一种新的多速率多播拥塞控制策略

本文提出了一种新的多速率多播拥塞控制策略,以满足分层多播接收者的可用带宽异构性。这种接收方驱动的拥塞控制策略,能够根据网络情况变化动态地调整分层的数量及层速率,运用最优层速率分配算法来满足接收者的可用带宽异构性,接收者的可用带宽可以用根据TCP友好经验公式计算出。仿真实验表明,该算法在TCP友好性上有良好的性能,同时它可以明显提高系统的吞吐量。     

新的多速率多播拥塞控制方案

提出了一种新的基于数据包束探测(packet-bunch probe)和TCP吞吐量公式的多速率多播拥塞控制方案PTMCC(packet-bunch probe and TCP-formula based multicast congestion control)。这种接收端驱动的拥塞控制,采用数据包束来探测网络的可用带宽,利用TCP吞吐量公式得到TCP友好速率,并采用了新的速率调节算法。仿真实验表明,PTMCC在收敛性、灵敏性以及TCP友好性上具有较好的性能。     

基于模糊逻辑的无线网络流量自适应控制

文章在分析现有提高无线TCP性能方案的基础上，提出一种新的流量控制方法，即基于显式窗口反馈的无线网络流量控制方案。在Snoop中引入有线网络的显示窗口自适应（EWA）算法，通过对BS共享缓存的实时监测，应用模糊控制算法预测当前拥塞窗口（cwnd）的大小，并显式反馈给发送端，使TCP的发送窗口能快速响应网络负荷状况的变化．避免分组的丢失。仿真结果表明．该方法增强了网络对拥塞的自适应性以及对无线信道差错的实时处理能力．提高了网络的吞吐量。     

确保最小发送速率的TCP友好拥塞控制算法

提出一种确保最小发送速率的TCP友好拥塞控制算法CQTCCA(certified quality TCP-friendly congestion control algorithm)。该算法通过将网络结点和端点相结合，在端点对UDP数据流采用基于公式的发送速率调整，使之体现对TCP数据流的友好性；在结点对RED进行改造，得到提供带优先级包标记的MRED算法，保证对实时多媒体数据流的最小带宽要求。仿真实验验证了本算法有效性。     

基于比例因子的TCP拥塞控制策略

基于自动控制原理的思想,提出了一种基于比例因子的TCP拥塞控制策略。NS2仿真表明,此策略能够减轻网络拥塞,增加网络的吞吐量,提高网络资源的利用率。     

TCP友好的速率控制

TCP友好的速率控制(TFRC)主要适用于实时数据传输的一种拥塞控制机制,具有突出的TCP友好性即在相同的环回时间(RTT)下可以和TCP流享有近乎相同的带宽,从而避免了由于UDP等传输层协议缺乏拥塞控制而带来的网络拥塞甚至崩溃.本文简要介绍了它的协议机制并通过一些仿真和试验的结果初步讨论了其性能.     

无线网络中TCP友好流媒体传输改进机制

为保持无线网络中多媒体业务对TCP的友好性，提出了一种适用于无线网络的动态自适应的流媒体传输速率调节机制。该机制通过在接收端区分网络拥塞丢包和链路错误随机丢包，准确判断网络的拥塞状况结合接收端缓存区占用程度，自适应实施多级速率调节，实现了TCP流友好性和流媒体服务质量（QoS）的折中。由于准确区分出无线链路误码丢包和动态调整流媒体QoS要求，该机制能维持较高的网络利用率。仿真实验结果显示在连接数为2和32，链路误码率从0到0．1变化时TCP,TFRC和吞吐量幅度下降幅度较大，WTFCC幅度下降相对较慢，最大相差达2M；在网络负载重时，尽管链路误码率较低，WTFCC区分链路错误与拥塞丢包，因此，端到端丢包率高于TCP和TFRC，但整体传输吞吐量也高于两者。归一化吞吐量显示WTFCC对TCP流友好。     

基于专家控制的无线网络拥塞控制机制的研究

由于无线网络中存在高误码、信号衰落、切换等原因，使得传统TCP的应用受到了挑战。本文提出了将专家控制用于无线网络的拥塞控制方案，它通过推理判断，确定当前的TCP连接状况，进而区分网络拥塞和无线链路差错，然后再针对不同的原因，选取正确的控制策略实施拥塞控制。仿真结果表明，该方法增强了网络对拥塞以及随机差错的实时处理能力，提高了网络的吞吐量，算法本身具有较强的顽健性。     

