【作者】 陈益新；

【导师】 顾冠群；

【作者基本信息】 东南大学 ， 计算机应用技术， 2005， 硕士

【摘要】 随着计算机网络技术和多媒体技术的迅猛发展,以视频会议,远程教育为代表的具有多播传输特性的多媒体业务不断涌现,并已在校园网和企业网中得到广泛的应用。多媒体多播业务发展的下一个重要阶段是实现在Internet环境下的部署和应用,这也是不断增长的用户需求驱动下的必然结果。传统的IP多播由于技术、市场两个方面的原因,很难在Internet上实现真正的部署。正是在这一背景下,多播服务研究领域的学者们考虑将多播功能从传统的网络层迁移到应用层来实现,应用层多播技术就是这样一种IP多播的替代方案。应用层多播是将多播功能从路由器转移到端系统,由端系统负责实现所有的多播服务功能,包括多播组的表示、组成员的管理、多播树的构建、多播数据的复制和转发等等。所有多播组组成员构成一个叠加在IP基础网络上的覆盖网络,然后在这个覆盖网络上运行特定的应用层多播路由协议,构建应用层多播数据转发树。本论文主要研究基于覆盖网络的应用层多播系统,侧重于原型系统的整体设计实现,以及面向多媒体应用的应用层多播逐跳拥塞控制两个方面。论文详细的研究和实现工作如下:分析当前应用层多播研究的现状,系统总结在系统体系结构和应用层多播路由协议方面的研究成果,阐明了基于代理服务器体系结构在商业化运作方面的天然优势。基于面向直播类型的流媒体应用,支持较大多播组用户规模以及在应用层提供一定程度的服务质量保证等设计因素的考虑,本文提出了一种新的基于P2P覆盖网络和树优先应用层多播路由协议复合构造的HMT-ALMS系统设计。为了适应覆盖网络节点之间虚拟链路带宽资源的动态变化,面向流媒体应用,在媒体数据采用单层的自适应编码方式下,本文提出了基于速率的应用层多播逐跳拥塞控制(RHBHCC)方案。该方案在跳内采用成熟的端到端拥塞控制机制,在跳间采用上下游速率的自适应调整。根据HMT-ALMS系统设计,实现了原型系统,并在此基础上开发了面向网络直播类的流媒体多播应用。该原型系统基于代理服务器的系统体系结构,分为接入网络和覆盖网络两个组成部分。在接入网络部分,系统整合了服务定制功能,客户端可以根据自身需求的特点定制服务;在覆盖网络部分,系统整合了基于速率的应用层多播逐跳拥塞控制方案,达到了对链路资源的自适应调整以及对其他应用的公平性要求。对原型系统的测试,功能测试结果表明系统各个功能模块运行正常,达到设计目标。在对星型和链型两种典型拓扑结构下的性能测试,表明该系统能够支持较大用户规模的多播服务,并能提供较为满意的服务质量。更多还原

【Abstract】 Along with the computer network and multimedia technologies having been developing rapidly, multimedia applications , such as video conference, distance learning and etc, which have multicast transmission characteristic, are used more and more widely at Intranet. And the next improvement stage is to be deployed at Internet, which is also motivated by the customer requirements. But because of the unsolved issues in technology and market, Traditional IP multicast can not be widely deployed at Internet. Under this background, the researchers turn to the application layer to implement all the multicast functions, and application level multicast is such an alternative technology.In application level multicast, multicast functions are moved from routers to end systems, such as the multicast group denotation, membership management, multicast tree generation, the duplication and distribution of data packets. All the group members is set up to be an overlay network on the top of the IP network, and then construct multicast tree by the application level multicast routing protocol.The research of the thesis focused on the application level multicast system, especially on the design of the prototype and the hop by hop congestion control. The following are the detailed content:Study on the research status of the application level multicast, summarize the research production of multicast system architecture and application level multicast routing protocol. In order to support streaming media application, large group membership and quality of service, the thesis proposed a new hybrid system design based on the P2P overlay network and tree-first application level routing protocol, which is called HMT-ALMS.To be adaptive to the dynamic change of the overlay link’s bandwidth, a new rate based application level multicast hop by hop congestion control-RHBHCC is proposed, which is streaming oriented and the multimedia data is single layer adaptive coded in it. RHBHCC apply the mature end-to-end congestion control mechanism within one hop, and apply adaptive adjustment between upstream and downstream hops.Based on the HMT-ALMS design, realize the application level multicast prototype and develop the streaming media multicast application. This prototype adopts the proxy-based architecture, including access network and overlay network. At access network, it fulfils the service customization, at overlay network, it fulfils the RHBHCC.Test about the HMT-ALMS prototype. The function test result shows that the system works well and reaches the design objective. The performance test under star and linear representative structures shows that it can support large group membership multicast service.更多还原