A domain is a logical grouping of network computers that share a central directory database. A directory database contains user accounts and security information for the domain. This database, which is known as the directory, is the database portion of Active Directory service—the Windows 2003 directory service. In a domain, the directory resides on computers that are configured as domain controllers. A domain controller is a server that manages all security-related aspects of user and domain interactions, centralizing security and administration.

Note:- You can designate only a computer running Microsoft Windows 2000 Server or Windows Server 2003 as a domain controller. If all computers on the network are running Windows XP Professional, the only type of network available is a workgroup.

A domain does not refer to a single location or specific type of network configuration. The computers in a domain can share physical proximity on a small LAN or they can be located in different corners of the world. They can communicate over any number of physical connections, including dial-up connections, Integrated Services Digital Network (ISDN) circuits, Ethernet networks, token ring connections, frame relay networks, satellite links, and leased lines.

The benefits of a domain include the following:

■ Centralized administration because all user information is stored in the Active Directory database. This centralization allows users to manage only a single user name and password, and enables domain administrators to control which users can access resources on any computer that is a member of the domain.

■ A single logon process for users to gain access to network resources (such as file, print, and application resources) for which they have permissions. In other words, you can log on to one computer and use resources on another computer in the network as long as you have appropriate permissions to access the resource.

■ Scalability, so that you can create very large networks with hundreds or thousands of computers.