【作者】 马凌霄；

【导师】 董金祥； 尹建伟；

【作者基本信息】 浙江大学 ， 软件工程， 2005， 硕士

【摘要】 近年来，Internet上的流媒体应用得到了迅猛的发展，然而媒体的质量并不能然人满意，主要原因在于Internet的原始设计主要是为了满足端对端系统的需求，传统的基于单播的传输方式很容易导致服务器端的性能瓶颈，并不能有效的支持流媒体的大规模数据分发。因此，研究人员提出了IP组播技术：在网络层提供把数据包发送到共享相同IP地址的一个主机组的服务，然而IP组播技术有其自身固有的限制而难以部署，主要包括协议本身的复杂性、网络异构性、以及缺少支持组播的可靠的、具有扩展性的拥塞控制机制等。因此尽管IP组播技术已经存在了数十年，仍然没有大规模的商业应用。 为了提高Internet上的流媒体的QoS，研究人员提出了基于P2P网络的媒体分发技术：P2PStreaming技术，即把组播的功能从网络层移到了应用层。本文首先介绍了P2PStreaming的技术框架，并对P2PStreaming的典型模型进行了分析，可以发现，不同的模型都是试图在网络带宽效率(bandwidth efficiency)、延时(delay)和可靠性(reliability)之间做出某种权衡。 本文提出了一新的模型CoopStreaming(Cooperative Streaming)，该模型融合了P2P技术和C／S技术的优点。可以在网络带宽效率、延时和可靠性三者之间做出更好的权衡。CoopStreaming通过C／S的方式组织节点而通过P2P的方式分发数据，其主要特点为：1)易于实现，节点通过服务器集中管理，无需构造和维护复杂的组播树，也不需要部署复杂的P2P组通讯协议。2)健壮性(robust)，节点不依赖于任何其它特定的节点。3)扩展性(scalability)，通过P2P的方式分发数据，用户越多，分发越快。4)带宽适应性(heterogeneity adaptive)，通过部署FGS，用户可以根据带宽情况控制自己的QoS。 此外，文章还对不同的P2PStreaming模型进行了抽象，提出了一个分层可扩展的P2PSteaming的设计框架，讨论了一些P2PStreaming设计与实现方面的问题。更多还原

【Abstract】 Multimedia streaming over the Internet is booming nowadays. However, the streaming quality is generally unsatisfactory. For large-scalable broadcasting, the traditional internet model of point-to-point unicast communication does not scale, So, the networking research community proposed IP multicast, a network layer service that allows a single source to distribute a data stream to many simultaneous receivers in an efficient manner. However, this network layer approach has met with limited success due to a number of factors including complexity of network protocol itself, its inability to address Internet heterogeneity, and its lack of support for efficient and scalable transport protocol s for reliability and congestion control. As a result, in spite of a decade of existence, the multicast protocol architecture remains just a research commodity with limited penetration into commercially deployed Internet.In order to improve the QoS of Streaming over the Internet, media over P2P network is proposed. First, we gave an overview of the P2PStreaming technical framework and summarized several classical models about media streaming on.P2P networks. Previous works have all demonstrated that there is always a tradeoff among bandwidth efficiency, delay and reliability.This paper presents a new P2PStreaming model: CoopStreaming (Cooperative Streaming), CoopStreaming tries to achieve a better trade-off, by leveraging the advances in both P2P and C/S. The core operations in CoopStreaming are very simple: every node periodically exchanges data availability information with a set of partners, and retrieves unavailable data from one or more partners, or supplies available data to partners. We emphasize four salient features of CoopStreaming: 1) easy to implement, as it does not have to construct and maintain a complex application multicast tree, it also does not have to deploy complex group management protocol, peers are managed by a central server; 2) robust and resilient, as the partnerships enable adaptive and quick switching among multi-suppliers; 3) scalability, as media data distributed in a P2P manner, more users, more quickly; and 4) heterogeneity adaptive, as deployed the fine granularity scalable coding (FGS).We also proposed a layer scalable framework for P2PStreaming to address some design and implementation issues.更多还原