This book constitutes the refereed proceedings of the IFIP-TC6 4th International Working Conference on Active Networks, IWAN 2002, held in Zurich, Switzerland, in December 2002.The 20 revised full papers presented were carefully reviewed and selected from 53 submissions. Among the topics addressed are router architectures, reconfigurable systems, NodeOS, service deployment, active network services, active network queries, network management agents, active network performance, mobile communications, programmable networks, network execution environments, active network architecture, group communication, peer-to-peer networks, and interaction detection.

If the Internet is seen as a single, vast, programmable machine, what is the proper programming paradigm to facilitate development of the new applications it must offer? This state-of-the-art survey deals with this question. The situation we face is similar to that in the 1960s, when a new hardware/software architecture was introduced and it took some time for the programming-language and operating-system specialists to come up with the proper programming paradigms. Now we have the new and exciting paradigm of mobile computing, where computations are not bound to single locations but may move around at will to best use the available computer network resources. This paradigm will have a profound impact on the way distributed applications, in particular Internet applications, are designed and implemented.