Tracker中一种具有拓扑意识的结点选择算法(TAPS)

BitTorrent系统是当前最流行的P2P文件共享系统,但因其Tracker采用随机的结点选择算法从而造成了大量的冗余网络流量。文章提出一种基于拓扑意识的结点选择算法TAPS,根据网络拓扑信息进行结点选择。经过仿真实验证明,TAPS(10,40,∞)在保证BitTorrent应用性能的前提下极大地减少了骨干网流量和网络负载。     

基于涌现视角的类BitTorrent性能分析模型

BitTorrent作为一种典型的实际P2P系统,在理论和实践中引起了广泛关注.给出一个有效的类BitTorrent系统分析模型一直是人们努力的一个方向.本文基于系统科学中的涌现概念,从微观到宏观来研究BitTorrent系统,给出了BitTorrent系统的微-宏观分析模型.首先从相对清晰的系统微观(结点)状态和行为入手,选取表征BitTorrent结点的参数,称为微观参数;根据BitTorrent的结点行为,基于这些微观参数,给出系统的微观行为描述;选取表征BitTorrent宏观态的变量,称为宏观变量;然后依据宏观变量与微观变量的关系,基于微观行为描述,建立系统的宏观演化方程;进而研究系统的宏观特性.实验表明该模型能够有效刻画BitTorrent系统的行为.     

BitTorrent系统节点行为研究

测量分析P2P文件共享系统是解决P2P优化、网络管理等问题的基础。当前P2P网络设计日趋复杂,并且部分运行机制直接导致测量数据不完整或测量周期过长,比如BitTorrent文件共享系统。针对这一问题,本文抽象出BitTorrent系统的3个测量层次,包括索引测量、节点测量和内容测量,并重点解决了3个层次中的测量难题,设计实现了一个面向BitTorrent的测量系统。在此基础上,本文对BitTorrent系统进行了持续测量,并重点分析了BitTorrent系统的节点行为:节点演化规律和节点到达模型。测量结果表明,节点演化规律和节点到达均呈现强烈的周期性。为此,本文改进了节点到达模型,新模型与实际测量数据拟合效果较好,进一步修正了节点到达模型。     

BitTorrent在嵌入式系统中的应用

开发具有低功耗、微内核、体积小,并且具有下载功能的嵌入式系统,是非常具有商业价值的。BitTorrent系统是P2P文件共享技术中应用较为广泛的一种,本文在分析通用的BitTorrent软件基础上,给出一种适合嵌入式系统的BitTorrent下载模型,并通过编码在嵌入式Linux之上实现了稳定快速的下载。     

一种基于网络编码的NC-BT文件共享系统设计与实现

为了克服目前流行BitTorrent系统工作中存在的文件分块调度算法复杂、文件下载稳定性等问题,提出在BitTorrent系统中采用网络编码技术解决这些问题的思路,设计并实现了基于网络编码的NC-BT系统.在实际网络环境中对该系统进行测试和分析,实验结果证明使用网络编码技术方案能够有效解决现有BitTorrent中存在的问题,从而增强系统的鲁棒性,降低系统调度算法复杂性等优点.     

层次化片上网络结构的簇生成算法

半导体工艺的发展及嵌入式电子产品复杂度的不断增长,系统芯片互连结构的吞吐量、功耗、信号完整性、延迟以及时钟同步等问题更加复杂.基于总线的片上通信结构不足以提供良好的通信能力,出现了以片上网络为核心的通信结构.本文提出了层次化片上网络设计中,根据实现工艺和应用需求,进行层次划分的簇生成算法.实验表明,通过使用该算法,能够有效的分配系统芯片的内部通信,提高系统性能,降低硬件实现开销,同时满足一定的服务质量需求.     

基于系统平均性能增益最大化的基站群协同分簇方案

提出了一种基于系统平均性能增益最大化的协同基站群分簇方案.首先,由基站间协同的信干比增益的概率分布得出基站间协同的平均信干比增益;然后,以系统平均性能增益最大化为标准生成簇结构.该方案在保证系统性能的同时降低了CSI失真对分簇带来的影响,且降低了系统开销.仿真结果表明,当信道变化因子和失真因子均为0.3时,该方案和现有利益树分簇方案相比,系统平均性能增益最大可提高0.7bit/s/Hz/cell.     

