Active network implementations

Active networks have been described as networks that allow routing elements to be extensively programmed by the packets passing through them. This allows computation previously possible only at endpoints to be carried out within the network itself, thus enabling optimizations and extensions of current protocols as well as the development of fundamentally new protocols (see "The Switchware Homepage", http://www.cis.upenn.edu/∼switchware/). Briefly, the main aim of active networks is to implement new communication architectures that allow for deployment of advanced networking services. We describe the architectural framework for active networks and we review and compare the design of several experimental implementations of active networks that exist today, outlining the different approaches used in each of the designs. The differences between two approaches to active networks i.e., a discrete approach and an integrated approach are illustrated. Finally, we provide examples of efforts to improve performance of applications using active networking.