TCP Vegas-O:一种新的基于延迟估计的TCP Vegas改进算法

针对TCP Vegas会出现慢启动过早结束、拥塞窗口过小导致带宽利用率下降的问题,以及在与Reno等基于丢包来判断拥塞的算法竞争带宽时的公平性差等问题,文中分别就慢启动和拥塞避免阶段进行了相应的改进,最后将其结合.仿真结果表明,该算法对慢启动过早结束、带宽公平性等TCP Vegas协议的缺陷有了明显的改善,特别是在高带宽时延乘积网络中.     

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.     

基于显式速率的TCP友好的UDP拥塞控制策略

本文提出了一种基于显式速率的UDP拥塞控制策略：通过源端和网络中的路由器相互配合，使得实时UDP应用能够根据网络的反馈以瓶颈链路的公平带宽为速率发送数据。此种控制策略对TCP应用是友好的，并且提高了网络的吞吐量和利用率。仿真结果表明：基于显式速率的UDP拥塞控制策略与采用TFRC(TCP—Friendly Rate Control)的UDP拥塞控制策略相比，在吞吐量、TCP友好性等方面性能有较大提高。     

面向卫星网络的TCP传输性能的研究

卫星信道的长时延、高误码率、大延时带宽积等的特性使TCP协议的性能受到了很大的影响.为了提高卫星网络下TCP的性能,在不破坏TCP端到端语义的前提下,文中利用在异构网络的边界处设置具有传输控制功能的性能增强代理(Performance Enhancing Proxies,PEP)的理论模型,在SACK TCP协议下对该模型实现了一种卫星网络的拥塞控制和拥塞恢复策略.仿真实验表明,新模型能够充分利用卫星网络的带宽,达到获得最佳有效吞吐量的目的.     

核心网深度优化之TCP加速解决方案研究

随着4G网络的全面覆盖,移动应用伴随着4G大宽带高速率特点不断地在演变,移动网络上4G流量中75%以上使用的是TCP协议,而TCP协议最初是在有线网络环境下设计的,无线网络环境下非拥塞导致的丢包可能性要大得多,加上无线网络环境的小带宽,大时延,可移动性等特点,TCP协议在无线网络环境上的工作效率远不如有线网络,TCP协议对于无线网络的高延时和中/低带宽的情况存在优化的空间。     

一种基于带宽估计的战术互联网TCP改进机制

无线的战术互联网通常面临复杂的电磁环境,高误码率、终端的频繁移动等恶劣的通信环境使得针对有线网络设计的TCP协议传榆性能急剧下降.针对战术互联网提出了一种基于带宽估计的TCP改进机制,该机制利用TCP确认帧携带的数据包到达时间来估算带宽,并用动态的低通滤波器来平滑带宽的估计值.在此基础上用带宽的估计值更新拥塞窗口,避免在发生链路错误时启动拥塞控制机制,由此提高TCP在战术互联网中的性能.实验结果表明,该算法能减少链路差错对TCP性能带来的影响,提高TCP在战术互联网上的传输性能.     

XCP拥塞控制算法研究

随着网络的发展,网络拥塞问题越来越受到人们的重视.现在网络中普遍采用的TCP拥塞控制算法不能很好地解决网络的拥塞,尤其是在高带宽时延乘积的网络中.新出现的XCP协议是一个优秀的协议,它的拥塞控制能更好地适应未来网络环境,提供更高的效率和更好的公平性.     

基于带宽测量技术的TCP拥塞窗口在线学习方法

为了改进传输层协议提高吞吐量,本文提出了一种基于ACK时间间隔的在线学习方法（TCP-Learning）,该方法采用可用带宽测量技术,快速学习网络链路中可用剩余带宽并能够迅速调整TCP拥塞窗口。仿真结果表明,在链路处于良好状态下,TCP-Learning吞吐量略优于Reno和Vegas等传统拥塞控制算法,但在链路较差情况下,TCP-Learning吞吐量明显优于Reno和Vegas等传统拥塞控制算法。     

网格计算中的TCP拥塞控制

目前IP网络所应用的TCP拥塞控制机制是基于1988年Jacobson所设计的算法(慢启动和拥塞避免),虽然TCP在许多不同类型的网络中应用得很好,但在网格计算中,现有的TCP拥塞控制算法已不能有效工作。本文分析了TCP传统算法在网格计算中的缺陷,并提出在网格计算中使用新的TCP拥塞控制算法——一个新的带宽增减算法。     

