The SwitchWare Active Network Implementation

This is an overview of work on the SwitchWare active network project, which began two years ago based on ideas about how to improve the exibility of networks by making the network programmable. The original ideas for active networks as a whole and some comparative analysis of possible architectures are surveyed in [33]. A variety of technology trends in computing power, communication speeds, programming languages, and security have made it worthwhile to investigate network programming interfaces that allow code to be downloaded into routers within the network and invoked by the packets passing through them. At the current time there are at least a dozen AN prototype architectures under development [34, 8, 22, 2, 19, 35], a few of which have released software. Our SwitchWare perspective was rst described in [16] and has been considerably re ned as we gained deeper insight into active networking. It was the rst active network prototype to be publically released, and is implemented largely in the Caml [12] dialect of the ML programming language, using the OCaml implementation. We were instigated to use Caml because of its success in several other distributed computing and networking projects such as Ensemble [15] and MMM [26]. We found ourselves able to achieve