构建Internet网络89TCP／IP协议简介

TCP/IP是一个允许不同软硬件结构计算机进行通信的协议族．Internet就是建立在TCP/IP协议之上的。一个协议族通常是由不同的层次所组成。对于TCP/IP协议来说，通常可分为四层如表1。     

大规模网络模拟的背景流量建模

大规模网络模拟的一个巨大挑战就是对计算资源的巨大需求,因此建立适合大规模网络模拟的背景流量模型具有十分重要的意义。本文提出的一种背景流量模型可实现3个目标:真实性、高效性和对网络动态的反馈性。该模型利用ON/OFF模型表达两种典型的应用(Web和P2P)的用户行为模型;在TCP层上采用fluid的抽象流量表示,以提高模拟效率;用微分方程表达拥塞避免行为,使得流量源具有对网络的响应能力。最后通过DaSSFNet建立了模型原型,通过实验模拟,该模型框架可以很好地表达自相似的流量特征,同时在模拟效率上也远远高于包级流量模型。因此,该模型适合作为大规模的网络模拟环境的背景流量发生器。     

提高无线网络TCP流量性能的方法

简述了目前无线网络中传输控制协议(TCP)的应用现状，探讨了三种改善TCP性能的基本解决方案：分离连接方法、端到端方法、链路层方法，并对每一轩方法的性能进行了比较分析，展望了基于无线链路的TCP将来的研究方向和发展趋势。     

自相似业务量的流量控制研究

由于自相似性是宽带网络中业务量的一个普遍特性,因此在进行宽带网络管理和流量控制时必须考虑它所带来的影响。目前,有关基于自相似业务量的流控机制的研究已经引起了人们广泛地注意。一些研究表明自相似业务量表现出了与传统模型不同的排队特征。本文围绕业务质量保证和流量控制机制。具体研究和分析了业务量的自相似性质对业务量成形、用法参数控制和呼收接纳控制等流量控制机制的影响,并得到了一些重要结论。     

改善无线自组织网络TCP性能的研究

本分析了在ad hoc网络中TCP协议的主要缺陷，并对目前提出的几种改进方案进行了比较分析，最后给出了结论和研究方向。     

面向网络空间靶场的网络行为模拟关键技术研究

在网络空间靶场中构建真实的网络场景,是开展科学研究以及网络攻防研究的基础条件,而在靶场环境下对真实的网络行为模拟,是构建网络场景的主要技术之一.本文针对网络靶场下,模拟真实网络流量的要求,提出了目标网络下多节点网络流量回放算法;针对群体用户的web行为无法直接获取和分析的问题,研究了基于网络流量内容的群体用户web行为...     

UDP流量对TCP往返延迟的影响

提出一个面向单条链路的TCP综合传输性能测度R,分析其与同一时间粒度内链路的占用带宽和UDP流量比例间的关系,使用中国和美国2条主干信道的实测数据进行了检验。结果表明R测度可表示为以占用带宽和UDP流量比例为参数的正态分布的随机过程。随后进行的CERNET链路R测度正态分布均值参数的拟合分析具有很高的可接受水平,拟合的结果给出的量化关系可用于流量的公平性评价。     

基于LFSN业务流量模型的网络拥塞控制算法

网络业务流的多分形本质可以用LFSN（线性分形稳定噪声）准确建模，文中提出了基于LFSN模型预测的网络拥塞控制算法并进行了仿真分析，结果表明该算法提高了网络链路吞吐量，减小了丢包率。     

基于格兰杰因果关系贝叶斯网络的大规模无线局域网流量预测方法

研究了大规模无线局域网内的流量特性,发现不同接入点间的流量存在格兰杰因果关系。流量的格兰杰因果关系说明,可以通过多个存在因果关系的接入点的历史流量,提高对目标接入点的当前流量预测的准确性。通过贝叶斯网络对存在因果关系的接入点流量进行建模,并利用多个接入点的历史流量对目标接入点的流量进行预测,提高了预测的准确性。最后,通过接入点数量大于 100 个的无线局域网的实际流量数据,验证了该方法的有效性及准确性,建立了一套完整的数据特征分析、建模及预测的流量数据处理流程。     

基于自相似业务的网络TCP拥塞控制算法

本文通过对自相似网络模型的分析,采用TCP协议可以直接观测的回环时间（Bound Trip Time)来进行拥塞程度预测,提出一种改进的TCP拥塞控制算法。仿真证明,改进算法在一定程度上提高了网络的整体性能,在自相似程度较高时尤为明显。     

Identifying online traffic based on property of TCP flow

Classification of network traffic using port-based or payload-based analysis is becoming increasingly difficult when many applications use dynamic port numbers, masquerading techniques, and encryption to avoid detection. In this article, an approach is presented for online traffic classification relying on the observation of the first n packets of a transmission control protocol (TCP) connection. Its key idea is to utilize the properties of the observed first ten packets of a TCP connection and Bayesian network method to build a classifier. This classifier can classify TCP flows dynamically as packets pass through it by deciding whether a TCP flow belongs to a given application. The experimental results show that the proposed approach performs well in online Internet traffic classification and that it is superior to naive Bayesian method.     

