I'm running ntpd 4.2.4p4 on several Ubuntu 9.04 ("Jaunty") servers. I'm associated with Stanford University and have been depending primarily on Stanford's own pool of stratum-2 servers.
Recently, in order to spread out my time base somewhat, I tried adding some outside servers (using the *.pool.ntp.org DNS names) to my NTP configurations. Since doing this, I've noticed that the nearby (Stanford) servers are uniformly "off" by several milliseconds, in comparison to more distant servers. Here, for example, is some output from the ntpq "peers" command (with host names turned off) on one of my servers: remote refid st t when poll reach delay offset jitter ============================================================================== 10.0.229.29 10.0.229.53 3 u 25 64 376 0.109 -3.955 0.130 -10.0.229.114 171.64.7.89 3 u 103 256 377 6.058 -5.277 3.545 -10.0.229.117 209.167.68.100 3 u 78 256 377 22.338 -8.460 5.624 +171.64.7.61 171.64.7.87 2 u 392 1024 377 5.614 -5.418 0.923 +171.64.7.55 171.64.7.87 2 u 393 1024 377 4.998 -5.405 0.977 -171.64.7.111 171.64.7.87 2 u 394 1024 377 5.598 -5.499 1.000 -207.150.167.80 209.51.161.238 2 u 387 1024 377 79.606 6.888 1.485 -72.36.170.170 132.163.4.102 2 u 368 1024 377 51.702 6.867 0.297 -66.254.57.165 18.26.4.105 2 u 386 1024 377 95.627 3.567 1.373 *131.234.137.24 .DCF. 1 u 449 1024 377 171.784 0.923 0.978 -89.16.178.36 195.66.241.3 2 u 442 1024 377 157.082 1.874 0.443 (The 10.0.229.* servers are on my home LAN; the 171.64.7.* servers are at Stanford; and the others are from various places around the world and have much larger delays than the nearby servers.) I also see that the above machine is currently syncing to a server in Germany (delay = 171 msec) -- possibly because it's on stratum 1. (I submitted a separate posting questioning whether stratum-1 servers should really be in the pools, but that's a separate issue.) Is this sort of behaviour to be expected? Does this mean that the NTP algorithm ought to be giving more weight to servers with shorter delays? Or, perhaps, does it suggest that there might be something wrong with the Stanford servers that is making them all cluster around a time that is several milliseconds different from the rest of the world? Rich Wales ri...@richw.org, richwa...@gmail.com _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions