The Open Systems Interconnection (OSI) reference model is essential to the world of computer networking. The model was created in 1977 by the International Standards Committee, in response to a difficulty that was facing computer networkers at the time (Shelly, Cashman, and Serwatka 142). In order to understand the difficulty, one must first realize that computer networks consist of computer hardware, the software that is to be used in conjunction with this hardware, and the medium (such as wiring or cabling) that will interconnect the computing devices that are in the network. The computer networkers job is to determine which hardware, software, and medium types will create the network that will best suit his clients needs. Then, the networker must combine these elements into a functional system of interconnected computers (Fortino and Villeneuve 112). It was in attempting this latter task that the computer networker of the late 1970s often found himself in a pickle. The problem was that each vendor of computing equipment had developed his own unique set of products; products that were incompatible with the products of other vendors. This incompatibility made it very difficult for a computer networker to combine the various network components into an operational computer network (Stamper 27). The OSI model provided for a solution to this problem. The model organized those tasks that are essential for computer network operation, into seven groups. These groups were called layers. All manufacturers of computing equipment were recommended to make their products compliant with the OSI model. This meant that each computing product was to perform the functions associated with a specific layer within the model; any method of accomplishing these functions was acceptable. In a network composed of equipment that operated according to OSI guidelines, a separate product would be used to perform each layer of OSI functionality. Thus, all elements...
