PSTCP：小缓存高速网络拥塞控制算法

针对当前网络拥塞控制算法在极小缓存高速网络中带宽利用率差的问题,研究了TCP机制本身造成的突发流量现象,提出一种新的拥塞控制算法——PSTCP。在整个网络连接过程中,该算法采用“隔开”平滑发送的思想;在网络拥塞发生时,采用公平因子c和减少因子decrement对窗口进行实时微调。实验表明,PSTCP在小缓存区、高带宽网络环境下,保障了高的带宽利用率,有好的收敛性和公平性。     

高速网络中TCP拥塞控制算法的研究

针对TCP在高速网络中的缺陷,提出了改进的BIC TCP拥塞控制算法。优化算法通过监控链路缓存的变化,调整探索可用带宽过程中的拥塞窗口增加值,当拥塞发生时将慢启动门限和拥塞窗口设为估计带宽和最小RTT乘积,达到降低网络拥塞频率和避免因高速数据流导致缓存区溢出的目的。实验结果表明优化算法的性能在高速网络中得到很大的提高。     

基于测量的TCP拥塞控制的公平性研究

通过分析传统TCP算法的局限性，讨论TCP Vegas、TCPW两种基于源端实时带宽测量拥塞控制算法的原理以及带宽分配的公平性，结合主动队列管理技术，提出一种基于加权缓存区容量分配RED算法．理论分析和仿真实验表明该算法提高了带宽分配的公平性．保持了网络的高吞吐量，并实现服务QoS保证.     

一种改进的TCP拥塞控制算法及仿真

TCP协议提供面向连接、可靠的服务,但应用于时延敏感的实时网络时,并不能保证实时性。当网络负载过大时,会出现拥塞、传输延迟和丢包等问题。为了降低网络拥塞概率,提出了一种改进的TCP拥塞控制算法TCP-EB。该算法根据确认数据包的速率估计网络可用带宽,调整拥塞窗口的大小,提高带宽利用率。出现拥塞时,对窗口衰减速度进行限制,保证传输的优先级高于其他数据流。最后将TCP-EB与传统拥塞控制算法TCP Reno、TCP Vegas进行比较,结果表明,提高了网络吞吐量和网络传输的平滑性。     

LEO卫星网络中一种改进的Vegas算法

针对SCPS-TP(Space Communications Protocol Standards Transport Protocol)协议的Vegas算法在LEO (Low Earth Orbit)卫星网络中吞吐量下降的问题,提出了一种自适应Vegas-AD(Adaptive)拥塞控制算法。该算法在分析Vegas的基础上,细化往返时延RTT的计算方法,使其能够更加精确地调整拥塞窗口;优化拥塞窗口的增长策略,提高了拥塞避免阶段的带宽竞争力;同时,提出基于网络拥塞程度的自适应窗口调整因子。仿真结果表明,Vegas-AD算法的带宽竞争力明显高于Vegas,并且该算法能较大幅度地提高网络吞吐量。     

一种改进的自适应无线网络拥塞控制方案

拥塞控制的主要目标是在变化的网络环境下达到较高的带宽利用率，公平性和响应性．然而这些目标相互冲突．很难达到平衡．本文提出一种能在竞争连接的条件下取得相对稳定且延迟较小的拥塞控制算法．该算法主要通过改变AIMD拥塞控制算法中的增加因子和减少因子。使原算法中的参数可根据当前网络条件动态改变．仿真实验表明改进后的算法能有效地避免延迟抖动．具有较强的稳定性．     

V2G网络中基于带宽自适应的拥塞控制协议优化

V2G网络下PLC链路带宽受限、高误码率等特点导致现有的TCP NewReno拥塞控制机制缺乏对丢包类型的有效判断,将链路上由噪声干扰的随机错误丢包与网络拥塞丢包统一当做拥塞事件处理,从而造成不必要的拥塞避免,导致了低吞吐量问题.根据此问题,提出了一种基于带宽自适应的拥塞控制算法.该算法通过分组预测拥塞等级感知网络状态,由此估计可用带宽来判断丢包类型,实现了拥塞窗口自适应调节.仿真结果表明该算法在拥塞窗口的增长、吞吐量、公平性、收敛性和友好性等方面都优于现有算法,V2 G网络的吞吐量得到明显提升.     

