Active networking offers a change in the usual network paradigm: from passive carrier of bits to a more general computation engine. The implementation of such a change is likely to enable radical new applications that cannot be foreseen today. Large-scale deployment, however, involves significant challenges in interoperability and security. Less clear, perhaps, are the "immediate" benefits of such a paradigm shift, and how they might be used to justify migration towards active networking. In this paper, we focus on the benefits of active networking with respect to a problem that is unlikely to disappear in the near future: network congestion. In particular, we consider application-specific processing of user data within the network at congested nodes. Given an architecture in which applications can specify intra-network processing, the bandwidth allocated to each application's packets can be reduced in a manner that is tailored to the application, rather than being applied generically....