I now have a second stratum 1 server, with an independent setup. This allows me to compare the two. Why does ntp1 have this very specific repeating pattern of local clock offset? It's roughly +7 us, -5 us, +2 us, -4 us and then repeats again, over and over. We can also see that in the histogram, which has three local peaks, as opposed to ntp2's which looks like a normal distribution.
Here are the two NTPviz URLs: https://ntp1.wiktel.com/day/ https://ntp2.wiktel.com/day/ The server hardware is the same... same chassis, same motherboard, CPUs, etc. Both have their respective PPS connected via a motherboard serial port. Both are running Ubuntu 18.04 with NTPsec 1.1.7. They are in different buildings. The hand-picked network servers they reference are slightly different, but I don't think that's relevant here. ntp1 uses the PPS refclock with a polling interval of 3 from a telecom GPSDO (OCXO): server 127.127.22.0 minpoll 3 maxpoll 3 prefer fudge 127.127.22.0 refid PPS ntp2 uses the SHM refclock with a polling interval of 1 from a ublox 7 timing evaluation kit via gpsd: server 127.127.28.2 minpoll 1 maxpoll 1 prefer fudge 127.127.28.2 refid GPS I could try fiddling around with the polling interval. Next steps might be to try raising the polling the interval to 4 and/or lowering it to 1. The driver_pps documentation states, "This driver incorporates a good deal of signal processing to reduce jitter using the median filter algorithm in the driver. As the result, performance with minpoll configured at 4 (16 s) is generally better than the kernel PPS discipline." Another idea might be to switch to the PPS refclock on ntp2 to see if it behaves similarly with the ublox PPS. Before I start blindly flailing about, does anyone have recommendations? As a second question, if you look at the ntp2 weekly graphs, there is a single huge transient. Any idea what that might be? I've seen these about once or twice a week since I put this in a couple weeks ago: https://ntp2.wiktel.com/week/ -- Richard _______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel
