Title:
Active Services for Programmable Media Gateways:
Taming Active Networks
Steven McCanne, U.C. Berkeley
Joint work with Elan Amir, U.C. Berkeley

Abstract:

Several recent proposals for an ``active networks'' architecture advocate the placement of user-defined computation within the network as a key mechanism to enable a wide range of new applications and protocols, including reliable multicast transports, mechanisms to foil denial of service attacks, intra-network real-time signal transcoding, and so forth. This laudable goal, however, creates a number of very difficult research problems, and although a number of pioneering research efforts in active networks have solved some of the preliminary small-scale problems, a large number of wide open problems remain. In this talk, I will an alternative approach to active networks that addresses a restricted and more tractable subset of the active-networks design space. Our approach, which we (and others) call ``active services'', advocates the placement of user-defined computation within the network as with active networks, but unlike active networks preserves all of the routing and forwarding semantics of current Internet architecture by restricting the computation environment to the application layer. Because active services do not require changes to the Internet architecture, they can be deployed incrementally in today's Internet.

I will develop and motivate our active services architecture by describing its evolution from Amir's work on media gateways to its present form as a novel substrate for injecting user programmable functionality like media transcoding into the network. To motivate this work, I will first outline the ITU model for multiparty communication (i.e., H.323) and point out some of its constraints and limitations. I will then show how these limitations can be overcome with active services and present the core building blocks and abstractions of our active service framework. I will also describe the impressive active service prototype called "AS1" that Amir has built on the Berkeley campus utilizing the Network of Workstations (NOW) compute cluster, and report on its use to mitigate bandwidth disparity among a number of real users attending a remote seminar from last Fall (see http://bmrc.berkeley.edu/courseware/cscw/fall97/index.html). Finally, I will describe ongoing work in our research group that is generalizing the active service framework for multimedia archive and reliable-multicast proxy networks.