Microsoft

Learning the registry entries that control Windows Time service

The Windows Time service controls time synchronization on your Windows 2000 network. It stores its configuration in the registry. Here are the values and settings you need to know if you want to optimize time synchronization on your server.


In the Daily Feature “Keeping time on your Windows 2000 server,” I showed you how to synchronize the time on your Windows 2000 servers with NTP servers on the Internet. As I pointed out, time synchronization in Windows 2000 relies on the Windows Time service. The Net Time /SETSNTP command makes changes to your server’s registry. You’re probably wondering what other registry entries exist for the Windows Time service. In this Daily Feature, I’ll introduce you to a few more of those entries.
This Daily Feature describes how to make changes to your server’s registry. Make sure you have complete backups of your server before doing anything suggested in this article. If you make a mistake when making changes to your server’s registry, you may cause your server to be unbootable, requiring a reinstallation of Windows. Proceed with extreme caution.
What is the Windows Time service?
The Windows Time service, also known as W32Time, ensures that date and time settings are synchronized across your network. Windows NT 4.0 servers primarily used the TimeServ utility to perform the identical function. Microsoft provided a version of W32Time to replace TimeServ, but it had a few limitations and wasn’t fully compatible with the W32Time implementation on Windows 2000.

As with most services in Windows 2000, you can control the Windows Time service in the Computer Management utility. Click Start | Programs | Administrative Tools | Computer Management. When the Computer Management console starts, select Services in the left pane from the Services And Applications hive.

You can scroll through the list of running services on your Windows 2000 server in the right panel until you see the Windows Time icon. You can then start, stop, or restart the service by right-clicking the Windows Time icon and selecting what you want to do from the menu that appears. You’ll need to come here and stop and restart the Windows Time service after you make changes in the registry. If you don’t, the changes won’t take effect.

Windows Time service registry settings
Naturally, to make changes to your server’s registry, you’ll have to use the Registry Editor. To start the Registry Editor, select Run from the Start menu, type regedit in the Open field and click OK. When the Registry Editor starts, navigate the left pane until you get to the HKEY_LOCAL_MACHINE\SYSTEM\Current
ControlSet\Services\W32Time\Parameters key. The values you’ll be most concerned with are the following:
  • AvoidTimeSyncOnWan—This is an optional value that prevents your server from synchronizing with a server that is at another site. You may want to set this value if you want to prevent time traffic from going across your WAN. This value has a type of REG_DWORD. Normally, this value is set to 0, which means that the server doesn’t care where the other servers are located. You can add this value and set it to 1 to make sure that your server doesn’t synchronize with a time source that is across a WAN or at a different site.
  • GetDcBackoffMaxTimes—This is an optional value that controls the maximum number of times to double the back-off interval when the domain controller attempts to find another domain controller to reference for time settings and fails. This value has a type of REG_DWORD. The default setting for this value is 7. You can set it to 0 to make sure there is no log of the event and that the wait between successive attempts is always minimized.
  • GetDcBackoffMinutes—This is an optional value with a type of REG_DWORD. It controls the number of minutes the domain controller waits before looking for another domain controller if its last attempt failed. The default setting for this value is 15 minutes.
  • LocalNTP—This is a mandatory value that you should see listed in the right pane of the Registry Editor. It has a type of REG_DWORD. If you set this value to 0, Windows 2000 won’t start the SNTP server unless this server is a domain controller. If you set it to 1, then Windows 2000 will start the SNTP server if the server is a member server or just a regular workstation.
  • NtpServer—This is an optional value with a type of REG_SZ. You’ll set this value to manually configure the server’s time source. You can set this to the DNS name or TCP/IP address of the NTP server from which you want to synchronize. The easiest way to change this value is to use the Net Time command.
  • Period—This is a mandatory value that can be one of two types: either REG_DWORD or REG_SZ. This value controls how often the time service synchronizes with external sources. You can set this value to one of the following settings:
    0—This setting synchronizes once a day.
    x—Here, x can be the number of times per day to synchronize
    65531 (REG_DWORD) or DailySpecialSkew (REG_SZ)—This setting synchronizes once every 45 minutes until the server completes one good synchronization. Synchronization will occur once every day after that.
    65532 (REG_DWORD) or SpecialSkew (REG_SZ)—This setting allows for synchronization once every 45 minutes until the server completes three good synchronizations. After that, the server synchronizes once every eight hours. (This is the default setting.)
    65533 (REG_DWORD) or Weekly (REG_SZ)—Use this setting to synchronize once every seven days.
    65534 (REG_DWORD) or Tridaily (REG_SZ)—Use this to synchronize once every three days.
    65535 (REG_DWORD) or BiDaily (REG_SZ)—Use this to synchronize once every two days.
  • ReliableTimeSource—This is an optional value that tells other servers on the network that this server has reliable time. When you issue the Net Time command with the /RTSDOMAIN switch, it looks for servers with this value set. This value has a type of REG_DWORD. Its default setting is 0, which means that the server isn’t marked as having reliable time. To indicate that time is reliable, change this setting to 1.
  • Type—This is a mandatory value that controls how the server synchronizes its time. It has a type of REG_SZ. The default setting is Nt5DS, which means that the server can synchronize with a source you specify or within the domain hierarchy. If you change the setting to NTP, the server will always synchronize to a manually configured source. Finally, if you change this setting to NoSync, the server won’t synchronize its time with anyone.

You may see two additional values in the right pane: Adj and msSkewPerDay. If these values exist, don’t touch them. They are used to preserve information about the server's clock between reboots.

Conclusion
The registry can be a scary place, but once you know your way around, you can easily tweak your server’s configuration. Many programs, including the Windows Time service, store their settings in the registry. All you have to do is know what values a program uses and how to make proper changes.
The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.

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