Active Directory: What Is It and How Does It Work?

The Active Directory is Microsoft’s directory service for identity management, authentication, and access control.

The Directory Services on which the Active Directory is based have been included with every version of Windows Server since Windows 2000. Before that, the concept of a domain existed in Windows NT Server, but the Active Directory itself was introduced with Windows 2000 Server.

What Is Active Directory?

Related: What Is Active Directory Users and Computers?

The Microsoft Active Directory is based on the Windows Directory Service and acts as a centralized location for managing users, computers, and other resources such as groups.

Before Microsoft introduced the concept of a domain in Windows NT, user accounts were stored on individual PCs. That meant that a user could only log on if they had an account on a particular PC. The Active Directory allows for the storage of user accounts in a centralized location, where they can be easily managed by an administrator.

What Are the Different Types of Active Directory Objects?

Active Directory user accounts are stored as objects. Although user objects may be most obvious object type associated with the Active Directory, a wide variety of objects are stored in the Active Directory database. For example, users can be organized into groups, which are another type of Active Directory object.

Computers are another common type of Active Directory object. When a computer is joined to an Active Directory domain, an Active Directory object is created that represents the domain-joined system.

Other Active Directory object types are structural. Such objects might include things like sites, subnets, domains, or organizational units.

What Is LDAP in Active Directory?

LDAP is the Lightweight Directory Access Protocol. It is essentially the protocol that is used to look up information within the Active Directory.

As a general rule, LDAP is used any time you perform an action that requires an Active Directory object to be created, looked up, or modified.

What Are the Benefits of Using Active Directory?

The primary benefit of using the Active Directory is that it allows for the centralized creation and management of user accounts.

Additionally, the Windows operating system is designed so that Active Directory users or groups can be granted access to resources. This means that a single Active Directory user account could conceivably be given access to resources on multiple computers.

Another Active Directory benefit is that it can apply group policies to Active Directory users and domain-joined computers. Group policies are collections of policy settings, essentially. For example, user policies are commonly used to define password length and complexity requirements. Computer-level group policies can be used to enforce the use of security features such as AppLocker or the Windows Firewall.

The Active Directory can also be configured in a way that helps to improve network performance, particularly as it relates to authentication. Organizations with multiple offices, for example, can use the concept of sites to build an Active Directory topology that mimics their physical architecture (such as having a different Active Directory site for each office). When a user logs in, they can be authenticated by a domain controller that is in close geographic proximity, rather than having to traverse a slow WAN link only to be authenticated by a domain controller in another part of the world.

How Can You Troubleshoot and Monitor Active Directory Performance?

Although large organizations tend to use third-party tools to monitor the health and performance of their Active Directory environments, the Windows operating system has several native Active Directory monitoring tools.  

The available tools include:

• Performance Monitor. Although the Performance Monitor tool is used for more than Active Directory, it can be used to monitor domain controller performance.
• Best Practices Analyzer. The Best Practices Analyzer can assess whether the Active Directory is configured and maintained following Microsoft’s best practices.
• Event Viewer. The Windows Event Viewer can track events that have occurred within the operating system. Events that are related to Active Directory can be found in the Event Viewer under Applications and Services Logs | Directory Service. It’s worth noting that the Active Directory has a dependency on DNS, and an unhealthy DNS can affect Active Directory. DNS-related logs are located at Applications and Services Logs | DNS Server.

Conclusion

The Active Directory has acted as Microsoft’s primary authentication and access control mechanism for over two decades. In addition to performing these key functions, the Active Directory can help maintain network security, such as by applying group policy settings to users and computers.