This paper describes a framework for Active Networks called ANTS. ANTS allows users to implement network functionality across an unrestricted set of nodes. Applications send special packets called capsules, in essence an extended IP packet which contains the actual service code to run on it, which are passed around via active node extensible routers.
ANTS decouples capsules from service code, caching service code for particular streams of packets and requesting code from a capsule's previously-visited active node if the current node doesn't have the service code cached. Capsules are kept from misbehaving by being greedy with resources or interfering with other payloads in the network by the ANTS sandbox in which their code is run.
The authors show graphs of ANTS latency and throughput versus capsule payload size and compare these results to impelementations of forwarding in Java and C. I had always heard people complain about how slow Java is compared to compiled languages like C, but I had never seen any results to verify that sentiment; these graphs were enough for me, as the C implementation can get about 4x the throughput of ANTS/Java. Hence, if the authors are more interested in ease of portability, they can stick with their Java implementation of ANTS, but if they want better performance, Java is not the answer.
Active Networks definitely seem to be in violation of the E2E principle: trying to implement functionality at the link layer for not much gain. Apparently Active Networks have applications such as multicast that they would be useful for distributing over the wide-area, but short of these few applications, it's difficult to see the real need for them.
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