What is a LAN?

LANs allow you to do the two main things you do with computers, only easier and faster: share information and print documents. The word "LAN" stands for Local Area Network, which basically means a groups of computers connected by cables that are all in a similar area- like an office. The words "Local Area" are used in LAN because these "networks" of computers are all usually in one building, even in one room, as opposed to computers that share information from one city to another. In this document, the word "LAN" and "network" are interchangeable, but remember that sometimes a "network" can be a connection between several computers that aren't even in the same state. Also, most LANs ("networks") are run on what's called the "Ethernet" protocol. Basically, a LAN is a type of network, and Ethernet is a type of LAN- the most common type.

Why do you need a LAN?

Think about what you do with your computer from day to day. Most likely, you print something at least once a day. You are lucky if you have a printer connected to your computer; otherwise, you have to copy the document to a floppy diskette, then move to another computer, and print it from there. The same happens when you want to give a document to a co-worker to edit or read over. (This process of copying to floppy and running around the office is affectionately called "SneakerNet.")

So essentially, you need a LAN so you don't have to run around using floppy disks. You might want to share printers, share files, share databases, allow people on your network to access the internet, including web browsing and e-mail. All of these are possible with LANs. You can set up a LAN so that all computers can print to a main printer, or even choose which of several printers to print from. You can also use a LAN to copy documents from one computer to another without using floppy diskettes. You can use a LAN to access a central database from several different computers.

However, LANs can be quite expensive to install, and involved to set up. Consider how much beyond sharing a printer you need- more often than not, small offices that want to connect the computers to one or more printers, but have no needs for shared databases or files can get away with a simple print-sharing setup, which is usually far more inexpensive than installing a full LAN.

There are two components to a LAN- the hardware, and the software:

Software: This is the most complicated part of a LAN, and the one which requires at least some minimal training. Macintosh systems and Windows 95 have built in LAN (or "networking") software, but there are many other "brands" of LAN software- including Windows NT, Novell and Lantastic. The software usually allows the LAN administrator to make different folders accessible to different users (so you might have an accounting folder, and a development folder), as well as providing some printing controls, such as making users able to choose between different printers, and deferring or cancelling print jobs, etc.

Hardware: There are two main types of LAN hardware, based on the cable you use, and these will decide how you physically set up your LAN. The cheapest kind of cable is called Coaxial cable (this is similar to the cable that is used for your cable TV.) Coaxial is an older method of networking so is often lower in cost, but sometimes a bit harder to maintain because of the physical layout.

The current standard is what's called RJ45 cable, also known at 10-Base T. (This wiring is very similar to phone and actually can be used for phone cables too.) This is easy to put in place because the cables connect like phone cables, but it's more costly because it requires more hardware (devices called "hubs") that handle the traffic from one machine to the other.

Whether you buy coaxial or RJ45 cable, you will need a "card" that inserts into your computer to which you can attach this cable. A lot of the newer computers already have network cards in them, so you should double check before you buy new ones- also, you might need a specific card for a specific machine, so you want to check with the vendor before you buy a network card for your computer.

Layout: The physical way in which you lay out your cables depends on the cables you buy. Coaxial cable (like your cable TV) runs from one computer to the next, to the next, to a printer perhaps, and keeps going. It's a single line connecting all the computers (what's called a "daisy-chain"). This is a good setup if you have a few computers that aren't going anywhere, or you are planning on running these cables a *long* distance (over 400 feet). The main problem with this set up is that if you want to add a computer or printer to the LAN, you have to either cut or unplug the cable, add a new cable going to the new machine, and add a cable going back to the previous line. This will disrupt the LAN, which means it should be done after hours; and you usually end up using a lot more cable than you had originally planned.

The RJ45 cable (like the phone cable) is set up in what's called a "Star" model because it has a single cable going from each computer and each printer to a central "hub," sort of like an octopus with a machine on the end of each of its tentacles. However, this means that you need to purchase a hub (or more than one) to set up your LAN. All hubs do is act as a "Grand Central Station" where information coming from one computer gets rerouted through the hub to another computer. Hubs generally connect anywhere from 4 to 18 computers at a time. To connect more machines, or if you have multiple floors, you can run a cable that connects to hubs together (so now you have two octopi connected by one of their limbs). Of course, you don't need to run the cable straight from the computer to the hub- the cables can go under desks, around corners, and to an out-of-the-way closet where the little hub sits with its blinking lights, thinking deep thoughts. The benefit with this set up is that it is easier to change (you can unplug one computer, and the rest stay connected to the hub, so the LAN still works).

Summary:

This document was prepared with the help of Mentor Jen Engst, Jen.Engst@sun.com