The Key Technologies Of Control Plane In Software Defined Network

With the rapid development of computer network technology,the shortcomings of tradi-tional networks have been gradually exposed.In this context,Software-Defined Networking(SDN)came into being.It simplifies network management and configuration operations,en-hances support for new network technologies and new protocols,and shortens the innovation cycle of network function,so it appeals to academic and industry.With its development,there are many key scientific problems that still need to be solved.This thesis focuses on the problems in the SDN control layer.On the basis of the existing methods and research results,the research work is carried out in control layer around the three research subjects of request selection,in-formation interaction and decision-making optimization.The three targets are minimizing the request delay,standardizing the information interaction and optimizing the decision path in this research.The specific research contents are as follows:Due to a switch is statically assigned to a single controller,the controller becomes over-loaded.This thesis first analyzes the existing solutions,and summarizes the switch migration load balancing(SFLB)scheme and centralized control load balancing(CCLB)scheme.After analyzing the advantages and disadvantages of SFLB and CCLB,this thesis proposes an active controller selection load balancing(ASLB)scheme.The switch actively selects the appropri-ate controller to process the request in order to shorten the controller response time and make better use of the controllers processing ability.In terms of system implementation,this thesis implements Coordinator based on ASLB and the open source software OpenVirtex.In SDN multi-controller architecture,the Coordinator acts on behalf of switch sends the request to the controller.Theoretical analysis proves that when the number of switches is greater than 3,the improvement effect of Coordinator on the request delay exceeds the delay caused by Coordinator itself.Meanwhile,if the number of switches in the network increases,the improvement effect of Coordinator is more obvious.In terms of algorithm design,an active selection controller al-gorithm(ACS)is proposed in order to solve the problem of herd behavior and tail latency.ACS uses Batch-Filling and scores the controller,which improves the effect of two choice algorithm.In order to verify the performance of ASLB,this thesis conducts an experimental evaluation on a real network test bed.Experimental results show that Active Controller Selection mechanism is superior to existing mechanisms in terms of minimizing latency,bandwidth utilization,and throughput.In view of the diversification of controller communication interfaces encountered by the SDN control plane,this thesis proposes to re-layer the existing SDN architecture,dismantle the original control layer functions,and improve the three-layer SDN architecture to four-layer architecture that is WECAN(West-East Communication And North API).After removing the personalized function,the original control layer assumes basic functions such as link discovery and flow table delivery in the dissemination and discovery layer.Above the dissemination and discovery layer,this thesis designs a decision layer to standardize information interaction.There are three core modules in the decision layer:heterogeneous controller management module(HCM),domain relationship management module(DRM)and controller selection management module(CSM).HCM collects network information from the controller,generates a domain-wide network view,and supports communication between different types of SDN controllers.DRM collects network information from HCM to generate a global view of the network.At the same time,DRM divides and manages the SDN network by domain.Therefore,this thesis also proposes a model of SDN domain division.CSM adopts the active controller selection mechanism,so that the requests sent by the switch can be handled by the controller with lower load and higher execution efficiency.In the experimental part,this article developed a prototype system to complete the WECAN test.The experimental results indicate that WECAN can not only support different types of SDN controllers to communicate with each other,but also have advantages over current distributed controllers and single controllers in terms of throughput and response time.Aiming at the problem of long-term flow and short-term flow sharing bottleneck links,this thesis proposes a path decision mechanism for scheduling short-term and long-term flows sep-arately.Taking the fat-tree data center network as an example,this thesis proposes a dynamic flow decision mechanism,FC-DLB,which optimizes the flow decision by using the global net-work view and flow characteristics provided by the SDN controller.According to the length of the flow,FC-DLB can dynamically control the flow in the data center,adjust the flow forward-ing strategy and optimize the routing scheme.FC-DLB uses two different algorithms to route short-term and long-term flows respectively.It uses the DLB algorithm as the default algorithm to route short-term flows,and dynamically changes the routing path for long-term flows,shifting long-term flows from the paths of high link utilization to low link utilization.The experimental results indicate that,compared with the ECMP and DLB algorithms,FC-DLB can effectively solve the problem of long-term and short-term flow sharing bottleneck links,while significantly improving link utilization and making full use of bandwidth.