The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition

4.8. Switch Application Environments

Large-scale LAN interconnection is generally implemented in a hierarchical manner, as depicted in Figure 4-17.

Such hierarchical structures are often employed for a number of reasons:

• The burden imposed on the internetworking device(s) is only that of the level at which it is deployed; for example, desktop switches need only accommodate the needs of the desktop environment. If a flat interconnection strategy were used (i.e., a single backbone interconnecting all users with no hierarchy), then every interconnection device would need to deal with the issues and complexities of enterprise-wide internetworking, resulting in the use of many more expensive devices.

• The burden imposed on the network administrator is similarly restricted to the level at which the given person operates. Local (departmental) administrators need deal only with the problems associated with the department or workgroup, and not the enterprise as a whole. Similarly, an enterprise administrator does not have to deal directly with the problems of individual users.

• Problems are more naturally isolated; network disruptions typically affect only the users or interconnection at the level of the fault. For most failure modes, the number of users affected by a network disruption is minimized. A failure of the enterprise backbone only disrupts inter-campus communications, and allows most workgroup computing to continue unimpeded. A failure of a desktop switch would affect only the users ...