[ntp:questions] Oddity Between A Couple Local LAN Sources

Jason Rabel jason at extremeoverclocking.com
Sun Apr 29 14:48:05 UTC 2007


Okay, here's a breakdown of my local NTP sources. I have a little Geode
based SBC running FreeBSD with a GPS/PPS directly hooked up to it. I also
have a Datum/Symmetricom TS2100 GPS connected to my network. Finally I have
a TrueTime/Symmetricom NTS-100 IRIG that gets its signal from the TS2100,
and it too is also connected to the network. The GPS signal goes through a
splitter so all GPS sources are using the same antenna.

Now, the odd thing is the TS-2100 has a higher delay and offset than the
NTS-100. I can see how the offset would be different since there is a delay
in generating the time code on the TS and processing it on the NTS. But
what's up with the delay? All 3 machines on are the same switch. I know for
a fact the NTS-100 only support NTP v3 (I have to code that in the conf
otherwise it won't connect), the TS2100 is supposed to support only up to
NTP v3, but showpeer says it support v4? Is the lack of delay due to v3
code?

[jason at gps ~]$ ntpq -p
     remote           refid      st t when poll reach   delay   offset
jitter
============================================================================
==
*GPS_JUPITER(0)  .GPS.            0 l   14   16  377    0.000    0.011
0.008
+192.168.0.2     .GPS.            1 u   23 1024  377    7.578   -1.458
0.008
+192.168.0.3     .IRIG.           1 u    9 1024  377    0.919   -0.055
0.067

[jason at gps ~]$ ntpstat 
synchronised to GPS/UHF radio at stratum 1 
   time correct to within 0.269 milliseconds
   polling server every 1024 s

ntpdc> showpeer 192.168.0.2
remote 192.168.0.2, local 192.168.0.12
hmode client, pmode mode#255, stratum 1, precision -19
leap 00, refid [GPS], rootdistance 0.00000, rootdispersion 0.00000
ppoll 10, hpoll 10, keyid 0, version 4, association 60311
reach 377, unreach 0, flash 0x0000, boffset 0.00400, ttl/mode 0
timer 0s, flags config, bclient
reference time:      c9df2c82.00000000  Sun, Apr 29 2007  9:38:58.000
originate timestamp: c9df2c82.d0d9de2d  Sun, Apr 29 2007  9:38:58.815
receive timestamp:   c9df2c82.d232f6a2  Sun, Apr 29 2007  9:38:58.821
transmit timestamp:  c9df2c82.d010904e  Sun, Apr 29 2007  9:38:58.812
filter delay:  0.00760  0.00757  0.00757  0.00757 
               0.00761  0.00766  0.00565  0.00566 
filter offset: -0.00146 -0.00145 -0.00142 -0.00142
               -0.00144 0.000513 -0.00042 -0.00047
filter order:  1        0        2        3       
               4        5        6        7       
offset -0.001458, delay 0.00757, error bound 0.13651, filter error 0.00276


ntpdc> showpeer 192.168.0.3
remote 192.168.0.3, local 192.168.0.12
hmode client, pmode mode#255, stratum 1, precision -16
leap 00, refid [IRIG], rootdistance 0.00000, rootdispersion 0.00011
ppoll 10, hpoll 10, keyid 0, version 3, association 60312
reach 377, unreach 0, flash 0x0000, boffset 0.00400, ttl/mode 0
timer 0s, flags config, bclient
reference time:      c9df2c90.1374bc6b  Sun, Apr 29 2007  9:39:12.076
originate timestamp: c9df2c90.1374bc6b  Sun, Apr 29 2007  9:39:12.076
receive timestamp:   c9df2c90.139e62be  Sun, Apr 29 2007  9:39:12.076
transmit timestamp:  c9df2c8f.d005beb9  Sun, Apr 29 2007  9:39:11.812
filter delay:  0.00102  0.00092  0.00084  0.00096 
               0.00108  0.00090  0.00096  0.01474 
filter offset: -0.00012 -0.00005 -0.00004 -0.00008
               -0.00015 -0.00004 -0.00008 0.006798
filter order:  1        0        2        3       
               4        5        6        7       
offset -0.000055, delay 0.00092, error bound 0.13675, filter error 0.00816




More information about the questions mailing list