Research And Simulation Implementation Of OpenFlow Protocol-based SDN Measurements

Software Defined Networks(SDN)separate switchers' control layer from data layer,which holds the advantages of centralized control,open programming interface and network virtualization.This has received an extensive attention and study from academia and industry.The measurement for SDN is the key part of SDN management activities.However,at present academia and industry mainly SDN control,while hardly research SDN measurement.The SDN controller performs data forwarding and management from the global perspective and in the centralized control way.This will lead to the controller to become the performance bottleneck of networks.Therefore,it is significantly important to provide a low-cost and high-precision SDN measurement method.Firstly,this thesis proposes an OpenFlow protocol-based low-cost SDN measurement approach called as the OpenFlow-based low-cost and low-error framework(OpenLL).OpenLL can measure the throughput,delay and packet loss rate per flow.Different from previous methods,OpenLL only measures the input and export switchers of each flow in the network to reduce network overhead.An adaptive sampling algorithm and a low-overhead topology discovery method for OpenLL are proposed to improve the OpenLL performance.The delay threshold is used to further raise the accuracy of the path delay measuremt.Additionly,this thesis analyzes the relationship among measurement accuracy,measurement overhead,measurement time,minimum sampling time,and network size.Secondly,this thesis studies how to select the measurement switchers from a global viewpoint to reduce the network measurement overhead when SDN hold multiple flows.The mathematical model is proposed to describe the selection problem of swichers with the minimal number of measurement flows.This model takes the measurement flow number as the subject function.Through solving this model,the appropriate swithers are selected to measure all the flows going through the network.This model is a NP problem.This thesis presents two greedy algorithms to solve this model.Accordingly,the measurement switchers and the number of measured flows are attained.Finally,this thesis uses the POX controller and Mininet platform to implement the proposed SDN measured methods.Then the detailed simulation experiments are conducted.Simulation results shows that the proposed measurement approaches hold the lower measurement overhead and higher measurement accuracy.