[ntp:questions] GPS Truetime NTP server and offset/jitter peak

Ralf Gross usenet at ralfgross.de
Tue Oct 18 09:08:26 UTC 2005


Hi,

I've a problem with a Truetime NTS-100-GPS device connected by RS232 to a
CentOS 4 Linux server (ntp-4.2.0.a.20040617-4).

Every night at 2am (CEST) offset an jitter suddenly shows very high values
and as a result ntpd loses sync to the GPS stratum 0 device for about 30
seconds.

14 Oct 02:00:08 ntpd[2758]: synchronized to         $IP, stratum 3
14 Oct 02:00:42 ntpd[2758]: synchronized to TRUETIME(0), stratum 0
15 Oct 02:00:11 ntpd[2758]: synchronized to         $IP, stratum 3
15 Oct 02:00:45 ntpd[2758]: synchronized to TRUETIME(0), stratum 0
16 Oct 02:00:03 ntpd[2758]: synchronized to         $IP, stratum 3
16 Oct 02:00:37 ntpd[2758]: synchronized to TRUETIME(0), stratum 0
17 Oct 02:00:05 ntpd[2758]: synchronized to         $IP, stratum 3
17 Oct 02:00:54 ntpd[2758]: synchronized to TRUETIME(0), stratum 0
18 Oct 02:00:07 ntpd[23139]: synchronized to         $IP, stratum 3
18 Oct 02:00:39 ntpd[23139]: synchronized to TRUETIME(0), stratum 0


02:00:07
      remote       refid   st t when poll reach   delay   offset  jitter
==============================================================================
*TRUETIME(0)     .TRUE.    0 l   16   16  376    0.000   -0.042    0.277
...                                                      ^^^^^^
---------------------------------  ok----------------------/

      
02:00:08
      remote       refid   st t when poll reach   delay   offset  jitter
==============================================================================
xTRUETIME(0)     .TRUE.    0 l    1   16  377    0.000  -999.57   999.525
...                                                     ^^^^^^^
---------------------------------- peak ------------------/               


02:00:39
      remote       refid   st t when poll reach   delay   offset  jitter
==============================================================================
*TRUETIME(0)     .TRUE.    0 l    -   16  377    0.000   -0.170   534.165
...                                                      ^^^^^^
----------------------------------- ok --------------------/


I thought it might be a cron job running at that time, but I can't find
anything related in the cron log file.

/var/log/ntp.log
17 Oct 02:00:05 ntpd[2758]: synchronized to         $IP, stratum 3
17 Oct 02:00:54 ntpd[2758]: synchronized to TRUETIME(0), stratum 0

/var/log/cron
Oct 17 01:01:01 WU5SN002 crond[22453]: (root) CMD (run-parts /etc/cron.hourly)
Oct 17 02:01:01 WU5SN002 crond[22456]: (root) CMD (run-parts /etc/cron.hourly)
Oct 17 03:01:01 WU5SN002 crond[22458]: (root) CMD (run-parts /etc/cron.hourly)

 
Any ideas what the reason for this peak might be?

Ralf





More information about the questions mailing list