What you need to know about SDN control and data planes
Maciej Kuźniar, Peter Perešíni, Dejan Kostić · Infoscience (Ecole Polytechnique Fédérale de Lausanne) · 2014
SDN and OpenFlow are actively being standardized and deployed.These deployments rely on switches that come from various vendors and differ in terms of their performance and available features.Understanding these differences and basic performance characteristics is essential for ensuring efficient deployments.In this paper we measure, report, and explain the performance characteristics of the control-and data-planes in three hardware OpenFlow switches.Our results can help controller developers to make their programs efficient.Further, we also highlight differences between the OpenFlow specification and its implementations, that if ignored, pose a serious threat to network security and correctness.Section Key finding 4.1 Few outstanding requests are enough to saturate the switch.4.2Rule updates get slower as the flow table occupation gets higher.4.3Using rule priorities may degrade update performance by an order of magnitude.4.4Rule update patterns matter and switches can take advantage of an update locality.4.5Barriers are costly at some switches.4.6Rule modifications are slower than additions/deletions.5.1 Barriers should not be trusted!Updates are often applied in hardware hundreds of milliseconds after a barrier that confirms them.One of the tested switches reorders updates despite the barriers.5.2Rule updates get reordered even if there is a barrier between them and they affect the same flows.Some switches ignore priorities.5.3Rule modification operation is non-atomic and switch may even flood packets for a transient period of time!