Chapter 3 Authentication for FortiOS 5.0 : SSO using RADIUS accounting records : User’s view of RADIUS SSO authentication
  
User’s view of RADIUS SSO authentication
For the user, RADIUS SSO authentication is simple:
• The user connects to the RADIUS server and authenticates.
• The user attempts to connect to a network resource that is reached through a FortiGate unit. Authentication is required for access, but the user connects to the destination without being asked for logon credentials because the FortiGate unit knows that the user is already authenticated. FortiOS applies UTM features appropriate to the user groups that the user belongs to.