FortiOS Handbook V2, Chapter 18: WAN Optimization, Web Cache, Explicit Proxy, and WCCP

You can use FortiGate WAN optimization and web caching to improve performance and security of traffic passing between locations on your wide area network (WAN) or from the Internet to your web servers. You can also use the FortiGate unit as an explicit web proxy server. If your FortiGate unit supports web caching, you can also add web caching to the web proxy server. This document describes how FortiGate WAN optimization, web caching, and web proxy work and also describes how to configure these features.