Web Services Oriented Transport Layer Fast Multi-path Loss Recovery Mechanism

TCP is the underlying transport protocol of most modern online Web services,it's transmission time is critical to the Web service performance.However,packet loss can lead to a significant decrease in TCP transmission performance,which greatly increases the access latency of Web services.By analyzing the real Web access data of one of the largest Internet companies in the world,we find that the network packet loss occurs seriously in the transmission process,and the inefficient packet loss recovery mechanism of TCP significantly increases the transmission time.Therefore,previous works try to add aggressiveness to TCP thus to speed up loss recovery,these schemes start proactive retransmission before fast recovery or retransmission timeout.But grasping the degree of aggressiveness is hard because of unknown network condition,usually,being too conservative will delay the loss recovery time and being too aggressive will increase network congestion.Recent work FUSO addressed this problem by leveraging multi-path diversity for proactive loss recovery,it used “good” paths to proactively retransmit the potentially lost packet on “bad” paths.However,because it's impossible to predict which packet is truly lost,FUSO tended to retransmit the oldest un ACKed packet.Through real data measurement analysis and comprehensive experiments,it's found that FUSO can't accurately recover lost packets in Web services,and the network performance is not improved enough.In view of the above problems,we make an indepth study on how to optimize TCP transmission performance under packet loss in Web services.The main work is as follows:(1)We prove the current inefficiencies of TCP and TCP improvement mechanisms in Web services by measuring the performance in transport layer of the real Web services.Specifically,we collect real Web service data from the world's largest Internet service providers.Firstly,through the analysis of its basic characteristics and overall performance,we show that there is still a large room for network performance improvement in Web services,especially the user-sensitive network latency needs to be improved.Secondly,by exploring the key factors affecting network latency,we confirm that the retransmission timeout caused by packet loss is an important reason for unsatisfactory network latency.Finally,the further exploration of the packet loss location verifies the limitations of the current improvement mechanism.(2)We propose the coding-based transport layer multi-path packet loss recovery scheme,Co FUSO.The scheme is divided into two parts: on the one hand,we prove the feasibility of proactive recovery by using the diversity of multi-path network conditions through experiment,and adopt the proactive recovery mechanism based on multi-path.On the other hand,through the targeted testbed experiment and analysis,we prove that the previous work FUSO is ineffective in the Internet Web service,therefore,we add the erasure correction code technology into multi-path proactive recovery.In terms of specific design,the scheme takes the combination of dynamic coding and path scoring selection at the sender: The worst and best sub-flows are selected based on the historical packet loss rate and RTT.And the appropriate number of coding packets is generated dynamically according to the historical packet loss rate of the worst sub-flow.Finally,these coding packets are retransmitted by the best sub-flow.And at the receiver,Co FUSO uses the coding packets to recover the lost packets in advance through the design of additional buffers,which reduces the flow completion time of the data.(3)We complete the implementation of the prototype system in the Linux kernel and experimental evaluation.We implement Co FUSO in Linux kernel with 2077 lines of code and verify it's realizability in the real environment.Meanwhile,the performance of Co FUSO is evaluated from various aspects in the small-scale testbed and NS-2 simulation.And the results show that this scheme can significantly accelerate the whole transmission time of data traffic in the network compared with other schemes.Network latency optimization of Web services is a hot topic at present,the challenge is how to accelerate TCP packet loss recovery.We propose a fast multi-path packet loss recovery mechanism based on coding at the transport layer,which can not only avoid the increase of network congestion but also carry out proactive recovery in advance efficiently,which greatly reduces the Web latency and improves the network performance.