Scheduling and fast response of SDN flow table updates

In software-defined networking (SDN), the overlapping among the matching fields of rules complicates flow table updates. One update often triggers the movement of multiple ternary content addressable memory (TCAM) entries, which increases the update times. In addition, the TCAMs in existing SDN switches are mostly designed with a single port. The TCAM update suspends the packet lookup which affects the packet forwarding in the data plane. Therefore, how to achieve fast update while supporting wire-speed packet lookup is an important research topic to improve network performance. This paper presents a TCAM-based SDN switch with a flow table update system. When multiple network application updates are integrated at the front end and simultaneously sent to the switch, the system can efficiently detect the dependencies between rules and prioritize the rules which need to be quickly updated, so that they can respond quickly. The update algorithm does not need to block the TCAM search operation and can provide interleaved execution of the packet lookups and rule updates. Tests show that these scheduling strategies improve the system performance by balancing the lookup first algorithm and the update first algorithm.