改善STARTUP阶段空窗现象的BBR单边适应算法  

BBR Unilateral Adaptation Algorithm for Improving Empty Window Phenomenon in STARTUP Phase

作　　者：马力文 周颖 MA Li-wen;ZHOU Ying(College of Automation&College of Artificial Intelligence,Nanjing University of Posts,Telecommunications,Nanjing 210023,China)

机构地区：[1]南京邮电大学自动化学院、人工智能学院,南京210023

出　　处：《计算机科学》2022年第2期321-328,共8页Computer Science

基　　金：国家自然科学基金(62073172)。

摘　　要：为了解决校园网中应用的BBR(Bottleneck Bandwidth and Round-Trip Time)拥塞控制算法在STARTUP阶段由于未收到ACK(Acknowledge Character)而引起的时延振荡和空窗问题,提出了BBR单边适应算法。该算法只运行在发送端,不受网络协议和上层应用的限制。通过改善时延估计器的加权系数,设计时延瞬时平均偏差估计器,将估算结果作为时延估计器的振荡平滑因子,提高时延估计器应对时延剧烈抖动的能力。为了尽可能解决不可避免的空窗问题和序号回绕,在发送端设计了流量状态机和STARTUP状态机来维持较高的链路吞吐量。根据具体的传输情况将流量分为6种状态:new,blocked,waiting,time_waiting,running,terminated,并根据流量反馈将STARTUP阶段的传输性能分为3个状态:GOOD,NORMAL,BAD。实验结果表明,改进后的BBR比原有BBR算法在STARTUP阶段具有更好的传输性能,且优于目前主要应用的被动拥塞控制算法(Reno,CUBIC)。In order to solve the problem of delay oscillation and empty window caused by the bottleneck bandwidth and round-trip time(BBR)congestion control algorithm in the STARTUP phase due to not receiving the acknowledge character(ACK)in the campus network,the BBR unilateral adaptation algorithm is proposed.The algorithm only runs on the sender,and it is not restricted by network protocols and upper-layer applications.By improving the weighting coefficient of the delay estimator,we design the instantaneous average deviation estimator of the delay and use the estimation result as the oscillation smoothing factor of the delay estimator to improve the ability of the delay estimator to deal with severe delay jitter.To solve the inevitable empty window problem and sequence number wraparound as much as possible,a flow state machine and a STARTUP state machine are designed at the sending end to maintain a high link throughput.According to the specific transmission situation,the traffic is divided into 6 states:new,blocked,waiting,time_waiting,running,terminated,and according to the traffic feedback,the transmission performance of the STARTUP stage is divided into 3 states:GOOD,NORMAL,BAD.Experimental results show that the improved BBR has better transmission performance in the STARTUP phase than the original BBR algorithm and is better than the passive congestion control algorithm(Reno,CUBIC)currently.

关 键 词：瞬时平均偏差 时延估计器 振荡平滑因子 流量状态机 STARTUP状态机 

分 类 号：TP393.06[自动化与计算机技术—计算机应用技术] TP393.18[自动化与计算机技术—计算机科学与技术]