Cognitive Networks: Towards Self-Aware Networks

6.8. Discussion

We have been looking at the ongoing work in the area of cross-layer design for wireless communications and networks throughout this chapter. Implicit in this entire discussion, as it is in most of the published research, is the existence and acceptance of a reference layered architecture. A good number of communication systems broadly follow the five-layer model, which is a hybrid between the two most commonly taught models: the OSI seven-layer model and the four-layer TCP/IP model. The question is, how did these models come about in the first place?

The four-layer TCP/IP model came into being as part of an initiative undertaken by the United States (US) Department of Defense to connect different kinds of packet-switched data networks. The idea was to enable a communication device connected to a packet-switched network to communicate with any other communication device connected to any other packet-switched network. Reference ^[] discusses the key considerations that motivated the development of some specific features of the TCP/IP protocols (for example a connectionless mode of communications with end-to-end flow and error control provided by the transport layer). In effect, the motivations elaborated in ^[] highlight the design principles of the Internet since, in time, the TCP/IP model became the model that shaped the Internet.

On the other hand, the OSI seven-layer model came into being as a result of an initiative taken up by the International Standards Organization ...