[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

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


Here's the output of ntpq -p:

tick# ntpq -p
remote           refid    st t when poll reach   delay   offset  jitter
oPPS(0)  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

( 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

enable pps
fudge flag3 1
fudge refid PPS

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

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