We will let the launch site speak for itself:

"Light the Fiber!

Welcome to the future! XCP - the XML Control Protocol - is a drop in replacement for traditional Transmission Control Protocol, or TCP. XCP has many advantages, some of which are outlined in our rationale section. With the advent of XCP/IP, connection-oriented networking will finally move from the legacy environment of inscrutable bits and bytes to a structured, human-readable world relying upon XML.  XCP is the first 4th Generation Protocol, or 4GP.  It is designed for a networking environment that is very fast and very reliable - the Internet of today!

XCP is a floor wax and a dessert topping.  The design of XCP allows it to be a simple point to point connection manager for a single session (e.g., a traditional client/server application model).  In addition, an XCP "server" can act as the end point for a stream through which any existing service can be "tunneled".  By using XCP in new applications, you get finer control over the various aspects of the connection.  However, you can begin using XCP immediately with your legacy applications when it is in "server" mode.

This site is dedicated to describing the architecture behind the project, coordinating project activities among its development community, promoting the use of XCP throughout the Internet, and making XCP-related products available to the general public."