Active network vision and reality: lessons from a capsule-based system

Summary

This paper describes active networks and some of the problems they face. The idea of active networks is to allow user-extensible network functionality. In other words users can run custom programs in the network. This has two potential benefits:

1. Enables a range of new applications
2. Allows services to be location independent

The main problems are performance and security. The authors describe the ANTS system which addresses these concerns.

ANTS allows users to send executable capsules to active nodes in the network. These capsules contain Java code of a limited size which is executed on a special JVM. This JVM contains security restrictions to prevent the code from damaging the underlying system.

The authors also evaluate the performance of ANTS capsules. They find them to be about twice as slow as a C implementation.

Finally, the authors argue that the main benefit of active networks is not a "killer app" but rather the flexibility to add functionality over time.

Thoughts

It is not entirely clear when active networks are better than a separate service running on a networked server. While the idea of decoupling services from a specific location sounds tantalizing, it would be very hard to implement in practice. In a way services such as Amazon EC2 have taken over many of the use cases Active Networks target. For example, services such as video trans-coding can be run on rented, networked, hardware in the EC2 cloud.