Multipath Congestion Control Algorithm Based On Round Trip Delay Gradient

With the continuous development of computer network technology,lower and lower cost of network bandwidth and a variety of network access devices make it possible to configure multiple network interfaces in multi-host terminals.But using multiple network interfaces to transmit data inevitably brings new problems.For example,how to use multiple network interfaces to make full use of redundant links,how to balance the transmission of traffic on different paths and how to optimize the performance of multi-path concurrent transmission,these problems promote the development of multi-path transmission protocol.Multi-path TCP was first proposed by IETF.It is an extension and standardization of TCP.The basic principle of multi-path transmission is to divide a single TCP stream at the transport layer into multiple sub-streams for transmission,and manage the sub-streams.According to the different management modes of sub-streams,it can be divided into coupled multi-path transmission,uncoupled multi-path transmission,and semi-coupled multi-path transmission.It not only makes full use of the redundant links of the network to improve the stability of transmission but also improves the network throughput.However,the application of multi-path transfer protocol to the actual network will face new problems.For example,when deployed on a mobile network,TCP and MPTCP coexist on the mobile network,which cannot ensure fair resource competition.For example,when the multi-path transmission protocol is applied to a data center,the change of network congestion cannot be accurately sensed due to the high bandwidth and low latency of the data center.According to the actual requirements of network,this paper puts forward the problem of fairness in multi-path transmission and the problem of accurately sensing network congestion,and analyzes and optimizes these two problems.The thesis mainly carries on the following work:(1)Introduces the specific working principle of MPTCP,including the structure,basic operation and design principle of MPTCP.The existing congestion control algorithm of MPTCP is analyzed.(2)In view of the fairness problem of MPTCP,the essence of fairness is firstly analyzed and the algorithm of minimum and maximum fairness based on delay is proposed.The algorithm takes the round-trip delay of sub-flows as a kind of resource.According to the principle of fair resource allocation,a fair bandwidth allocation method is finally found after continuous iterative allocation,which ensures the fairness of multi-channel runoff and single-channel runoff competing resources.(3)In view of the fact that MPTCP could not accurately perceive the change of network congestion,the multi-path transmission architecture was designed firstly,and the sub-flow management was carried out in an uncoupled way.In addition,by calculating the gradient of round-trip delay,the gradient is used as the control parameter of congestion window to conduct fine-grained window adjustment,so as to achieve the purpose of timely perception and timely adjustment.Further improve network throughput.