View source for ICAP

The Internet Content Adaptation Protocol, as specified in RFC 3507 and [http://www.measurement-factory.com/std/icap/ errata] (these latter maintained by the [http://www.measurement-factory.com/ Measurement Factory]. I've written an introductory guide, "[https://nick-black.com/faqicap.html The Working Man's Guide to ICAP]". Implementors and users of ICAP technology will likely also require extensive knowledge of encapsulated protocols, most usually [[HTTP]]. The book ''[http://www.amazon.com/Content-Networking-Architecture-Protocols-Practice/dp/1558608346 Content Networking: Architecture, Protocols and Practice]'' has pretty good ICAP/[[HTTP]] coverage. A closely related protocol is [https://tools.ietf.org/html/rfc4037 OPES/OCP].

==Implementation notes==
===Squid===
* Squid 3.0 was released in December 2007, advertising far better ICAP support than previous releases.
* Squid 3.0 seems to postpend headers to the HTTP body when a REQMOD is answered with Request-Satisfaction, as well as drop the CRLF between headers and the body. This results in a browser stall (''personal observation'').
* Squid 3.0RC6 is reported to break X-TE handling ([http://www.mail-archive.com/squid-dev@squid-cache.org/msg06270.html bug report]).
===WebWasher===
* The 6.0+ series sends "X-Encapsulated-Protocol", with values of "http", "https", "ftp" or "smtp".
* The 6.0+ series sends "X-Proxy-Addr", with the numeric IP address of the ICAP client as its value.
* The 6.0+ series sends "X-Chunk-Extensions", with values including "req-cont" and "req-stop".
===BlueCoat===
* When previews are enabled, the Proxy SG sends "X-Scan-Progress-Interval".
===NetCache===
* The NetCache C1300 sends the "NetCache-TE" header, as opposed to "X-TE".
===Symantec Anti-Virus Engine===
* Sends "X-Infection-Found" and "X-Violations-Found with arbitrary string values

==See Also==
* [http://www.chtsanti.net/c-icap/index.html The c-icap ICAP server]
* [http://www.icap-forum.org/ The ICAP Forum]
* [http://tech.groups.yahoo.com/group/icap-discussions/ Yahoo discussion board]
* [http://spicer.measurement-factory.com/ Traffic Spicer], an ICAP server from the [http://www.measurement-factory.com/ Measurement Factory]
* [http://devel.squid-cache.org/icap/ Squid's ICAP page]
* [http://www.icap-forum.org/documents/specification/draft-stecher-icap-subid-00.txt Draft extensions], aka draft-stecher-icap-subid-00.txt
* RFC 3040, "Internet Web Replication and Caching Taxonomy"