Cooperative Rule Caching for SDN Switches

Abstract

Despite the tremendous success of SDNs in datacen-ters, their wide adoption still poses a key challenge: the packet-forwarding rules in switches require fast and power-hungry memories. Rule tables, which serve as caches, are of limited size in cheap and energy-constrained devices, motivating novel solutions to achieve high hit rates. In this paper, we leverage device connectivity in the fast data plane, where delays are in the order of few milliseconds, and propose multiple switches to work together to avoid accessing the control plane, where delays are orders of magnitude greater. As a low priority rule in a cache entails caching higher priority rules, we pose the problem of cooperative caching with dependencies. We provide models and algorithms for cooperative rule caching with dependencies, accounting for dependencies among rules implied by existing switch memory types. We develop caching algorithms for several typical use cases and study the difficulty to find an optimal cooperative rule placement as a function of the matching pattern, which lay the foundations of cooperative caching with dependencies.