无线Mesh网中基于网络编码的多路径TCP研究

在无线多跳网络中,本地重传和网络编码已经被成功地应用到多路径技术上以增加吞吐量并减少丢包。然而,在提高UDP传输性能的同时,也产生了数据包重排序和延迟等副作用,严重影响了TCP性能。针对此问题,主要提出一种基于网络编码的多路径传输方案NC-MPTCP,即在无线mesh网络的多条路径中引入网络编码、执行拥塞控制以及使用一个基于信用的方法控制节点的传输速率,提高网络的吞吐量以及增加网络传输的可靠性。该方案使用一个简单的算法,评估丢包率以及发送线性组合数据包的速率,用来降低目的节点的数据包解码延迟和防止TCP的超时重传。仿真结果表明设计的NC-MPTCP有效。     

TCP-Friendly拥塞控制机制及协议

当前实际网络中传输实时多媒体流使用用户数据报协议(UDP),而UDP不具备拥塞退避机制。在拥塞的网络环境中,UDP流将大量抢占TCP流的网络带宽,同时自身的丢包也迅速增加,并可能带来系统拥塞崩溃的潜在危险,因此提出了TCP友好的概念。文章介绍了TCP-Friendly的提出背景以及实现策略,并对各策略做出评价。     

Evaluating the impact of emerging streaming media applications onTCP/IP performance

Emerging streaming media applications in the Internet primarily use UDP transport. The difficulty with supporting this type of traffic on the Internet is that they not only generate large volumes of traffic, but they are also not as responsive to network congestion as TCP-based applications. As a result, streaming media UDP traffic can cause two major problems in the Internet: congestion collapse and unfair allocations of bandwidth among competing traffic flows. A solution to these problems is available in many Internet environments. The Internet backbone, various ISPs, and DSL access networks rely on ATM as their layer 2 transport technology, and in such environments, ATM's available bit rate service can efficiently address these problems. ABR is able to avoid congestion collapse and provide fair bandwidth allocations by distributing the unutilized bandwidth fairly among competing flows. This article presents simulation results and empirical measurements that illustrate the congestion collapse and unfairness problems, and ATM ABR's effectiveness in addressing those problems     

一种无线传感器网络公平数据收集方案(英文)

To solve the slow congestion detection and rate convergence problems in the existing rate control based fair data collection schemes, a new fair data collection scheme is proposed, which is named the improved scheme with fairness or ISWF for short. In ISWF, a quick congestion detection method, which combines the queue length with traffic changes of a node, is used to solve the slow congestion detection problem, and a new solution, which adjusts the rate of sending data of a node by monitoring the channel utilization rate, is used to solve the slow convergence problem. At the same time, the probability selection method is used in ISWF to achieve the fairness of channel bandwidth utilization. Experiment and simulation results show that ISWF can effectively reduce the reaction time in detecting congestion and shorten the rate convergence process. Compared with the existing tree-based fair data collection schemes, ISWF can achieve better fairness in data collection and reduce the transmission delay effectively, and at the same time, it can increase the average network throughput by 9.1% or more.     

Adaptive Congestion Control of mSCTP for Vertical Handover Based on Bandwidth Estimation in Heterogeneous Wireless Networks

This paper proposes a new congestion control scheme of mobile Stream Control Transmission Protocol (mSCTP) for vertical handover across heterogeneous wireless/mobile networks. The proposed scheme is based on the estimation of available bandwidths in the underlying network as a cross-layer optimization approach. For congestion control of mSCTP, the initial congestion window size of the new primary path is adaptively configured, depending on the available bandwidth of the new link that a mobile node moves into. By ns-2 simulation, the proposed scheme is compared with the existing congestion control schemes in the throughput perspective. From the numerical results, we can see that the proposed mSCTP congestion control scheme could give better performance than the existing schemes in the wireless networks with an amount of background traffic.     

Theoretical analysis of the SABUL congestion control algorithm

Several new protocols such as RBUDP, User-Level UDP, Tsunami, and SABUL, have been proposed as alternatives to TCP for high speed data transfer. The purpose of this paper is to analyze the effects of SABUL congestion control algorithm on SABUL performance metrics such as bandwidth utilization, self-fairness, aggressiveness and average packet losses. We propose simple deterministic and stochastic models of SABUL congestion control algorithm and use the models to assess these metrics. Our results explain SABUL throughput oscillations, derive bounds on its aggressiveness/responsiveness, show that SABUL can be self-fair, and identify conditions under which SABUL connections may experience excessive packet losses. This work was sponsored in part by the National Science Foundation grant No. NSF-9901004, DOE SciDAC grant DE-FC02-01ER25484, and IBM Corp. Shared University Research Program.     

