Modeling and optimization of packet forwarding performance in softwaredefined WAN Abstract   As a novel network paradigm, SoftwareDefined Networking (SDN) offers numerous benefits for widearea networks (WAN), like promoting application performance and reducing deployment costs. However, it also comes along with an inherent penalty to essential network performance such as packet forwarding delay, primarily due to the involvement of logically centralized controllers. This paper is motivated to provide an accurate queueing system of packet forwarding performance in softwaredefined WAN based on modeling its controller cluster and OpenFlow switches. In particular, we approximate the packetin message processing of the controller cluster as an     M  xe2x88x95  M  xe2x88x95  n     queue based on the derivation of its message arrival process. Meanwhile, we characterize the packet processing of an OpenFlow switch as an     M  xe2x88x95  G  xe2x88x95  1     queue after taking an insight into its packet switching process. As a further step, we build an optimization model of controller cluster deployments to obtain the optimal number of controllers in the cluster. Finally, our proposed queueing model of SDN controller cluster is evaluated with the prevalent benchmark OFsuite_Performance by experiments, and their results indicate that our proposed model provides a more accurate approximation of controller cluster performance. Furthermore, we perform numerical analysis on packet forwarding delay and solve the optimal number of controllers for different varying parameters, which offer effective guidelines for softwaredefined WAN deployments.

Minimizing MultiController Deployment Cost in SoftwareDefined Networking Aiming at various issues, such as performance, loadbalance and robustness, of SoftwareDefined Networking (SDN) controller cluster, several deployment strategies have been proposed. As a supplement, our work delivers a costeffective multicontroller deployment strategy in terms of economic benefits. In this paper, we formalize a Costoptimized MultiController Deployment (COMCD) problem by concerning the controllerxe2x80x99s deployment cost and the network servicexe2x80x99s delay cost. Meanwhile, we characterize the communication between the controller and the switch using a queuing system, and design an algorithm to determine the optimal deployment in the specified environment. Simulation results validate that the proposed algorithm can always obtain a deployment solution which minimizes the economic cost of the entire SDN network. This work aims at being a useful primer to provide insights regarding the economic impact of multiple controllers in the realistic SDN deployment, so that network owners plan their investments more rationally.