Estimating the Flow Rule Installation Time of SDN Switches When Facing Control Plane Delay

Abstract

The software defined networking (SDN) paradigm has numerous benefits for network operators, including cost aspects, flexibility, and programmability. Using the SDN approach of a separated control and data plane, the controller can order the installation of flow rules in the switches it manages, e.g., via FlowMod messages in case of the OpenFlow protocol. Since the processing time of these messages has a direct impact on the reaction time of the network, it is a key performance indicator for switches and quantifying it in a reliable manner is required for ensuring state consistency between the control and the data plane. Furthermore, real world deployments not only consist of different data plane hardware, but may feature varying control plane delays. Hence, in this work, we investigate the impact of such a delay on the FlowMod processing time of OpenFlow switches. Firstly, we identify a significant heterogeneity between data plane hardware in terms of processing times as well as the underlying TCP-level behavior. Secondly, we show that despite this heterogeneity, combining switch specific information with delay measurements at the controller can be used to reliably infer FlowMod processing times. We confirm our results with measurements in a dedicated testbed that is comprised of three different hardware switches, three different SDN controllers, and several high precision measurement devices.