Wide Area Networks
Wide area networks (WANs) made a brief appearance in Sect. 1.2. We now look at WANs in a little more detail. The chapter starts with a consideration of the general characteristics of WANs. After a brief mention of the use of the public switched telephone network (PSTN) for computer networks, there is a description of the packet-switching technology frame relay. Integrated Services Digital Network (ISDN), an all-digital, circuit-switched service, comes next. Then, there is a description of digital leased lines. We follow this with coverage of digital subscriber line and cable modem, which offer alternative ‘always-on’ broadband services. Then, we look at some ways of accessing LANs remotely. Next is a section on routers, which are devices that are used to connect networks together. We cover the use in WANs of two technologies that were described in Chap. 4, ATM and Ethernet. Finally, we consider cloud computing, in which information technology services are offered over the Internet.