【作者】 乐春晖；

【导师】 杨宗凯；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2005， 博士

【摘要】 随着宽带网的普及,多媒体业务在互联网上越来越普遍。一般认为,多媒体业务将会占据下一代互联网上的主要流量,其中,很大一部分应用都基于一对多传输方式。组播是节约这类业务传输带宽的有效方式。为了保证多媒体传输的服务质量,网络运营商需要通过接纳控制来控制网络上传输的会话数量,以保证已接入会话不会因网络过载导致服务质量下降。近年来,接纳控制的可扩展性日益受到人们的关注。传统的接纳控制多与逐跳预留资源的RSVP 协议协同工作,这些算法要求每个节点都实现较为复杂的接纳控制功能,从而影响了节点的可扩展性。为此,研究人员提出了各种可扩展的接纳控制方案,这些方案多从整网或网络域的角度进行接纳控制。然而,这些方案多数仅仅考虑到了单播的情况,往往不能应用于组播传输。由于组播路由的树形拓扑与动态性,组播接纳控制的设计比单播更为困难。可扩展的组播接纳控制问题很可能将成为未来的大量多媒体业务的技术瓶颈。接纳控制技术大致可分为基于探测的接纳控制、基于模型的接纳控制和基于测量的接纳控制三类方法。本文针对可扩展的组播接纳控制这一专题,在基于探测的组播接纳控制、基于模型的组播接纳控制(在本文中也称基于资源预留的组播接纳控制)、基于测量的组播接纳控制三个方面开展了较为全面的研究,取得了以下研究成果: (1) 在基于探测的组播接纳控制方面,本文发现了后续请求问题及其改进方案,并总结、比较了基于探测的组播接纳控制的探测方法。本文发现并提出了后续请求问题,并对该问题进行了建模分析,说明了该问题对基于探测的组播接纳控制方法可扩展性的严重潜在影响。仿真表明,该模型能够较好地描述后续请求问题。在此基础上,本文提出了以互补探测机制为核心的改进方案,通过模型和仿真验证了改进方案的有效性,并且对该改进方案在区分服务网中的实现以及渐进部署问题进行了详细探讨。本文总结了基于探测的组播接纳控制的探测方法,并通过模型分析和仿真实验从接纳正确性和组成员变化的可扩展性两个方面对其进行了分析比较。(2) 在基于资源预留的组播接纳控制方面,提出了一种基于虚拓扑的网络资源管理机更多还原

【Abstract】 Multimedia services are more and more popular in Internet with the widely use of broadband network. It is widely accepted that multimedia services will consume most of the link bandwidth in the next generation Internet. Among multimedia applications, a large number of them are based on point to multipoint transmission. Multicast is an efficient approach to saving bandwidth for this category of application. To guarantee the quality of service for multimedia communication, admission control is required to control the online session number, so that the QoS of the admitted sessions will not be violated. For this sake, admission control has been a hotspot for years. In recent years, scalability of admission control is widely concerned, and various scalable admission control schemes are proposed. However, these schemes only consider unicast case. Admission control for multicast has become a potential bottleneck for the future vast multimedia applications. Admission control could be classified into three categories: probe-based, model-based and measurement-based admission control. Focused on scalable multicast admission control, all the three categories of admission control are studied. The work is introduced in the dissertation. The dissertation contributes in following aspects. (1) In probe-based admission control area, the dissertation finds and enhances the subsequent request problem. Probe schemes in probe-based admission control are also summarized and compared. Subsequent request problem prevents the multicast group from admitting subsequent requests in heavy loaded scenario, which do not consume any more resource of bottleneck link. This seriously influences the scalability of probe-based admission control for multicast. This problem is first found, modeled and analyzed the dissertation. An enhanced scheme using complementary probing is proposed, and validated with analytical models and simulation results. The implementation of the enhanced scheme in DiffServ network, as well as the incriminatory deployment, is also discussed. Probing scheme, which is the soul of probe-based admission control, is also summarized, and compared via analytical model and simulation results from admission correctness and dynamic group scalability. (2) In probe-based admission control area, the dissertation proposed VloQ, a virtual-topology-based network resource management mechanism, and an edge reservation-based admission control scheme for multicast. The concept of multicast virtual link is proposed in the dissertation. Using the concept, a resource management mechanism –VloQ is introduced, which could efficiently reduce the QoS states to maintain. A scalable reservation-based edge admission control scheme is proposed, which employs VloQ and a two layered distributed bandwidth broker architecture. We develop a simulation platform based on discrete control event. Using this platform, Quota management issue is investigated. (3) In measurement-based admission control area, a practical effective bandwidth algorithm is deduced for generalized homogeneous traffic, and a measurement based edge admission control scheme is proposed. Generalized homogeneous traffic, which is extended from homogeneous traffic, is more practical than homogeneous traffic. Using statistical network calculus, a practical effective bandwidth algorithm is deduced for generalized homogeneous aggregation traffic. This algorithm only requires shaper type on edge nodes, whereas the conventional effective bandwidth theory needs the knowledge of source model. A measurement-based multicast admission control scheme is proposed, which utilizes effective bandwidth algorithm and edge multicast admission control framework. A packet-based simulation platform for multicast admission control is developed. The dissertation introduced the design and development of the platform. Using the platform, simulations are designed to evaluate the proposed measurement-based admission control scheme.更多还原