【作者】 刘威；

【导师】 杨宗凯；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2004， 博士

【摘要】 自上个世纪90年代以来,服务质量的保证研究成为通信网络研究领域最为活跃的课题。近年来,采用区分服务网络技术解决当前互联网的服务质量问题已经成为研究界的普遍共识,采用保证转发服务为多媒体业务提供订购带宽保证的技术也基本成熟。然而,随着多媒体应用在互联网上的发展和普及,以流媒体点播应用为代表的多媒体流量占据了当今互联网流量的绝大部分,给通信网络带来了新的挑战和压力,具体表现在以下几个方面:? 网络应对突发流量的能力。随着全球一体化的加剧,由某个局部的热点事件 (如2004年雅典奥运会)的发生而导致大规模突发流量的可能性增加,对网络 的健壮性提出了更高的要求,具体到路由器设备上即队列性能应对流量负载变 化时的健壮性问题。? 网络提供全面服务质量保证的能力。全面的服务质量保证既包括可定量的性能 指标(如吞吐量、时延和分组丢失等)的保证,也包括可用性、公平性等特性 的保证。现有保证转发服务虽然可以提供吞吐量的定量保证,但是不能提供时 延和分组丢失率性能的定量保证,也缺乏对带宽分配公平性的支持。? 网络提供面向应用的边缘服务的能力。随着更多流媒体分发应用在互联网上的 部署,仅为骨干网络提供服务质量保证并不能有效改善信息传输系统的性能和 资源利用率,以代理缓存服务器等代表的网络中间构件成为提高系统扩展性和 改善IP路由器之间数据性能的重要手段。 本文针对上述问题,研究区分服务网络多媒体传输分发技术。本文的研究从四个方面展开:(1)区分服务节点的队列健壮性建模与分析;(2)区分服务网络提供时延和分组丢失率定量保证的研究;(3)区分服务网络提供服务间带宽分配公平性的研究;(4)交互式流媒体内容在网络边缘的分发。这些工作得到国家自然科学基金“基于媒体传输特性的无线多媒体技术的研究”(No.60202005)和“基于Internet的交互式流媒体分发技术研究”(No.60302004),以及澳大利亚研究院基金“交互式视频点播在远程教育中的应用”(No.LX0240468)、华中科技大学优秀博士论文基金“多媒体业务的QoS保证与内容分发技术研究”的资助。 本文取得的研究成果包括如下几个方面:1. 区分服务网络节点的队列稳定性模型:本文对区分服务网络节点常用的RIO算 法的稳态队列性能进行了分析和建模,在流态假设下计算获得队列系统的稳态 工作点,从而建立了分析RIO队列系统健壮性问题的讨论模型,对其问题的成 因进行了深入的分析。 I<WP=5>2. 支持时延及分组丢失率定量保证的自适应队列管理算法:针对保证转发服务只 能提供多服务级别间时延和分组丢失率的定性区分的问题,本文提出了两种自 适应的RIO改进算法(ARIO-D和ARIO-L),可以在保证吞吐量性能的同时提 供稳定和可区分的时延和分组丢失率性能。3. 支持多服务队列间带宽分配公平性的自适应加权调度机制:针对固定权值调度 在网络负载发生变化时不能为各服务队列提供公平带宽分配的问题,本文提出 了一种可与各种加权调度算法联合部署的加权调度机制。该机制依据本地性能 估算和动态调整权值以改善剩余带宽分配的公平性。4. 交互式流媒体应用中用户请求负载的生成模型:现有对流媒体点播应用中的用 户交互动作的研究较少,而且忽略了用户行为的交互性问题,不能有效的模拟 媒体内容受访热点的形成。本文提出了一种新的交互式用户点播行为的生成模 型,其生成过程更加符合用户的自然行为。5. 流行度敏锐的交互式流媒体代理缓存算法:现有媒体代理缓存算法假设用户从 媒体内容的起始部分播放;然而实际中用户请求的热点可能是媒体内容的任意 部分。本文提出基于分段的流行度敏锐(Popularity-wise)缓存算法,在不同的 用户交互强度下都可以提供较现有分段缓存算法更低的用户响应时延和链路占 用带宽。更多还原

【Abstract】 The research on Quality of Service (QoS) has been an active area in telecommu-nication society since 1990s. In recent years, Di?erentiated Service (Di?Serv) networkhas been recognized as the main solution for the QoS problem for current Internet.The Assured Forwarding (AF) has been adopted to provide guaranteed subscribedbandwidth for multimedia services. However, with the deployment of more and moremultimedia applications over Internet, the multimedia tra?c represented by media-on-demand application takes the largest portion in the current Internet tra?c. This bringsnew challenges and pressures to networks in the following issues: ? The ability of network responding to burst tra?c. With the world becoming an earth village, the possibility of large-scale burst tra?c caused by a local event (such as Athens 2004 Olympic Games) increases. This calls for strict requirement on the robustness of network, which can be speci?ed by the queue robustness of in the view of routers. ? The ability of network to provide comprehensive QoS. The comprehensive QoS not only includes the measurable performance metrics (such as throughput, delay and loss ratio), but also includes the characteristics of availability, fairness and so on. Although current AF service can support guaranteed throughput, there is a lack of the quantitative di?erentiated guarantees in delay and loss ratio, also a lack of the support in the fairness of bandwidth allocation. ? The ability of network to provide edge service. With the deployment of more and more multimedia delivery applications, just providing QoS for backbone network cannot improve the scalability of information transmission system. The middle- boxs represented by Proxy Caching has been an important method to improve the data delivery performance between IP routers. To solve the above problems, this thesis addresses on the multimedia transmis-sion and delivery technologies in Di?Serv networks. The content of this thesis includesfour issues: (1) modeling and analysis of the queue robustness of Di?Serv router; (2)provision of quantitative guaranteed delay and loss ratio in Di?Serv network; (3) fair-ness of excess bandwidth allocation among multiple service classes; (4) delivery ofinteractive streaming content at the network edge. The works in this thesis has beensupported by the National Science Foundation of China “Investigation of WirelessMultimedia Techniques based on Multimedia Transmission Property”(No.60202005)and “Internet-based interactive streaming delivery technique”(No.60302004) respec-tively, and also supported by the Australian Research Council Foundation “Interactive III<WP=7>video-on-demand for e-Learning”(No.LX0240468) and the excellent Ph.D thesis foun-dation in Huazhong University of Science and Technology “QoS guarantees and Con-tent Delivery of Multimedia Services”. The contributions of this thesis include: 1. The stability model of RIO queue in Di?Serv router: this thesis analyzes the steady queue performance of RIO queue in Di?Serv router. Based on ?uid model assumption, the steady working state of RIO queue system is given. Then the understanding model for the robustness problem of RIO queue is proposed as well as the fully discussion on its origin. 2. Adaptive queue management algorithm to provide quantitative guarantees in delay and loss ratio: Current AF service in Di?Serv can only provide qualitative service di?erentiation in delay and loss ratio. This thesis proposes two adaptive variants of RIO algorithm (ARIO-D and ARIO-L), which can provide stable and di?erentiated performances of delay and loss ratio as well as the guaranteed throughput. 3. Adaptive weighted scheduling scheme to provide fair excess bandwidth allocation among service classes: Current ?xed weighted scheduling in Di?Serv can not respond to the changes of tra?c load either provide fa更多还原