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Kb > Knowledgebase Article KB2001.002

KB2001.002
Problem: W32Time service turns itself back on

This article applies to Domain Time.

Last Updated: 11 June 2015

Problem

    The Windows Time (W32Time) service turns itself back on, either after you have purposely set it to Disabled, NoSync or have installed Domain Time II 2.5 or later.

Details

    If the W32Time service has been Disabled or set to NoSync mode, it may be re-enabled and/or switch back to NT5DS or NTP modes seemingly at random times.

    The behavior is not random at all. It is often a side-effect of running NET TIME or W32tm commands from the command-line. For example, the documentation for NET TIME /setsntp says this will clear the list of SNTP servers stored in the registry. It does indeed do this, but it also assumes you mean for the W32Time service to be set back to its default mode, which is NT5DS (that is, get the time from a domain controller using the Windows Active Directory services to locate a time server).

    When you run NET TIME /setsntp:server, the documentation says this will set the server(s) you supply as the SNTP time sources in the registry. While doing so, it also changes the mode to NTP, assuming you wouldn't be setting the sources if you didn't want to use them.

    Many W32tm commands can also re-enable or reset Windows Time Service settings, such as the W32tm /register command. The use of the W32tm utility is highly discouraged if Domain Time is installed.

Background

    The W32Time service may be set to one of five modes:

    1. Disabled -- the service does not run
    2. NT5DS -- use the Active Directory method of locating a server, and use either the NetRemoteTOD protocol (older) or the Windows-authenticated NTP protocol
    3. NTP -- use the servers you specify, and use the SNTP/NTP protocol
    4. AllSync -- use all available synchronization methods
    5. NoSync -- run and answer queries, but don't check or set the time

    The default W32Time behavior varies somewhat between operating system versions, but, in general with most recent versions workgroup members are set to NTP mode, while domain members are set to NT5DS mode.

    This presents challenges for running a replacement time service such as Domain Time. If two time services are each trying to manage the clock, a "tug of war" may occur, with one service setting the time, then the other correcting the change, which triggers the first to correct again, and so forth in an annoying and unproductive loop. Aside from wasting CPU time and network bandwidth, the accuracy of the clock will suffer, sometimes dramatically. Also, only one service may own a particular network port on any IP address, so two time services set to answer the same protocol (such as NTP) will contend for the port, with whichever service starts first usually being able to bind and the other service fails.

    Therefore, when Domain Time is installed, the W32Time service's mode is changed or disabled to prevent conflicts. Which changes are made depends on the version:

    • Version 5.x and later: W32Time is disabled on all systems except for Cluster Server, where it is set to NoSync mode. More info
    • Versions 2.5 through 4.1: W32Time is set to NoSync mode on Domain Controllers and Cluster Server; otherwise it is set to Disabled. More info
    • Older versions: W32Time is disabled.

Solution

    If you have Domain Time installed and inadvertently set the W32Time service to either NTP or NT5DS, you may change it back to its default settings by setting the Windows Time mode on the Advanced property page of the Domain Time applet and restarting the Domain Time service. Domain Time will enforce the W32Time setting you select when it starts. Alternately, you may remove and reinstall Domain Time, which will make the necessary changes for you.

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