RFC 2186 (rfc2186) - Page 1 of 9

Internet Cache Protocol (ICP), version 2

Alternative Format: Original Text Document
Next >
Network Working Group                                         D. Wessels
Request for Comments: 2186                                     K. Claffy
Category: Informational                  National Laboratory for Applied
                                                   Network Research/UCSD
                                                          September 1997

                Internet Cache Protocol (ICP), version 2

Status of this Memo

   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 (RFC 2187) 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.

1.  Introduction

   ICP is a message format used for communicating between Web caches.
   Although Web caches use HTTP[1] for the transfer of object data,
   caches benefit from a simpler, lighter communication protocol.  ICP
   is primarily used in a cache mesh to locate specific Web objects in
   neighboring caches.  One cache sends an ICP query to its neighbors.
   The neighbors send back ICP replies indicating a "HIT" or a "MISS."












Wessels & Claffy             Informational
Next >