Most computer systems have integrated Real Time Clocks (RTC) used to maintain time and date information. Invariably, real time clocks are battery backed so that time and date information can be maintained even when the PC is powered down. The PC clock provides accurate time and date information to many operating system processes and also to user applications.
Often this simple approach is adequate, however, for many networked applications PC time may need to be synchronised with other computers. For transaction processing in a networked environment or for scheduling purposes, the system time and date may need to be synchronised with every other PC on the local network. Microsoft Windows 2003 has an integrated time service that provides synchronisation between PC's in a domain. This article describes how the Windows 2003 Time Service synchronises time and date information on servers to a domain controller.
It also describes how the Windows Time Service utilises the Network Time Protocol (NTP) to achieve network time synchronisation of servers in a domain. In networked environments, a completely automated time synchronisation service is required to automatically set the clocks on each client to that of a master reference clock. The Windows 2003 Time Service provides such functionality. The service is installed by default on any Windows 2000, XP and Server 2003 machine. On power-up, the Windows 2003 time service starts automatically and attempts to synchronise time and date information with a domain controller using the NTP protocol. NTP is an Internet protocol developed for the transfer of accurate time.
The Network Time Protocol provides accurate time information along with network transmission delay information, so that a precise time can be obtained. A domain controller can be configured as either a trusted or an un-trusted time reference. A Windows Time Client will always attempt to synchronise time periodically with a trusted domain controller. In this manner networked Windows 2003 servers maintain synchronisation with a domain controller and each other. The Windows 2003 time synchronisation service configuration settings are contained in a global group policy.
The settings are stored as registry entries in the registry at HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32Time. Below is a description of some of the more useful configuration settings. The 'AnnounceFlags' registry entry indicates whether the server is a trusted time reference.
Set the 'AnnounceFlags' registry entry to 5 indicating a reliable time reference. The 'Type' registry entry specifies which network peers to accept synchronisation. Set the 'Type' registry entry to 'NTP' to specify synchronization to a NTP time server.
The 'SpecialPollInterval' registry entry defines how often the Windows 2003 operating system should poll the time server, the value should be specified in seconds. A recommended value is 900, which equates to a polling period of every 15 minutes. The 'NtpServer' parameter is used to provide domain names or IP addresses of NTP time servers that the operating system can synchronize to. Each domain name or IP address should be separated by a space.
For a number of years, David Evans has been involved in the computer time synchronisation industry. David is a technical author with a long history of involvement in installing and configuring computer network timing systems. David has also provided a technical authoring service to many time server and reference clock manufacturers. Click here for more information about Windows 2003 time server systems.