Overview of the Active Directory Domain Services (AD DS)

Microsoft’s Active Directory Domain Services (AD DS) is a core role that allows users to build a scalable and centralized Windows network. 

Furthermore, the AD DS takes care of user logins, security permissions, and other crucial network services.

The AD DS is a function of the Active Directory, which manages users, groups, organizational units, and computers, allowing IT administrators to structure users into logical hierarchical units.

In this article, we’ll cover some AD DS’s basic terminologies, services, and other features.

First, let’s have a look at the Active Directory (AD).

Active Directory

Active Directory is a Microsoft technology that is installed when the Active Directory Domain Services is set up in the Domain Controller.

As the name suggests, the Active Directory is a repository or database that stores objects such as groups, computers, printers, file shares, group policies, and file permissions.

The most crucial role of the Active Directory is to handle user authentication in the domain network. It accomplishes this by allowing only authorized users to log into the network.

Additionally, the AD centralizes security by storing user accounts and their passwords in one location, instead of storing them in client computers.

IT administrators can create and delete users, configure or allow users to change their passwords, and create group policies, which determine how users interact with their PCs in the domain environment.

Without an Active Directory, IT administrators are forced to set up local users on each PC and reset the password for every user on their computers.

The AD DS is the fundamental framework for domain management. Each domain forms part of an Active Directory Forest, which can also comprise of more than one domain arranged into various organizational units.

Categories of Active Directory objects

Active Directory objects can be categorized into two main categories:

  • Container objects: These are objects that contain other objects inside them, such as Forests, Trees, Domains, and organizational units.
  • Leaf Objects: These are objects that do not contain other objects, such as users, printers, and computers.

Key Terminologies of Active Directory Domain Services

  • Schema: This is a set of instructions that govern attributes and objects in the AD DS.
  • Global Catalog: This is a repository of objects contained in the AD. It’s in the Global Catalog that you’ll find users’ details such as names and contacts.
  • Sites: This represent the network topology of a Windows network.
  • Query and Index Mechanism: This feature ensures users can locate each other in the Active Directory. A perfect example is when you start typing a user’s email address in the client’s recipient field and the possible matches are displayed.
  • Lightweight Directory Access Protocol: Commonly abbreviated as LDAP, this protocol enables the Active Directory to communicate with LADP enabled directory services in the network.
  • Replication Service: As the name suggests, replication ensures the Domain Controller is replicated onto another Domain Controller, thereby having the same schema and catalog.

Services provided in the Active Directory Domain Services

The Active Directory provides a myriad of services that fall under the Active Directory Domain Services.

Here is a description of some of the services.

  • Domain Services

The AD DS offers core services such centralization of data and management of communication between users in the domain, search functionality, as well as login authentication.

  • Lightweight Directory Services

This feature supports applications that are directory enabled using the LDAP protocol.

  • Rights Management

Rights management handles information rights. It encrypts and limits the access to personal content such as emails, documents, and other confidential data.

  • Directory Federation Services

DFS provides a single-sign-on functionality that enables secure user authentication, especially when they are interacting with multiple web applications during a single session.

  • Certificate Services

These features allow for the generation, management, and sharing of security certificates. The certificates encrypt data sent over the Internet and guarantee their privacy and confidentiality, thereby averting attempts by hackers to steal the information.

Functions of Domain Controllers with Active Directory Domain Services

A Domain Controller (DC) is a server in the Windows network that allows users to access domain resources. Its main purpose is to authenticate users in a network.

The DC listens to authentication requests from users in the network and verifies them based on their usernames and passwords.

The Domain Controller hosts the Active Directory Domain Services as well as a wide range of other services that complements Active Directory Domain Services.

These services include:

  • NetLogon: It’s a service that runs silently in the background. Its main purpose is to validate users’ login credentials in the domain network. If stopped, many server functions would be adversely affected and users in the domain would be unable to access their accounts. Additionally, any services that depend on it will also fail.
  • Kerberos Key Distribution Center (KDC): KDC is basically a service that issues, validates, and performs encryption of Kerberos tickets. It consists of an Authenticating Server and a Ticket Granting Server (TGS). The service authenticates users when the Kerberos protocol is used. Kerberos is a protocol designed for security and authentication purposes. It provides a mechanism for authenticating users to use the services on a Windows network; for example, accessing a file server while, at the same time, encrypting the connections between clients and servers.
  • W32time service: Also referred to as Windows time, W32time is a service that uses Network Time Protocol (NTP) to synchronize time and date for all computers joined to the Active Directory. The NTP synchronizes all the clocks on the computers in the domain network. For Kerberos to function properly, it demands that date and time for all computers in the network are synchronized.
  • Intersite Messaging (IsmServ). This is a service that allows the exchange of information between computers in a networked environment with Windows servers. This protocol also allows replication between mail sites by employing SMTP over a TCP/IP network.


