MPLS-based reduction of flow table entries in SDN switches supporting multipath transmission

Abstract In this paper, the problem of resource utilisation improvement in software-defined networking (SDN) is addressed. The need for resource optimisation is understood here be twofold. First, bandwidth in links should be saved when congestion appears. Second, the internal resources represented by table entries of SDN switches should be minimised to ensure fast processing and flexibility. Here, both types of resources are optimised with a new mechanism for flow aggregation. The mechanism is accompanied with a multipath transmission supporting reaction when network conditions change. The proposed mechanism uses classical MPLS labelling, which enables flow aggregation together with multipath transmission; therefore, neither involves any definition of new protocols nor requires the application of legacy signalling protocols. Only simple yet powerful modifications of the existing solutions assured by flexibility of the OpenFlow protocol are necessary. Furthermore, the proposed solution can be incrementally deployed in legacy networks. The aggregation results in a low number of flow entries in core switches in comparison to legacy OpenFlow operation. The simulations show that the number of flow entries in core switches can be reduced by as much as 93%, while the overall network traffic is increased by around 171%. This type of scalability improvement of flow processing is obtained as a result of the introduction of a centrally managed MPLS label distribution performed by an SDN controller. Moreover, the proposed method of multipath transmission improves network resource utilisation. Additionally, independently of the traffic pattern, the proposed approach significantly reduces the communication overhead between the controller and the switches.