APAIMD算法及基于此算法的APTCP协议

本文提出了一种可调参数AIMD算法和一种在接收端实现该算法的适合在Internet上传输多媒体流的可调参数传输控制协议。UDP不适合传输多媒体数据，因为它没有拥塞控制机制。TCP遇到单个数据包丢失传输速率就减半，会造成速率剧烈抖动，也不适合传输多媒体数据。在APTCP控制下传输的多媒体流具有良好的速率平滑性，并能够与竞争的TCP流公平的分享带宽。APTCP便于升级到组播多媒体业务，可用于非对称网络。     

拥塞／速率控制算法及其在多媒体数据传输中的应用

基于Internet的以UDP为传输协议的实时多媒体数据传输,需要在保证实时性和可靠性基础上,能够与Internet其他服务所使用的TCP协议合理共享有限的带宽,在研究多种拥塞控制算法的基础上,提出了一种简单实用的TCP友好拥塞／速率控制算法,并将该算法应用在一个实用的IP电话软件中,取得了预期的效果。     

TCP友好拥塞／速率控制算法及其在多媒体数据传输中的应用

基于Intenret的以UDP为传输协议的实时多媒体数据传输,需要在保证 实时性和可靠性基础上,能够与Internet其它服务所使用的TCP协议共享有限的带宽,基于这种需要,该文在研究了多种拥塞控制算法的基础上,提出了一种简单实用的TCP友好拥塞／速率控制算法,并将该算法应用在一个实用的Internet IP电话软FreePhone中,通过试验证明,该方法实用有效,并取得了预期的效果。     

基于Fuzzy丢包区分的TCP自适应拥塞控制算法

针对在有线/无线的异构网络中,传统有线环境下的传输控制协议(TCP)把所有丢包简单地归因于网络拥塞,严重影响了混合网络环境下的TCP传输性能的问题,提出了一种新的基于模糊理论的自适应控制算法。该算法选取了新的网络参数,运用Fuzzy方法对网络状态进行综合评价,并基于反馈理论的方法建立了新的自适应控制模型,即对评价结果集进行加权求和,得出网络性能指数,将其作为输入因子进入下一次计算过程,并调整各参数权重。仿真表明,该算法能够较好反映混合网络的真实拥塞状况,具有较好的网络适应性,比当前主要TCP算法具有更好的拥塞控制效果。该算法对在多参数,使用模糊方法背景下,混合网络拥塞及其自适应控制研究进行了新的探索。     

基于TCP的流量控制和拥塞控制分析

网络的信息流量协调与控制是Internet的QoS的重要内容,本文着重讨论了TCP/IP协议流量控制和拥塞控制的策略与算法,分析了在具体的网络传输中重传时间的确定,并对基于TCP的流量和拥塞控制策略进行了对比性探讨.     

有线无线网络TCP友好流媒体拥塞控制机制

在TCP友好拥塞控制方法比较基础上,为了实现流媒体平滑传输以及保证TCP流友好性,提出了TCP友好速率控制算法WTFCC。该算法能够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。仿真实验结果表明,该机制对TCP流是友好的,并且保障了媒体播放质量,在有线无线混和网络中具有很好的性能。     

基于模糊RED算法的IP拥塞控制机制

TCP／IP拥塞控制不能有效地支持Internet多媒体业务，模糊逻辑提供了解决复杂性、动态性和健壮性问题的一种非解析方法，文章基于模糊RED算法和区分服务提出了新的IP拥塞控制机制。与丢尾算法和普通RED算法相比，在保证QoS的同时，该算法不仅改善了TCP的吞吐量，而且使流量抖动较平缓，并克服了区分服务对连接公平性差的缺点。     

视频通信的网络自适应传输控制技术

针对视频传输中的拥塞控制问题，对网络自适应传输控制技术进行了研究，该技术综合了UDP与TCP的传输特性，能够对网络拥塞进行自适应控制。提出了该技术的技术框架和实现方案，并将其应用在一个端到端的视频传输系统中。实验结果表明，网络自适应传输控制技术可以为视频通信提供良好的传输质量保障。     

一种基于Bloom filter的加强队列公平性改进算法*

随着Internet基于非TCP的应用不断涌现,基于异质流网络拥塞控制公平性研究越来越重要。针对流与流之间传输的公平性问题,基于BLUE算法,结合Bloom filter,提出了一种改进的AQM算法EFBLUE。通过仿真实验对新算法从分组丢失率、吞吐量、延时等方面的性能进行了测试并与RED算法进行了性能对比。NS2仿真实验结果表明,该算法只需使用极少量的状态位和很小的缓存空间就能较好地鉴别出非响应流,并限制其速率,保护TCP流免受非响应流影响,实现了流量传输的公平性。最后对EFBLUE的性能优化问题作了进一步的分析。     

