What is Azure Active Directory Domain Services?

Azure Active Directory Domain Services (AD DS) provides managed domain services such as domain join, group policy, lightweight directory access protocol (LDAP), and Kerberos/NTLM authentication. You use these domain services without the need to deploy, manage, and patch domain controllers (DCs) in the cloud.

An Azure AD DS managed domain lets you run legacy applications in the cloud that can’t use modern authentication methods, or where you don’t want directory lookups to always go back to an on-premises AD DS environment. You can lift and shift those legacy applications from your on-premises environment into a managed domain, without needing to manage the AD DS environment in the cloud.

Azure AD DS integrates with your existing Azure AD tenant. This integration lets users sign in to services and applications connected to the managed domain using their existing credentials. You can also use existing groups and user accounts to secure access to resources. These features provide a smoother lift-and-shift of on-premises resources to Azure.

Take a look at our short video to learn more about Azure AD DS.

How does Azure AD DS work?

When you create an Azure AD DS managed domain, you define a unique namespace. This namespace is the domain name, such as aaddscontoso.com. Two Windows Server domain controllers (DCs) are then deployed into your selected Azure region. This deployment of DCs is known as a replica set.

You don’t need to manage, configure, or update these DCs. The Azure platform handles the DCs as part of the managed domain, including backups and encryption at rest using Azure Disk Encryption.

A managed domain is configured to perform a one-way synchronization from Azure AD to provide access to a central set of users, groups, and credentials. You can create resources directly in the managed domain, but they aren’t synchronized back to Azure AD. Applications, services, and VMs in Azure that connect to the managed domain can then use common AD DS features such as domain join, group policy, LDAP, and Kerberos/NTLM authentication.

In a hybrid environment with an on-premises AD DS environment, Azure AD Connect synchronizes identity information with Azure AD, which is then synchronized to the managed domain.

Azure AD DS replicates identity information from Azure AD, so it works with Azure AD tenants that are cloud-only, or synchronized with an on-premises AD DS environment. The same set of Azure AD DS features exists for both environments.

• If you have an existing on-premises AD DS environment, you can synchronize user account information to provide a consistent identity for users. To learn more, see How objects and credentials are synchronized in a managed domain.
• For cloud-only environments, you don’t need a traditional on-premises AD DS environment to use the centralized identity services of Azure AD DS.

You can expand a managed domain to have more than one replica set per Azure AD tenant. Replica sets can be added to any peered virtual network in any Azure region that supports Azure AD DS. Additional replica sets in different Azure regions provide geographical disaster recovery for legacy applications if an Azure region goes offline. Replica sets are currently in preview. For more information, see Replica sets concepts and features for managed domains.

The following video provides an overview of how Azure AD DS integrates with your applications and workloads to provide identity services in the cloud:

To see Azure AD DS deployment scenarios in action, you can explore the following examples:

Azure AD DS features and benefits

To provide identity services to applications and VMs in the cloud, Azure AD DS is fully compatible with a traditional AD DS environment for operations such as domain-join, secure LDAP (LDAPS), Group Policy, DNS management, and LDAP bind and read support. LDAP write support is available for objects created in the managed domain, but not resources synchronized from Azure AD.

The following features of Azure AD DS simplify deployment and management operations:

• Simplified deployment experience: Azure AD DS is enabled for your Azure AD tenant using a single wizard in the Azure portal.
• Integrated with Azure AD: User accounts, group memberships, and credentials are automatically available from your Azure AD tenant. New users, groups, or changes to attributes from your Azure AD tenant or your on-premises AD DS environment are automatically synchronized to Azure AD DS.
  • Accounts in external directories linked to your Azure AD aren’t available in Azure AD DS. Credentials aren’t available for those external directories, so can’t be synchronized into a managed domain.
• Use your corporate credentials/passwords: Passwords for users in Azure AD DS are the same as in your Azure AD tenant. Users can use their corporate credentials to domain-join machines, sign in interactively or over remote desktop, and authenticate against the managed domain.
• NTLM and Kerberos authentication: With support for NTLM and Kerberos authentication, you can deploy applications that rely on Windows-integrated authentication.
• High availability: Azure AD DS includes multiple domain controllers, which provide high availability for your managed domain. This high availability guarantees service uptime and resilience to failures.
  • In regions that support Azure Availability Zones, these domain controllers are also distributed across zones for additional resiliency.
  • Replica sets can also be used to provide geographical disaster recovery for legacy applications if an Azure region goes offline.

