What Is a Directory Service?

Introduction: What Is a Directory Service?

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. This introduction to the concepts and technologies behind Active Directory describes its purpose, provides an overview of how it works, and outlines the key business and technical benefits it offers organizations.

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. 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 organization's ability to define and maintain the network infrastructure, perform system administration, and control the overall user experience of a company's information systems.

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Why Have a Directory Service?

The need for an ever more powerful, transparent, and tightly integrated directory service is driven by the explosive growth of networked computing. As local area networks (LANs) and wide area networks (WANs) grow larger and more complex, as networks are connected to the Internet, and as applications require more from the network and are linked to other systems through corporate intranets, more is required from a directory service. 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 synchronization support for popular directories.

A directory service is both a management and user tool. As the number of objects in a network grows, the directory service becomes essential. The directory service is the hub around which a large distributed system turns. To address these needs, Windows 2000 Server introduces Active Directory, an integrated set of directory services that improve the management, security, and interoperability of the Windows network operating system.

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What Is Active Directory?

Active Directory is an essential and inseparable part of the Windows 2000 network architecture that improves on the domain architecture of the Windows NT® 4.0 operating system to provide a directory service designed for distributed networking environments. Active Directory lets organizations efficiently share and manage information about network resources and users. In addition, 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 organizations apply standardized business rules to distributed applications and network resources, without requiring administrators to maintain a variety of specialized directories.

Active Directory

Active Directory provides a single point of management for Windows-based user accounts, clients, servers, and applications. It also helps organizations 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. Active Directory thus increases the value of an organization's existing network investments and lowers the overall costs of computing by making the Windows network operating system more manageable, secure, and interoperable.

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The Microsoft Directory Service Strategy

Many vendors build specialized repositories or directory services into their applications and devices to enable the specific functionality their customers require. For example, e-mail products include directory services that let users look up and send mail to others. And server operating systems use directory services for features such as user account management and storing configuration information about applications. Because these directory services are targeted narrowly to the needs of the application or device and often lack standards-based interfaces, most companies have found that they are responsible for many different directories that can't be managed centrally or interoperate easily with each other. Having many incompatible directory services means that:

* End users must use multiple user accounts and passwords to log in to different systems, and they must know the exact locations of information on the network.

* Administrators must understand how to manage each directory within the network and must duplicate many steps when procedures, such as adding a new employee to a company, involve many different directories.

* Application developers must write different logic for every directory that their applications need to access.

The proliferation of customized directory services translates directly into a continually rising cost of ownership: it requires greater management, necessitates more complex applications, and