What's in a LAN?

Local area networks, which link personal computers, come in all flavors. A technical consultant can help you select the LAN that is right for your organization. But before you begin your search for a LAN or a consultant, it's best to become acquainted with the network's structure and functions.

Hardware. You can link PCs by setting up a LAN: physically connected hardware and software located close by one another. Within an association publishing department, for example, editors, designers, and production staffers might be linked together on a network. LAN hardware usually consists of a file server, workstations, network cards, and wiring. A file is a personal computer that houses LAN software and centrally located files that users can share on a LAN. In other words, the file server keeps files of all users. Thus, a LAN server usually has a large disk drive, or data storage device, that consists of hundreds of megabytes.

In most systems, the file server is dedicated to the LAN; you can't use it as a personal computer. In other systems, you can use the file server as a personal computer, which saves purchasing an additional PC to manage the LAN.

Each personal computer in a LAN becomes a workstation. As a LAN workstation, the personal computer can do everything it did before it became part of the network. As part of the network, the PC can run software residing on the network and share files. The personal computer, for example, could run a copy of WordPerfect residing only on a personal computer. It could also run WordPerfect residing only on the local area network.

To run on a network, each PC workstation requires a network card--an integrated circuit board that fits inside the PC and connects to the network wiring. Depending on the network, these boards cost between $250 and $750.

Network wiring is the final LAN hardware component. A wire is strung from the file server to each PC in a network, allowing the network signal--known as a token--to carry information around the network.

Software. Software is the brain of the network. The software enables you to know who is using the system, to assign rights or security levels to users, to account for the time users are on the system, to send messages, and so forth.

Advantages A LAN allows users to share data so that an organization doesn't have to keep multiple copies. Thus, an organization is able to integrate data and avoid mistakes created by changing information in one file without changing the same information in all files. This also saves an organization from distributing file updates.

Having a local area network also allows your organization to purchase network versions of software packages. For example, instead of purchasing individual copies of Lotus for 10 separate PCs, you can purchase a network version that is licensed for 10 users. In the long run, this method is usually cheaper per copy. It also makes software maintenance easier because you fix bugs and upgrade the system centrally.

With a local area network, several users can share expensive peripheral resources such as niodems, facsimile machines, and printers. There is no need to dedicate equipment to a single user.

LANs allow you to centrally back up files daily. A LAN also allows you to limit user access to different areas of the network. For example, you can limit who accesses specific files, who installs software, and so forth.

Disadvantages. First, local area networks don't run themselves. They require attention: backing up data nightly, applying network operating system software upgrades, adding and deleting users, and troubleshooting problems. The services of good LAN administrators are usually pretty expensive.

Second, a local area network may sometimes have problems and become inoperative. When this happens, users cannot use the centralized resource. With individual PCs, if one PC goes down, other users are an unaffected.

Finally, it's easy for LAN users to forget they are not the only ones using the network. For example, one LAN user might delete records that another user may want. LANs require coordination among users.

Steven L. Harrison is vice president of information systems at Electronic Realty Associates, Overland Park, Kansas.