ABSTRACT
This chapter looks at the Open Systems Interconnection reference model, which is commonly used to describe the functions involved in data communication networks. It examines different local area networks, metropolitan area networks and wide area networks (WAN) including the Internet. There are at least two reasons for needing standard protocol architecture such as the open systems interconnection reference model. First, the uphill task of understanding, designing and constructing a computer network is made more manageable by dividing it into structured smaller subtasks. Second, the proliferation of computer systems has created heterogeneous networks: different vendors, different models from the same vendor, different data formats, different network management protocols, different operating systems. For a WAN communication is achieved by transmitting data from the source node to the destination node through a network of intermediate switching nodes. The Internet is a global network of computer networks that exchange information via telephone, cable television, wireless networks and satellite communication Technologies.
