vwvr6vw wrote: > I'm new to ntp, but have been asked to debug an issue with our NTP > configuration. First, here is our setup. We have two processors which > each have a third party application reading time off a serial line from > two different sources and then disciplining the internal clock on each > processor with the "adjtime" system call. xntpd runs on each of these > processors with only internal time as a source. One processor is > fudged at stratum 0 and the other at stratum 2. Currently, xntp is > configured with "enable pll". My first change will be to change > "enable pll" to "diable pll" as I believe that we shouldn't have two > different applications(our third party app and xntp) discipling the > internal clock at the same time. > > These two processors act as the NTP servers to all other processors on > our network. I've read here that having two servers is a bad situation > and that it is better to have four, but that just about > anything(including just 1) is better than having two. I believe we our > finding that out first hand, so I work to resolve that as well. > > When I checked the ntp logs for some client processors on our network, > I see that occasionaly there are large(upto 1 second) differences > between our two servers. On top of this, the clients can not decide > which one to sync with and we get stuck in a loop as follows. > > restart min polling > step time/sync to server1 at stratum 0 > restart min polling due to step > step time/sync to server2 at stratum 2 > > This exact sequence repeats over and over on appx 5 minute intervals > due to the min polling time. I realize that I have many problems here, > but I would like to know why ntp toggles between syncing/stepping to > server1 and server2 after each polling period. I would have thought > that the resultant action would be the same after each polling period. > But instead it is consistent that the client steps time to the opposite > server that it stepped to last time, like so. > > 25 Mar 16:36:58 xntpd[7752]: time reset (step) 0.421856 s > 25 Mar 16:41:55 xntpd[7752]: synchronized to 192.6.1.21, stratum=1 > 25 Mar 16:41:54 xntpd[7752]: time reset (step) -0.421930 s > 25 Mar 16:46:33 xntpd[7752]: synchronized to 192.6.1.22, stratum=3 > 25 Mar 16:46:34 xntpd[7752]: time reset (step) 0.419369 s > 25 Mar 16:51:31 xntpd[7752]: synchronized to 192.6.1.21, stratum=1 > 25 Mar 16:51:30 xntpd[7752]: time reset (step) -0.419446 s > 25 Mar 16:56:09 xntpd[7752]: synchronized to 192.6.1.22, stratum=3 >
Your description sounds like it broke the cardinal rule: you must not have more than one application disciplining the clock. It sounds like you do have more than one, but I can't be sure. The application should have been implemented as a refclock and let ntpd figure out the rest. fudging to stratum 0 is illegal, that's reserved for the refclock itself. Everything else is derived from there. At best your server would be stratum 1 if your time was being set up as a refclock. You'd need to understand the what the third-party application is doing to figure out how well it's disciplining the clock. It's probably not doing a good job and clock-hopping like this is not unlikely. Danny _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
