An active network allows applications to inject customized programs into network nodes. This enables faster protocol innovation by making it easier to deploy new network protocols, even over the wide area. We argue that the ability to introduce active protocols offers important opportunities for end-to-end performance improvements of distributed applications. We begin by describing several active protocols that provide novel network services and discussing the potential impact of these kinds of services on end-to-end application performance. We then present and analyze the performance of an active networking protocol that uses caching within the network backbone to reduce load on both servers and backbone routers.