Active Network Vision and Reality: Lessons from a capsule based system

This paper written by David Wetherall is a reflection after their creation of ANTS active network toolkit. The idea of Active Networking was first described in a paper in 1996, also by the same author. Active networking allows for customized programs to be executed within the network. This allows for easy creation of new Internet services, including custom forwarding and routing tables at each node. But active networking has also been controversy because of performance and security concerns. However, the author in this paper tries to reflect upon the experience of implementing an active network.

He first explains the essentials of active network, and how it works. Basically there are active nodes in the network which acts as a programmable router. Users are provided an interface to program "capsules" which are passed around the network. As the capsules travel through active nodes, different services can occur, which the users can specify. Several advantages of this approach includes it's ability for gradual deployment, since not all nodes need to be active nodes. We are able to gradually deploy this service, and only the nodes that belong to the active node set will process the capsules. The implementation of active networks also contains some inherent properties. The author lists 4, which are expressible, compact, fast, incrementally deployable. Expressible is the fact that the service a user wishes to create must be expressed by the API and interface which is provided to the user. It must be compact because there is a limit of 16KB of code so the network isn't flooded with service code. It must be fast because the routine must run to completion at each node. And lastly, it must be incrementally deployable, meaning that the service must not fail if there are nodes that aren't active. Currently, it still seems that performance and the factors above will limit the usefulness of active networking. but with more research and time, it is a good platform to experiment with new services from the network.