Chapter 23 WAN Optimization, Web Cache, Explicit Proxy, and WCCP : Peers and authentication groups
  
Peers and authentication groups
All communication between WAN optimization peers begins with one WAN optimization peer (or client-side FortiGate unit) sending a WAN optimization tunnel request to another peer (or server-side FortiGate unit). During this process, the WAN optimization peers identify and optionally authenticate each other.
This chapter describes:
Basic WAN optimization peer requirements
How FortiGate units process tunnel requests for peer authentication
Configuring peers
Configuring authentication groups
Secure tunneling
Monitoring WAN optimization peer performance