Adrian von Bidder wrote:
> On Wednesday 03 October 2007 18.05:04 Chuck Swiger wrote:
>> NTP prefers higher-stratum good clocks, but it prefers good clocks with
>> low jitter more.
>
> Do you have numbers on this? I've never seen ntpd prefer higher stratum
> clocks more than a few minutes after startup (until the error correction
> algo had enough data). But then, I've only had big differences in delay
> and not much in jitter.
I have an example, yes:
3-sec# ntpq -np ntp0.codefab.com
remote refid st t when poll reach delay offset jitter
==============================================================================
127.127.1.1 .LOCL. 10 l 45 64 377 0.000 0.000 0.000
+18.145.0.30 .PSC. 1 u 78 512 377 9.285 0.172 0.284
-17.254.0.26 17.106.100.13 2 u 80 512 377 85.593 0.606 0.240
*209.51.161.238 .CDMA. 1 u 152 512 377 5.618 0.527 3.967
+198.82.1.201 198.82.247.40 2 u 107 512 377 16.585 0.388 0.146
199.103.21.227 199.103.21.233 3 u 340 512 376 0.187 0.106 0.172
-199.103.21.228 65.212.71.103 2 u 191 512 376 0.000 -0.998 0.938
-199.103.21.226 208.184.49.9 2 u 341 512 376 0.021 14.651 0.279
4-sec# ntpq -np ntp1.codefab.com
remote refid st t when poll reach delay offset jitter
==============================================================================
127.127.1.1 LOCAL(1) 10 l 1 64 377 0.000 0.000 0.002
+66.250.45.2 18.26.4.105 2 u 712 2048 377 4.379 -0.513 2.070
-18.26.4.105 .CDMA. 1 u 583 2048 377 20.009 -4.832 5.520
+128.59.59.177 128.59.39.48 2 u 679 2048 377 5.333 0.852 0.087
-128.118.25.5 .WWV. 1 u 685 2048 377 32.870 -20.846 1.222
*199.103.21.233 209.51.161.238 2 u 234 512 373 0.275 0.048 0.171
+199.103.21.228 65.212.71.103 2 u 237 512 376 0.002 -1.198 0.455
-199.103.21.226 208.184.49.9 2 u 137 512 376 0.124 14.729 0.194
Notice that the second machine has chosen to select ntp0.codefab.com aka IP
199.103.21.233 because that machine has a very low jitter (it's a Sun E450
running SunOS 5.8).
--
-Chuck
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