Active Directory Domain Services is a key feature in a networked Windows environment.

Therefore, understanding how it operates can assist in maintaining the optimal operations of your network.

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Active Directory Domain Services Overview

Active Directory (AD) is a Microsoft-developed technology that consists of a set of processes for managing domains centrally, managing access privileges to networked resources, and managing other directory-related identity-based services. 

While AD consists of multiple directory services, the one that performs the core activities is Active Directory Domain Services (usually abbreviated as AD DS). Essentially, AD DS keeps information about the resources in the domain, authenticates their permissions, and determines their access rights. 

In this article, we’ll give an overview about the AD Domain Services.

Advantages of AD DS

The Active Directory Domain Services offer a wide range of advantages to the management of computing resources.

Here are some of them:

  • A directory is often implemented by building structures that store data based on the logical and hierarchical organization of information. The data stored in the directory usually has all the information about the various Active Directory objects, such as network printers, servers, shared volumes, and individual computer accounts. Consequently, this allows for data to be organized based on the users’ needs and preferences. 
  • AD DS provides multi-master replication and multi-master authentication capabilities. This allows an administrator to manage the entire directory from any location on the network.
  • AD DS comes with built-in redundancy capabilities. As such, if the performance of one Domain Controller (DC) fails, another DC takes over the load.
  • AD DS uses policy-based administration to make the work of system administrators easy, especially in a complex network infrastructure. Every access to network resources occurs through AD DS, which ensures the access rights are managed centrally. 

Common terminologies and concepts in AD DS

Let’s define some terminologies and concepts that are commonly used in Active Directory Domain Services.

  • Schema: It is a set of rules used to define objects and attributes within the directory. Schemas also define the limits on instances and how they are represented in the directory. A schema is preferably stored in its own partition within the directory and replicated among all existing domains in the forest.
  • Global Catalog: It contains all the information about every object defined in the directory, enabling both users and administrators to locate directory information easily—even if the data is on a different domain.
  • Query and Index Mechanism: Query indexing enables users and applications to locate objects and their properties within the directory. This feature comes in handy when looking for specific information in the directory structure.
  • Replication Service: This dedicated service distributes data all over the network; it’s what ensures that every DC contains the same Schema and Global Catalog. All changes made in the Active Directory Domain Services are usually replicated to every DC in the domain. The DCs usually track any changes made and only implement the updates that have taken place since the last replication. The update tracker has two roles: first, it changes what has not been received or need to be replicated at the destination; second, it resolves conflicts arising from simultaneous changes to an object.
  • Lightweight Directory Access Protocol (LDAP): It’s the protocol responsible for providing a common language for interaction between clients and servers across platforms. 

Role of Domain Controllers with AD DS

The servers running the Active Directory Domain Services are called Domain Controllers (DC). Every DC responds to requests for authentication and stores the AD Domain Services data.

Furthermore, the DCs host other essential services, which are complementary to the functions of the AD Domain Services.

Here are some of them:

  • NetLogon: A service that incessantly runs in the background to authenticate users and other services available in a domain. 
  • Kerberos Key Distribution Center (KDC): A service that validates the Kerberos tickets that the Active Directory Domain Services utilize for authentication. 
  • Intersite Messaging (IsmServ): A service that enables Domain Controllers to interact with one another for replication and site-routing purposes.

Every Active Directory should have at least a single DC. The Domain Controllers serve as containers for the domains. Furthermore, every domain is a component of an Active Directory forest, which consists of at least a single domain that is categorized in organizational units.

It’s the Active Directory Domain Services that manage trusts amongst various domains, allowing users to be granted access rights and communication privileges. So, while AD DS is the basis for domain management, DC is the computer that is used to access the Active Directory. 


An Active Directory network infrastructure provides a centralized storage and management of objects. It allows the system administrator, through group policies, to manage the access and availability of shared network resources securely.

An Active Directory Domain Service acts as a foundation for identifying users and also provides a central basis for authenticating and authorizing all the server roles in a typical Windows Server Operating System.

Some of the distinct features found in the latest Active Directory configurations include system auditing, password and account lockout policies, read-only domain controllers, ability to restart domain services, and an Active Directory Database Mounting Tool.