[ntp:questions] Win2k3 Server as NTP server?

Martin Burnicki martin.burnicki at meinberg.de
Wed Dec 9 16:15:36 UTC 2009

Why Tea wrote:
> Hi Martin, thanks for the info and reference to your previous
> post. David and Richard have also highlighted issues with
> Windows clock tick resolution and performance under load.
> We are dealing with some old legacy systems which
> consist of many proprietary HW and a Windows 2003 server.
> Instead of a proprietary embedded ntpd, we would like to
> have an alternative in order to cut cost. It looks like putting
> an off-the-shelf ntpd on Windows 2003 is a good option. BTW,
> the Windows 2003 server is NOT a PDC. But the question is
> if Windows 2003 is up to the task to provide the accuracy and
> resolution required for an ntp server? Here are my specific
> questions:
> 1) Has anybody used Windows 2003 as an ntp server and
>     is happy/unhappy with it?

We are running ntpd on a Win 2003 server without problems. However, that is
a standalone server and not a member of an Active Directory domain.

> 2) If I were to do a trial run of ntpd on Windows 2003, how do
>     I measure its ntpd performance in order to make a
>     judgment?

Except what I've written earlier regarding potential problems in an AD
domain, an additional problem can be the limited resolution of the Windows
system time (i.e. about 16 ms timer ticks).

Ntpd tries to interpolate the time between two timer ticks using the Windows
PerformanceCounter API. However, that API can be implementing using
different timers available in the computer, depending on the CPU type (e.g.
AMD vs. Intel), chipset, and exact Windows version/patch level.

This may fail if the CPU's TSC is used for the PerformanceCounter. If the
CPU's clock speed is reduced for power saving (e.g. Intel SpeedStep or AMD
Cool'n'Quiet) then the PerformanceCounter values are garbage and thus time
interpolation fails.
> 3) I've downloaded the Mienberg ntp package and installed
>     it. How I judge it's performance?

If you run ntpd simply watch the offset and jitter displayed by the "ntpq
-p" command, or enable generation of the loopstats file. Also look at the
Windows event log. If the offset settles at a low value (e.g. a couple of
milliseconds or less) and there are not event log messages saying "time
reset" in certain intervals then ntpd works fine on your system.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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