Active Directory Domain Services (AD DS) is a crucial server role within Microsoft’s Active Directory (AD) platform that allows IT teams to manage and store information about enterprise resources. It helps IT teams organize those resources — both users and computing devices — in a logical hierarchical structure.
Organizations can use AD DS to provide integrated security through single sign-on (SSO) and rights management. This post explains how AD DS works, its essential services, and the terms you need to know.
What Is AD DS?
AD DS is the main service in AD, which is a crucial identity and access management (IAM) solution within the Windows Server operating system (OS) environment. AD DS stores and manages information about users, services, and devices connected to the network into a tiered structure. AD DS allows IT teams to streamline IAM services by serving as a centralized point of administration for all the activities on the network.
The servers that host AD DS are domain controllers (DCs). An organization can have multiple DCs, with each one storing a copy of the AD DS for the entire domain. Most organizations use AD DS to manage on-prem IAM in Windows environments. However, you can also replicate it in Azure if you’re hosting your applications partly on-prem and partly in Azure.
A Brief History of AD DS
The modern IAM space largely kicked off with the lightweight directory access protocol (LDAP). Many directories have emerged in the IAM space, including email systems, internet white pages, and even domain name systems (DNS). However, none of them define the standards for a true directory service like LDAP.
At the time, LDAP served as a basis for two major directory services solutions: Microsoft AD and open source LDAP (OpenLDAP), among many other smaller solutions. However, AD went on to become a commercial market leader while OpenLDAP led the open source market.
Both solutions became widely regarded as the underlying protocols for identity providers (IdPs) worldwide. The idea behind an IdP was to create a central user and data store for an organization. User accounts would then be stored within the IdP alongside IT resource information.
These two sets of objects would then be interrelated to connect users to the IT resources they needed. These resources, such as systems, applications, networks, and more, would each be tied directly to the user identities that needed them, as well as limited by the privileges of that specific user’s role.
In the case of Active Directory Domain Services, this was done largely for Windows networks and resources. Because the average IT network at the time was virtually all Windows-based, AD DS made a great deal of sense. A user could log in to their machine, and the AD DS would enable access to whatever the user needed and was authorized to.
How Does AD DS Work?
AD DS relies on various standards and protocols, including LDAP, Kerberos, and DNS, to organize information into a hierarchy. This allows multiple domain services to connect with them while users access or manage them. The hierarchy includes the following components:
An AD domain is a set of objects such as users, endpoints, or groups that share the same AD database. A domain can have multiple sub-domains, which can then have their own sub-domains. Authenticating users within the domain operates through a transitive trust relationship.
A tree is a group of domains within the AD network that share the same boundary and namespace. Each domain has exactly one parent or root, which forms a hierarchical tree structure. However, two different trees cannot share the same namespace.
A forest is the highest-level logical container in any AD DS configuration and contains domains, devices, users, and group policies. Each forest shares one database security boundary and has a single global address list. By default, an IT administrator or user in one forest cannot access another forest.
Organization unit (OU)
It is the smallest unit to which IT teams can assign account permissions or group policy settings. Each organization unit can contain multiple OUs with it. However, all the attributes within the OU cannot have AD objects from other domains.
What Services Does AD DS Support?
AD DS provides a range of services for enterprise IT environments.
AD DS contains a centralized directory that lets domains and users communicate. For example, when users log in to Windows domain-based PCs, AD DS checks the submitted credentials and verifies whether they are IT administrators or regular users.
Lightweight Directory Services (LDS)
It is similar to Domain Services. However, it leverages the LDAP that provides cross-platform capabilities. For example, IT teams can use AD LDS to enable Linux-based systems to function on an AD network.
Federation Services (FS)
AD FS provides SSO authentication capabilities. This allows users to sign in only once and access multiple services or applications in the same session.
Rights Management Services (RMS)
AD RMS provides persistent data protection capabilities by enforcing access policies and rights management. For example, it determines which folders users can access in the AD domain.
Certificate Services (CS)
AD CS allows DCs to create and manage digital certificates, signatures, and asymmetric key cryptography. Users can leverage AD CS to encrypt and digitally sign electronic documents.
JumpCloud Directory: A Modern Alternative to AD DS
While AD has dominated the IAM market for some time, it is struggling to keep up with a fast-paced and ever-changing IT environment. Since the mid-2000s, the IT space has seen companies adopting heterogeneous devices under the bring-your-own-device (BYOD) framework and supporting OSs like Linux and macOS, as well as mobile OSs like Android, iOS, and iPadOS.
These components introduce new access requirements, creating a hassle for IT teams to maintain security, compliance, and efficiency. This is largely because AD focuses on Windows environments. Besides heterogeneous IT environments, virtually all organizations are embracing cloud-based solutions. Such a cloud-forward status presents a significant challenge to organizations grounded on-prem with AD DS.
While an organization can replicate AD DS in Azure as an on-prem and cloud IAM solution, the solution can only work seamlessly for Windows-based systems. In other words, Azure AD DS cannot seamlessly integrate with heterogeneous resources that rely on macOS or Linux systems.
The JumpCloud Directory Platform can help you streamline IAM in heterogeneous IT environments. You can use it as a complete cloud extension for AD DS and a bridge to non-Windows systems like macOS and Linux, or a fully functional replacement for Active Directory Domain Services.