Designing a successful IP network is one of the essential elements surrounding modern internetworking. A poorly designed network affects the performance of the routers, as well as the entire network. As networks become an essential part of any successful business, scaling and faster convergence also play a major role.
This chapter presents the process of designing large networks. Specifically, it addresses a network design: first, with respect to the enterprises; then, with respect to the ISPs. The discussion of enterprise includes two case studies, and an additional case study for ISP design:
• The first case study deals with a typical large, worldwide corporation that considers OSPF the IGP.
The chapter case studies also discuss a merger between two large companies with their own Internet connections. The two companies intend to use each other's connection as a backup.
• The second enterprise case study concerns a large hub-and-spoke design, which is widely used by large banks, airlines, and retail stores. This case study examines a situation in which networks need information from each of the remote sites, but must avoid problems arising from their flaps or instabilities. Core routing should remain stable for this design.
• The third case study shows the design of a large ISP network. This example focuses on issues such as addressing, network management, IGP and interdomain routing, multicast, and QoS. The emphasis in this case study remains on actual configuration details, and advances many of the architectural ideas present in earlier chapters.
Case Study 1: The Alpha.com Enterprise
In this case study, the customer, Alpha.com, is a large manufacturing corporation with research facilities in North America (California) and Europe (Germany). Chip fabrication plants are located in New Mexico, Texas, and Arizona (North America), as well as in Malaysia and Taiwan (Asia). A network outage causes enormous revenue losses for this company, so it wants to build a completely fault-tolerant network. Therefore, Alpha.com wants complete Layer 2 and Layer 3 redundancy.
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