改进的网络拥塞控制策略算法研究

研究网络拥塞优化控制问题.针对网络承载量的不断增加,使得网络传输效率降低.传统网络拥塞控制算法要求系统根据无线网络的容量实时编号,动态调整TCP拥塞窗口的大小,难于建立准确的数学模型,从而导致网络带宽利用率低,网络拥塞严重.为了降低网络拥塞的概率,提出了一种改进的无线TCP拥塞控制算法.算法主要是集中解决在TCP拥塞窗口的大小调整问题上,首先利用BP神经网络对参数进行训练,有效地解决了TCP拥塞窗口大小的调整,从而实现了拥塞避免、快速重传和快速恢复机制,改善网络性能.实验结果表明改进的算法提高了网络平均吞吐量,带宽利用率更高,有效避免了网络拥塞.     

显式拥塞控制研究

随着互联网络技术的发展,高带宽延迟积的高速网络成为主流网络,TCP拥塞控制算法因为协议固有的设计缺陷,无法理想地处理高速网络中的拥塞问题,显式拥塞控制协议有效地克服TCP的设计缺陷,较为理想地解决这些问题。论述显式拥塞控制的工作流程以及三种显式拥塞控制协议XCP、EMKC和JetMax。     

高速网络中TCP拥塞控制研究综述

通过分析现行TCP算法在高速网络中的局限性,介绍几种最新的高速网络拥塞控制算法:BIC TCP、FASTTCP、STCP、HTCP和HSTCP.从带宽利用率、公平性和友好性方面对上述算法进行分析和比较,指出算法存在的不足,提出研究方向.     

Perturbation Analysis for Stochastic Fluid Queueing Systems

Recent study for congestion control in high speed networks indicates that the derivative information for the congestion at the common buffer for multiple sources could be useful in achieving efficient and fair allocation of the bandwidth (Kelly, 1997; Kelly et al., 1998). In this paper we present an algorithm that estimates such derivatives for multiple on-off sources. The algorithm has its root in the infinitesimal perturbation analysis (IPA) for the classical queueing systems. Although the traditional IPA algorithm does not give unbiased derivative estimates for multi-class arrivals, we are able to prove the unbiasedness in the case of multi-class ON-OFF sources. The results in this paper may motivate a new look at the end-to-end congestion control issue.     

一种基于Smith预估器的主动队列管理(AQM)拥塞控制算法

有效的拥塞控制机制是保证Internet稳定运行的关键因素之一,网络拥塞控制系统本质上是一个时滞系统,传输时延是网络拥塞控制必须考虑的一个重要因素.本文应用Smith预估控制原理,在进行适当模型拟合处理的基础上,提出了一种基于Smith预估器的主动队列管理(AQM)算法(AQMAlgorithmbasedonsmithpredictor算法,简称Smith-PI),新算法结构简单,易于配置,具有良好的鲁棒性和网络控制性能,同时克服了大时滞给队列稳定性造成的不利影响。通过仿真表明,采用Smith-PI算法,对于限制系统振荡超调量的作用非常明显,同时能使网络具有更快的响应速度及更平稳的队列,而当网络时延增大时,算法能使网络的动态性能依然保持良好,使得缓存队列迅速收敛到稳定值。     

基于带宽预测的VCP拥塞控制改进算法

反馈信息不足导致VCP无法根据网络拥塞程度进行相应窗口调整,在网络突发业务流情况下存在慢收敛问题.针对高带宽延时网络特性,本文提出一种基于带宽预测的VCP拥塞控制改进算法VCP-BE.该算法结合端到端可用带宽预测和2位显式拥塞反馈信息提高拥塞反馈精度,为源端拥塞窗口调节提供更精细的拥塞控制信息.仿真结果表明,VCP-BE能够有效适应高带宽时延网络环境,具有比VCP及MLCP更快的公平收敛速度.     

