ADFS 2.0 is an add-on role for Windows Server 2008 that was released in May. The idea is simple: Users log in once to the Active Directory environment and can use those credentials through claims-based authentication to access other applications, as long as they are identity-aware...ADFS 2.0 supports SAML 2.0, which is also used by several major third-party cloud services. There is a hodgepodge of different elements that allow for authentication between an Active Directory environment and the application in question (on-premise and cloud based, for example) to provide the passthrough in a secure manner, including Web Services Federation (WSFed), WS-Trust, and SAML...

Read the complete article by J. Peter Bruzzese in InfoWorld.