ABSTRACT
Wide Area Networks (WANs) represent a class of networks that are not bounded by physical size. WANs generally involve relatively long transmit times with relatively high error rates. WANs are used to provide a communication interface between widely separated nodes or networks. Most WANs consist of packet switching networks with multiple intervening nodes and communication links between two communicating nodes. This chapter focuses on the International Telephone and Telegraph Consultative Committee (CCITT) X.25 packet switching recommendation and the Integrated Services Digital Network (ISDN). The Packet Assembly/Disassembly (PAD) is a device which provides dumb character terminal emulation while using a complex packet-switched network. Packet-switched networks are most efficient when exchanging relatively large blocks of data. A character mode terminal typically is set up to send and receive one byte or character at a time. There are a variety of PADs used to fit different terminal arrangements.
