A proprietary storage area network (SAN) developed by IBM for a high speed serial interface between mainframe computers and peripherals such as external disk drives. ESCON supports data transfer rates up to 17 MBps in half-duplex (HDX) over distances up to 43 km. ESCON is yielding to Fibre Connections (FICON), a faster technology that runs over Fibre Channel. See also Bps, Fibre Channel, FICON, HDX, mainframe, peripheral, SAN, and serial.