Constructing a LAN within the confines of a building or campus immediately focuses you on the physical topology of your LAN environment. Let's take a look at how you can apply the topologies we've discussed to a physical implementation. Connecting Network Segments Within a Building: The BackboneYou can think of a backbone as the spine of your network. The backbone integrates all the other LAN segments in one cohesive structure and facilitates the communication among these different segments. Take a look at Figure 2.12. You can see how a star topology “based backbone has been used to tie together three separate segments in this fictitious three-story building. Figure 2.12. A network backbone connects other LAN segments to create a larger network.
Backbones can be implemented with copper wiring, but fiber- optic cables are far more popular for a few reasons:
Backbones can also span buildings . Once again, an important point to keep in mind is the distances with which you are working. If you design beyond the specifications of the network technology you are using, be prepared for a poor performing or inoperable LAN environment. Design Considerations in a Campus LAN EnvironmentIntegrating the LANs of several buildings creates a campus network. As a LAN grows to this scale, you face a few more design challenges: scalability, redundancy, and fault tolerance. Now give some thought to just some of the design considerations you have to keep in mind when designing a campus LAN environment (see Figure 2.13). Figure 2.13. The topology for a campus network is more complex than a simple bus or star.
You will notice two buildings that are three stories tall as you look at Figure 2.13. Suppose that each "node" represents 100 computer workstations. If this were the case, you would have 300 computer workstations per floor, 900 per building, and 1,800 for the entire campus. ScalabilityScalability is the capability of the design to meet all the network traffic requirements and to continue to accommodate them as the company grows. The scalability question enters into several areas in your network design. Let's consider just a few of them:
RedundancyRedundancy is the capability of the network to fail-over to secondary paths when your primary paths are cut or experience some other type of hardware failure. How much redundancy to deploy is often a cost issue. The more redundancy in a network, the greater the cost in implementation. On the other hand, if nodes or some part of your network infrastructure should fail, added redundancy can insolate your network from extended periods of downtime, which can be even more costly. Referring to Figure 2.13, consider the design from a redundancy standpoint, giving some thought to the following questions:
Fault ToleranceFault tolerance is the aspect of your network that defines how resilient it is to the various problems that will inevitably crop up. Keeping the fault tolerance of the design in mind, consider just a few questions on this topic:
Whew! And you thought designing a campus LAN would be easy! But don't worry, everything you need to know is discussed in detail in the following chapters. |