Internet Content Adaptation Protocol
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The Internet Content Adaptation Protocol (ICAP) is a lightweight
content filters in transparent HTTP proxy caches. Content adaptation
refers to performing the particular value added service (content manipulation) for the associated client request/response.
ICAP concentrates on leveraging edge-based devices (
content filtering
. 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.
History
ICAP was proposed in late 1999 by Peter Danzig and John Schuster[1] from Network Appliance.[2] Don Gillies took over the project in the spring of 2000 and enhanced the protocol in three main ways:
- To allow pipelined ICAP servers. One web page could be streamed through virus-scan, content-filtering, and language translation servers, quickly.
- To support all 3 content encodings (content-length, chunked, and TCP-close) in HTTP 1.1. This replaced original store-and-forward protocol with continuous streaming of content through many servers at once.
- To provide a feature called "content preview" that allowed the ICAP server to look at the first few hundred bytes of content before deciding to process the content or not. This was implemented by embedding the preview argument size in the ICAP webserver URL when configured on the ICAP client.
Gillies prototyped the first ICAP client and server for the
Jive in real time.[3] With knowledge learned from the prototyping experience, Gillies revised the IETF draft standard to make RPCs using only chunked encoding, greatly simplifying the ICAP protocol.[1]
References
- ^ .
- ^ "Internet Content Adaptation Protocol (ICAP)" (PDF). NetApp. 2001-07-30.
- ^ Gillies, Donald. "ICAP Installation Instructions". UBC ECE Dept. Retrieved 2016-01-04.
External links
- RFC 3507
- ICAP Forum
- A page from ICAP Beta Testing translated from Yahoo News into Jive! (Sept 20, 2000)