High Accuracy W32time Requirements

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Mon, 29 Oct 2007 03:18:09 GMT

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re: High Accuracy W32time Requirements

andrea_scintilla — Fri, 16 Nov 2007 18:32:05 GMT

Spect.le DS Team,

anyway, wich are best w32Time registry settings to get most high accuracy possible?

2 seconds instead of 4 could be a good result for us.

Best Regards

re: High Accuracy W32time Requirements

NedPyle — Fri, 16 Nov 2007 22:24:13 GMT

Hi Andrea,

We actually don't like to get into specifics with regards to high accuracy time, because we flat out cannot guarantee they will stay consistent using the x86/x64 motherboards real-time clock. All we will guarantee from a support standpoint is 300 seconds, so that Kerberos will function.

If you are really looking for that 1-2 second kind of accuracy, we always recommend you invest in replacement hardware clocks that override the PC's RTC and give you extreme accuracy (think nanoseconds).

That being said, you can look over http://technet2.microsoft.com/windowsserver/en/library/b43a025f-cce2-4c82-b3ea-3b95d482db3a1033.mspx for a complete list of the time registry settings and how they can be used to try and get time closer to a few seconds of drift.

- Ned

re: High Accuracy W32time Requirements

bobdrake — Tue, 27 Nov 2007 17:43:27 GMT

Once again I would have to point to an alternate time solution for your needs. W32time was not designed to maintain that degreee of accuracy.

If you wanted to test registry keys since an alternate method could not be accomplished you can test adjusting the keys noted (again this is not guaranteed):

PhaseCorrectRate

MinPollInterval

MaxPollInterval

UpdateInterval

Taken from http://technet2.microsoft.com/WindowsServer/en/library/b43a025f-cce2-4c82-b3ea-3b95d482db3a1033.mspx?mfr=true

PhaseCorrectRate

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config

Version

Windows XP and Windows Server 2003

This entry controls the rate at which the phase error is corrected. Specifying a small value corrects the phase error quickly, but might cause the clock to become unstable. If the value is too large, it takes a longer time to correct the phase error.

The default value on domain members is 1. The default value on stand-alone clients and servers is 7.

MinPollInterval

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config

Version

Windows XP and Windows Server 2003

This entry specifies the smallest interval, in log2 seconds, allowed for the system polling interval. Note that while a system does not request samples more frequently than this, a provider can produce samples at times other than the scheduled interval. The default value for domain controllers is 6. The default value for domain members is 10. The default value for stand-alone clients and servers is 10.

MaxPollInterval

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config

Version

Windows XP and Windows Server 2003

This entry specifies the largest interval, in log2 seconds, allowed for the system polling interval. Note that while a system must poll according to the scheduled interval, a provider can refuse to produce samples when requested to do so. The default value for domain controllers is 10. The default value for domain members is 15. The default value for stand-alone clients and servers is 15.

UpdateInterval

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config

Version

Windows XP and Windows Server 2003

This entry specifies the number of clock ticks between phase correction adjustments. The default value for domain controllers is 100. The default value for domain members is 30,000. The default value for stand-alone clients and servers is 360,000.

- Bob

High accuracy time, and why we don't support it

Windows Time Service — Tue, 10 Jun 2008 21:46:48 GMT

More than any other, the most often asked question of the Windows Time Service is "How do I configure

What W32tm is it anyway?

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re: High Accuracy W32time Requirements

hgerstung — Thu, 02 Apr 2009 10:34:07 GMT

Thanks a lot for taking the time to answer this questions. We experience quite a lot of inquiries from Windows users exactly asking the same question.

Our standard answer exactly matches your reply (Kerberos, better than 5 min) although we sometimes see better results with W32time and our time server appliances. For customers requiring a better accuracy, we offer a Windows port of Dave Mills' reference implementation of NTP, i.e. the very same code that runs on almost every Unix-based OS around, and that does a very good job (better than 100ms), although we still experience problems with Vista (working on that).

The only drawback with using NTP on Windows instead of W32time is the fact that automatic time synchronization does not work, i.e. the workstations do not automatically determine the domain controller as a time server, most probably because the NTP service does not register itself in the directory as a time source.

If someone from Microsoft would be willing to spend some time on this and assist us (the NTP opensource project AKA ntp.org), please contact me at heiko dot gerstung at meinberg dot de !

Again, thanks for your article, a good reference to point customers to!

Regards,

Heiko