Active Directory (AD) and Azure Active Directory (AAD) are both directory services offered by Microsoft, but they have distinct differences in their design, functionality, and purpose.
1. Design and Scope:
AD is an on-premises directory service primarily designed for managing and authenticating users, computers, and other resources within a Windows Server environment. It is commonly used in traditional client-server networks and provides features like user authentication, group policy management, and domain services.
AAD, on the other hand, is a cloud-based directory service that is specifically built to support web-based services and applications. It is designed to be used with cloud-based services like Office 365, Azure, and other SaaS applications. AAD extends the capabilities of AD to the cloud and enables single sign-on (SSO) and identity management for cloud services.
2. Protocols and Interfaces:
AD primarily uses the Kerberos and LDAP protocols for authentication and directory services. It supports various Windows-based authentication mechanisms and interfaces like LDAP, NTLM, and RPC.
AAD, being focused on cloud services, uses different protocols and interfaces. It supports industry-standard protocols like Security Assertion Markup Language (SAML) and OAuth 2.0 for authentication and authorization. These protocols enable AAD to integrate with a wide range of cloud-based applications and services, including non-Microsoft platforms.
3. Web-based Services Integration:
AD is mainly intended for managing on-premises resources, such as Windows-based servers, desktops, and applications. While it can integrate with some cloud services, it is not designed to provide the same level of integration and identity management capabilities as AAD.
AAD, being a cloud-based service, is optimized for integrating with various web-based services and applications. It provides a centralized identity and access management platform for cloud services like Office 365, Azure, SharePoint Online, and more. With AAD, users can have a single set of credentials to access multiple cloud services, enabling seamless SSO and simplified user management.
4. Scalability and Availability:
AD is typically deployed within an organization’s own infrastructure, which means its scalability and availability are limited to the capacity of the on-premises infrastructure. Scaling up an AD environment can require additional hardware and resources.
AAD, as a cloud service, benefits from the scalability and availability of the underlying cloud platform. It can handle a large number of users, applications, and services, and Microsoft ensures high availability and reliability of the AAD infrastructure. This makes it suitable for organizations of all sizes, from small businesses to large enterprises.
While AD is designed for on-premises network management, AAD is specifically built for cloud-based services and web applications. AAD offers a more scalable, flexible, and web-centric approach to managing identities, enabling seamless integration with a wide range of cloud services using industry-standard protocols.