Chapter 1 What’s New for FortiOS 5.0 : WAN optimization and Web Caching : Policy-based WAN optimization configuration changes summary : On the server side
  
On the server side
New features:
New wanopt interface which represents the WAN optimization tunnel.
Add a firewall policy with incoming (source) interface set to the wanopt interface to accept WAN optimization tunnel sessions (only required on the server side).
For active/passive WAN optimization, set the server side to passive.
For manual mode no WAN optimization policy required.
WAN optimization profiles inherited by the server side.
You can add Security feature inspection to security policies that accept WAN optimization traffic.