A Crash Course in Networks

We deal with networks every day, but do we really know what they are?

by / February 28, 1998
The network is down until further notice! Welcome to the wonderful world of networks and networking!

Whether sweating the driver's test at the Department of Motor Vehicles, calling the state Department of Revenue to confirm that the check is really in the mail or buying groceries, most citizens encounter at least one computer network almost every day. Moreover, many people now spend much of their business and professional life working directly with computer networks. The phenomenal growth of networks over the last decade has woven them into the fabric of our life and society -- a trend that will continue as we move into the 21st century.

This growth trend goes well beyond universal acceptance of networking technology. Citizens now expect the efficiency and convenience of networks while loathing the network delays and downtime that inevitably occur. Those expectations will soon skyrocket as high bandwidth moves into the home.

For many cash-strapped localities, networking technology is a vital link in the effort to leverage thinning resources while delivering on promises of better service.

So, what is a network? Where did networks originate and where are they going? Before these questions are answered, we must first define some basic terms, including the definition of "networking," and outline some of the topics that fall under this general heading.


Although there are many fine, modern definitions, the origins of the word "network" predate the electronic era by quite some time and provide some interesting insight. (Interestingly, the first published use of the word noted by the Oxford English Dictionary was in 1560.) For example, the 1913 edition of Websters Dictionary, courtesy of , contains the following:

"2. Any system of lines or channels interlacing or crossing like the fabric of a net; as, a network of veins; a network of railroads."

The roots of the word itself are even older. The derivation of "net" traces to the Latin word "nodus" meaning "knot" and "nectere" meaning "to bind."

The Free On-line Dictionary of Computing defines networking as: "Hardware and software data communication systems."

And finally, ZDNET's Webopedia definition is: "A group of two or more computer systems linked together."

These definitions cover a lot of ground. Some are simple, while others don't even relate to electronics, yet they all seem to describe a core concept: Two or more points or nodes (a point could be a railroad station or a computer) connected in some fashion (railroad tracks or telephone lines) involving interchange (goods and people across a railroad line or data bits on a computer network) forming a system (railroad track switching and routing of trains or the routing of packets over computer networks) for the purpose of speeding up the exchange of things (people and commodities on a railroad network or business information on a computer network).

So, networks exist to facilitate the exchange of communication and the delivery of goods or services, and they evolved from a need to speed up and enhance this exchange.


Useful and technologically successful networks change society. Consider, for example, the impact on civilization of the Roman army's system of roads (parts of which are still in use today); the way the railroad network of the 1800s helped open the West; or how different America looks since the introduction of telephone and television networks during the 20th century.

Although many successful networks have transformed their societies, one of the most remarkable characteristics of computer networks is the speed with which they have effected radical change -- even when compared to the railroad or telephone networks that transformed society in record time. What's more, all indications point to the conclusion
that we've only glimpsed the broader changes to come -- the Internet (a "network of networks") promises to open doors to new types of media and new ways of communicating in the not too distant future.

Into this swirl of change, we define a "computer network" as: A system of interconnected electronic hardware and software technologies intended to improve the quality, speed, value, efficiency or volume of communication. This definition may require amendment over time, but chances are good that the core reasons for building and using networks will not change.


Even though managers and network professionals are bombarded with new acronyms and technologies on a daily basis, the fundamentals of networking have not changed all that much. It is, therefore, helpful to keep those fundamentals in mind when evaluating new technology. In the early days of computer networking, the International Standards Organization (ISO) developed and released a model of network communication intended to provide the basis for interoperable networked systems. Alas, the model, known as the Open System Interconnection (OSI) reference model, was never implemented on any large scale, although it is still widely used for comparison purposes and teaching networking. Most discussions about networks assume at least a passing familiarity with it.

OSI divides the entire process of successful network communication into smaller, more manageable pieces or "layers." These layers are really just different aspects or parts of what it takes to successfully communicate over a network.

For example, for a ground-based network of fast personal and commercial transportation to work well, certain things must be in place. First, vehicles must exist and be available. Next, highways must be built. The vehicles and highways must conform to some standard; it does no good to have 10-foot-wide vehicles trying to get somewhere on 6-foot-wide highways. The highways should conform to some standard of construction that defines things as smoothness, allowable sharpness of turns, durability, etc. This part of building the network might be called the layer or "physical level."

Another layer of this network might describe the acceptable behavior of vehicles traveling between two points on the network; this would include standards for the correct speed and the proper signaling used to inform other drivers when changing lanes or slowing down. It might include rules governing what will happen to vehicles -- or their drivers -- that don't follow the rules.

A larger view of the network, what might be called the "network layer," would be another piece. It would define standards to help people get from their starting point to their intended destination; this would include naming conventions -- how do we name the roads and their exits so drivers will understand where they are and where they need to go? It would also include maps so drivers could see an overview of the network and could work out the best way to get where they are going. On modern highways, it might consist of roadside signs to let drivers know of upcoming road congestion, so they can route around the problem.

Each use of this network would involve all of its layers. For example, a common use might be something like this: Decide to make a trip, plan the route, get in the car, get onto the highway, take the correct exit, take local roads to the intended destination and, finally, arrive at grandma's for Thanksgiving dinner.

ISO's model divides network communication into seven layers. The top level is the program that uses network
services; this includes things such as e-mail programs or Web browsers, which need to send or receive information over the network. Under the OSI model, a message originates in an application, moves down through each layer of the model and is finally sent over the wire at the physical
layer. At the receiving end, the communication is picked up from the wire (or cable, fiber, etc.) and moves up through the seven layers to arrive at the receiving application.

This model can be used to give structure to the subject of network communication and a framework for understanding different network solutions, but the actual implementations vary widely in their characteristics, advantages and disadvantages. For example, many network solutions combine entire OSI layers into a single layer. Whatever the exact implementation, all face similar issues. Some of the most common are:

* Connectivity -- The ability of two or more machines to connect to each other and exchange data. It entails a wide range of hardware and software issues that span the levels of the network model. For software, connectivity is determined by "protocols" that are "rules governing transmitting and receiving of data" (Computer Desktop Encyclopedia). Each layer of a network implementation has a corresponding protocol that defines how that level carries on its business. Generally, it is important to ensure all machines on a network share compatible protocols, but when they don't, interpreters can be used to translate from one protocol to another; this just complicates network setup and maintenance.

* Bandwidth -- The measure of a network's carrying capacity and speed or how much data it can transfer and how fast. This is a particularly important issue for the Internet, because new and emerging Internet applications require more bandwidth than is universally available.

* Security -- A problem that spans all layers of network implementations. This is a critical problem for state and local agencies that must keep personal information about citizens private while simultaneously making public information broadly available.

* Software or Applications -- With the exception of the lowest physical layer of a network, software is an issue throughout all network implementations. Perhaps most pertinent to IT managers, however, are the software applications needed by end users. A dizzying array of network applications exist today, and more are on the way.


More and more, the importance and usefulness of personal computers is being measured by the networks they're connected to or the network applications they are running. It isn't that word processors and spreadsheets are losing importance or value; they aren't. But their role is changing -- from being personal productivity applications used by an individual -- into tools used by and for a section, department or agency. For IT managers, this means that networking must assume a key role in any long-term strategic decisions about software, hardware or services.

David Aden and John Stanard are senior consultants for Webworld Studios -- a Northern Virginia-based Web application development consulting company. They can be reached at and , respectively.

More information is available at .

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David Aden
David Aden DAden@webworldtech.com is a writer from Washington, D.C.