This part of ISO/IEC 11518 defines the control for HIPPI physical layer switches. HIPPI by itself is an efficient simplex high-performance point-to-point interface. The physical switch control allows the interconnection of multiple HIPPI based equipments with HIPPI physical layer switches. Characteristics of this HIPPI physical switch control protocol include: - support for both source routing and destination addresses; - I-Fields and CCIs can span multiple physical layer switches within a fabric; - when a Destination end-point receives a packet, it can easily manipulate the I-Field received to return a reply packet to the Source; - support for physical layer switches with differing numbers of ports, all within the same fabric; - specified reserved addresses to aid address self-discovery, switch management, and switch control. The purpose of this part of ISO/IEC 11518 is to facilitate the development and use of the HIPPI in computer systems by providing common physical switch control. It provides switch control structures for physical layer switches interconnecting computers, high-performance display systems, and high-performance, intelligent block-transfer peripherals. This part of ISO/IEC 11518 also applies to point-to-point HIPPI topologies.