Active Directory Fundamentals: Domain Controllers and Network Security

Understanding Domain Networks and Active Directory

A domain is a collection of computer networks that share a database of a central directory. This directory database contains user accounts and security information for the domain. This structure has been in place since the advent of Windows NT Server and has evolved in features and capabilities since then.

In Windows 2000 and 2003 Server, the database holding all domain information, services, and resources is called Active Directory. The introduction of Active Directory is the main difference between Windows 2000/2003 and Windows NT.

The Role of the Domain Controller

In a domain, the directory is located on the computer configured as a Domain Controller (DC). A Domain Controller is a server running the Windows 2000/2003 Server operating system that manages all aspects of security and user interactions within the domain. Security and administration are centralized.

Only computers running Windows 2000/2003 Server can be designated as Domain Controllers. Computers running other operating systems cannot serve as DCs, although they may be members of the domain and utilize its resources.

Advantages of Domain Networks

Implementing a network based on a domain offers many advantages compared to the peer network model, although it requires more complex planning and management.

Key Advantages:

• Centralized Administration: A domain allows centralized administration because all user information is stored centrally. If a user changes their password, the change is replicated throughout the domain automatically.
• Unique System Entry Process: A domain provides a unique process for entering the system, allowing users to access network resources such as files, printers, and application resources for which they have permission. In other words, a user can log into one computer and utilize the resources of another computer on the network, provided they have the appropriate privileges.
• Scalability: A domain provides scalability, allowing the administrator to create networks that increase in size and performance over time as needs arise.

Types of Computers in a Domain

The following types of computers can be found within a domain structure:

Domain Controllers with Windows 2000/2003 Server

Each Domain Controller stores and maintains a copy of the directory. User accounts are created once within the domain, and the system stores them in the directory. When a user logs into a domain computer, the Domain Controller checks the username, password, and restrictions in the directory to authenticate the user. When there are multiple Domain Controllers, they periodically replicate and synchronize directory information.

Member Servers with Windows 2000/2003 Server

These are computers that serve resources to others but do not hold a copy of the directory. They provide shared resources such as folders or printers.

Client Computers

Client computers provide a desktop environment for the user, allowing them to access domain resources. Any version of Windows operating systems designed for desktop computers can be installed on these machines.