PPM is most likely parts per million.
glenn
Michael Hrivnak wrote:
I run ntpd on a Mandriva machine in my home and sync the rest of my machines
to it. It keeps very good time, and according to ntpq, the offsets and
jitters relative to higher-stratum machines are quite low.
Then there's my desktop machine which has serious problems keeping time. It
runs ntpd configured as so:
/*------------------
#/etc/ntp.conf
server 192.168.12.1 prefer maxpoll 7
driftfile /etc/ntp/drift
multicastclient # listen on default 224.0.1.1
broadcastdelay 0.008
-------------------*/
The clock tends to rapidly gain time. 24 hours after manually syncing the
time (ntpdate 192.168.12.1) and then starting ntpd, here's where it sat:
/*----------------
# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
192.168.12.1 128.2.181.91 3 u 21 128 377 0.261 -101968 1243.16
--------------------*/
Apparently it's exceeding the maximum tolerable drift value, as seen here in
the logs:
/*----------------
# zgrep ntpd /var/log/syslog.*
syslog.5.gz:Nov 20 02:03:54 localhost ntpd[3844]: synchronized to
192.168.12.1, stratum=3
syslog.5.gz:Nov 20 02:08:11 localhost ntpd[3844]: frequency error -512 PPM
exceeds tolerance 500 PPM
syslog.5.gz:Nov 20 02:12:29 localhost ntpd[3844]: time reset -1.441427 s
syslog.5.gz:Nov 20 02:12:29 localhost ntpd[3844]: frequency error -512 PPM
exceeds tolerance 500 PPM
syslog.5.gz:Nov 20 02:22:09 localhost ntpd[3844]: synchronized to
192.168.12.1, stratum=3
syslog.5.gz:Nov 20 02:22:09 localhost ntpd[3844]: frequency error -512 PPM
exceeds tolerance 500 PPM
syslog.5.gz:Nov 20 02:29:37 localhost ntpd[3844]: time reset -1.529274 s
syslog.5.gz:Nov 20 02:29:37 localhost ntpd[3844]: frequency error -512 PPM
exceeds tolerance 500 PPM
----------------*/
There are several questions here. Foremost, what can I do to keep better
time? Other questions are: What exactly is "jitter"? I can't even find what
it's units are. My understanding is that the frequency error is in
milliseconds, but what does PPM stand for? Why won't it tolerate a greater
frequency error?
Thanks!
Michael
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