Dear NTP community. I've noticed a strange behavior of ntpd-4.2.3.
Two hosts - configured to act as peers to each other - with an unreachable external time source - the local clock configured as fallback both select their local clock and stay in this mode, even when the offset between them grows and grows. With ntp 4.2.0, one of them took over control so that they stayed at least in- sync with each other. Example: The host involved are ipcop, chip & chap. Configuration on chip: server 127.127.1.0 iburst minpoll 4 maxpoll 4 fudge 127.127.1.0 stratum 10 server ipcop burst iburst minpoll 4 maxpoll 6 peer chap burst iburst minpoll 4 maxpoll 4 Configuration on chap: server 127.127.1.0 iburst minpoll 4 maxpoll 4 fudge 127.127.1.0 stratum 10 server ipcop burst iburst minpoll 4 maxpoll 6 peer chip burst iburst minpoll 4 maxpoll 4 With ipcop being unreachable, the ntpq -p on chip & chap looks like this. # ntpq -p chip chap server remote refid st t when poll reach delay offset jitter ========================================================================== chip *LOCAL(0) .LOCL. 10 l 10 16 377 0.000 0.000 0.001 chip ipcop .INIT. 16 u - 64 0 0.000 0.000 0.000 chip chap LOCAL(0) 11 u 14 16 376 0.133 12.538 0.038 server remote refid st t when poll reach delay offset jitter ========================================================================== chap *LOCAL(0) .LOCL. 10 l 2 16 377 0.000 0.000 0.001 chap ipcop .INIT. 16 u - 64 0 0.000 0.000 0.000 chap chip LOCAL(0) 11 u 1 16 377 0.166 -12.522 0.055 These two hosts are not really a realiable redundancy pair for their ntp clients. Isn't it? Running away from each other, they both are marked as falstetickers soon. :-( Using the same configuration with ntpd-4.2.0, the result looks much better. # ntpq -p chip chap server remote refid st t when poll reach delay offset jitter ========================================================================== chip *LOCAL(0) LOCAL(0) 10 l 1 16 377 0.000 0.000 0.001 chip ipcop .INIT. 16 u - 64 0 0.000 0.000 4000.00 chip chap 192.168.1.1 12 u 2 16 376 0.237 0.043 0.012 server remote refid st t when poll reach delay offset jitter ========================================================================== chap LOCAL(0) LOCAL(0) 10 l 3 16 377 0.000 0.000 0.001 chap ipcop .INIT. 16 u - 64 0 0.000 0.000 4000.00 chap *chip LOCAL(0) 11 u 1 16 377 0.232 -0.043 0.017 I originally raised this as a bug (Bug ID 748). However, Steve Kosteke proposed to move the topic to the newsgroup. Brian Utterback already made some proposals: 1. Use different stratum settings for the local clocks. -> This doesn't change the behaviour. (Even wit stratum differences > 2) 2. Don't configure the local clocks. -> This doesn't work for the startup case. It seems that something has been changed in the internal selection algorithms between version 4.2.0 and version 4.2.3. Bug/Feature introduction/removal? That's the question. ;-) Juergen _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
