【作者】 罗辉琼；

【导师】 聂瑞华；

【作者基本信息】 华南师范大学 ， 计算机软件与理论， 2007， 硕士

【摘要】 在Internet上提供大规模的VoD(Video on Demand)服务是一项具有挑战性的工作。传统的视频流播放方式是基于Client／Server(C／S)集中式网络模式，面临网络带宽受限的问题，表现在媒体服务器负担过重，支持客户数目有限，节目播放效果较差。P2P技术打破了传统的C／S模式，在网络中的每个结点的地位都是对等的。每个结点既充当服务器，为其他结点提供服务，同时也享用其他结点提供的服务，很好地解决了网络带宽瓶颈问题。P2P技术以其可扩展性、高容错性、健壮性等特点已得到迅猛的发展，并逐步应用到视频技术领域。本文提出了一种基于P2P(peer to peer)方法的VoD服务体系PeerVoD，它能够以较小的服务器代价实现大规模的VoD应用。中的每个节点均使用定长的FIFO缓存队列来保存其最近所接收到的数据，以便为后续到达的节点提供服务。它具有如下特点：1)采用分布式控制协议以支持节点的加入和离开，系统具有良好的可扩展性。通过在每个节点上维护有限个其他节点的状态信息，使得当节点加入时，能够在短时间内找到合适的父节点；而当节点上发生离开或者失效行为时，子节点能够通过其所维护的状态信息快速而准确地找到新的父节点；2)节点的失效或离开一般不涉及到服务器，从而减轻了服务器的负载；3)服务被中断的节点在进行中断恢复时，考虑了节点对目标节目接收的完整性；4)考虑了节点在网络带宽等资源方面所体现出来的异构性。仿真实验表明：PeerVoD体系具有良好的性价比。同等条件下，与同类体系P2VOD比较，PeerVoD体系在服务器负载、节点加入时被拒绝的概率、网络资源利用率以及节目完整性等性能指标上，均优于同类体系P2VoD。更多还原

【Abstract】 Providing video on demand service over the Internet in a scalable way is achallenging problem. The traditional play mode of video frequency is based onClient/Server (C/S) concentrated network mode, facing the problems of restrainednetwork bandwidth. For example, the overbalance of the media server stress, therestrained number of the clients, the worse playing effect of the programs. Thetechnology of P2P breaks the traditional C/S mode, each node in the net is peer topeer. Each node acts as server which provide service for other nodes, as well asregales on service which other nodes offered, which commendably resolve thebottle-neck problem of the network bandwidth. Resorts to its expansibility and highresilience to failure and haleness, the technology of P2P has developed swiftly andviolently, and gradually applies to the field of video frequency technology.This paper proposes an architecture for video on demand streaming inpeer-to-peer environment, which is able to implement the large-scale VoDapplications with the lesser cost of server. In PeerVoD each peer node has a fixed-sizeFIFO buffer to cache the most recent content of the video stream it receives and canprovide service to subsequent reached proper peer nodes. It has the followingproperties: 1) It utilizes a distributed control protocol to support the joining andleaving processes of peer nodes in a scalable way, the system has favorableexpansibility. By maintaining the status messages of restricted other nodes, it can findthe appropriate father node when peer nodes join; when peer nodes leave or abate, thechild nodes can find the new father nodes fleetly and exactly by the status messages itmaintained. 2) The invalidation and departure of the nodes currently don’t come downto the servers, so that it can alleviate the server stress. 3) It considers the issue ofintegrity of the received program in service recovering process of the interruptednodes. 4) Take into account the isomerous nature of the network bandwidth resources.Performance studies based on simulation are carried out, the results show that thesystem architecture outperforms a recently proposed system architecture P2VoD in a number of important performance metrics such as the server’s load, client joinrejection probability, network resource usage ratio, program integrity ratio and so on.更多还原