MPLS网络主动式流量和拥塞控制机制及性能分析

MPLS是具有大带宽一时延迟的网络,用传统的TCP解决MPLS拥塞问题显得十分困难,该文结合MPLS的网络特点,提出了一种适合MPLS网络的主动式流量和拥塞控制机制,在网络边缘节点引入拥塞反馈处理,对实验模型进行了性能仿真分析,实验证明,与传统的TCP协议相比,该机制将流量和拥塞控制从用户端点扩展到MPLS边缘路由器,能够更及时地检测和控制网络拥塞,缩短了控制时延,可以进行较精确的流量调节,实现了提高吞吐量和改善缓冲区利用率的目的。     

TFRC friendliness and the case of ECN

The TFRC protocol has been proposed as a TCP‐friendly protocol to transport streaming media over the Internet. However, its deployment is still questionable because it has not been compared to other important protocols, analysed in the presence of important mechanisms, such as the explicit congestion notification (ECN), and studied under more realistic network conditions. In this paper, we address these three aspects, including other congestion control protocols not considered before in the same investigation, such as TCP Tahoe, Reno, Newreno, Vegas, Sack, GAIMD, and the Binomial algorithms, the effect of using ECN in the friendliness of the protocols, and the fairness of the protocols under static and dynamic network conditions. We found that TFRC can be safely deployed in the Internet if competing with TCP Tahoe, New Reno and SACK since fairness is achieved under all scenarios considered. We also found that ECN actually helps in achieving better fairness. However, fairness problems arise when TFRC competes with TCP Reno, GAIMD, SQRT or IIAD in static or dynamic conditions, or both. We used normalized throughput, fairness index, and convergence time as the main performance metrics for comparison. Copyright © 2004 John Wiley & Sons, Ltd.     

TCP拥塞控制研究综述

系统深入地研究了TCP协议中的拥塞控制机制,TCP改进协议中研究最多的就是对TCP拥塞窗口调节机制的改进.从这个方面来看主要可以分为三种改进类型,即基于分组丢弃反馈的拥塞窗口调节方式;基于路径延时反馈的拥塞窗口调节方式;基于显式反馈和带宽测量的拥塞窗口调节方式.另外还针对无线网络的固有特性讨论了无线网络上TCP协议的一些改进方案.深入地分析了一些典型的算法,对它们的优劣做了详细的分析和总结,并提出了今后的一些研究方向.     

Performance evaluation of HTTP/TCP on asymmetric networks

As the number of Internet users grows, new network technologies are emerging. Those include ADSL and cable modem, which essentially provide asymmetric bandwidth for uplink and downlink to the user's connection. In this paper, we investigate the behaviour of HTTP/TCP protocols on such asymmetric networks, and present the analytic results of the mean throughput of TCP. The transfer time of Web documents by HTTP over TCP is also derived. In the analysis, we consider newer HTTP/TCP protocols, HTTP/1.1 and TCP Vegas, in addition to HTTP/1.0 and TCP Tahoe. We then investigate the appropriate combination of HTTP and TCP protocols on the asymmetric network. The results show that the effect of HTTP/1.1 is quite small, but TCP Vegas can improve the performance in asymmetric networks if it is appropriately modified as in our proposal. Copyright © 1999 John Wiley & Sons, Ltd.     

一种基于协议重构的内外网逻辑隔离方法

提出了一种基于协议重构的内外网逻辑隔离新方法,通过重构现有公共通信协议,形成专有协议,实现内网专有用户与公共用户隔离。在内网中,公共用户能访问外网,而专有用户与外网“逻辑隔离”。相对于物理隔离方法,这种方法在保证内网安全性能的前提下,满足了内网用户对外信息的需求,提高了信息交流的灵活度;相对于传统协议隔离方法,这种方法投入小、技术风险低,实用性更强。     

Modbus/TCP协议在远程数据处理中的应用

文中进行了基于Modbus协议和TCP/IP协议的远程数据通讯的实践和研究。运用Matlab软件编程,使得运行Matlab软件的主机可以通过网络,远程获得遵循Modbus/TCP协议的数据,并在由施耐德PLC等组成的电力系统参数检测机构中实现了网络通信。该研究为之后的远程故障数据获取和诊断打下了基础。     

