RFC - 2186

Internet Cache Protocol (ICP), version 2

Original:	ftp://ftp.isi.edu/in-notes/rfc2186.txt
Authors:	D. Wessels [National Laboratory for Applied Network Research/UCSD], K. Claffy [National Laboratory for Applied Network Research/UCSD]
Date:	September 1997
Category:	Informational

---

Referred by:	11 RFC
Refers to:	3 RFC

---

Status

This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Abstract

This document describes version 2 of the Internet Cache Protocol (ICPv2) as currently implemented in two World-Wide Web proxy cache packages[3, 5]. ICP is a lightweight message format used for communicating among Web caches. ICP is used to exchange hints about the existence of URLs in neighbor caches. Caches exchange ICP queries and replies to gather information to use in selecting the most appropriate location from which to retrieve an object.

This document describes only the format and fields of ICP messages. A companion document (RFC2187) describes the application of ICP to Web caches. Several independent caching implementations now use ICP, and we consider it important to codify the existing practical uses of ICP for those trying to implement, deploy, and extend its use for their own purposes.

---