Optical Networks - _Chapter 13 Deployment Considerations_142

Optical Networks - _Chapter 13 Deployment...

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13 chapter Deployment Considerations I n 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 per- spective, 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/MPLS, and Ethernet. 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 tech- nologies, and network operators often employ sophisticated network design tools to help them understand the cost trade-offs between different approaches. The exam- ples 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. We have seen the WDM optical layer play an increasing role in these networks. 707
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708 Deployment Considerations Several factors are causing service providers to reexamine the way they build their transport network. The first driver is obviously the enormous growth in network traffic, but the traffic mix is unpredictable and changing. Another driver is that the traffic growth is dominated by IP and Ethernet traffic. This traffic is a mix of Internet traffic and private leased lines, which in turn support a variety of services such as file downloads (e.g., Web traffic and file sharing), voice, video, and gaming. A third driver is the advent of increased competition, which is causing service providers to rethink how they deploy services. In contrast to a world where a new service request for bandwidth could take weeks to months to be fulfilled and require long- term contractual agreements, service providers are increasingly entering a world where services need to be deployed rapidly without long-term contracts at highly competitive rates. Moreover, there is now a new generation of carriers who operate under sig- nificantly different business models than more established carriers. These different business models require different architectures. A carrier providing services to inter- connect Internet service providers has very different requirements than a traditional carrier servicing voice and private circuit-switched lines. We also now have a new set of carriers’ carriers. These are carriers providing bulk bandwidths (say, at 622 Mb/s
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Optical Networks - _Chapter 13 Deployment...

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