Research On Flow Table Timeout And Routing Algorithm For SDN

With the rapid development of the network,the traditional network has low flexibility and can no longer meet the current demand.In recent years,Software-defined Network(SDN)has received extensive attention and gets a fast development.SDN is a new type of network architecture.It decouples the control plane and the data plane.The control plane centrally controls the data plane equipment with a global network view and can more easily obtain network status information.More new functions can be realized through programming and deployment management becomes more convenient.Open Flow protocol is the most popular standard protocol in SDN.However,TCAM with high cost and high power is needed for flow table matching of Open Flow switch,and so the flow table space of storage flow table items is greatly limited,which affects the forwarding performance of switch.Therefore,it is necessary to store more flow table entries in switch without increasing TCAM and improve the utilization rate of the flow table space.This paper will study the optimization of Open Flow switch flow table storage.The work of this paper mainly includes the following aspects:(1)Firstly,the characteristics of the flow table item timeout mechanism,the main characteristics of the data flow and the control right of the timeout value setting are analyzed,and then a flow table adaptive timeout mechanism running in the switch is designed on this basis.The mechanism uses a two-level flow table architecture,which divides the flow table into a main flow table and a secondary flow table.The flow table entries of the main flow table have higher priority.According to the characteristics of the flow arrival time,relying on the two-level flow table,the timeout is dynamically adjusted and the flow table entries that may be invalid are transferred to the secondary flow table,in order to delete the invalid flow table entries more effectively and improve the utilization rate of the flow table space.Finally,a simulation test was performed on the mechanism.Through comparative testing,it was found that the mechanism can improve the utilization of the idle flow table space,and can effectively reduce the number of packet-in,thereby reducing the controller burden and communication overhead.(2)Due to the advantages of the SDN architecture,the controller can easily obtain network status information,so this paper proposes an ACO-BRA algorithm based on the ant colony algorithm.The ACO-BRA algorithm uses network status information such as delay,bandwidth,and flow table space occupancy rate to reduce the delay of data packet transmission and avoid the overflow of the flow table space of a single switch from affecting forwarding.After that,we design a model and built an experimental platform.By comparing the ant colony algorithm and Dijkstra algorithm,it was found that the algorithm proposed in this paper has lower latency and could more flexibly utilize the resources of the whole network for routing,thus slowing down the arrival of the time of running out of the flow table space of a single switch.