[c-nsp] NTP Servers

Sat Jun 30 22:39:36 UTC 2012

> Or you can ask the it guys to use a windows server... Eg:
> 
> http://support.microsoft.com/kb/816042

That is a joke Jared?  You left off the smiley.

Windows doesn't do NTP out-of-the-box (Microsoft assertions to the contrary notwithstanding).  You can build a reasonably working standard daemon, however don't expect time to be very accurate.  Windows out-of-the-box can keep time +/- 10 minutes or so using the Microsoft lets-pretend-NTP.

You can build the current standard NTPD distribution on Windows.  You can also spend lots of time to make it "work as well as possible" (once you manage to get it to compile, that is).  Even so, when you have configured it to the optimality of accuracy, this is what you can expect:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+tic.nrc.ca      .PPS.            1 u   13   64  377   55.544    5.913   0.870
-tac.nrc.ca      .ATOM.           1 u   48   64  377   56.188    4.768   3.041
-toc.nrc.ca      .ATOM.           1 u    1   64  377   55.485    4.758   0.981
+tick.usask.ca   .GPS.            1 u   34   64  377   19.566    6.942   5.699
*tock.usask.ca   .GPS.            1 u   29   64  377   19.665    5.955   1.937
-clock.isc.org   .GPS.            1 u   37   64  377   53.091    8.311   0.649
+clock.sjc.he.ne .CDMA.           1 u   48   64  377   43.591    6.066   2.501

offset:               0.005955 s
frequency:            23.346 ppm
poll adjust:          -30
watchdog timer:       47 s

is about the best you will get.  Statistics are pretty awful:

Date        #     O.Avg     O.Median  O.Range   O.CI      O.Skew    O.Kurt    F.Avg     F.Median  F.Range   F.CI      F.Kurt
2012-01     899   0.765559  0.004198  20.05221  0.000371  -0.56023  0.751151  21.31698  20.9705   2.9685    0.108050  -0.88068
2012-02     9673  0.237434  -7.46502  59.75607  0.000156  -1.43583  8.609085  19.01126  19.3495   5.2995    0.040683  -0.54578
2012-03     1380  -0.02157  -14.8416  44.00043  0.000124  -1.08589  4.559049  18.08941  16.822    7.536     0.045387  0.268831
2012-04     1322  0.196654  21.16261  106.1250  0.000141  -0.48643  26.05868  17.56811  16.812    6.111     0.040561  -0.38021
2012-05     8849  0.118125  27.44213  72.01526  0.000161  0.296114  8.939429  17.88685  15.2595   9.3195    0.080186  1.121740
2012-06     1457  0.409662  -20.2809  63.32684  0.000114  -1.44144  11.98237  20.50724  19.5425   6.7425    0.042372  -0.08891
            6102  0.201651  21.16261  106.1250  6.065429  -0.84354  13.78161  18.71838  16.1125   10.1725   0.023443  1.215941

This is from a custom ntpd build using the highest precision that it can manage to coerce from Windoze.

Of course, this may be accurate enough for most uses -- at least it does not have to time-step.

Doesn't compare to ntpd on linux on an 80286 with 640K ram booting from a floppy, which can maintain time sync within less than 1 ms easily.

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