Internet Cache Protocol (ICP)

ICP, or Internet Cache Protocol, is a protocol developed in 1995 to allow arrays of proxy servers to communicate and work together over a network.

What is ICP (Internet Cache Protocol)?

A protocol developed in 1995 to allow arrays of proxy servers to communicate and work together over a network. Internet Cache Protocol (ICP) lets individual proxy servers query neighboring proxy servers to try to locate cached copies of requested objects. If these queries fail, the object is requested from the Internet.

ICP has some inherent drawbacks:

  • ICP arrays use queries to determine the location of cached information, a process that generates additional network traffic.
  • ICP arrays have negative scalability - the more proxy servers in the array, the more query traffic is generated.
  • ICP arrays tend to become highly redundant, with each cache containing similar information (the URLs of the most frequently visited sites).

Microsoft’s solution to these problems is the Caching Array Routing Protocol (CARP), which it developed for Microsoft Proxy Server version 2.