ESCON

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ESCON (or Enterprise Systems Connection) is an optical serial interface between IBM mainframe computers and peripheral devices such as storage and tape drives. ESCON is capable of half-duplex communication at a rate of 17 MB/second over distances of up to 43 kilometers. ESCON was introduced by IBM in 1990 to replace the older, slower (max. 4.5 MBps), copper-based Bus & Tag channel technology of 1960-1990 era mainframes. The substantially faster FICON channel, which runs over Fibre Channel, is in turn supplanting ESCON.

ESCON (Enterprise Systems Connection) is a fiber based channel architecture for mainframes and peripherals. It was announced by IBM in September 1990. It initially operated at 10MBps and has since been raised to 17MBps.

ESCON allows the establishment and reconfiguration of channel connections dynamically, without having to take equipment off-line and manually moving the cables. ESCON supports channel connections using serial transmission over a pair of fibers. It replaces much bulkier traditional parallel bus and tag facilities. The ESCON Director supports dynamic switching and allows the distance between units to be extended up to 60km over a dedicated fiber. “Permanent virtual circuits” are supported through the switch.

Switching could actually be achieved prior to ESCON using non-IBM products. Switching is clearly superior to a collection of point-to-point links. A peripheral previously capable of accessing a single mainframe can now be connected simultaneously to up to eight mainframes, providing peripheral sharing. Fiber is much more compact in diameter and weight and hence could likely save installation costs in new data centers and save space in existing data centers. Space and labor could also be minimized since fewer physical links are required because of ESCON's switching function.

However, ESCON is a vendor-proprietary technology and it does not follow any existing standard, including FDDI, SONET & BISDN.