9.4 - System design and categories

The consideration of the design of data cabling systems is beyond the space available here, if only because of their diversity. A local area network (LAN) is, as the name indicates, confined to a particular location. It may cover, for example, the data requirements for a small organisation, or the departmental requirements of a larger one. Normally, a LAN will use only one category of data cable. The network is likely to be used for transmission of e-mail between the computers connected to it, and to attach all of these computers to a wide area network (WAN) or to the Internet. All the computers connected to the LAN can usually share programs loaded onto any of them, security being provided by the use of passwords for certain access options.

A wide area network (WAN) is one that usually connects together a series of local area networks. The distance involved may be small, where the LANs connected are all in the same building, but may be very large indeed if they are in separate cities or even in different continents. In the latter case, satellites or transoceanic cabling are likely to be used for interconnection..

All data cabling is divided into categories depending on the bandwidth that the cabling can transmit. Categories 1 and 2 cover systems installed generally before 1995; categories 3 and 5 are being installed in the late 1990s. Category 4 is seldom used, having been overtaken by category 5, and the very high speed categories 6 and 7 are about to appear as the second millennium dawns. Table 9.2 shows some applications of the various categories and further data can be found in Table 9.9..