Chapter 15 Unified Threat Management for FortiOS 5.0 : ICAP
  
ICAP
ICAP is the acronym for Internet Content Adaptation Protocol The purpose of the feature is to off load work that would normally take place on the firewall to a separate server specifically set up for the specialized processing of the incoming traffic. This takes some of the resource strain off of the FortiGate firewall leaving it to concentrate its resources on things that only it can do.
Off-loading value-added services from Web servers to ICAP servers allows those same web servers to be scaled according to raw HTTP throughput versus having to handle these extra tasks.
ICAP servers are focused on a specific function, for example:
Ad insertion
Virus scanning
Content translation
HTTP header or URL manipulation
Language translation
Content filtering
 
ICAP does not appear by default in the web-based manager. You must enable it in System > Config > Features to display ICAP in the web-based manager.
The following topics are included in this section:
The Protocol
Offloading using ICAP
Configuration Settings
Example ICAP sequence
Example Scenerio