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? >> >> uwe >> > > 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 > gods! > > 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 is lost. 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 source) ? uwe _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
