[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 18:18:41 UTC 2006


Probably solved my problem -- forcing the stratum of the PPS unit
("fudge 127.127.22.0 stratum 0") causes both the proper stratum to be
used, and the proper refid.  Still waiting for the system to stabilize,
but it looks like this works.

John
----

John Ackermann N8UR said the following on 04/16/2006 12:29 PM:
> 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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> 




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