[ntp:questions] Getting NTP to correct only the clock skew

Spoon devnull at ntp.isc.org
Sat Apr 14 08:43:57 UTC 2007


Harlan Stenn wrote:

> Are you running the kernel time discipline stuff?
> If so, please see http://bugs.ntp.isc.org/740

I'm not sure exactly what "kernel time discipline stuff" means.
(I'm running Linux 2.6.20.5-rt8 and glibc 2.3.6)
My observations do not correspond to the problem described in bug 740.

>> I have to remove the drift file, and let ntpd spend 15 minutes (?) in
>> state 3 to compute the correct frequency offset, then 15-60 minutes
>> to fix the time offset.
> 
> Do you reboot the machine after removing the drift file? Again, I'm asking
> about the kernel time stuff.

I start from scratch every time:
Clean reboot, remove drift file, no kernel correction.
Only then do I start ntpd.

>> I'm trying to get my boss to test a GPS-based solution. The problem
>> is that the systems will be running in underground server rooms, and
>> some clients don't like having to run a cable to a GPS antenna.
> 
> You might be able to use a single (decent) real PPS source and get the
> signal propagated that way.  Also note the RIPE driver, which uses a Trimble
> GPS unit where all the smarts are in the GPS antenna.  The RIPE driver can
> use standard ethernet wiring to get the signal to its desired location.

Could you provide the exact reference for this GPS unit?
How much does it cost?

Here are some links for my own reference:

http://ntp.isc.org/bin/view/Support/ConfiguringRefclocks
http://ntp.isc.org/bin/view/Support/RefclockUsers
http://ntp.isc.org/bin/view/Support/TrimblePalisadeAcutimeRefclockUsers
http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver43.html

http://www.trimble.com/timing.shtml
http://www.trimble.com/tmg_acutime2k.shtml -> EOL
http://www.trimble.com/acutime_gold.shtml
http://www.trimble.com/tmg_resolutiont.shtml

> And if you get cell phone coverage, there are some CDMA refclocks, too.

What is the price range of these solutions?

Regards.




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