A novel high speed transport protocol based on explicit virtual load feedback

Since traditional TCP congestion control is ill-suited for high speed networks, designing a high speed replacement for TCP has become a challenge. From the simulations of some existing high speed protocols, we observe that these high speed protocols make the round-trip time bias problem and the multiple-bottleneck bias problem more serious than for standard TCP. To address these problems, we apply the population ecology theory to design a novel congestion control algorithm. By analogy, we treat the network flows as the species in nature, the sending rates of the flows as the population number, and the bottleneck bandwidth as the food resources. Then we extend the construction method of population ecology models to design a control model, and implement the corresponding end-to-end protocol with virtual load factor feedback, which is called Explicit Virtual Load Feedback TCP (EVLF-TCP). The virtual load factor is computed based on the information of the bandwidth, the aggregate incoming traffic and the queue length in routers, and then senders adjust the sending rate based on the virtual load factor. Theoretical analysis and simulation results validate that EVLF-TCP achieves high utilization, fair bandwidth allocation independent of round-trip time, and near-zero packet drops. These characteristics are desirable for high speed networks.     

Achieving high throughput and TCP Reno fairness in delay-based TCP over large networks

The transport control protocol (TCP) has been widely used in wired and wireless Internet applications such as FTP, email and http. Numerous congestion avoidance algorithms have been proposed to improve the performance of TCP in various scenarios, especially for high speed and wireless networks. Although different algorithms may achieve different performance improvements under different network conditions, designing a congestion algorithm that can perform well across a wide spectrum of network conditions remains a great challenge. Delay-based TCP has a potential to overcome above challenges. However, the unfairness problem of delay-based TCP with TCP Reno blocks widely the deployment of delay-based TCP over wide area networks. In this paper, we proposed a novel delay-based congestion control algorithm, named FAST-FIT, which could perform gracefully in both ultra high speed networks and wide area networks, as well as keep graceful fairness with widely deployed TCP Reno hosts. FAST-FIT uses queuing delay as a primary input for controlling TCP congestion window. Packet loss is used as a secondary signal to adaptively adjust parameters of primary control process. Theoretical analysis and experimental results show that the performance of the algorithm is significantly improved as compared to other state-of-the-art algorithms, while maintaining good fairness.     

Distributed bandwidth allocation based on alternating evolution algorithm

In a network, end nodes have to compete for bandwidth through some distributed congestion control algorithms. It is a great challenge to ensure the efficiency and fairness of the distributed control algorithms. TCP congestion control algorithms do not perform well in terms of their efficiency and fairness in high speed networks. In this paper, we propose a novel asymptotic evolution algorithm based on the Logistic Model to allocate limited bandwidth resource. The algorithm introduces an explicit bandwidth pre-allocation factor. The factor is carried by the packet and is computed in routers based on the information of the router capacity, the aggregate load, and the instantaneous queue length; therefore the algorithm does not require the routers to keep the per-flow state. According to this pre-allocation bandwidth factor, the senders asymptotically adjust their sending rate and the bandwidth factor changes asymptotically along with the variation of the aggregate load and the queue length in the routers; therefore the sending rate and the pre-allocation bandwidth factor form alternating evolution and eventually reach a steady state.     

小时间尺度网络拥塞研究*

基于窗口的拥塞控制算法通常忽略了比往返时间级更小的时间尺度上的网络拥塞,因此不能达到设计的预期效果。重点从理论上研究了窗口更新算法与小时间尺度网络拥塞之间的相互关系,提出了窗口递增算法的小时间尺度突发性度量方法,并分析了小缓冲高速网络环境下传统TCP窗口递增算法的效率。     

基于逐段RED的组播拥塞控制机制研究

提出了一种基于逐段RED的网络层组播拥塞控制机制，并对其有效性进行了数学推证，证明了信息包在不同优先级的转发约束下，STSR拥塞控制模型的缓冲区共享策略发生拥塞的概率小于分用策略，且STSR具有更高的敏感度和更大的网络吞吐量。利用NS-2对STSR拥塞控制进行了模拟，证明了STSR能保证对TCP流的友好，并实现了较粗粒度下的分布式控制。这一结果的取得对于组播拥塞控制的相关研究具有很大的指导意义。