[ntp:questions] How should an NTP server fail?
Kasper Pedersen
spam at kasperkp.dk
Fri Jun 11 17:43:51 UTC 2010
On 06/11/2010 04:47 PM, David L. Mills wrote:
> My scenario did include the condition of eight valid sample before
> pulling the plug The first missed poll response did result in one
> MAXDISPERSE sample in the filter, but that is completely irrelevant. The
> point is the poll routine calls clock_select() for every poll sent when
> the last four samples in the reach register are missing, so it is
> guaranteed that the server be marked down after that.
For entertainment value, 'ntpq cartoons' with 4 samples, and 8 samples:
At 2 minutes after pulling the plug, there is a difference.
4:
10.5.5.254 10.5.5.16 2 u 1 8 1 0.284 -0.294 0.000
10.5.5.254 10.5.5.16 2 u 1 8 3 0.340 -0.217 0.078
10.5.5.254 10.5.5.16 2 u 8 8 7 0.285 -0.121 0.140
*10.5.5.254 10.5.5.16 2 u 3 8 17 0.286 0.044 0.265
*10.5.5.254 10.5.5.16 2 u 9 8 36 0.286 0.044 0.265
*10.5.5.254 10.5.5.16 2 u 17 8 74 0.286 0.044 0.265
*10.5.5.254 10.5.5.16 2 u 24 8 170 0.286 0.044 0.265
*10.5.5.254 10.5.5.16 2 u 33 8 360 0.284 -0.294 0.224
*10.5.5.254 10.5.5.16 2 u 43 8 340 0.284 -0.294 0.224
*10.5.5.254 10.5.5.16 2 u 49 8 300 0.284 -0.294 0.224
*10.5.5.254 10.5.5.16 2 u 61 8 200 0.284 -0.294 0.224
*10.5.5.254 10.5.5.16 2 u 64 8 0 0.285 -0.121 0.135
*10.5.5.254 10.5.5.16 2 u 158 8 0 0.286 0.044 0.000
*10.5.5.254 10.5.5.16 2 u 337 8 0 0.286 0.044 0.000
8:
10.5.5.254 10.5.5.16 2 u 3 8 1 0.294 2.971 0.000
10.5.5.254 10.5.5.16 2 u 1 8 3 0.295 3.434 0.463
10.5.5.254 10.5.5.16 2 u 1 8 7 0.288 3.092 0.256
*10.5.5.254 10.5.5.16 2 u 2 8 17 0.277 3.141 0.198
*10.5.5.254 10.5.5.16 2 u 2 8 37 0.277 3.141 0.200
*10.5.5.254 10.5.5.16 2 u 4 8 77 0.277 3.141 0.186
*10.5.5.254 10.5.5.16 2 u 3 8 177 0.277 3.141 0.182
*10.5.5.254 10.5.5.16 2 u 1 8 377 0.277 3.141 0.224
*10.5.5.254 10.5.5.16 2 u 11 8 376 0.277 3.141 0.304
*10.5.5.254 10.5.5.16 2 u 18 8 374 0.277 3.141 0.304
*10.5.5.254 10.5.5.16 2 u 27 8 370 0.277 3.141 0.304
*10.5.5.254 10.5.5.16 2 u 36 8 360 0.277 3.141 0.306
*10.5.5.254 10.5.5.16 2 u 43 8 340 0.277 3.141 0.334
*10.5.5.254 10.5.5.16 2 u 49 8 300 0.278 2.932 0.317
*10.5.5.254 10.5.5.16 2 u 58 8 200 0.283 2.750 0.443
*10.5.5.254 10.5.5.16 2 u 67 8 0 0.283 2.750 0.409
*10.5.5.254 10.5.5.16 2 u 73 8 0 0.283 2.750 0.178
10.5.5.254 10.5.5.16 2 u 82 8 0 0.283 2.572 0.000
10.5.5.254 10.5.5.16 2 u 88 8 0 0.283 2.572 0.000
10.5.5.254 10.5.5.16 2 u 94 8 0 0.283 2.572 0.000
10.5.5.254 10.5.5.16 2 u 104 8 0 0.283 2.572 0.000
As to whether this difference means anything, I will let others decide.
The above is 4.2.7p34. Also tested on 4.2.4p7. Spaces were shortened
to fit.
/Kasper Pedresen
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