Internet Content Adaptation Protocol

Internet Content Adaptation Protocol ( ICAP ) is a protocol for simple routing of content for HTTP, HTTPS and FTP -based services.

Target

General ICAP is a lightweight protocol for executing a " remote procedure call " for HTTP ( S) and FTP. ICAP clients to HTTP data to pass on to an ICAP server, which in turn transforms or edited ( " adapted" ) the contents. The server sends the data after the processing to the client. Normally the adapted content HTTP ( S) / FTP requests or responses.

There are products known which use ICAP in a modified version email filtering, such as Webwasher.

Function

An ICAP client is normally a proxy, the HTTP ( S) / FTP requests answers from a browser. The data is sent to an ICAP server to be processed. This processing may be a review of the URL, a virus scan etc.. The server returns a response, which then the ICAP client back to the browser and is displayed there.

For forwarding the HTTP ( S) / FTP data is packed into a ICAP package and forwarded to the server. A distinction is made in the forwarding between two modes. For inquiries there REQMOD (request modification ) and for the content RESPMOD (response modification ). This distinction allows for example, content filtering, even to save bandwidth in addition to the blocking of unwanted requests. Requests that are already blocked in REQMOD, cause no further charging of Internet content, thus saving bandwidth.