During the past two decades there has been a tremendous increase in the numbers and sizes of networks. Many of the networks, however, were built using different implementations of hardware and software. As a result, many of the networks were incompatible and it became difficult for networks using different specifications to communicate with each other. To address this problem, the International Organization for Standardization (ISO) researched many network schemes. The ISO recognized that there was a need to create a network model that would help network builders implement networks that could communicate and work together (interoperability) and therefore, released the OSI reference model in 1984. This chapter explains how standards ensure greater compatibility and interoperability between various types of network technologies. In this chapter, you will learn how the OSI reference model networking scheme supports networking standards. In addition, you will see how information or data makes its way from application programs (such as spreadsheets) through a network medium (such as wires) to other application programs located on other computers on a network. As you work through this chapter, you will learn about the basic functions that occur at each layer of the OSI model, which will serve as a foundation as you begin to design, build and troubleshoot networks. 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. Wh...
