OVERVIEW

In Chapters 3, 4, 5, and 6 we studied networks from the viewpoints of the physical layer (bit ways) and the bearer services they provide. Datagram networks provide best-effort transfer of messages, circuit-switched networks dedicate bandwidth along a route for transfer of constant bit rate streams, and ATM networks can dedicate resources for transfer of variable bit rate traffic with differentiated quality of service. In Chapter 7 we studied wireless networks, the principal means for providing "anytime, anyplace" access to telephone and data networks. In Chapters 8, 9, and 10 we studied the technical and economic means of network control. Finally, in Chapters 11 and 12 we described optical-link and fast switching technologies that make high-speed networking affordable.

In this brief chapter we take a broader perspective starting with two questions. The first question asks, what will be the distinctive features of the global, multimedia network of the next century? We address this question by discussing five necessary attributes of a global network. These attributes accommodate service quality variation, heterogeneity, mobility, extensibility, and security.

The second question asks, what advances are needed to build a network with these five attributes? We frame these advances as challenges to three technology areas: signal processing, networking, and applications. (This book is primarily concerned with networking technology. However, the two other technology areas are essential to a successfully deployed network: without successful applications there will not be enough users, and without signal processing advances, it will be prohibitively expensive to use the network...