The Microsoft Windows operating systems from Windows 2000 onwards has a built-in time synchronization service – ‘Windows Time'. This article describes how to configure the Microsoft Windows 2003 and Windows 2000 time service as a NTP time server. It shows how to modify registry entries to configure the Microsoft Windows Time Service. The Windows Time service allows a Windows network to provide synchronisation of all machines within a domain.

Windows 2003 Server Configuration

Windows 2003 has expanded on the original Windows 2000 time service by providing a true NTP implementation. The time service, installed by default, can synchronise to a NTP Server. Indeed, by manipulating registry settings for the service it can act as both an NTP server and client to synchronise other network clients in the domain.

The 'Windows Time' service should be present in the systems service list. The application executable is 'w32time.exe'. The parameter list for w32time can be found in the registry at:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time

Before modifying registry entries it is good a dood idea to backup the registry settings. The registry can then be restored in the event of problems being encountered.
To configure a Windows 2003 machine to synchronise to an external NTP server, edit the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags

Set the ‘Announce Flags' registry entry to 5, to indicate a reliable time source.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPClient\SpecialPollInterval

The ‘Special Poll Interval' registry entry defines the period in seconds that the Windows 2003 machine should poll the NTP server. A recommended value is 900 seconds, which equates to every 15 minutes.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\NtpServer

The ‘NTP Server' parameter is used to provide a list of IP addresses or DNS names, separated by a space, of NTP servers that the Windows 2003 machine can synchronise to.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPServer\Enabled

Changing the ‘Enabled' flag to the value 1 enables the NTP Server.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type
Change the server type to NTP by specifying ‘NTP' in the ‘Type' registry entry.

Windows 2000 Time Service Configuration

Windows 2000 has an integrated time synchronisation service, installed by default, which can synchronise to a NTP Server. Indeed, by manipulating registry settings, the service can act as both an SNTP client and SNTP server to synchronise other network clients.

Before modifying registry entries it is good a dood idea to backup the registry settings. The registry can then be restored in the event of problems being encountered.
The 'Windows Time' service should be present in the systems service list. The application executable is 'w32time.exe'. The parameter list for w32time can be found in the registry at:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters

Windows 2000 can operate as an NTP client and synchronise to an NTP server by setting parameter 'NTP Server' to the IP address of a NTP Server.

By default, the Microsoft Windows 2000 machine will synchronise to the specified NTP time server every 8 hours (or 3 times a day), which may not be enough to maintain accurate synchronisation. The period can be reduced by setting the 'Period' parameter to how many times a day synchronisation is required. Setting the period to 48 will activate synchronisation with the NTP server once every half hour.
Windows 2000 can also be configured to act as an NTP server by setting the 'Local NTP' parameter to '1'.

After editing any of the registry entries for the windows time service, the service must be restarted for the settings to take effect. The services can be started or stopped from the service control applet in 'administrative tools'. Alternatively the service can be controlled via the DOS net command thus:

net start w32time
net stop w32time

NTP Troubleshooting

A number of problems can be encountered when configuring the Windows Time Service. NTP operates using the UDP protocol over TCP/IP. Therefore the TCP/IP network infrastructure must be operational for NTP to be effective. Synchronisation issues may arise when NTP attempts to synchronise to an inaccurate time reference or if network delays are excessive.

Synchronising Time on Network Devices

As well as synchronising Microsoft Windows servers and workstations, NTP can also be used to synchronise network devices, such as hubs, switches and routers. Any network device that can synchronise to a NTP server can be pointed to the Windows server to achieve time synchronisation. In this way the whole network and accompanying infrastructure can be synchronised.