What is the primary purpose of Active Directory Federation Services (AD FS)?

The primary purpose of Active Directory Federation Services (AD FS) is to complement the access management features of Active Directory Domain Services (AD DS). AD FS is designed to enable single sign-on (SSO) across different applications and systems that may not be in the same domain or network. By doing this, organizations can authenticate users across various platforms and applications using a unified set of credentials without requiring them to enter multiple sets of usernames and passwords.

This is particularly beneficial in environments that utilize multiple SaaS (Software as a Service) applications or where users need to access external resources securely. AD FS facilitates this by allowing secure sharing of identity information across security and organizational boundaries.

In contrast to the other options, AD FS does not replace Active Directory Domain Services, nor does it specifically enhance features related to Active Directory Rights Management Services or Active Directory Certificate Services. Instead, it serves as an additional layer that extends and enhances the ability of AD DS to manage user access and identity in a federated environment.