Network SecurityComputer Network Security Center

The concept of layers will help you understand the action that occurs during communication from one computer to another. Shown in the Figure are questions that involve the movement of physical objects such as highway traffic, or electronic data. This motion of objects, whether it is physical or logical, is referred to as flow. There are many layers that help describe the details of the flow process. Other examples of systems that flow, are the public water system, the highway system, the postal system, and the telephone system.

Now examine the Figure “Comparing Networks” chart. What network are you examining? What is flowing? What are the different forms of the object that is flowing? What are the rules for flow? Where does the flow occur? The networks listed in this chart give you more analogies to help you understand computer networks.

Another example of how you might use the concept of layers to analyze an everyday subject is to examine human conversation. When you create an idea that you wish to communicate to another person, the first thing you do is choose how you want to express that idea, then you decide how to properly communicate it, and finally, you actually deliver the idea.

Imagine a young boy seated at one end of a very long dinner table. On the other end of the table, quite a distance away, sits the young boy’s grandmother. The youngster speaks English. The grandmother prefers to speak Spanish. The table has been set with a wonderful meal that the grandmother has prepared. Suddenly the young boy shouts at the top of his lungs, “Hey, you! Give me the rice!” and reaches across the table to grab it. In most places, this action is considered quite rude. What should the young boy have done to communicate his wishes in an acceptable manner?

To help you find the solution to this question, analyze the communication process by using layers. First there is the idea – the young boy wants rice; then there is the representation of the idea– spoken English (instead of Spanish); next is the method of delivery – “Hey, you”; and finally, the medium – shouting (sound) and grabbing (physical action) across the table for the rice.

From this group of four layers, you can see that three of them prevent the young boy from communicating his idea in an appropriate/acceptable manner. The first layer (the idea) is acceptable. The second layer (representation), using spoken English instead of Spanish, and the third layer (delivery), demanding instead of a politely requesting, most definitely do not follow acceptable social protocol. The fourth layer (medium), shouting and grabbing from the table rather than politely requesting assistance from another person seated nearby, is unacceptable behavior in most any social situation.

By analyzing this interaction in terms of layers you can understand more clearly some of the problems of communication in both humans or computers, and how you might solve them.

Analysing Network in Layers

Comparing Networks