Chapter 3 Authentication for FortiOS 5.0 : Introduction to authentication : Types of authentication : Firewall authentication (identity-based policies) : FSSO
  
FSSO
Fortinet Single Sign on (FSSO) provides seamless authentication support for Microsoft Windows Active Directory (AD) and Novell eDirectory users in a FortiGate environment.
On a Microsoft Windows or Novell network, users authenticate with the Active Directory or Novell eDirectory at logon. FSSO provides authentication information to the FortiGate unit so that users automatically get access to permitted resources. See “Introduction to FSSO agents”.