[ntp:questions] Server stopped syncing to PPS?

Peter Eriksson peter at ifm.liu.se
Fri Feb 3 10:09:55 UTC 2006


How can one find out *why* a server suddenly decieded that the
PPS signal should be ignored (even though it looks just fine)
after having been running fine for a day or so? (It choose the PPS
source after a little while just as it should behave).

System: Sun Ultra 5, Solaris 9, NTP 4.2.0a, ARBITER GPS clock

# /ifm/bin/ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+ntp1.sp.se      .PPS.            1 u   66   64  376   12.803    1.646   3.563
+ntp2.sp.se      .PPS.            1 u   45   64  377   15.386    2.901   2.184
+Time1.Stupi.SE  .PPS.            1 u   57   64  377   11.445    3.674   3.145
+Time2.Stupi.SE  .PPS.            1 u   21   64  377   10.441    3.154   1.139
+ntp0-rz.rrze.un .GPS.            1 u   17   64  377   74.422    2.797   2.686
+ntps1-0.cs.tu-b .PPS.            1 u   70   64  176   75.067    3.061  11.140
+time.nist.gov   .ACTS.           1 u   50   64  377  157.545    2.023   3.557
-time-b.nist.gov .ACTS.           1 u   15   64  377  124.831   -6.468   4.648
+timekeeper.isi. .GPS.            1 u   53   64  177  197.808    3.831   7.902
+cornelis.lysato 192.36.134.17    2 u   46   64  377    5.733    3.328   3.954
*GPS_ARBITER(0)  .GPS.            0 l   59   64  376    0.000    0.020   0.022
-PPS(0)          .PPS.            0 l   24   64  377    0.000    0.053   0.010

On a related issue - what's the correct procedure to adjust the offset for
the GPS and PPS signals so that my server will be more in "sync" with
other NTP servers around the world?

As you can see from the list I added a number of stratum 1 servers to my
config in order to try to see what the offset really should be, but it's
kind of hard to really decided that it should be. And 'time-b.nist.gov'
seems to be really off a lot of time...

Another issue that I've seen is that if I unplug the serial cable from
the GPS and then after a while reinsert the cable it seems like NTPD never
starts talking to the GPS again. Dunno why though... This is a bit annoying
(think power outage that temporarily kills the GPS receiver but not the
server).

Config file:

# more /etc/ntp.conf
enable pps

server ntp1.sp.se
server ntp2.sp.se

server time1.stupi.se
server time2.stupi.se

server ntp0.fau.de
server ntps1-0.cs.tu-berlin.de

server time.nist.gov
server time-b.nist.gov

server timekeeper.isi.edu

server cornelis.lysator.liu.se

### Arbiter GPS clock
server 127.127.11.0 prefer
fudge 127.127.11.0 time1 0.02015 

### PPS Discipline
server 127.127.22.0 
fudge 127.127.22.0 flag3 1
#fudge 127.127.22.0 time1 0.002

driftfile /etc/ntp.drift

statsdir /var/ntp/ntpstats/
statistics loopstats clockstats 
filegen loopstats file loopstats type day link enable
filegen clockstats file clockstats type day link enable


- Peter

-- 
-- 
Peter Eriksson <peter at ifm.liu.se>            Phone:    +46 13  28 2786
Computer Systems Manager/BOFH                Cell/GSM: +46 705 18 2786
Physics Department, Linköping University     Room:     Building F, F203




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