基于双重AIMD的TCP拥塞控制

简要地介绍了AIMD(a,b)算法，提出了一种基于双重AIMD的TCP拥塞控制机制(简称D_AIMD)．D-AIMD仍基于AIMD(a，b)算法，但在一个连接的通信过程中a，b并不惟一．其基本思想是将较大a，b下的拥塞控制机制用于系统稳态，将较小a，b下的拥塞控制机制用于系统稳态．理论分析和仿真验证表明，D_AIMD具有如下特点：①实现简单，系统额外开销小；②系统哲态时，应用能快速地使用网络中的有用资源，网络拥塞程度加重时，又能快速减轻网络拥塞；③系统稳态时，数据发送速率波动性小，提高了资源利用率；④可以与TCP之间实现网络资源的公平竞争．     

TCP Vegas拥塞避免机制的改进算法

TCP Vegas协议在许多方面的性能都比传统TCP协议优越,但是研究表明TCP Vegas在拥塞避免机制上存在一些问题,包括与New Reno竞争时性能较差,对先前的连接不公平等问题。针对上述问题提出了一种改进的拥塞避免算法——TCP Vegas-W。该算法不依赖于路由器端的缓冲队列管理,可以在端节点单独运行。仿真实验结果表明,改进的算法在有线网络中能获得更好的性能,对解决上述Vegas存在的问题达到了良好的效果。     

LIAD: Adaptive bandwidth prediction based Logarithmic Increase Adaptive Decrease for TCP congestion control in heterogeneous wireless networks

For accessing plentiful resources in the Internet through wireless mobile hosts, diverse wireless network standards and technologies have been developed and progressed significantly. The most successful examples include IEEE 802.11 WiFi for wireless networks and 3G/HSDPA/HSUPA for cellular communications. All IP-based applications are the primary motivations to make these networks successful. In TCP/IP transmissions, the TCP congestion control operates well in the wired network, but it is difficult to determine an accurate congestion window in a heterogeneous wireless network that consists of the wired Internet and various types of wireless networks. The primary reason is that TCP connections are impacted by not only networks congestion but also error wireless links. This paper thus proposes a novel adaptive window congestion control (namely Logarithmic Increase Adaptive Decrease, LIAD) for TCP connections in heterogeneous wireless networks. The proposed RTT-based LIAD has the capability to increase throughput while achieving competitive fairness among connections with the same TCP congestion mechanism and supporting friendliness among connections with different TCP congestion control mechanisms. In the Congestion Avoidance (CA) phase, an optimal shrink factor is first proposed for Adaptive Decreasing cwnd rather than a static decreasing mechanism used by most approaches. Second, we adopt a Logarithmic Increase algorithm to increase cwnd while receiving each ACK after causing three duplicate ACKs. The analyses of congestion window and throughput under different packet loss rate are analyzed. Furthermore, the state transition diagram of LIAD is detailed. Numerical results demonstrate that the proposed LIAD outperforms other approaches in goodput, fairness, and friendliness under diverse heterogeneous wireless topologies. Especially, in the case of 10% packet loss rate in wireless links, the proposed approach increases goodput up to 156% and 1136% as compared with LogWestwood+ and NewReno, respectively.     

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.     

一种改进的TCP拥塞控制算法

目前，TCP拥塞控制算法作为一种可靠的数据传输被广泛应用在因特网中．在保证网络数据传输可靠性的基础上，数据流之间的公平性是算法设计的重要的性能指标之一．在单瓶颈网络环境下对TCP数据流之间的研究算法已经被提出，但对多瓶颈网络环境下TCP数据流之间的公平性研究至今不多见．因此，根据网络层的显示拥塞指示Marking Relay ECN（explicit congestion notification，ECN）技术，研究了在多瓶颈网络环境下TCP数据流的公平性，提出了一种改进的TCP拥塞控制算法，并使该算法在IP网络中得以实现．仿真结果证明，此算法在多瓶颈网络环境下能使TCP流达到较好的数据流之间的公平性；而且所提出的算法与传统的TCP算法相比，有更高的吞吐量和更快的响应．总之，所提算法性能表现良好．     

TCP／IP拥塞控制研究

综述了Internet上TCP／IP拥塞控制研究方面一些最新的工作,分析了拥塞控制的原理、TCP／IP拥塞控制所使用的典型技术,并着重论述了TCP／IP拥塞控制所面临的问题,这包括自相似性问题、效率问题、公平性问题、算法改进、区分服务和多点广播中拥塞控制和TCP／IP在特殊网络（ATM网和卫星网）上拥塞控制等问题,并提出了其进一步的研究方向。     

