Minimizing the Number of Rules to Mitigate Link Congestion in SDN-based Datacenters

Link congestion due to regular traffic and link flooding attacks (LFA) are two major problems in datacenters. Recent usage growth of software defined networking (SDN) in datacenters enables dynamic and convenient configuration management that makes it easy to reconfigure the network to mitigate the LFA. The reconfiguration that redirects some of the traffic can be done in two ways: the shortest alternative path and the minimum changes in rule path. The SDN switches have a limited capacity for the rules and the performance dramatically drops when the number of stored rules is higher. Besides, it takes some time to adopt the changes by the SDN switches which causes interruption in flow. In this paper, we aim at minimizing the number of rule changes while redirecting some of the traffic from the congested link. We formulate two problems to minimize the number of rule changes to redirect traffic. The first problem is the basic and it considers a congested link and a flow to direct. We provide a Dijkstra-based and a rule merging based solution to the problems. The second problem considers multiple flows and we propose flow grouping and rule merging based solutions. We conduct extensive simulations and experiments in our datacenter to support our model.