[ntp:questions] Meinberg software running under Vista/Windows 2008

unruh unruh at wormhole.physics.ubc.ca
Wed Jul 6 18:54:14 UTC 2011


On 2011-07-06, Chris Albertson <albertson.chris at gmail.com> wrote:
> On Wed, Jul 6, 2011 at 8:41 AM,  <Radu.Popa at technomatic.de> wrote:
>> Thank you for your answer, but can this limit be specified in the config
>> file or command line, please?
>
> I found it.
> http://www.eecis.udel.edu/~mills/ntp/html/clock.html
>
> Looks like I was wrong.   From my read of the above 2 minutes is under
> the "panic" limit and NTP should attempt to correct the offset.   It
> will "step" the clock in jumps of 125 milliseconds.    So it would
> take 1,000 steps to correct a 2 minute offset.   So take a look every
> few hours and you should see it slowly correct itself.    As I wrote
> above 2 minutes is a large and unrealistic test, try two seconds.
> Two seconds is close to the error you might see in a network outage.

Unless the network outage lasts for weeks, no you would not expect to
see 2 sec errors due to network outages. ntp should discipline the rate
to a few PPM, so it would lose 2 sec in about 1000000 sec, which is
about 12 days.
>
> Read the link above.  It's explained there
>
>
> The problem, or the reason NTP can't close a large offset is that NTP
> tries to control the RATE of the clock.  How can it close a 2 minute
> offset unless it runs the clock faster than it should?   This is a
> fundamental problem because there is no "right" answer.  The only
> option is to correct one error (the offset) by creating another (A
> clock that runs faster than one second per second).

>
>




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