Active networking is a communication paradigm that allows packets flowing through a communication network to dynamically modify the operation of the network. The active network architecture is comprised of execution environments (similar to a unix shell that can execute active packets), a node operating system capable of supporting one or more execution environments, and active hardware, capable of routing or switching as well as executing code within active packets. This differs from the traditional network architecture which seeks robustness and stability by attempting to remove complexity and the ability to change its fundamental operation from underlying network components.

References:

Towards an Active Network Architecture (1996), David L. Tennenhouse, et al., Computer Communication Review

Active Networks and Active Network Management: A Proactive Management Framework by Stephen F. Bush and Amit Kulkarni, Kluwer Academic/Plenum Publishers, New York, Boston, Dordrecht, London, Moscow, 2001, 196 pp. Hardbound, ISBN 0-306-46560-4.