[ntp:questions] PPS Driver -- getting wrong REFID and stratum when peer isn't local refclock

John Ackermann N8UR jra at febo.com
Sun Apr 16 16:29:15 UTC 2006


Hi --

I'm not sure if this is a bug, or a configuration problem.  I'm running
ntp-stable-4.2.0a-20050720 on a FreeBSD 5.4 system with PPS kernel enabled.

I am trying to use the PPS driver with a refclock that provides only a
PPS signal on the DCD line, but no other timecode.  Therefore, I am
using an external system as the prefer peer, and this, I think is the
problem.

Although the logs and billboard show that I am sync'd to the PPS signal
and all appears well (ntptime also shows expected kernel pps results),
there are two anomalies:

1.  The "refid" is showing as the IP address of the (remote) prefer peer.

2.  The stratum of the PPS clock shows as 1, not 0.  As a result, the
machine advertises itself to remote hosts as a stratum 2 box.

Attached below are the output of ntpq -p, plus my ntp.conf file.

This behaviour breaks the ability to properly use a standalone PPS
source like a Cesium clock.  Should it work this way?  Is there
something wrong with my configuration?  As a workaround, I'm wondering
whether the dreaded local refclock might be usable as the prefer peer,
since I'm using kernel time discipline to keep it sane.  Does that make
sense?

Thanks,

John
----
Here's the output of ntpq -p:

tick# ntpq -p
remote           refid    st t when poll reach   delay   offset  jitter
==============================================================================
oPPS(0)    192.168.1.230  1  l   24   64  377    0.000    0.001   0.004
+tock.febo.com   .PPSG.   1  u   20  256  377    0.465   -0.021   0.041
-toe.febo.com    .PPSW.   1  u   19  256  377    0.484   -0.034   0.083
+databox.febo.co .PPSG.   1  u   18  256  377    0.335   -0.047   0.005

(192.168.1.230 is tock.febo.com)

Here's ntp.conf:

# tick ntp.conf
logfile /var/log/ntpd
driftfile /etc/ntp.drift
statsdir /var/log/ntpstats/
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable

# PPS
enable pps
server 127.127.22.0
fudge 127.127.22.0 flag3 1
fudge 127.127.22.0 refid PPS

server tock.febo.com prefer iburst
server toe.febo.com iburst
server databox.febo.com iburst



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