CARP for squid 1.2

From: Eric Stern <>
Date: Sun, 31 May 1998 13:09:40 -0400 (EDT)

Well, I just whipped up a patch to add CARP to squid 1.2. You can get it

Not sure what CARP is? I'll include a bit of the README here.

Well, Microsoft actually went and developed something cool and useful
for a change. CARP (Cache Array Routing Protocol) intelligently divides
up between a number of proxy servers. This patch adds CARP support to

A squid running CARP is intended to be a "front end" for 1 or more other
cache servers. It accepts requests, and then retrieves the objects from
the caches sitting behind it. A CARP squid does not need to cache anything
itself (and probably shouldn't).

I quote the Abstract from the CARP White Paper (Copyright Microsoft Corp.)

Microsoft Proxy Server 2.0 uses the Cache Array Routing Protocol (CARP) to
provide seamless scaling and extreme efficiency when using multiple proxy
servers arrayed as a single logical cache. CARP uses hash-based routing
to provide a deterministic "request resolution path" through an array of
proxies. The request resolution path, based upon a hashing of proxy array
member identities and uniform resource locators (URLs), means that for any
given URL request, the browser or downstream proxy server will know
where in the proxy array the information will be stored - whether already
cached from a previous request, or making a first Internet hit for
and caching.
     CARP provides two powerful benefits:
    1) Because CARP provides a deterministic request resolution path,
is none of the query messaging between proxy servers that is found with
conventional Internet Cache Protocol (ICP) networks, a process that
a heavier congestion of queries the greater the number of servers.
    2) CARP eliminates the duplication of contents that otherwise occurs
an array of proxy servers. With an ICP network, an array of five proxy
can rapidly evolve into essentially duplicate caches of the most
requested URLs. The hash-based routing of CARP keeps this from happening,
allowing all five proxy servers to exist as a single logical cache. The
is a faster response to queries and a far more efficient use of server

/ Eric Stern - PacketStorm Technologies - (519) 837-0824 /
/ /
/ WebSpeed - a transparent web caching server - available now! /
Received on Sun May 31 1998 - 10:29:01 MDT

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