How To Configure Windows Server as a NTP Server

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_MACHINESYSTEMCurrentControlSetServicesW32Time

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_MACHINESYSTEMCurrentControlSetServicesW32TimeConfigAnnounceFlags
Set the �Announce Flags� registry entry to 5, to indicate a reliable time source.

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeTimeProvidersNTPClientSpecialPollInterval
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_MACHINESYSTEMCurrentControlSetServicesW32TimeParametersNtpServer
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_MACHINESYSTEMCurrentControlSetServicesW32TimeTimeProvidersNTPServerEnabled
Changing the �Enabled� flag to the value 1 enables the NTP Server.

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeParametersType
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_MACHINESYSTEMCurrentControlSetServicesW32TimeParameters

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.

Biography:
Dave Evans is involved in the development of NTP Server synchronisation solutions to ensure accurate time on PC�s and computer systems. Dave has developed dedicated NTP server systems, NTP synchronised digital clock systems and atomic clock time synchronisation products. Click here to find out more about NTP Server Systems.

Time Servers and the Importance of Synchronisation

Time servers are like other computer servers in the sense they are usually located on a network. A time server gathers timing information, usually from an external hardware source and then synchronises the network to that time.

Often time servers are synchronised to a UTC (Coordinated Universal time) source which is the global standard time scale and allows computers all over the world to synchronised to exactly the same time. This has obvious importance in industries where exact timing is crucial such as the stock exchange or airline industry.

There are various sources that a time server can use as a timing reference. The Internet is an obvious source, however, internet timing references from the Internet such as nist.gov and windows.time can not be authenticated, leaving the time server and therefore the network vulnerable to security threats.

There are authenticated alternatives to the Internet, the most common being to use the GPS network. As the Global Positioning System is reliant on knowing exactly what time it is to ensure reliable location information, this information can be utilised by a time server.

A simple GPS antenna connected to the time server will allow the GPS timing reference to be regularly checked by the time server. A GPS time server will be accurate to within a few hundred nanoseconds (a nanosecond = a billionth of a second).

There are also a number of national radio broadcasts such as the WWVB signal from Colorado in the US, the MSF signal from Cumbria in the UK and the DCF-77 signal from Frankfurt in Germany.

These radio signals are limited in their range though and even in major cities such as London it can be difficult to receive a decent enough signal.

Most timing servers use NTP (Network Time protocol) there are other protocols available but NTP is predominately used and is thought of as the standard for timing protocols. NTp has been around for over 25 years and is currently on version 4 but is always being updated which is probably why it is by fat the most common timing protocol.

NTP time servers work within the TCP/IP suite and rely on UDP (User Datagram Protocol). A less complex form of NTP - Simple Network Time Protocol (SNTP) is used in some devices and applications where high accuracy timing is not as important and is also included as standard in Windows software (although more recent versions of Microsoft Windows have the full NTP installed and the source code is free and readily available on the Internet from ntp.org).

Copyright 2008 © Richard N Williams

Richard N Williams is a technical author and a specialist in the telecommunications and network time synchronisation industry helping to develop dedicated time server products; ethernet clocks, GPS time servers, NTP servers, digital wall clocks, atomic clock servers and SNTP time servers. Please visit us for more information about NTP servers and NTP products This article may be republished and reprinted in its complete form or in part without seeking permission providing a relevant link to this site is maintained. It is a violation of copyright law to reprint or publish this content without following these terms.

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