Active Directory (AD)

Active Directory (AD) is a directory service developed by Microsoft for Windows domain networks. It helps organizations manage permissions and access to network resources. At its core, Active Directory consists of a database (or directory) and services. The database contains detailed information about the network, such as users, computers, and permissions. For example, it may store user accounts with data like job titles, phone numbers, and passwords.

The services provided by AD are critical for maintaining security and efficiency in an IT environment. They authenticate users by verifying their credentials, like usernames and passwords, and ensure that users can only access the data and resources they are permitted to use. This process is known as authorization.

Active Directory offers several key benefits. It simplifies administrative tasks by centralizing user and rights management. Administrators can configure user settings and permissions through Group Policy, a feature that enforces policies for various objects within AD. Users benefit from single sign-on, allowing them to authenticate once and gain access to multiple resources without needing to log in again.

The main service in Active Directory is Active Directory Domain Services (AD DS), which is integrated into the Windows Server operating system. Servers that run AD DS are called domain controllers (DCs). These controllers replicate the directory's data across all DCs, ensuring consistency. A special type of domain controller, the Global Catalog server, stores complete information about its domain and partial information about others, facilitating resource searches across the network.

AD is structured hierarchically into domains, trees, and forests. A domain groups related objects like users and computers. Multiple domains can form a tree, and multiple trees can form a forest, which is the top-level container in an AD environment. Each domain in a forest shares a common schema, allowing for streamlined management and security.

The Active Directory database stores various objects such as users, computers, and groups. Each object has attributes, some visible (like usernames) and some behind-the-scenes (like security identifiers). The database schema defines what types of data can be stored and how they are organized.

Through careful planning and management, Active Directory significantly enhances security, simplifies administrative tasks, and improves collaboration within an organization's IT infrastructure.