A proprietary specification for storage area network (SAN) developed by IBM for a high-speed serial interface between mainframe computers and peripherals such as external disk drives. FICON supports data transfer rates up to 400 MBps in full duplex (FDX) over distances up to 100 km. FICON is replacing the earlier and slower Enterprise System Connection (ESCON). See also Bps, ESCON, FDX, Fibre Channel, mainframe, peripheral, SAN, and serial.