Unruh wrote: > [EMAIL PROTECTED] (Kay Hayen) writes: > >> Hello David, > >>>> When I say "restrict" it is our own system that decides that ">x ms" >>>> offset is too bad and prevents ntpd from talking to it any further with a >>>> "restrict" command. If all 2 servers of an "other host" are "restricted", >>>> it will crash the software. >>> You are overriding NTP's selection algorithms. Effectively you are no >>> longer running NTP. > >> How would it be difference from using the restrict command manually? > >> And why would it not be NTP? > >>>> All of that is own our making and control. >>>> >>>> Regarding the poll values. I am not sure why we do it the external NTPs >>>> as well. Could be that the dispersion can be brought down quicker this >>>> way >>> You are misusing "dispersion". Dispersion is an estimate of worst case >>> drift and reading resolution errors. > >> Well, dispersion is going down only with more samples to base estimation on, >> isn't it? And we need that quick, if we want the server to influence the >> hosts behind it quickly, say after a "NTP LAN" failure ended (some people >> have dedicated LANs for NTP). > >>>> on "entry hosts" and allow the "other hosts" to synchronize faster with >>>> them, or could be that we never considered it worthwhile to optimize it >>>> away. Well yes, but between 2 queries from the same client the ntpd will >>>> have made a certain adjustment. If the client gets to know this value, it >>>> will have to >>> ntpd is making adjustments at least every 4 seconds (old versions) and >>> as often as every clock tick. It does this by adjusting frequency not >>> by directly adjusting time. > >> I was not concerned with how the kernel makes the adjustments, but rather >> that >> the a fixed time change over the period is known. The slew rate is known, >> isn't it? > >> Let me use a car analogy, these things work. :-) > >> Lets assume a three lane high way with 3 cars that try to drive at the same >> speed. The car to the left is driving at (near) constant speed. The driver >> in >> the middle accelerates and braces according to his motor behaviour as well >> as >> the observed difference in speed between him and the other one. Now what >> should the driver to the right do? > > The cars have the road as a reference. However without the road, how does > car 3 know that car 2 is accelerating and decelerating and that it is not > hiw own car that is misbehaving? He does not. All he > can do is collect more cars and use the average behaviour to determine who > is behaving badly.
Car 3 has a speedometer! > > With two other cars only as a reference there is no way of deciding which > is weird. > > And if he has the road as a reference, then use the road, not either of the > other cars ( ie buy yourself a GPS receiver with PPS and then you will not > have to worry about what other cars are doing). > > >> In my view, he could take the acceleration of his neighbour into account >> when >> making estimates of his own error. > >> Best regards, >> Kay Hayen _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
