5 – Network Models and Internetworking Concepts

This chapter takes an updated look at the OSI and IP internet models, as well as concentrates on how encapsulation makes internetworking possible, and the different kinds of systems that move data across network boundaries. This chapter introduces the fundamental of OSI (Open System Interconnection) and DoD/Internet (US Department of Defense) internetworking models. This chapter explains perhaps the single most important concept for internetworking; Encapsulation – it is the process by which a message can be wrapped up for delivery by entities other than those doing the communicating. Also revisited in this chapter are some of the fundamental network components, looking at them again as they behave within structure provided by the internetworking models: bridges - device used to physically connect two (or more) networks of the same type, switches - a multiport bridge, and routers - any device that can behave as a gateway between two or more different layer 2 protocols, or between two or more physical networks using the same layer 2 protocol.