Research On Accurate Congestion Control Mechanism Based On SDN

The computer network plays a huge role in industry and daily life.Congestion control mechanism is closely related to network availability and user experience.In the traditional network,it is difficult to accurately feedback the network state due to the hardware limitations of the intermediate nodes,and the modification of the congestion control mechanism may also bring compatibility problems such as ECN-non-ECN unfairness.The introduction of SDN brings programmability and flexibility to the network.This paper do research on the performance,compatibility and fairness of network congestion control mechanism based on SDN.The research on accurate congestion control is done for the lack of performance and compatibility.For the compatibility and fairness,the ECN flow restrain non-ECN flow is studied.Specifically,the main work of this article includes the following content:1.To solve the problem of insufficient performance and compatibility of existing congestion control mechanisms,this paper proposes an accurate congestion control mechanism.The mechanism utilizes the protocol-independent,hardwareindependent network programmability provided by SDN to allocate bandwidth to the data flows according to the bandwidth allocation method selected by the network administrator when the network is congested.The mechanism then uses the method of modifying the advertisement window to accurately feed back the actual carrying capacity of the network to the sender.This mechanism only needs to modify the intermediate node logic to ensure compatibility with the source congestion control mechanism.The experimental results show that the mechanism can reduce the retransmission of packets in the network and improve the utilization of network resources.Especially when the constant flows and the burst flows coexist,the throughput increase by 31.54% and 22.33% respectively compared with TCP new Reno and DCTCP.2.To solve the problem of insufficient compatibility and fairness of existing congestion control mechanisms,this paper proposes a state imitation mechanism.At present,there are still many situation where ECN flows coexisting with non-ECN flows.ECN flows has an inhibitory effect on non-ECN,which causes the ECN-non-ECN unfairness problem.This is the embodiment of the lack of compatibility and fairness of the existing congestion control mechanism,and precisely what the state imitation mechanism aimed to solving.This mechanism uses the data plane programmability provided by SDN to collect the average bandwidth of the ECN flows at the intermediate node and convert it to the non-ECN expected sending rate.This mechanism then uses the method of modifying the advertisement window to enable the non-ECN to obtain the corresponding expected sending rate to solve the ECN-non-ECN unfairness problem.The experiment results show that the state imitation mechanism works as expected and has a performance improvement over traditional method.In addition,this mechanism is independent of special environment,like VMware ESXi,thus has more flexibility.3.Finally,by abstracting the above two mechanisms,this paper develops a software-defined congestion control prototype,which aims to ease the workload of network administrators and researchers,and help them quickly develop and test new congestion control mechanisms.Through the RESTFUL interface exposed by this prototype,the administrator can quickly combines different module components to achieve the desired functions.In addition,administrators can write their own components and deploy to the prototype quickly.