一种基于阈值的无线异构网络基站分簇方法

为抑制小区间干扰,提高系统性能,研究了异构网络中的基站分簇问题,提出了一种基于阈值的协作基站分簇方法.该方法在异构组网场景下,以最大化接收端传输速率为目标,通过选择满足设定阈值的基站进行协作,考虑了用户所属基站信号强度和非所属基站的干扰情况,分析了不同分簇方法下的用户传输速率变化情况.仿真结果表明,所提算法在系统传输速率性能方面优于现有方法.     

成簇阶段恶意节点识别与剔除模型研究及实现

无线传感器网络节点成簇是实现对传感器网络高效节能管理和应用的有效途径.网络安全问题中恶意节点尤为突出,它们破坏网络系统的正常工作规则,影响网络的工作效率和整体存活寿命.为了提高网络的整体性能,希望能在网络成簇阶段及时将破坏作用的恶意节点识别出来并别除.采用LEACH层次化网络通信思路,应用一种基于LEACH算法的密钥预...     

一种基于应用层特征的BitTorrent流量测量系统的实现

以BitTorrent为代表的对等网络(P2P)应用已经成为最流行的网络信息共享工具,测量与分析对等网络的流量特性对于认识和提升该网络的性能具有重要的意义,如何准确地在Internet流量中识别出BT流量成为此研究的关键问题。在对BitTorrent的流量识别分析过程中,就基于应用层特征的流量识别方法进行了研究,并采用VC 工具在WinPcap网络工具包的基础上,实现了BT流量的测量系统,并根据实验结果验证了此系统的有效性。     

A performance study of BitTorrent-like peer-to-peer systems

This paper presents a performance study of BitTorrent-like P2P systems by modeling, based on extensive measurements and trace analysis. Existing studies on BitTorrent systems are single-torrent based and usually assume the process of request arrivals to a torrent is Poisson-like. However, in reality, most BitTorrent peers participate in multiple torrents and file popularity changes over time. Our study of representative BitTorrent traffic provides insights into the evolution of single-torrent systems and several new findings regarding the limitations of BitTorrent systems: (1) Due to the exponentially decreasing peer arrival rate in a torrent, the service availability of the corresponding file becomes poor quickly, and eventually it is hard to locate and download this file. (2) Client performance in the BitTorrent-like system is unstable, and fluctuates significantly with the changes of the number of online peers. (3) Existing systems could provide unfair services to peers, where a peer with a higher downloading speed tends to download more and upload less. Motivated by the analysis and modeling results, we have further proposed a graph based model to study interactions among multiple torrents. Our model quantitatively demonstrates that inter-torrent collaboration is much more effective than stimulating seeds to serve longer for addressing the service unavailability in BitTorrent systems. An architecture for inter-torrent collaboration under an exchange based instant incentive mechanism is also discussed and evaluated by simulations     

The Design Trade-Offs of BitTorrent-Like File Sharing Protocols

The BitTorrent (BT) file sharing protocol is very popular due to its scalability property and the built-in incentive mechanism to reduce free-riding. However, in designing such P2P file sharing protocols, there is a fundamental trade-off between keeping fairness and providing good performance. In particular, the system can either keep peers (especially those resourceful ones) in the system for as long as possible so as to help the system to achieve better performance, or allow more resourceful peers to finish their download as quickly as possible so as to achieve fairness. The current BT protocol represents only one possible implementation in this whole design space. The objective of this paper is to characterize the design space of BT-like protocols. The rationale for considering fairness in the P2P file sharing context is to use it as a measure of willingness to provide service. We show that there is a wide range of design choices, ranging from optimizing the performance of file download time, to optimizing the overall fairness measure. More importantly, we show that there is a simple and easily implementable design knob so that the system can operate at a particular point in the design space. We also discuss different algorithms, ranging from centralized to distributed, in realizing the design knob. Performance evaluations are carried out, both via simulation and network measurement, to quantify the merits and properties of the BT-like file sharing protocols.     

