Reliability And Latency-aware Controller Placement In Software Defined Networks

Control plane is decoupled from data plane in Software-Defined Networking(SDN),which makes SDN more flexible,manageable and scalable.Multiple-controller architectures are often exploited in SDNs to achieve good system performance,which incurs the controller placement problem.That is,intelligent controller placement need to decide where to place the controllers and how to map switches to controllers.Well-designed strategy of controller placement can significantly improve the performance,reliability and stability of the network.In this thesis,we tackle the controller placement problem to improve the communication reliability and the communication latency in SDNs.We explore two important and challenging issues in controller placement:(1)We tackle the controller placement problem to improve the communication reliability.Network failures disable the controllers to respond to the flow set-up requests from the switches.Controller placement strategy has an impact on the flow set-up request response rate while different switches have different number of flow set-up requests.We introduce a new reliability metric that considers the number of dropped flow set-up requests from switches to controllers due to the single-link-failure.We formulate a novel SDN controller placement problem with the goal to minimize the average number of dropped flow set-up requests.We propose two algorithms SROC(flow Set-up Requests quantity Oriented Controller placement)and SROC-Fast.The proposed algorithms can reduce the average number of dropped flow set-up requests.At the same time,the proposed algorithms can also decrease the average communication latency of total flow set-up requests and the average number of requests forwarded by the switches.(2)We investigate the controller placement problem by jointly taking into account both the communication reliability and the communication latency between controllers and switches if any link in the network fails.We first introduce a new latency metric that considers both the communication reliability and the communication latency between the switches and the controllers due to the single-link-failure.We then formulate a novel SDN controller placement problem with the aim to minimize the communication delay,for which we propose an efficient algorithm.We also show there is a non-trivial trade-off between a primary path and its backup path in terms of communication delay.We finally conduct experiments through simulations.Experimental results demonstrate that the proposed algorithm is very promising.