MCF message exchange is mainly used in a WAN (wide-area network) for communications between a system that contains OpenTP1 and a system that lacks OpenTP1. For example, the non-OpenTP1 system might be controlled by a large-scale host computer. Communications with non-OpenTP1 systems require compatibility with the communication protocol used in that system. OpenTP1 provides such compatibility via particular OpenTP1 products: each product provides compatibility with a different protocol.

Communication via MCF messages rather than RPCs is also possible even in a LAN environment because the product TP1/NET/TCP/IP is available for the TCP/IP protocol.