XTP: a communications protocol for real-time distributed systems

Modern factory control systems are no longer a collection of machines and controllers connected by point-to-point wiring; instead, factory automation has become yet another example of a real-time distributed system. Control and monitoring systems are implemented routinely by using local area network technology. In this context, it is the choice of communications protocol which determines the power and utility of the resulting system. Not only must the control program deal with traditional communications services such as control messages and file transfers, but it must also support new functionalities such as electronic mail, real-time transactions, image transmission, multimedia, and teleconferencing. We discuss the design features, functionality, and performance of the Xpress Transfer Protocol, a new communications protocol specifically intended to support real-time distributed systems.<>