Designing Large Scale Lans

Chapter 4.  Local Area Network Technologies

This chapter focuses on the selection of appropriate LAN technologies for a network. Many options are available. At the more traditional end of the LAN technology spectrum, we have various flavors of Ethernet and Token Ring. Competing with these technologies are some very interesting modern alternatives such as ATM and wireless networking. Each of these different technologies has its strengths and weaknesses. Some are strikingly effective in certain situations, while awkward and difficult in others.

Selecting Appropriate LAN Technology

You should consider four main factors when selecting a LAN technology:

• Cost efficiency

• Installed base

• Maintainability

• Performance

Cost Efficiency

One of my central assumptions throughout this book is that the network is built for some business reason. It may not directly involve making money, but there must be some benefit to having the network that justifies the expense of building it. Clearly, the benefit is never infinite, so as network designers, we have a responsibility to build a network that meets the requirements for the lowest possible cost.

This problem is particularly important in the selection of network technologies. The classic example is that Token Ring cards for PCs are more expensive than the equivalent Ethernet cards. This fact alone has explained why so many organizations have undergone expensive changes in their LAN infrastructure to use more cost-effective options. As discussed previously, ...