Local Area Network (LAN)

Introduction

When was the last time you mailed a package to a friend or institution? Whether you mailed it through UPS, Federal Express, or the U.S.Postal Service, you probably found yourself filling out some type of form (or label) and handing it over to the carrier. From that point, you probably never gave it any further thought - unless of course, the package was lost or returned! You might even have received a notice that the package was received.

Let's examine this scenario behind the scenes. After you leave, your package is placed on a conveyor belt and moved to an area for later sorting and routing. Once the correct destination is determined, your package and other packages are probably placed in a truck, driven to a larger holding station, and merged with other packages of similar destinations. Later, your package is driven to the airport where it is loaded onto a plane and flown to another distribution point. Once the plane lands at its destination, your package is either loaded onto a truck and shipped to another distribution point or it is loaded onto another plane which takes it closer to its destination.

Before actually reaching its final destination, your package might well be routed and rerouted numerous times. Depending on the type of mailing or whether there are any unexpected delays, your package might be held overnight at one or more locations.

Most of us can relate to the above scenario yet we are confused about data communications networks. Why? Conceptually, data communications networks work similarly. For example, let's look at an electronic mail message. Before you send an electronic mail message, you must know and supply an address of who is to receive the message (or its destination). Albeit a strange address, this is similar to the label you fill out to send a package or letter. The message is then sent out and is routed electronically from one computer system to another until it reaches its destination. In some cases, the message is held at a computer system somewhere in the electronic route until it can be delivered.

The analogy with the way paper mail is routed and delivered is helpful for understanding how networks function. Technical concepts are often much easier to digest if you can describe them in terms of something that makes sense to you personally. Feel free to associate your own examples if they make more sense to you.

This brochure is designed as a quick reference to the Eller network. In it, use of the characters: <RET> indicates that you should press the ENTER or RETURN key on your computer keyboard. Bold face items in examples are words or commands you would normally type.

A View of the Network
The McClelland Hall Network
Electronic Network Routing
The University Network
The Rest of the World