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