Performance Analysis of SDN Switches with Hardware and Software Flow Tables

Nowadays data centers are increasingly becoming larger and dynamic due to virtualization. Software-Defined Networking is the leading approach to network virtualization and flexible management. The wide variety of hardware implementations have brought strong heterogeneity to the market of networking devices which are different in terms of OpenFlow features and performance. In this paper we address the issue of heterogeneity of four hardware OpenFlow switches by characterizing selected performance relevant parameters for the hardware and software flow tables. We characterize maximum size of hardware flow tables for each switch including the behavior of a rule promotion engine that moves the rules between tables. We show that in the worst case forwarding packets using software table decreases the throughput by two orders of magnitude (from 940 to 14 Mbit/s). Our results can help the developers of SDN applications to account performance limitations of hardware and software processing as well as limited hardware support for a specific rule types.