Tactical Wireless Communications and Networks: Design Concepts and Challenges

1.1 The OSI Model

Every computer networking book, in one way or another, emphasizes the OSI model. The OSI model has its roots in the IBM definitions of networking computers from the early days. Defining such interfaces, while the science of computer networking was a new field, was an effective approach to accelerate the development of networking protocols. With the OSI model, there are different protocol stack layers, with each stack layer performing some predefined functions. These protocol stack layers are separated and utilize standard upward and downward interfaces. These layers work as separate entities and are peered with their corresponding layers in a remote node. Figure 1.1 demonstrates a conventional OSI with seven layers: the application layer, the session layer, the transport layer, the network layer, the DLL, the MAC layer, and the physical layer. These layers communicate to their peer layers (A and B are peer nodes) as shown by the horizontal arrows. Traffic flows up and down the stack, based on well-defined interfaces as indicated by the vertical arrows. Note that some text books may have different variations of these layers. For example, some textbooks may present a presentation layer under the application layer and before the session layer to perform data compression or encryption. Other models (especially for point-to-point links) omit the MAC layer, but we are especially interested in the MAC layer in this book since it is an important part of multiple-access ...