstats, each of which is described in this note.

peerstats

The following data are collected in the peerstats files. The files are
reduced to summary data using the peer.sh shell script. See the peer.awk
script for further information. A line in the file is produced upon
reception of each valid update from a configured peer.

  49236 30.756 140.173.96.1 9474 0.000603 0.37532

  49236             modified Julian day number
  30.756            time of day (s) past midnight UTC
  140.173.96.1      peer identifier (IP address or receiver identifier)
  9474              peer status word (hex) (see NTP specification)
  0.000603          offset (s)
  0.08929           delay (s)
  0.37532           dispersion (s)

loopstats

The following data are collected in the loopstats files. The files are
reduced to summary data using the loop.sh shell script. See the loop.awk
script for further information. A line in the file is produced at each
valid update of the local clock.

  49236 11.897 -0.000004 -35.9384 0

  49236             modified Julian day number
  11.897            time of day (s) past midnight UTC
  -0.000004         time offset (s)
  -35.9384          frequency offset (ppm)
  0                 phase-lock loop time constant

clockstats

The following data are collected in the clockstats files. The files are
reduced to summary data using the clock.sh shell script, which also
updates the ensemble, etf, itf and tdata data files as well. See the
clock.awk, ensemble.awk, etf.awk, itf.awk and tdta.awk scripts for
further information. A line in the file is produced at each valid update
received from a configured radio clock. Data are at present recorded for
several radios. The first part of each data line is similar for all
radios, e.g.:

  49234 60517.826 127.127.4.1   93 247 16:48:21.814

  49234             modified Julian day number
  60517.826         time of day (s) past midnight UTC
  127.127.4.1       receiver identifier (Spectracom 8170/Netclock-2)
  93 247 16:48:21.814  timecode (format varies)

In the case of the Austron GPS receiver, a good deal of additional
information is extracted from the radio, as described below. The formats
shown consist of one line with all the fields shown in order. The
timecode formats specific to each radio follow. See the file
README.timecodes for detailed information on the timecode formats used
by these radios.

Spectracom 8170/Netclock-2 WWVB receiver

  49234 60517.826 127.127.4.1 ?A93 247 16:48:21.814

  The '?' and 'A' characters are present only when the receiver is
  unsynchronized; otherwise, they are replaced by space ' ' characters.

IRIG audio decoder

  49234 60517.826 127.127.6.0 247 16:48:21?

  The '?' character is present only when the receiver is unsynchronized.

Austron 2200A/2201A GPS receiver

  49234 60580.843 127.127.10.1 93:247:16:49:24.814?

  The '?' character is present only when the receiver is unsynchronized.

Depending on the installed options, the Austron 2200A/2201A recognizes a
number of special commands that report various data items. See the
refclock_as2201.c source module for a list of the commands used. These
data are collected only if the following line is included in the
configuration file ntp.conf:

  fudge 127.127.10.1 flag4 1    # enable extended statistics collection

The format of each data line returned is summarized in the following
list.

External time/frequency data (requires input buffer option IN)

These data determine the deviations of external time/frequency inputs
relative to receiver oscillator time. The following data are typical
using an external cesium oscillator PPS and 5-MHz outputs.

  49234 60580.843 127.127.10.1 93:247:16:49:24.814 ETF

  -85.9             time interval (ns)
  -89.0             average time interval (ns)
  4.0               time interval sigma (ns)
  +1.510E-11        time interval rate
  -4.500E-11        deltaf/f
  +1.592E-11        average deltaf/f
  5.297E-13         sigma deltaf/f
  500               number of samples

Model and option identifiers

These data show the receiver model number and option configuration.

  49234 60708.848 127.127.10.1 93:247:16:51:32.817 ID;OPT;VER

  GPS 2201A         model ident (must be "GPS 2200A" or "GPS 2201A")
  TTY1              rs232 option present (required)
  TC1               IRIG option present (optional)
  LORAN             LORAN assist option present (optional)
  IN                input buffer option present (optional)
  OUT1              output buffer option present (required)
  B.00              data processor software version ("B.00" or later)
  B.00              signal processor software version ("B.00" or later)
  28-Apr-93         software version date ("28-Apr-93" or later)

Internal time/frequency data

These data determine the deviations of the receiver oscillator with
respect to satellite time.

