Unruh wrote: [] > If you mean you have a refclock attached, they have round trip time of > 0. Thus there is never a minimum and all get used. Ntp's algorithm in > short is: Save the last 8 polls. Check if the current poll has a > larger > roundtrip time than any of those 8. If it does, do not use it. > If the round trip times are all 0, then the current one is never > larger > so it is always used. > > Now, the round trip time on the net is a random variable, but from > experience, on average only about 1 in 8 are used. ( actually it is a > bit better than > that so that about 1/7 are actually used.) > > This is to avert bias on the theory that longer round trip times are > probably biased ( the delay is caused by one of the legs being > longer than the other), but as a result, the actual average poll > interval is > roughly 7 times longer than the requested interval. Also since the > time > constants must be longer than the longest poll interval, this helps > the system > to have a very long time constant (ie respond extremely slowly to > changes).
That makes some sense, Bill, and probably more if I study it more carefully. Thanks, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
