What Is Windows Time Service?

  • Article

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2, Windows Server 2008, Windows Server 2008 Foundation, Windows Server 2008 R2, Windows Server 7

 

In this section

  • Importance of Time Protocols

Note

This topic explains only what the Windows Time service (W32Time) is. For information about how to configure the Windows Time service, see the following topics:

If you are implementing a new domain controller or external time device to handle time synchronization, see Configuring a time source for the forest (https://go.microsoft.com/fwlink/?LinkId=111146).

The Windows Time service (W32Time) provides network clock synchronization on computers running Microsoft Windows Server 2003 without the need for extensive configuration.

As the Internet assumes a more significant role in today’s business world, network clock synchronization is becoming a matter of increasing concern for many administrators. Minor time inaccuracies on a small network become more problematic when a computer on that network connects to the Internet. For example, if a company manages its finances by means of an online banking service and the individuals who oversee those finances are located in two different geographic locations, network clocks in both locations must be accurate so that finance managers in both locations have access to the same recorded transactions. Discrepancies between computer clocks at these locations could lead to transactions being recorded before the open or after the close of the business day, or money being credited to an account before it is withdrawn from another.

The Windows Time service is essential to the successful operation of Kerberos authentication and, therefore, to Active Directory–based authentication. Any Kerberos-aware application, including most security services, relies on time synchronization between the computers that are participating in the authentication request. Active Directory domain controllers must also have synchronized clocks to help ensure accurate data replication.

The Windows Time service is implemented in a dynamic link library called W32Time.dll. W32Time.dll is installed by default in the Systemroot\System32 folder during Windows Server 2003 setup and installation.

W32Time.dll was originally developed for Windows 2000 to support a specification by the Kerberos V5 authentication protocol that required that clocks on a network be synchronized. W32Time.dll in Windows Server 2003 provides increased accuracy in network clock synchronization over the Windows 2000 operating system and, in addition, supports a variety of hardware devices and network time protocols by means of time providers. Although originally designed to provide clock synchronization for Kerberos authentication, many current applications use timestamps to ensure transactional consistency, to record the time of important events, and other business-critical, time-sensitive information. These applications benefit from the Windows Time Service providing synchronized time between computers.

Importance of Time Protocols

Time protocols communicate between two computers to exchange time information and then use that information to synchronize their clocks. With the Windows Time service time protocol, a client requests time information from a server and synchronizes its clock based on the information that is received.

The Windows Time service uses the Network Time Protocol (NTP) to help synchronize time across a network. NTP is an Internet time protocol that includes the discipline algorithms necessary for synchronizing clocks. NTP is a more accurate time protocol than the Simple Network Time Protocol (SNTP) that is used in some versions of Windows; however W32Time continues to support SNTP to enable backward compatibility with computers running SNTP-based time services, such as Windows 2000.