The Active Directory service is a central component of the Windows 2000 operating system platform. Understanding Active Directory is important to understanding the overall value of Windows 2000.

Today, networked computing is more important than ever for businesses to remain competitive. As a result, modern operating systems require mechanisms for managing the identities and relationships of the distributed resources that make up network environments, including domain trees and forests.
A directory service provides a place to store information about network-based entities, such as applications, files, printers, and people. It provides a consistent way to name, describe, locate, access, manage, and secure information about these individual resources.

Further, a directory service acts as the main switchboard of the network operating system. It is the central authority that manages the identities and brokers the relationships between these distributed resources, enabling them to work together. Because a directory service supplies these fundamental network operating system functions, it must be tightly coupled with the management and security mechanisms of the operating system to ensure the integrity and privacy of the network. It also plays a critical role in an organisation's ability to define and maintain the network infrastructure, perform system administration, and control the overall user experience of a company's information systems.

Active Directory lets organisations store information in a hierarchical, object-oriented fashion, and provides multi-master replication to support distributed network environments.

A directory service is one of the most important components of an extended computer system because it:

• Simplifies management. Provides a single, consistent point of management for users, applications, and devices.
• Strengthens security. Provides users with a single sign-on to network resources and provides administrators with powerful and consistent tools to manage security services for internal desktop users, remote dial-up users, and external e-commerce customers.
• Extends interoperability.
• Supplies standards-based access to all Active Directory features as well as synchronisation support for popular directories.

Active Directory acts as the central authority for network security, letting the operating system readily verify a user's identity and control his or her access to network resources. Equally important, Active Directory acts as an integration point for bringing systems together and consolidating management tasks. Combined, these capabilities let organisations apply standardised business rules to distributed applications and network resources, without requiring administrators to maintain a variety of specialised directories.

It also helps organisations integrate systems not using Windows with Windows-based applications, and Windows-compatible devices, thus consolidating directories and easing management of the entire network operating system. Companies can also use Active Directory to extend systems securely to the Internet. This makes the Windows network operating system more manageable, secure, and interoperable.

Totally integrated with Windows 2000 Server, Active Directory gives network administrators, developers, and users access to a directory service that:

• Simplifies management tasks.
• Strengthens network security.
• Makes use of existing systems through interoperability.

Active Directory services within Windows 2000 provide a focal point for managing and securing Windows user accounts, clients, servers, and applications. In addition, Active Directory is designed to integrate with the non-Windows directories within existing systems, applications, and devices to provide a single place and a consistent way of managing an entire network infrastructure.