  49234 60564.846 127.127.10.1 93:247:16:49:08.816 ITF

  COCO              current mode (must be "COCO")
  0                 code coast mode (must be zero)
  +6.6152E-08       code sigma (s)
  -3.5053E-08       code delta t (s)
  -4.0361E-11       deltat/t
  -6.4746E-11       oscillator ageing rate
  500.00            loop time constant
  4.984072          electrical tuning (V)

GPS/LORAN ensemble data (requires LORAN assist option LORAN)

These data determine the deviations and weights to calculate ensemble
time from GPS and LORAN data.

  49234 60596.852 127.127.10.1 93:247:16:49:40.812 LORAN ENSEMBLE

  +9.06E-08         GPS t (s)
  +3.53E-08         GPS sigma (s)
  .532              GPS weight
  +3.71E-08         LORAN t (s)
  +3.76E-08         LORAN sigma (s)
  .468              LORAN weight
  +6.56E-08         ensemble t
  +6.94E-08         ensemble sigma (s)

LORAN stationkeeping data (requires LORAN assist option LORAN)

These data determine which stations of the LORAN chain are being
tracked, together with individual signal/noise ratios, deviations and
weights.

  49234 60532.850 127.127.10.1 93:247:16:48:36.820 LORAN TDATA

  M                 station identifier; data follows
  OK                status (must be "OK" for tracking)
  0                 cw flag
  0                 sw flag
  1162.17           time of arrival
  -4.6              snr (-30.0 if not "OK" status)
  1.67E-07          2-sample phase-time deviation
  .507              weight (included only if "OK" status)
  W AQ 0 0 3387.80 -31.0  station identifier and data
  X OK 0 0 1740.27 -11.2 2.20E-07 .294  station identifier and data
  Y OK 0 0 2180.71 -4.6 2.68E-07 .198  station identifier and data
  Z CV 0 0 3392.94 -30.0  station identifier and data

Oscillator status and environment

These data determine the receiver oscillator type, mode, status and
environment. Nominal operating conditions are shown below.

  49234 60628.847 127.127.10.1 93:247:16:50:12.817 OSC;ET;TEMP

  1121 Software     Control  oscillator model and mode (must be
                    "Software Control")
  Locked            status (must be "Locked")
  4.979905          electrical tuning (V)
  44.81             oscillator cavity temperature

Receiver position, status and offsets

These data determine the receiver position and elevation, together with
programmable delay corrections for the antenna cable and receiver.

  49234 60788.847 127.127.10.1 93:247:16:52:52.817 POS;PPS;PPSOFF

  +39:40:48.425     receiver latitude (N)
  -075:45:02.392    receiver longitude (E)
  +74.09            receiver elevation (m)
  Stored            position status (must be "Stored")
  UTC               PPS/PPM alignment (must be "UTC")
  0                 receiver delay (ns) (should be zero for calibrated
                    receiver)
  200               cable delay (ns)
  0                 user time bias (ns) (must be zero)

Satellite tracking status

These data determine how many satellites are being tracked. At the
present state of constellation development, there should be at least
three visible satellites in view. Much of the time the maximum of
seven are being tracked; rarely this number drops to two.

  49234 60612.850 127.127.10.1 93:247:16:49:56.820 TRSTAT

  24 T              satellite prn and status (T = track, A = acquire)
  16 A 13 T 20 T 18 T 07 T 12 T  list continued

UTC leap-second information

These data determine when the next leap second is to occur. The exact
method to use is obscure.

  49234 60548.847 127.127.10.1 93:247:16:48:52.818 UTC

  -1.2107E-08       A0 term (s)
  -1.2790E-13       A1 term (s)
  +9.0000E+00       current leap seconds (s)
  +2.0480E+05       time for leap seconds (s)
  +2.0100E+02       week number for delta leap (weeks)
  +1.9100E+02       week number for future leap (weeks)
  +4.0000E+00       day number for future leap (days)
  +9.0000E+00       future leap seconds (s)

David L. Mills
University of Delaware
[e-mail]
23 October 1993