Regulating traffic on heterogeneous communication networks

Summary form only given. Today\´s communication networks, such as the Internet, can be seen as superfast expressways, transporting packets from sources to destinations along most efficient routes, while respecting priorities and quality-of-service specifications. They are heterogeneous, in terms of both the traffic they can accommodate and the services they offer. The quest for regulating traffic in such a medium, with utmost efficiency, has been and still is the driving force behind the technological advances in this area. Some of this regulation is done by the network itself (specifically, the service providers), through fast switch and router designs, protocol designs, capacity expansions, and admission policies, and some of it is done by the individual users under incentives or disincentives provided by the network (such as price structures), aimed at achieving a certain pattern of usage of the available resources (such as bandwidth). The users are faced with a multitude of issues, among which are (i) at what (flow) rate to inject packets into the network, and (ii) how to adjust these rates in response to (delayed) congestion information received from the network. Occasionally, users are also faced with the task of making decisions on routing, again based on information received from the network. The overall system is a very complex one, involving a very large number of "players" with little if any cooperation, and operating under minimum information. Several branches of engineering (particularly, control, communications, and computing) as well as economics (particularly, game theory) provide tools (conceptual and technological) necessary for architecting such networks and ensuring that the operate harmoniously in spite of their heterogeneity. Control theory plays a particularly important and relevant role here, as design of robust distributed feedback loops under decentralized information is an indispensable component of an effective architecture. This plenary - - talk describes the underlying issues in such a design, discusses what the current technology provides, and challenges for future research.