[ntp:questions] Using both Server and Peer in ntp.conf
uwe_klein_habertwedt at t-online.de
Thu Feb 8 20:11:58 UTC 2007
Richard B. gilbert wrote:
> Uwe Klein wrote:
>> A question in this context:
>> How is an orphaned server that was well
>> synced for some time degraded in
>> quality and/or stratum
>> with/without the local clock
>> being used as (additional) server
>> over time?
> The answer is: It depends! (God I love to be helpful!!!!)
We value intention ;-)
> When the server loses its connection to the upstream source, ntpd
> continues to discipline the clock using the last known good frequency
> correction. It cannot compensate for variations in the environment, of
> which the temperature is the most important.
> How many minutes, hours, or days of "holdover" with reasonably correct
> time you may get depends on the quality of the local clock, the
> stability of the temperature, the phase of the moon and the whims of the
> If you must have the correct time, take precautions such as getting one
> or more hardware reference clocks, redundant internet connections,
> redundant servers, etc.
> It might be interesting to try the experiment! Get a server "well
> synchronized", "orphan" it, and plot the deviation of the clock from the
> correct time versus elapsed time. (It's possible that you would be
> wasting your time; someone may already have done this.)
Is the ntp algo similar enough to a kalman filter to have an
idea of "value" drift and noise/quality ? I think so, right?
With the then known quality of the local clock one should be able to
"deteriorate" the reported clock time/quality over time while contact
i.e. if you plot offset and jitter in yerror style you should get a slightly
inclined (drift:up/down) "trumpet" (jitter:increasing) ?
Q: stratum is a purely hierarchical thing (hop distance from first class sync
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