What Is a Domain Controller?

User authentication and authorization are critical for protecting your network infrastructure. It ensures that only trustworthy and relevant users can access the network. A Windows Server domain logically groups users, PCs, and other objects in a network, while a domain controller authenticates access requests to the domain’s resources. It also stores information about user accounts and devices and enforces security policies.

Learn the important role of a domain controller within a network infrastructure, and set it up with fault tolerance.

What Does a Domain Controller Do?

Each PC has its own local accounts, but these accounts cannot be used to access the network. This is because it makes more sense for the IT administrators to configure and manage user accounts centrally, not separately on each PC. Also, centrally managed user accounts that are not tied to a particular device allow users to access network resources from just about any workstation. And that is exactly why domain controllers are essential for your organization’s IT infrastructure.

In a network infrastructure, domains are used to group computers and other devices in the network for ease of administration. And within a domain, the domain controller is used to authenticate and authorize users and store account information centrally instead of individually on each computer.

Domain controllers are security essentials for Windows Server domains and were initially introduced in Windows NT (first released in 1993). Basically, a domain controller is a server computer that acts like a brain for a Windows Server domain. It stores user credentials and controls who can access the domain’s resources. Whenever a user tries to access a domain, the request must go through the domain controller, which then runs the login process for validating the user. The domain controller also determines access privileges based on user roles, e.g., regular users and system administrators. It ensures that bad actors stay out, and only authorized users can access the relevant resources in the domain they control.

Why is a Domain Controller Important?

Domain controllers oversee everything within domain access, preventing unwanted access to domain networks while allowing users to use all approved directory services.

Because the domain controller controls all network access, it’s critical to safeguard it with additional security features like:

Networks that are secure and isolated.
Security measures and encryption are used to safeguard data being stored and transmitted.
On controllers, unsecured protocols like remote desktop protocol are disallowed.
Deployment is carried out within a physically restricted area.
Patch and configuration management completed quickly.
Domain controllers’ access to the internet is restricted.

Because domain controllers handle all of the access to a company’s computing resources, they have to be built to withstand attacks and then still be able to function in the face of adversity.

What Is Active Directory?

Microsoft introduced Active Directory (AD) for centralized domain management in Windows Server 2000. But later in the 2008 Windows Server, Active Directory also included other services such as Directory Federation Services for Single Sign-On, security certificates for public-key cryptography, rights management, and Lightweight Directory Access Protocol (LDAP).

Essentially, an Active Directory is a framework for managing several Windows Server domains, while a domain controller is a critical part of the Active Directory. The server runs the Active Directory and authenticates users based on the data stored in the Active Directory.

An Active Directory stores information as objects organized into forests, trees, and domains. Each AD forest can have multiple domains, and domain controllers manage trusts between those domains to grant users from one domain access to another domain. Several types of trusts exist between domains:

One-way trust: Users of one domain can access the resources of another domain, but not vice versa.
Two-way trust: Users of one domain can access another domain and vice versa.
Transitive trust: A two-way trust relationship that is created automatically between a parent and child domain.
Explicit trust: A trust that is created manually by the system administrator.
Forest trust: A trust between two forests. Selective authentication can also be implemented in this type of trust.
External trust: A trust between domains that belong to different forests.

System administrators can also set security policies through domain controllers, such as password complexity.

Setting up Domain Controllers in Active Directory

Domain Assessment
- Firstly, you must evaluate the domain in which the domain controller will be installed. This evaluation includes deciding what sorts of domain controllers are required, where they will be installed, and how they will interact with the domain’s existing systems.
New Addition/Deployment
- Set the domain controller location and any resources required to run the centralized domain controller and any virtual domain controllers, whether you’re planning a new deployment of AD domain controllers or adding a new controller to an existing domain.
Security by Design
- Protecting a domain controller from both internal and external threats is crucial. Also, ensure that the domain controller architecture is safe against service disruptions caused by network outages, power outages, or any kinds of failures.