Some key aspects of a managed domain include the following:

• The managed domain is a stand-alone domain. It isn’t an extension of an on-premises domain.
  • If needed, you can create one-way outbound forest trusts from Azure AD DS to an on-premises AD DS environment. For more information, see Resource forest concepts and features for Azure AD DS.
• Your IT team doesn’t need to manage, patch, or monitor domain controllers for this managed domain.

For hybrid environments that run AD DS on-premises, you don’t need to manage AD replication to the managed domain. User accounts, group memberships, and credentials from your on-premises directory are synchronized to Azure AD via Azure AD Connect. These user accounts, group memberships, and credentials are automatically available within the managed domain.

Next steps

To learn more about Azure AD DS compares with other identity solutions and how synchronization works, see the following articles:

What is Azure Active Directory?

Azure Active Directory (Azure AD) is Microsoft’s cloud-based identity and access management service, which helps your employees sign in and access resources in:

External resources, such as Microsoft 365, the Azure portal, and thousands of other SaaS applications.

Internal resources, such as apps on your corporate network and intranet, along with any cloud apps developed by your own organization. For more information about creating a tenant for your organization, see Quickstart: Create a new tenant in Azure Active Directory.

To learn the difference between Azure AD and Active Directory Domain Services, see Compare Active Directory to Azure Active Directory. You can also use the various Microsoft Cloud for Enterprise Architects Series posters to better understand the core identity services in Azure, Azure AD, and Microsoft 365.

Who uses Azure AD?

Azure AD is intended for:

IT admins. As an IT admin, you can use Azure AD to control access to your apps and your app resources, based on your business requirements. For example, you can use Azure AD to require multi-factor authentication when accessing important organizational resources. Additionally, you can use Azure AD to automate user provisioning between your existing Windows Server AD and your cloud apps, including Microsoft 365. Finally, Azure AD gives you powerful tools to automatically help protect user identities and credentials and to meet your access governance requirements. To get started, sign up for a free 30-day Azure Active Directory Premium trial.

App developers. As an app developer, you can use Azure AD as a standards-based approach for adding single sign-on (SSO) to your app, allowing it to work with a user’s pre-existing credentials. Azure AD also provides APIs that can help you build personalized app experiences using existing organizational data. To get started, sign up for a free 30-day Azure Active Directory Premium trial. For more information, you can also see Azure Active Directory for developers.

Microsoft 365, Office 365, Azure, or Dynamics CRM Online subscribers. As a subscriber, you’re already using Azure AD. Each Microsoft 365, Office 365, Azure, and Dynamics CRM Online tenant is automatically an Azure AD tenant. You can immediately start to manage access to your integrated cloud apps.

What are the Azure AD licenses?

Microsoft Online business services, such as Microsoft 365 or Microsoft Azure, require Azure AD for sign-in and to help with identity protection. If you subscribe to any Microsoft Online business service, you automatically get Azure AD with access to all the free features.

To enhance your Azure AD implementation, you can also add paid capabilities by upgrading to Azure Active Directory Premium P1 or Premium P2 licenses. Azure AD paid licenses are built on top of your existing free directory, providing self-service, enhanced monitoring, security reporting, and secure access for your mobile users.

For the pricing options of these licenses, see Azure Active Directory Pricing.

Azure Active Directory Premium P1 and Premium P2 are not currently supported in China. For more information about Azure AD pricing, contact the Azure Active Directory Forum.

