Research On Congestion Control Mechanism Of SDN Based Data Center Network

Data center networks plays an increasingly important role in the growing demand of computation and storage,with the characteristics of shallow switch cache and multipath.Low-latency,high-bandwidth,and high-tolerance traffic demand causes serious congestion in the data center network transmission process.However,the traditional congestion control mechanism cannot adapt to the data center network,and the static load balancing does not take full advantage of multipath.Recently,software defined networks provide new ideas for solving data center network congestion problems with the advantages of centralized control and network programmability.To solve the congestion problem of data center,controller can intuitively obtain network status and directly adjust TCP parameters or dynamically schedule the traffic.This research explores the application of SDN technology in the data center network congestion problem and improve the performance of current congestion control algorithms for data centers.Based on this,a centralized hybrid congestion control architecture suitable for a host-side modifiable scenario is proposed.This architecture is different from traditional centralized architectures only operates on switches,it is also extended to be able to centrally control the host-side and make full use of the host-side.Utilize the advantages of the host to collect status information and deliver control message,while significantly reducing the analysis overhead of the switch.This architecture also has pre-configured flow table entries capabilities,the ability to customize and replace different congestion control mechanisms.In the centralized hybrid congestion control architecture,a centralized hybrid TCP congestion control algorithm is designed to solve queue accumulation problems caused by switch congestion.The algorithm detects port queue lengths through the OpenFlow switch and hierarchically reports the queue congestion status.The controller selects the flow that needs to adjust the rate by reporting different congestion states.Then,sends a window adjustment message to the target host.After host receives the control message,it adjusts the TCP sending rate to relieve the congestion in network.Experimental results show that this algorithm has certain advantages in the stability of the queue length and the reduction of the mice flow completion time.In the centralized hybrid congestion control architecture,a rerouting-based congestion control algorithm is designed to solve the problem of link load imbalance in data center network.The algorithm collects information on the host side and periodically reports traffic status information to controller.The controller determines the congested link and identifies the large flow to be scheduled.Then,the rerouting algorithm calculates a new path for the large flow and update the flow entry in OpenFlow switch.The algorithm uses SDN to implement dynamic traffic scheduling,which can reduce the load of the congested link and fully utilize the advantages of multiple equal-cost paths in the data center network to load balance the traffic.Experimental results show that this algorithm can effectively reschedule large flows and reduce the utilization of congested links.