On Tue, Apr 29, 2008 at 6:27 PM, Unruh <[EMAIL PROTECTED]> wrote: > [EMAIL PROTECTED] (maxime louvel) writes: > > >Hi, > > >I have know run a lot of tests. > >Just to let you know what I've got so far. > >I have tried NTP, and NTP + PTP (Precision Time Protocol). > >I haven't tried Chrony nor TSClock. > >I have used the software only implementation of PTP (ptpd). > > >With NTP only I have got an accuracy around 1ms, > > accuracy? Do you mean the variation of the offset between ntp and the > remote ntp server? YOu need to tell us what you mean by the term. >
By accuracy I actually meant the offset between my nodes. > > > >with one node synchronising to public NTP server, the others nodes > >synchronising to it with PTP I got 10 usec (between the nodes). > >I haven't used any hardware support (not GPS,PPS, for PTP). > > Then you do not really know what the accuracy is of the other nodes. For > example, your system could have a 100us assymmetry in communication which > would make the accuracy 50us, but with a fluctuation of 10us. > You're right on this point, what I actually get with PTP is delay of 100 usec, with a variation of 10 usec. But I'm only interested in the variation as the 100usec can be removed easily because it's constant > > > >I might try the other solutions, if yeI do I'll send an email to complete > >the results. > > As I said, I am completely at a loss to know why you would only be getting > 1ms using ntp to synchronize. That is much worse than my experience. (Look > at flory on www.theory.physics.ubc.ca/chrony/chrony.html which uses ntp vs > the other machine which all use chrony. flory's fluctutations are > certainly not 1ms.) > I have to say that I 'm also surprise of the bad performance of NTP, I will try chrony if it is suitable to my nodes (embedded cards, with the latest linux kernel). > _______________________________________________ > questions mailing list > [email protected] > https://lists.ntp.org/mailman/listinfo/questions > -- Maxime Louvel 0044 7964 5555 80 43 Allen road Whitemore reans WV60AW Wolverhampton United Kingdom _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
