Reactive logic in software-defined networking: Measuring flow-table requirements

The capability of a network is ultimately bounded by limitations of the devices that compose it. In this paper we argue that Software-Defined Networking (SDN) can increase the importance of certain limitations, such as the size and the flexibility of switches forwarding tables. In particular we focus on the implications of reactive installation of flow entries in the switch fabric: by analyzing traffic traces captured in different scenarios we show the existence of a trade-off between the size of the flow table and the rate of dynamic installation of a missing or expired rule. We leverage on this finding to further show that reactive flow (re-)configuration is a promising mechanism for improving the traffic engineering flexibility with no additional requirement in terms of flow table size. We examine links located in various parts of the network and we consider different flow definitions to evaluate the feasibility of using SDN controllers in both access and core network scenarios.