Performance comparison of scheduling algorithms for peer-to-peer collaborative file distribution

Peer-to-Peer file sharing applications in the Internet, such as BitTorrent, Gnutella, etc., have been immensely popular. Prior research mainly focuses on peer and content discovery, overlay topology formation, fairness and incentive issues, etc. However, little attention has been paid to investigate the data distribution problem which is also a core component of any file sharing application. In this paper, we present the first effort in addressing this collaborative file distribution problem and formally define the scheduling problem in a simplified context. We develop several algorithms to solve the problem and study their performance. We deduce a theoretical bound on the minimum download time experienced by users and also perform simulations to evaluate our algorithms. Simulation results show that our graph-based dynamically weighted maximum-flow algorithm outperforms all other algorithms. Therefore, we believe our algorithm is a promising solution to be employed as the core scheduling module in P2P file sharing applications     

On the Efficiency of Peer-to-Peer File Sharing

In Peer-to-Peer (P2P) file sharing networks, the average download time is determined by how efficiently the upload bandwidth of each peer can be utilized. In this paper, we will first propose a stochastic model for P2P file sharing networks. By numerically solving the proposed model, we will be able to gain interesting insight on how the performance of a P2P file sharing network is affected by different parameters such as the piece numbers of the file, the number of neighbors of a peer, and the seed departure rate etc. We will also validate the stochastic model through simulations and provide some useful guidelines on how to design an efficient P2P system based on our results.     

ISEFF: An ID-Based Scalable and EFficient Distributed File Sharing Technique in Vehicular Ad Hoc Networks

Using new wireless capabilities in vehicles, various applications have appeared in Vehicular Ad Hoc Networks (VANETs). Multimedia data sharing is one of these applications, which has recently been given so much attention. Most of presented schemes in this field have focused on direct opportunistic meetings between vehicles or request/response broadcast in the whole network, which are inefficient and un-scalable due to VANET characteristics. In this paper, we propose an ID-based Scalable and EFficient distributed File sharing technique that increases efficiency and scalability via taking advantages of BitTorrent protocol and consistent hashing technique. The results of simulations show that our approach increases the received file ratio, reduces total download time of files and message overhead. Consequently, it can enhance efficiency and performance.     

A study of an hybrid CDN–P2P system over the PlanetLab network

In this work we propose an hybrid CDN–P2P architecture for video contents delivery based on the NextShare platform. Experiments were conducted over the PlanetLab network using a number of peers which encompass real network behaviors. Results show that although the NextShare is based on the original BitTorrent file sharing mechanism, the implemented tools can efficiently deliver video over a heterogeneous and time varying network if peers can rely on an intermediate distribution layer between the CDN and the final users. Among the other benefits, CDN edge servers are significantly offloaded and peers can experience low start-up delays. Architecture design and simulation results are taking place in the context of the European FP7 project COAST.     

基于XML/Web Services的P2P文件共享系统的实现

联网计算机之间没有主次之分,各自具有独立的网络自主权,端到端(Peer-to-Peer,P2P)模型能有效地实现计算能力和数字资源的共享和整合.本文介绍一个采用端到端的,层次分布化模型的文件共享系统,定义了关键的系统场景,分析了利用XML/Web Services实现方法,并给出了一个P2P设计模型.     

使用BT技术测试视频点播系统的可行性

使用BT技术测试视频点播系统的可实现性.由于BT是针对传输一般文件所设计,其片段选择(Piece Selection)方法并不适用于传输影音多媒体串流.利用原有BT的架构提出较适合的片断选择方法,使得文件下载完成前就可以实时播放,并且可以平顺且连续收看完影片,减少跳格机会的产生.另外由于设计上不会改动到BT的协议,可以兼容于现有的BT环境,即来源Peer使用的软件也可以是一般的BT软件.