AFTM: An Adaptive Flow Table Management Scheme for OpenFlow Switches

Software-Defined Networking (SDN) is an emerging network platform, which decouples the control and data planes. As the most popular southbound protocol and standard, OpenFlow converts network forwarding policies to rule entries and stores them in the flow table. However, the capacity of the flow table is restricted, which can lead to table-overflow if the space is inefficiently used. In this paper, we propose an adaptive flow table management scheme (AFTM) on the control plane, which combines assigning dynamic timeout and proactive eviction to manage the limited flow table resources. The timeout assignment module and the proactive eviction module are not independent parts but work collaboratively. The timeout assignment module sets suitable timeouts for rule entries according to flow characteristics, so that entries of short-lived flows are quickly removed while entries of flows with large packet intervals are retained. When the table space is insufficient, the proactive eviction module removes rule entries to protect the flow table from table-overflow. In our design, the eviction thresholds and parameters in both modules can be adaptively adjusted according to the network load. Experimental results show that AFTM can effectively manage the flow table resource and reduce the number of packet drop rates by up to 81% compared with existing schemes.