Service offered by Windows Azure that provides authentication and authorization for web applications and services
Windows Azure Active Directory Access Control -- also known as Access Control Service (ACS) 2.0 -- is a service that handles authentication and authorization for web application and services, either directly or through integration with widely used authentication systems such as Facebook, Google and Windows Live. Upon successful authentication, Windows Azure Active Directory Access Control generates a cryptographically signed token, containing a set of claims that tell what the user can do in the application.
Windows Azure Active Directory Access Control support several standards widely used in authentication and authorization of web applications, such as OAuth, SAML and WS-Trust.
Windows Azure Active Directory Access Control can be managed through a web portal or OData API, defining the applications that need its services and how to generate the claims.
Windows Azure Active Directory Access Control is also used to handle authentication in Windows Azure Service Bus.