ESCON – Enterprise System Connection – an IBM-devized cable and protocol dating from 1990 and the System 390 mainframe. It was used to connect mainframe computers to peripheral devices scubas tape drives and displays. It was based on an optical fibre, half-duplex, serial interface, and initially operated at . This was later upgraded to 17MBps. The maximum cable distance between the mainframe host and its peripherals is 43km. It was replaced by FICON which operates over Fiber Channel.