Introduction to the OSI Model

   Introduction

The first networking protocols were developed by computer manufacturers. Each manufacturer developed its own protocols for its own platforms. Some manufacturers even had multiple protocols, because protocols were developed independently for different computer platforms. IBM, for example, had more than a dozen protocols back in the 1960s.

However, computers and programs must use a common protocol to communicate. If many different protocols for data communication exist, it is difficult to link computers into common networks.

Thus, to correct the chaos of multiple protocols, computer vendors developed communication standards, both official and de facto. One of the most important of these is the OSI model.

The OSI model is not a protocol, but a reference model, or an abstract structure that describes the functions and interactions of various data communication protocols. It provides a conceptual structure that helps us discuss and compare network functions, just as other classification systems help biologists or chemists talk about their fields.

As a networking professional, there are two good reasons you must have a solid understanding of the OSI model:

The OSI model is widely used in networking literature. Data communication texts structure their presentations by the OSI model.

Many software and hardware vendors use the OSI model as a guide for the development and documentation of products. When you understand the OSI model, you can quickly learn many different types of networking protocols, products, and services.

   Objectives

At the end of this lesson you should be able to:

1.

Explain why the OSI model was created

2.

Name the layers of the OSI reference model

3.

Describe what an open standard is and why it benefits both vendors and customers

Key Point
The layers of the OSI model provide a framework for understanding networking.