Hi--
On Jul 21, 2009, at 2:30 PM, mm_202 wrote:
This may be a stupid question, but when you have multiple S1's that
differ greatly, how do you know which one to trust?
Try adding some stratum-2 or -3 servers, and see which of the S1's
tend to keep time close to that of the other sources.
I have 3 configured (Im not going
to keep all 3, but just setup the server in a new colo and want to
see which one is
best), and they are almost 20ms off from each other.
*216.14.97.75 .CDMA. 1 u 67 128 377 32.364
1.141 3.421
+68.216.79.113 .ACTS. 1 u 59 128 377 59.689
18.731 1.403
+128.118.25.5 .WWV. 1 u 60 128 377 22.239
-18.805 1.877
All three use different methods, are certain methods less reliable
than others?
The intersection algorithm chose the timesource in the middle. Most
timesources use GPS-derived clocking; but the older WWV is a shortwave
radio broadcast, and I believe ACTS is a dialup modem timesource that
can also provide a reliable PPS signal. Historically, I've found that
WWV timesources do tend to have a ~20 ms offset lagging behind the
time reported by other sources.
Also, of course, you should not be polling a stratum-1 faster than
1024 or maybe 512 seconds without making prior arrangements with
them....
Regards,
--
-Chuck
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