A Computation Framework for an Extensible Network Router : Design, Implementation and Evaluation

Dynamic addition of computation in the interior of the network holds significant promise for improving overall end-to-end application performance, either by exposing and exploiting global network context, or by placing functionality strategically within the network. This observation has motivated the study of extensible router architectures, especially for routers at the network edge. In this paper we present and study a simple, but powerful framework for composing and performing computation in an extensible network router. The key design goal of the framework is to provide a router extension mechanism that does not compromise safety and performance of the system in the face of dynamic extensibility, while allowing performance isolation between flows that have computation interposed in their datapath. The framework achieves these goals through a combination of intra-address space protection, explicit flow context and CPU scheduling. We first identify and isolate a minimal set of functions that form the router’s core. A set of abstractions is then presented, in terms of which computation is composed and resources allocated. A set of services exposed by the core is then presented, that forms the mechanism for composing and carrying out this computation. Asynchronous control flow and explicit flow context allow the core to run a dataflow-driven CPU scheduler that controls the progress of computation in the system in accordance with the performance requirements of flows, and avoids redundant scheduling decisions. We present an implementation and performance evaluation of the proposed framework to put the design decisions in context.