17 An Architecture for Active Networking Samrat Bhattacharjee, Kenneth L. Calvert, Ellen W. Zegura Networking and Telecommunications Group College of Computing, Georgia Institute of Technology, Atlanta, GA 30332. email: {bobby, cal vert, ewz }@cc.gatech. edu Abstract Active networking offers a change in the usual network paradigm: from passive carrier of bits to a more general computation engine. The implementation of such a change is likely to enable radical new applications that cannot be foreseen today. Large-scale deployment, however, involves significant challenges in interoperability, security, and scalability. In this paper we define an active networking architecture in which users control the invocation of pre-defined, network-based functions through control information in packet headers. After defining our active networking architecture, we consider a problem (namely, net- work congestion) that may benefit in the near-term from active networking, and thus may help justify migration to this new paradigm. Given an architecture allowing applications to exercise some control over network processing, the bandwidth allocated to each applica- tion's packets can be reduced in a manner that is tailored to the application, rather than being applied generically. Our results show that the ability to gracefully adapt to congestion makes a good case for active networking. Keywords active networks, congestion control, MPEG, early packet discard 1 INTRODUCTION As the cost of computing power decreases, it is worthwhile to consider the benefits of adding computing to various types of systems, either to enhance services or to trade off against other costs such as time, bandwidth and stor- age. Active Networking (AN) refers to the addition of user-controllable com- puting capabilities to data networks*. With active networking, the network is no longer viewed as a passive mover of bits, but rather as a more general computation engine: information injected into the network may be modified, stored, or redirected as it is being transported. Obviously, such a capability opens up many exciting possibilities. However, active networking also raises a number of issues, including security, interoperability and migration strategy . All of these are influenced in large part by the active networking architecture, 'In this paper we focus on packet- and cell-switched networks. We follow Tennenhouse and Wetherall [7] in adopting the term active networking; the differences between our approach and theirs are elucidated later. A. Tantawy (ed.), High Performance Networking VII © Springer Science+Business Media Dordrecht 1997