What is a Domain Controller? - Definition & Function

Instructor: Sudha Aravindan

Sudha has a Doctor of Education degree in math education and is currently working as a Information Technology Specialist.

In today's digital world, everything has a password. You need a password to access your computer and shared resources at work. In this lesson, we'll learn about managing passwords in a networked environment through the use of domain controllers.

What is a Domain Controller?

Each of the employees in Kate's office has a key to the building. One weekend Kate had some important work to do, but when she reached her office she realized she had forgotten her key. She called the security officer, who authenticated her as an employee before letting her in.

A domain controller is in some ways similar to the security officer of an office building. In an office there are many computers, each one requiring the user to login with his or her own user name and password. Suppose there are a hundred office computers. From the perspective of an Information Technology (IT) professional, it is difficult to manage the authentication of each individual machine. A simpler solution is to configure one computer to manage the authentication of all the others. All the office computers will then be connected to this main computer to form a network. The main computer is known as the domain controller, while the other computers it authenticates are known as clients. In such set up, the client computers are said to be on the Windows domain. Now the IT person finds that the login credentials will not have to be managed on each individual computer. instead, the user names and login credentials of all authenticated users in the office can be managed much more easily through one machine, the domain controller.

Active Directory

Active Directory is the central database on a domain controller where the login credentials of all client computers, printers, and other shared resources in the network are stored. When someone tries to login, their login credentials must match those saved in Active Directory. If the login credentials do not match, the user will be denied access. All client computers on the domain share this common Active Directory. Only an administrator or IT professional has authority to add computers or shared resources to the domain, further strengthening security.

Functions of a Domain Controller

The domain controller saves plenty of headaches in the office. Take Sue, for instance. She works as an administrative assistant on the second floor. She has a meeting on the fifth floor with more than 20 attendees. Since Sue's computer is on the domain, Sue can print from a printer on the fifth floor without even leaving her own desk. Now the documents will be waiting for her when she heads to the meeting.

Another advantage is that any one in the office can login to any other computer on the domain using their own login credentials and still have access to all their personal files. In the above example, Sue can login to Mark's computer on the fifth floor with her own user name and password, and she would still have access to all her personal documents. File security is also ensured because, even when Sue logs into Marks computer as herself, she does not see any of Mark's files. Sue only sees the files and printers that she has access to.

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