Matchmaker: Maintaining network programmability for Software-Defined WANs under multiple controller failures

Software-Defined Networking (SDN) provides great opportunities to improve the network performance of Wide Area Networks (WANs). In Software-Defined WANs (SD-WANs), SDN controllers dynamically route flows based on network status by managing underlying switches. However, under controller failures in SD-WANs, existing solutions are unadaptable and thus cannot efficiently map offline switches, which were controlled by failed controllers, to active controllers. Thus, flows, which traverse offline switches, become offline and lose their programmability, which means they cannot be rerouted to accommodate to traffic variation. Consequently, the network programmability degrades. In this paper, we propose Matchmaker, an adaptive solution to recover offline flows under controller failures in SD-WANs. Matchmaker smartly changes the paths of some offline flows to adjust the control cost of offline switches based on given control ability of active controllers. As a result, Matchmaker can efficiently map offline switches to active controllers and increase the number of recovered flows. The simulation results show that Matchmaker outperforms existing solutions by increasing the number of recovered offline flows up to 45% under ATT topology and up to 77% under Belnet topology.