数据流的活动队列管理算法:MBLUE

MBLUE(Modified BLUE)是一种面向数据流的活动队列管理算法.它不是使用平均队列长度指示缓冲区拥塞状态,而是使用数据报丢弃的频率和队列空闲程度来管理网络拥塞.探测瓶颈连接早期的拥塞信息,通过数据报的丢弃和标记避免拥塞.它只维护一个先进先出队列,以较少的数据流状态信息,在不同流之间公平的分配网络带宽.能够适应瞬时的猝发流,能合理控制非TCP数据流,又能够保持较短的平均队列长度,从而控制、减轻网络拥塞.通过TCP/IP网络的模拟,证实算法在公平的分配网络带宽和降低数据报的丢失率上具有较好的鲁棒性.     

一种新的逐跳TCP友好的主动分层多播拥塞控制方案

基于Internet的多媒体多播应用的迅猛发展对多播拥塞控制提出了要求.分层多播是适应网络异构性较有效的方案.针对现有分层多播存在的问题,将主动网技术思想引入到分层多播拥塞控制中,提出了一种逐跳TCP友好的主动分层多播拥塞控制方案(HTLMA),采用主动标记分层、逐跳探测TCP友好可用带宽,以及主动速率控制机制.仿真实验表明,HTLMA方案大大改进了分层多播拥塞控制的性能,具有较快的拥塞响应速度、较好的稳定性和TCP友好特性.     

FCA-ItswTCM:区分服务中一种公平的拥塞自适应标记算法

 本文提出了一种新的滑动窗口标记算法——公平的拥塞自适应标记算法(FCA-ItswTCM).算法近似识别TCP流和UDP流,适度区分标记,规避拥塞控制机制对公平性的影响;细粒度描述拥塞,预测拥塞,以此自适应调节各流注入黄包比例,兼顾网络拥塞状态对公平性的影响.仿真实验表明,与其他几种滑动窗口标记算法相比,FCA-ItswTCM对确保TCP流和UDP流带宽共享的公平性、提高资源利用率及系统稳定性有较好的效果.     

Bandwidth estimation schemes for TCP over wireless networks

The use of enhanced bandwidth estimation procedures within the congestion control scheme of TCP was proposed recently as a way of improving TCP performance over links affected by random loss. This paper first analyzes the problems faced by every bandwidth estimation algorithm implemented at the sender side of a TCP connection. Some proposed estimation algorithms are then reviewed, analyzing and comparing their estimation accuracy and performance. As existing algorithms are poor in bandwidth estimation, and in sharing network resources fairly, we propose TIBET (time intervals based bandwidth estimation technique). This is a new bandwidth estimation scheme that can be implemented within the TCP congestion control procedure, modifying only the sender-side of a connection. The use of TIBET enhances TCP source performance over wireless links. The performance of TIBET is analyzed and compared with other schemes. Moreover, by studying TCP behavior with an ideal bandwidth estimation, we provide an upper bound to the performance of all possible schemes based on different bandwidth estimates.     

Efficient Transmission of MPEG-2 Coded Video Traffic over ATM Networks

Video traffic is expected to account for a significant share of the traffic volume in the future asynchronous transfer mode (ATM) networks. MPEG-2 proposed by Moving Picture Expert Group is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The Leaky Bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism to police the VBR sources. We proposed a new Adaptive Dynamic Leaky Bucket (ADLB) congestion control mechanism, which is based on the LB scheme. Unlike the conventional LB, the leak rate of the ADLB is controlled using delayed feedback information of available bandwidth sent by the network. This scheme allows sources to get varying amounts of bandwidth over time, while reserving a minimum guaranteed bandwidth (MCR) for the entire duration of the connection. At the time of congestion, the leak rate of the ADLB is adjusted according to the feedback indicating the currently available bandwidth to the connection. The simulation results show that the end-to-end cell transfer delay and cell loss of each source has been improved significantly.     

一种新的分层多播拥塞控制协议

提出了一种新的自适应分层多播拥塞控制方案(ALM)。ALM是发送方与接收方共同驱动、由路由器辅助流量控制的拥塞控制方案,通过把发送方的动态分层和接收方的自适应速率调整有机结合,不仅增强了分层多播的适应能力,提高了系统的吞吐量,而且较好地满足了TCP友好性。仿真实验表明,ALM能有效地利用网络带宽,解决网络带宽的异构性问题,并能通过接收端计算TCP友好速率,使接收端达到与TCP流公平竞争网络资源的目的。