Thanks, I am actually using 4 public NTP server, which whom my node-1 synchronises to. Then node-1 broadcasts the time to all the other nodes in the subnet.
My goal is to achieve a synchronisation between the nodes (not with the public NTP server) within 50 usec. I don't care if the synchronisation to the public NTP is accurate around half a second. I think it's possible, because the nodes are close to each other and every communication is using gigabit ethernet (cards + switch). I achieve to get a small offset when nothing else than linux and ntpd is running on the nodes (offset arount 10 usec). I have a program which sends data from one node to another. The sending/reception are timestamped and the delay is then computed. I would like the measured delay to be constrained in a 50usec wide range. Do you think it should be possible ? I have tried to run the test for 24h and didn't get the expected results. The range of the measured delay is 2 milliseconds (between -1ms and +1ms) with some spikes (ten or so for a milion measurments). The mean delay is -0.066087 (ms) and the std dev is 0.22849 Do you think the spikes can influence ntp ? thanks very much Maxime On Tue, Apr 22, 2008 at 1:15 PM, Danny Mayer <[EMAIL PROTECTED]> wrote: > maxime louvel wrote: > > > Thanks for your answer, > > > > I can't have a step on the clock because that would screw up my > > applications. > > However if I keep the load within a certain range I should fine, don't I > > ? > > I am synchronising one node to several public NTP servers, and the > > others > > nodes are synchronised to the first one. > > There are 2 to 24 nodes in my sub net. > > Do you think that should be feasible ? > > > > Maxime > > > > You need at least 3 and preferably 4 public NTP servers in order for your > local server to make decisions about which one is giving the most accurate > and reliable time at any moment. 2 is not enough since there's no way to > decide which is better. 3 allows 2 to gang up on the third. > > 2-24 nodes is nothing. Even bombarding the NTP server with queries will > barely be noticed. Don't forget at a minimum a node won't send a query more > frequently than once every 64 seconds unless you are using a badly > implemented NTP client. > > Danny > -- 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
