OVERVIEW

In Chapters 3 through 5 we studied packet- and circuit-switched networks.Those networks are suitable for message and constant bit rate traffic, respectively. In this chapter we examine the Asynchronous Transfer Mode or ATM networks. ATM networks combine the good features of both types of networks, making them suitable for both constant bit rate (CBR) and variable bit rate(VBR) traffic. ATM networks potentially can provide bearer services with a specified quality of service to meet the needs of all traffic types. Whether this potential can be realized depends on how well the problems of management and control of ATM networks can be solved. Those problems are discussed in Chapters 8 and 9.

This chapter presents the concepts of ATM. It offers a simple model to calculate the delay of an ATM network. By the end of this chapter you will understand the ATM layered architecture, the addressing and routing standards, and the formats for different services. You will also know the important proposals for ATM LANs and for IP service over ATM. With these proposals, ATM becomes backward-compatible with existing LAN equipment and IP software.

We saw in section 2.2 that different applications impose different performance requirements on the network bearer services in terms of delay, bandwidth,and loss. If all these applications are to share the same network resources(links, buffers, switches) and this is very desirable to gain the economies of scale and service integration the network must be able to allocate its resources differently to different applications. Because switches or routers...