考虑慢启动影响的TCP吞吐量模型

TCP吞吐量模型的研究是网络协议研究的一个重要方面,同一些其它模型相比,Padhye提出的TCP吞吐量模型比较精确地描述了TCP吞吐量与往返时间、丢包率和超时时限的关系,但在丢包率很高的场合,Padhye模型误差较大,本文分析了高网络负荷下TCP传输的性能,提出了一个高网络负荷下TCP吞吐量的改进Padhye模型,实验表明,该模型在高网络负荷环境下更接近实际情况.     

WLAN技术对传输层性能的影响

IEEE802.11系列标准被用于支持无线局域网(WLAN)中的数据传输,而在其上层工作的传输控制协议(TCP)还是为传统有线网络传输设计的,所以TCP的性能必然会受到影响。文章首先详细阐述了在WLAN基础工作模式下的各种因素对TCP性能的影响,然后简要介绍了基于不同设计思路的改善TCP性能的方案,最后提出了一种可应用于WLAN的综合改进方案。     

基于CBR与TCP移动白组网路由协议分析

移动自组网是由无线移动主机组成的没有基础设施或集中管理中心的临时性网络。在其组建应用过程中,路由协议起着重要的作用。文中基于仿真软件NS2对移动自组网三种典型路由协议DSDV、DSR、TORA在TCP与CBR业务下的性能进行了比较分析。仿真结果表明,在发送速率144kb／s时,DSR与DSDV性能优于TORA,且TCP业务性能优于CBR业务。     

Transport layer protocols and architectures for satellite networks

Designing efficient transmission mechanisms for advanced satellite networks is a demanding task, requiring the definition and the implementation of protocols and architectures well suited to this challenging environment. In particular, transport protocols performance over satellite networks is impaired by the characteristics of the satellite radio link, specifically by the long propagation delay and the possible presence of segment losses due to physical channel errors. The level of impact on performance depends upon the link design (type of constellation, link margin, coding and modulation) and operational conditions (link obstructions, terminal mobility, weather conditions, etc.). To address these critical aspects a number of possible solutions have been presented in the literature, ranging from limited modifications of standard protocols (e.g. TCP, transmission control protocol) to completely alternative protocol and network architectures. However, despite the great number of different proposals (or perhaps also because of it), the general framework appears quite fragmented and there is a compelling need of an integration of the research competences and efforts. This is actually the intent of the transport protocols research line within the European SatNEx (Satellite Network of Excellence) project. Stemming from the authors' work on this project, this paper aims to provide the reader with an updated overview of all the possible approaches that can be pursued to overcome the limitations of current transport protocols and architectures, when applied to satellite communications. In the paper the possible solutions are classified in the following categories: optimization of TCP interactions with lower layers, TCP enhancements, performance enhancement proxies (PEP) and delay tolerant networks (DTN). Advantages and disadvantages of the different approaches, as well as their interactions, are investigated and discussed, taking into account performance improvement, complexity, and compliance to the standard semantics. From this analysis, it emerges that DTN architectures could integrate some of the most efficient solutions from the other categories, by inserting them in a new rigorous framework. These innovative architectures therefore may represent a promising solution for solving some of the important problems posed at the transport layer by satellite networks, at least in a medium‐to‐long‐term perspective. Copyright © 2006 John Wiley & Sons, Ltd.     

A Dynamic Adaptive Layered Multicast Congestion Control Mechanism

To solve the problem that most of existing layered multicast protocols cannot adapt todynamic network conditions because their layers are coarsely granulated and static,a new congestioncontrol mechanism for dynamic adaptive layered multicast(DALM) is presented.In this mechanism,anovel feedback aggregating algorithm is put forward,which can dynamically determine the number oflayers and the rate of each layer,and can efficiently improve network bandwidth utilization ratio.Additionally,because all layers is transmitted in only one group,the intricate and time-consuminginternet group management protocol(IGMP) operations,caused by receiver joining a new layer orleaving the topmost subscribed layer,are thoroughly eliminated.And this mechanism also avoids otherproblems resulted from multiple groups.Simulation results show that DALM is adaptive and TCPfriendly.