A cause of self‐similarity in TCP traffic

We analyse the statistical properties of aggregated traffic flows generated by TCP, in order to clarify a possible cause of self‐similarity in Internet traffic. Using ns‐2 simulation, we first show that aggregated traffic flows by TCP can be characterized by phase transition phenomena between non‐congested and congested phases in statistical physics. Interestingly, although the traffic exhibits self‐similarity with the Hurst parameter H ≈ 1.0 at the critical point between them, it is close to Poissonian away from the critical point. This result is consistent with results from real WAN traffic measurement. The main contribution of our work is to show that TCP itself contains a mechanism for generating self‐similarity, without assuming self‐similarity or long‐range dependency (LRD) in the application layer (e.g. packet inter‐arrival, connection arrival, and file size distribution). Moreover, we find that the value of the Hurst parameter at the critical point is determined by the simple feedback control called stop‐and‐wait flow control. Namely, it appears even without any packet retransmission events and is independent of the explicit rate increment algorithm such as slow‐start and congestion avoidance. Additionally, we demonstrate that the value of the Hurst parameter at the critical point depends on the constant bit rate algorithm and topology of network. Finally, we indicate that the time series of the round trip time follow the same statistics at the critical state. Copyright © 2005 John Wiley & Sons, Ltd.     

An energy‐aware transmission mechanism for WiFi‐based mobile devices handling upload TCP traffic

This paper presents an energy‐aware transmission mechanism that improves the throughput and reduces the energy consumption of mobile devices in wired‐cum‐wireless TCP networks. The proposed mechanism places an agent at the base station, which identifies the cause of packet losses in the underlying network. When the mobile device acts as a TCP source, it adjusts the size of the congestion window adaptively according to the cause of packet losses with the aids of the agent in order to improve the transmission performance. In addition, the proposed mechanism lets the communication device to stay in sleep mode after completing the transmission in order to reduce the energy consumption. As a result, the cooperation between the mobile device and the agent improves the transmission performance as well as the energy efficiency greatly. To evaluate the performance of the proposed mechanism, we analyzed the effect of TCP on the communication device for mobile devices and present a power model. With extensive simulations based on the power model, we demonstrate that the proposed mechanism significantly improves the transmission performance, and reduces the energy consumption over a wide range of both wired and wireless packet losses. Copyright © 2008 John Wiley & Sons, Ltd.     

一种网络流量平稳化方法

由于网络流量的不稳定性,会影响流量模型的准确性。平稳化的目的是使得流量成为平稳或更为接近平稳,以提高流量模型的准确性。差分是一种常用的平稳化方法,它对具有线性趋势的时间序列有很好的平稳化效果。本文提出一种统计分析的方法对流量进行平稳化处理,可以在一定程度上消除流量不稳定性对流量建模的影响。     

An empirical study on TCP flow interarrival time distribution for normal and anomalous traffic

In this paper, we study the effects of anomalies on the distribution of TCP flow interarrival time process. We show empirically that despite the variety of data networks in size, number of users, applications, and load, the interarrival times of normal flows comply with the Weibull distribution, whereas specific irregularities (anomalies) causes deviations from the distribution. We first estimate the scale and shape parameters and then check the discrepancy of the data from a Weibull distribution with the estimated parameters. We also utilize the Weibull counting model to recheck the conformance of small flow interarrival times with the distribution. We perform our experiments on a diverse variety of traffic data sets from backbone connections to endpoints of academic and commercial networks. Moreover, we propose a window‐based anomaly detection method as a possible application of our findings in which we first estimate the Weibull parameters of interarrival times in each window and then check the discrepancy of the data with a Weibull distribution with the estimated parameters and set an alarm whenever the difference is significant. We apply this method on one of our data sets and present the results to clarify the idea and show its capability in detecting volume anomalies. Copyright © 2014 John Wiley & Sons, Ltd.     

适合TCP的网络编码重传机制

通过理论分析,看出基于反馈的重传方法比定量重传的方法有更低的解码延迟。提出了一种新型的基于反馈的网络编码(FNC)重传机制,利用seen机制中的隐含信息来获取接收方解码所需的重传分组个数,并改变了编码规则使部分分组可以提前解码。该机制不仅可以处理有固定误码率的随机分组丢失,还可以有效地应对大量突发性分组丢失。仿真结果显示,该机制在高误码率下也能保持较高的吞吐量,且极大地减少了解码延迟,传输过程基本不受分组丢失的影响,有效地对拥塞控制协议隐藏了链路错误。算法简单有效,更适于在实际系统中应用。     

APS-FeW适用于无线网络的TCP增强方案

TCP的控制隐含了一个假设,即分组丢失都是由网络拥塞引起的,而这一点对于无线网络不成立.因此在无线情况下,会引入了冗余控制,使得传输性能下降.浮点窗口算法(FeW)通过限制TCP的分组注入量,减少冗余控制,在此基础上,提出了改进方案自适应包长算法(APS).仿真数据表明,基于FeW的APS算法(APS-FeW)比FeW算法提升了10%～25%的吞吐量.     

混合网络下的TCP拥塞控制跨层优化算法

针对混合网络中并行链路间TCP流的不公平性,提出一种新的算法.此算法利用跨层设计的思想,以传输层的数据重传率为参数来调整TCP流不公平性,也就是说MAC层上的竞争窗口将根据重传率的动态变化而改变,其目的在于抑制并行链路TCP流接入信道能力的不公平性.并且用仿真工具NS2进行仿真的结果表明,采用改进算法后的网络公平性指数比未改进前提高了17.9％.该算法能明显改善并行链路间TCP流的不公平性.     

基于FBM模型的自相似流量建模仿真

网络流量建模是网络规划与性能评价的重要基础,传统的业务模型大多基于泊松模型和马尔可夫排队模型,只具有短程相关性,随着网络业务的不断研究发现,实际网络业务流在很长的时间范围内都具有长程相关性,即一种自相似性。本文采用RMD算法和Fourier变换法对网络流量的自相似模型-FBM模型进行了建模及仿真研究,生成了所需的自相似流量序列。然后分别采用R/S法和方差时间图法对其进行自相似参数检测。结果验证了仿真算法所产生的序列存在着自相似性,并同时对RMD算法和Fourier变换法的优缺点进行了分析。