Fortinet black logo

Handbook

Overview

6.0.0
Copy Link
Copy Doc ID 4afb0436-a998-11e9-81a4-00505692583a:522251
Download PDF

Overview

ICAP is an application layer protocol; its specifications are set out in RFC 3507. It is, in essence, a lightweight protocol for executing a "remote procedure call" on HTTP messages and is a member of the member of the TCP/IP suite of protocols.

The default TCP that is assigned to it is 1344. Its purpose is to support HTTP content adaptation by providing simple object-based content vectoring for HTTP services. ICAP is usually used to implement virus scanning and content filters in transparent HTTP proxy caches. Content adaptation refers to performing the particular value added service, or content manipulation, for an associated client request/response.

Essentially it allows an ICAP client, in this case the FortiGate firewall, to pass HTTP messages to an ICAP server like a remote procedure call for the purposes of some sort of transformation or other processing adaptation. Once the ICAP server has finished processing the content, the modified content is sent back to the client.

The messages going back and forth between the client and server are typically HTTP requests or HTTP responses. While ICAP is a request/response protocol similar in semantics and usage to HTTP/1.1 it is not HTTP nor does it run over HTTP, as such it cannot be treated as if it were HTTP. For instance, ICAP messages can not be forwarded by HTTP surrogates.

Overview

ICAP is an application layer protocol; its specifications are set out in RFC 3507. It is, in essence, a lightweight protocol for executing a "remote procedure call" on HTTP messages and is a member of the member of the TCP/IP suite of protocols.

The default TCP that is assigned to it is 1344. Its purpose is to support HTTP content adaptation by providing simple object-based content vectoring for HTTP services. ICAP is usually used to implement virus scanning and content filters in transparent HTTP proxy caches. Content adaptation refers to performing the particular value added service, or content manipulation, for an associated client request/response.

Essentially it allows an ICAP client, in this case the FortiGate firewall, to pass HTTP messages to an ICAP server like a remote procedure call for the purposes of some sort of transformation or other processing adaptation. Once the ICAP server has finished processing the content, the modified content is sent back to the client.

The messages going back and forth between the client and server are typically HTTP requests or HTTP responses. While ICAP is a request/response protocol similar in semantics and usage to HTTP/1.1 it is not HTTP nor does it run over HTTP, as such it cannot be treated as if it were HTTP. For instance, ICAP messages can not be forwarded by HTTP surrogates.