Azure Active Directory Free. Provides user and group management, on-premises directory synchronization, basic reports, self-service password change for cloud users, and single sign-on across Azure, Microsoft 365, and many popular SaaS apps.

Azure Active Directory Premium P1. In addition to the Free features, P1 also lets your hybrid users access both on-premises and cloud resources. It also supports advanced administration, such as dynamic groups, self-service group management, Microsoft Identity Manager (an on-premises identity and access management suite) and cloud write-back capabilities, which allow self-service password reset for your on-premises users.

Azure Active Directory Premium P2. In addition to the Free and P1 features, P2 also offers Azure Active Directory Identity Protection to help provide risk-based Conditional Access to your apps and critical company data and Privileged Identity Management to help discover, restrict, and monitor administrators and their access to resources and to provide just-in-time access when needed.

«Pay as you go» feature licenses. You can also get additional feature licenses, such as Azure Active Directory Business-to-Customer (B2C). B2C can help you provide identity and access management solutions for your customer-facing apps. For more information, see Azure Active Directory B2C documentation.

For more information about associating an Azure subscription to Azure AD, see Associate or add an Azure subscription to Azure Active Directory and for more information about assigning licenses to your users, see How to: Assign or remove Azure Active Directory licenses.

Which features work in Azure AD?

After you choose your Azure AD license, you’ll get access to some or all of the following features for your organization:

Category	Description
Application management	Manage your cloud and on-premises apps using Application Proxy, single sign-on, the My Apps portal (also known as the Access panel), and Software as a Service (SaaS) apps. For more information, see How to provide secure remote access to on-premises applications and Application Management documentation.
Authentication	Manage Azure Active Directory self-service password reset, Multi-Factor Authentication, custom banned password list, and smart lockout. For more information, see Azure AD Authentication documentation.
Azure Active Directory for developers	Build apps that sign in all Microsoft identities, get tokens to call Microsoft Graph, other Microsoft APIs, or custom APIs. For more information, see Microsoft identity platform (Azure Active Directory for developers).
Business-to-Business (B2B)	Manage your guest users and external partners, while maintaining control over your own corporate data. For more information, see Azure Active Directory B2B documentation.
Business-to-Customer (B2C)	Customize and control how users sign up, sign in, and manage their profiles when using your apps. For more information, see Azure Active Directory B2C documentation.
Conditional Access	Manage access to your cloud apps. For more information, see Azure AD Conditional Access documentation.
Device Management	Manage how your cloud or on-premises devices access your corporate data. For more information, see Azure AD Device Management documentation.
Domain services	Join Azure virtual machines to a domain without using domain controllers. For more information, see Azure AD Domain Services documentation.
Enterprise users	Manage license assignment, access to apps, and set up delegates using groups and administrator roles. For more information, see Azure Active Directory user management documentation.
Hybrid identity	Use Azure Active Directory Connect and Connect Health to provide a single user identity for authentication and authorization to all resources, regardless of location (cloud or on-premises). For more information, see Hybrid identity documentation.
Identity governance	Manage your organization’s identity through employee, business partner, vendor, service, and app access controls. You can also perform access reviews. For more information, see Azure AD identity governance documentation and Azure AD access reviews.
Identity protection	Detect potential vulnerabilities affecting your organization’s identities, configure policies to respond to suspicious actions, and then take appropriate action to resolve them. For more information, see Azure AD Identity Protection.
Managed identities for Azure resources	Provides your Azure services with an automatically managed identity in Azure AD that can authenticate any Azure AD-supported authentication service, including Key Vault. For more information, see What is managed identities for Azure resources?.
Privileged identity management (PIM)	Manage, control, and monitor access within your organization. This feature includes access to resources in Azure AD and Azure, and other Microsoft Online Services, like Microsoft 365 or Intune. For more information, see Azure AD Privileged Identity Management.
Reports and monitoring	Gain insights into the security and usage patterns in your environment. For more information, see Azure Active Directory reports and monitoring.

Terminology

To better understand Azure AD and its documentation, we recommend reviewing the following terms.