Active Directory vs Domain Controller

Microsoft launched Active Directory to provide centralized domain management. Users can connect to network resources using this database to complete their tasks. Huge amounts of data can be stored in the form of objects arranged in forests, trees, and domains. Additionally, it offers other services including Lightweight Directory Access Protocol, Single Sign-On (SSO), security certificates for public-key cryptography, and authorization access rights management (LDAP).

Every system has its own local accounts, says the domain controller. Such user accounts require central management and configuration by IT administrators. Accounts that are centrally controlled can also access network resources. Domain controllers evaluate authenticated accounts to ensure they may access network resources.

The Benefits of a Domain Controller

Benefits of a domain controller include:

Domain controllers that support protected authentication and transport protocols increase the security of the authentication process.
Domain controllers enable smooth interaction with directory services like Microsoft AD by checking for access to file servers and other network resources.
Across company networks and the wide-area network, replicated and distributed domain controllers impose security policies and fend off any unwanted access.
Companies may authenticate all directory service requests using a centralized domain controller for domain controller administration.

Why Should I Have a Secondary Domain Controller?

A domain controller authenticates and authorizes users, which is a primary security function in a network infrastructure. It has all the keys to the realm of your Windows Server domain. Now, if your domain controller goes down, there will be no way for your users to authenticate themselves and access any of the domain’s resources. All applications, services, and even business-critical systems that require Active Directory authentication will be inaccessible. Automatic designation of Internet Protocol (IP) addresses will fail, forcing system administrators to revert to manual assignments.

You may even have to rebuild your entire server from scratch, which could take days and even weeks if your company does not have an established backup protocol. This is why resilience is so important for ensuring business continuity and minimal or no downtime. Investing in a secondary domain controller can reduce downtime considerably in the event of domain controller failure. While your IT team works to restore the failed domain controller, a secondary domain controller will ensure that your users are able to access important domain resources and that business-critical systems and services keep running until everything goes back to normal.

With a secondary domain controller, you can avoid complete failure. Having a recent backup at the infrastructure level can speed up and simplify the restoration process for the primary domain controller. It may look like an additional burden initially, but it can save your IT team from investing time and resources in reconstructing the entire infrastructure from scratch under extreme pressure as business operations come to a halt.

How Can Cloud Directory Services Help?

Previously, IT infrastructure was largely Microsoft-based, so companies relied entirely on Microsoft’s Active Directory for access management. But now, as IT networks are increasingly shifting to the cloud, cloud-based access management options have also emerged. Cloud directory services are a modem alternative to the traditional, on-premises Active Directory. Delivered through the cloud, these services can be used to build an identity management system from scratch or extend your company’s Active Directory services across cloud and on-premises environments.

Cloud directory services provide similar functionality to Microsoft Active Directory services along with the added security, scalability, and convenience of the cloud. For companies running on a single domain controller, cloud directory services, such as Azure Directory, make it extremely simple and quick to set up a secondary domain controller in the cloud. With a secondary domain controller within the Azure cloud, your Network infrastructure can enjoy business continuity and resilience at a very low cost.

By setting up a secondary domain controller in Azure, your company can leverage the comprehensive identity and access management solution provided by Azure Active Directory. This includes managing users and groups and providing secure access to users across a number of Software as a Service (SaaS) applications. This could also bring your company a step closer to compliance with General Data Protection Regulation (GDPR) and Cyber Essentials.

Parallels RAS Uses Active Directory Authentication

Parallels^® Remote Application Server (RAS) provides consolidated access management by making use of Active Directory and supports Microsoft Azure Directory services. Parallels RAS Client Group Policy enables IT administrators to enforce client policies on Active Directory groups and endpoint devices to keep corporate data safe regardless of the end-user, the device, and the location from which the network is accessed.

Parallels RAS Enrollment Server enrolls and manages digital certificates and authenticates users without them having to enter their Active Directory credentials by communicating directly with the Microsoft Certificate Authority. Companies can easily configure a third-party identity provider like Azure with Parallels RAS to provide a true single sign-on (SSO) experience across subsidiaries.

Centrally control, manage and restrict access for your users.

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