Rich <richwa...@gmail.com> writes:
>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?
If the stanford machines all cluster around a time sever milliseconds
different from the rest of the world they are wrong. There may be some
problem with assymetric delays to the stanford machines.
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