Overview

In this chapter, we will study some of the issues facing network operators as they build new networks or upgrade their networks to higher and higher capacities. We will start by understanding how the network is changing from a services perspective, and then understand the changes happening to the network infrastructure. Chapter 1 provided an overview of some of these changes, but we will examine them in detail in this chapter. We will try to understand the various architectural choices available to carriers planning their next-generation networks, in terms of the roles played by SONET/SDH, IP, and ATM. We will discuss the role played by the optical layer and the economic considerations underlying the deployment of WDM and TDM optical layer technologies in the network. We will see that long-haul networks and metro networks have different requirements that influence the choice of technology deployed. In general, it is difficult to decide between the different technologies, and network operators often employ sophisticated network design tools to help them understand the cost trade-offs between different approaches. The examples and problems in this chapter will help the reader gain a better understanding of these trade-offs.

13.1 The Evolving Telecommunications Network

The legacy transport network in place in networks run by established carriers is based on SONET and SDH. Over the past decade, we have seen the WDM optical layer play an increasing role in these networks.

Several factors are causing service providers to reexamine the way they build their transport network. The...