Active networks were proposed in 1997 by Tennenhouse et al. The idea is that in a network, packets could be considered as programs requesting some way to be treated. This could reduce network traffic, since a Web page that was very popular could be served in one packet requesting multicast, instead of one packet per request. This research is being carried out in the SwitchWare project at the University of Pennsylvania. PLAN is a scripting language for composing active-network services.
PLAN is declarative and functional but has no looping mechanism.
The routers are protected from malicious code by typechecking, and the network is protected by resource limits on the code. Considerable security problems need to addressed in implementing active networks. Already there exist security problems in just researching active-network technology. SRI runs an active network testbed with machines hosted at different sites across the country. Each site wants to determine its own security policy, but they must all agree on a security protocol.