Data Communications Networking Devices: Operation, Utilization and Lan and Wan Internetworking, 4th Edition

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WIDE AREA NETWORKS

Building upon our examination of fundamental wide area networking concepts presented in Chapter 1, we will now turn our attention to the operation and utilization of several types of wide area networks. In doing so we will examine circuit switching networks, packet switching networks, the collection of interconnected networks, referred to as the Internet, and two special types of networks. The first special type of network actually represents two proprietary IBM networks—System Network Architecture (SNA) and Advanced Peer-to-Peer Networking (APPN). Although the direction of networking is towards open systems, IBM's domination of the mainframe market makes it highly probable that a large base of SNA and APPN networks will continue to be used for the fore-seeable future. In fact, at the time this book was prepared there were over 50 000 SNA and APPN networks in operation, some connecting over 10 000 terminal devices. The second special type of network we will examine was developed to provide an integrated capability which combines some of the features of circuit switching and packet switching to enable voice, data, video, and images to be transported via a common network infrastructure. That network technology is referred to as Asynchronous Transfer Mode, or ATM.

Although we will briefly discuss the role of several types of networking devices in this chapter, we will defer a detailed explanation of their operation and utilization to succeeding chapters. Instead, ...