Chapter 3 Authentication for FortiOS 5.0 : Introduction to authentication : Single Sign On authentication for users
  
Single Sign On authentication for users
“Single Sign-On” means that users logged on to a computer network are authenticated for access to network resources through the FortiGate unit without having to enter their username and password again. FortiGate units directly provide Single Sign On capability for:
Microsoft Windows networks using either Active Directory or NTLM authentication
Novell networks, using eDirectory
In combination with a FortiAuthenticator unit, the FortiGate unit can provide Single Sign-On capability that integrates multiple external network authentication systems such as Windows Active Directory, Novell e-Directory, RADIUS and LDAP. The FortiAuthenticator unit gathers user logon information from all of these sources and sends it to the FortiGate unit.
Through the SSO feature, the FortiGate unit knows the username, IP address, and external user groups to which the user belongs. When the user tries to access network resources, the FortiGate unit selects the appropriate security policy for the destination. If the user belongs to one of the permitted user groups, the connection is allowed.
For detailed information about SSO, see
“SSO using a FortiAuthenticator unit”
“Agent-based FSSO”