基于差分服务的贪婪流问题解决算法

贪婪流问题是网络拥塞控制范畴的问题，泛指不遵从标准TCP拥塞控制机制的流。贪婪流给网络带来不公平性。提出了一种新的甄别算法，通过对目标流发送窗口随分组丢弃变化关系的分析，对不合规范的流进行检测。算法采用定长列表结构，具有实现简单、扩展性强的特点，提出了一种基于差分服务模式的体系结构，对传统Internet服务哲学进行了扩展，从根本上支持新型流式应用，实现了端到端的流量监管功能。     

TCP拥塞控制机制定量性能分析

TCP协议承载着因特网超过70%的传输流量,其拥塞控制机制可以有效地改善网络拥塞现象。剖析了慢启动、拥塞避免、快速重传、快速恢复等拥塞控制机制,研究了Tahoe、Reno、NewReno和SACK等几种常见的TCP拥塞控制算法。借助于网络模拟器NS2对这几种算法的性能进行了定量分析。结果证明:相对于Tahoe、Reno拥塞控制算法而言,NewReno和SACK TCP可以更快、更平滑地摆脱网络拥塞恢复到正常工作状态。     

TCP is Competitive with Resource Augmentation

The well-known Transport Control Protocol (TCP) is a crucial component of the TCP/IP architecture on which the Internet is built, and is a de facto standard for reliable communication on the Internet. At the heart of the TCP protocol is its congestion control algorithm. While most practitioners believe that the TCP congestion control algorithm performs very well, a complete analysis of the congestion control algorithm is yet to be done. A lot of effort has, therefore, gone into the evaluation of different performance metrics like throughput and average latency under TCP. In this paper, we approach the problem from a different perspective and use the competitive analysis framework to provide some answers to the question “how good is the TCP/IP congestion control algorithm?” We describe how the TCP congestion control algorithm can be viewed as an online, distributed scheduling algorithm. We observe that existing lower bounds for non-clairvoyant scheduling algorithms imply that no online, distributed, non-clairvoyant algorithm can be competitive with an optimal offline algorithm if both algorithms were given the same resources. Therefore, in order to evaluate TCP using competitive analysis, we must limit the power of the adversary, or equivalently, allow TCP to have extra resources compared to an optimal, offline algorithm for the same problem. In this paper, we show that TCP is competitive to an optimal, offline algorithm provided the former is given more resources. Specifically, we prove first that for networks with a single bottleneck (or point of congestion), TCP is ${\mathcal{O}}(1)The well-known Transport Control Protocol (TCP) is a crucial component of the TCP/IP architecture on which the Internet is built, and is a de facto standard for reliable communication on the Internet. At the heart of the TCP protocol is its congestion control algorithm. While most practitioners believe that the TCP congestion control algorithm performs very well, a complete analysis of the congestion control algorithm is yet to be done. A lot of effort has, therefore, gone into the evaluation of different performance metrics like throughput and average latency under TCP. In this paper, we approach the problem from a different perspective and use the competitive analysis framework to provide some answers to the question “how good is the TCP/IP congestion control algorithm?” We describe how the TCP congestion control algorithm can be viewed as an online, distributed scheduling algorithm. We observe that existing lower bounds for non-clairvoyant scheduling algorithms imply that no online, distributed, non-clairvoyant algorithm can be competitive with an optimal offline algorithm if both algorithms were given the same resources. Therefore, in order to evaluate TCP using competitive analysis, we must limit the power of the adversary, or equivalently, allow TCP to have extra resources compared to an optimal, offline algorithm for the same problem. In this paper, we show that TCP is competitive to an optimal, offline algorithm provided the former is given more resources. Specifically, we prove first that for networks with a single bottleneck (or point of congestion), TCP is O(1){\mathcal{O}}(1)-competitive to an optimal centralized (global) algorithm in minimizing the user-perceived latency or flow time of the sessions, provided we allow TCP O(1){\mathcal{O}}(1) times as much bandwidth and O(1){\mathcal{O}}(1) extra time per session. Second, we show that TCP is fair by proving that the bandwidths allocated to sessions quickly converge to fair sharing of network bandwidth.     

一种分阶段自适应RED／ECN参数模型

TCP拥塞控制技术是IP网络性能的研究重点之一,目前已经出现了多种改进方案,然而采用这些方案后,TCP连接仍然面临大量的包丢失,尤其是在网络拥塞时。为此IETF提出了IP网络的拥塞控制问题并建议在网络中采用主动队列管理机制。RED／ECN算法是一种主动队列管理算法,它具有很多优点,但算法对其静态参数的依赖性很大,没有充分考虑链路中复用的活动连接数,因而不能很好地适应网络负荷的变化。为此,提出了一种分阶段动态调整RED／ECN算法参数的模型（GARED）,通过仿真实验说明该模型改进了RED／ECN算法的性能,能够有效地降低丢包率,保证网络链路的高利用率。