The telephone industry has gone through a transition from analog to digital transmission, and more recently introduced wireless cellular technology. The infrastructure for the cable industry was devised, and video broadcast is now starting a transition to digital formats. Various forms of technology convergence have emerged, such as Asynchronous Transfer Mode. There is still a motivation and need to explore and develop new network technologies. Current areas of exploration include wireless networking, wavelength division multiplexing of fiber optics, new technology for network access to the home, and data and telephony over satellite.
Protocols represent the codification of required behavior.
A well specified protocol will allow two independently conceived implementations to interoperate successfully, and the understanding of how to design protocols so that this can be achieved is a major intellectual achievement. Early protocol specifications were not perfect in this respect, and much has been learned about how to design and document protocols successfully. While the design of protocols is an interesting exercise in its own right, and sometimes requires the solution of very difficult problems, the most important consequence of a successful protocol is the functions that it enables at a higher level. Since protocols are enablers, the other aspect of protocol design is the identification of what particular functional semantics should be supported in order to meet some important higher level goal. Protocol designers are thus in the same situation as operating system designers of a decade or so ago, who looked at what application builders were doing, and proposed the services that an operating system ought to provide to ease the job of constructing applications.