[ntp:questions] Request: Query on ntp step threshold value

Sowmya Manapragada skoganty at gmail.com
Mon May 15 18:23:11 UTC 2017


Hello All,
A request, have a query on how to verify modifications done to ntp step
threshold value in ntp.conf:

ntp version: 4.2.8p9
OS: windows 7 in a small lan, clients configured to sync with timesync ntp
servers.
*Modifications done* :
*ntp.conf*
# Specifies the step threshold in seconds. The default without this command
is 0.128 s. If set to zero, step adjustments will never occur.# Note: The
kernel time discipline is disabled if the step threshold is set to zero or
greater than 0.5 s. Further details are on the
#  Clock State Machine page (https://www.eecis.udel.edu/~m
ills/ntp/html/clock.html).
tinker step 0.128  => changed this to    ==>  tinker step 3

The snapshot of the logs are below , please correct me if my understanding
is incorrect:

my changes:>
ntp.conf:>> (enabled tinker step and stepout values)
tinker step 3
tinker stepout 300

ntp-logs:>

10 Apr 22:08:05 ntpd[9828]: 0.0.0.0 0613 03 spike_detect +5.707447 s
10 Apr 22:25:34 ntpd[9828]: 0.0.0.0 061c 0c clock_step +5.739099 s
10 Apr 22:25:40 ntpd[9828]: 0.0.0.0 0615 05 clock_sync
10 Apr 22:25:41 ntpd[9828]: 0.0.0.0 c618 08 no_sys_peer

here since spike_detect is +5.70 >3 sec the clock will step  (expected).is
this correct interpretation ?

If so, then how do we intrepret this log
10 Apr 21:40:28 ntpd[9828]: 0.0.0.0 0613 03 spike_detect -2.691201 s
10 Apr 21:42:42 ntpd[9828]: 0.0.0.0 061c 0c clock_step -2.679624 s
10 Apr 21:42:39 ntpd[9828]: 0.0.0.0 0615 05 clock_sync
10 Apr 21:42:40 ntpd[9828]: 0.0.0.0 c618 08 no_sys_peer
10 Apr 21:53:25 ntpd[9828]: 0.0.0.0 0628 08 no_sys_peer

here since spike_detect is -2.6 < 3 sec, so ideally clock_step should not
happen (instead a slew is expected ? is correct analogy?
i was going  by the definitions:

*>> spike_detect This is informational in that a difference between
the local clock and the valid servers was temporarily greater than the
128ms max offset.
*>* > clock_step Normally modifies the local system clock frequency to
adjust for differences between it and the valid servers. If the offset
is greater than 128ms (in our case 3 sec since we modified tinker step
3), then unless
*>* > configured otherwise, will step the system clock.*

thanks,
Shyam


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