【作者】 张伟；

【导师】 雷为民；

【作者基本信息】 东北大学 ， 通信与信息系统， 2014， 博士

【摘要】 IMS (IP Multimedia Subsystem, IP多媒体子系统)具有端到端全IP化、系统架构模块化、业务与控制分离、业务与接入方式无关等多方面的技术优势,被业界普遍认为是下一代电信技术的基本趋势和主要方向。IMS最重要的原则和优势在于具有完善的业务信令控制体系以及服务质量保证机制。然而,目前IMS应用和服务总体上仍然处于初级阶段且进展缓慢,其技术层面还存在诸多问题：1)IMS基于传统路由技术构建的单径媒体传输模式落后,难以适应和支撑快速成长的宽带通信应用需求；2)IMS业务匮乏,难以满足用户的通信需求。针对这些问题,本文旨在从IMS系统的承载网络层面和业务网络层面提出相应的解决方案,为下一代网络提供一种新颖的IMS技术架构,主要研究内容以及创新点包括：(1)多径传输是提高媒体传输服务质量的一种重要方式。为了实现多径传输,关键问题之一是如何构建源端和目的端之间的多条路径。本文提出一种基于应用层中继的多径传输系统通用框架,利用由控制服务器和中继服务器组成的中继服务系统建立多径传输条件,摆脱现有多径传输技术对网络环境的依赖,作为重叠节点的中继服务器不关心端到端的业务传输需求,仅提供UDP转发服务,其行为得到大大简化,且有助于中继服务的标准化。为了便于开展专业化的中继传输服务,在多径传输通用框架的控制平面设计了一种标准化的中继服务控制协议OpenPath。为了将多径传输通用框架应用到IMS系统,提出了一种支持媒体多径传输的IMS会话协商管控机制,使得IMS网络侧能够对媒体传输过程进行管理,为IMS系统中的媒体传输提供多径传输功能。该多径传输通用框架适用于各种上层应用类型,对用户终端的网络环境以及网络基础设施无任何要求和改造,而且集中式控制有利于从宏观角度调配传输带宽等网络资源。(2)针对中继重叠网络的拓扑组织问题,本文提出基于应用层流量优化和应用感知的中继重叠网络两层拓扑模型,利用网络运营商提供的底层网络信息,将中继服务器按照底层网络拓扑信息进行有效组织,并通过中继服务器之间的性能探测过程,获取中继重叠网络的多项传输性能。该中继重叠网络拓扑模型具有物理网络感知、应用感知以及可伸缩性强的特点。针对优质中继路径的分配问题,在中继重叠网络两层拓扑模型的基础上,本文提出基于应用层流量优化和应用感知的中继路径分配方案,包括一种结合路由开销、传输性能、中继服务器处理能力等多种因素的中继路径路径代价评价方法,以及最优中继路径生成算法。该中继路径分配方案,不仅在选择优质中继路径方面具有较优性能,同时又能够灵活地均衡运营商定义域之间以及中继服务器之间的负载。(3)针对多径传输中的负载分发问题,本文提出一种支持多种应用类型的负载分发机制,引入一种新的划分粒度——流块,流块的划分方法以及大小均是与应用类型有关的,用于满足多种应用类型的不同传输需求。针对可靠非实时应用类型,提出了最早空闲路径优先的可靠多径传输负载分发算法,用于最大化用户终端的数据吞吐量；针对具有实时传输需求的应用类型,提出了失序可控的实时多径传输负载分发算法,用于最小化目的端的数据包乱序风险。在多径传输通用框架的数据平面,本文设计了能够支持多种业务传输需求的易扩展的多径传输协议族,每个具体的多径传输协议旨在满足一种特定类型的上层应用的传输需求。(4)针对IMS业务匮乏以及云计算缺少管控和质量保证机制的问题,本文提出一种基于IMS体系的云计算服务管理模式IMSCloud,将云计算服务置于IMS信令控制下,利用IMS体系的信令控制、QoS策略决策以及计费策略等能力对各种云计算服务进行有效管控。对于电信运营商而言,IMSCloud在不改变现有IMS体系结构的情况下,可快速部署内容丰富且有商业价值的云计算业务,利用策略与计费控制框架可以为用户提供质量可保障的云计算服务,促进IMS体系的普及和成长。对于云计算服务提供商而言,可以充分利用IMS已有的完善的认证、策略和计费控制机制,实现云计算服务的商业运营以及云计算服务管理接口的标准化。更多还原

【Abstract】 IMS (IP Multimedia Subsystem) has lots of technical advantages including end-to-end integrated all-IP networks, modular system architecture, separation of services and access technologies. It is generally believed as the underlying trend and the main direction of the next generation telecommunications technology. The most important principles and advantages of IMS are having service signaling control system and quality of service assurance mechanism.However, IMS applications and services are still in its infancy and progress slow currently. This is because there are many problems in the technical aspects of IMS.1) The single-path media transmission mode builded by the traditional routing technology in IMS lags behind, which is difficult to adapt to and support the rapid growth of broadband communication application demands.2) The value-added services in IMS are scarce, which is difficult to meet the communication needs of users. For these problems, this dissertation aims to put forward the corresponding solutions at the bearer network level and the service network level in IMS system, providing a novel IMS technical architecture for the next generation network. The main contents and innovations are as follows:(1) Multipath transport has been shown to be an effective way to improve the efficiency of data delivery. In order to achieve multipath transport, one of the key issues is how to build multiple paths between source and destination. This dissertation presented a general framework of multipath transport system based on application-level relay (MPTS-AR). A relay service system composed of control server and a large amount of application-level relay servers is deployed to provide multipath conditions between source and destination, getting rid of the dependence on the network environments in the existing multipath transmission technologies. As overlay nodes, relay servers don’t care about the end-to-end transmission requirements and only provide UDP-based forwarding service. So relay server’s behavior is greatly simplified and it is helpful to the standardization of the relay service. In order to facilate the specialized relay transmission service, a relay service control protocol named OpenPath was defined in the control plane of MPTS-AR. A session negotiation control mechanism supporting media multipath transport was presented in order to apply MPTS-AR framework to IMS system. A new multipath transport service was defined to enable IMS network side to manage media transmission process and provide multipath transport function. MPTS-AR is general and can be applied to various application programs, and has no requirements and modifications to the network setting of endpoints and network infrastructure. And the centralized control of MPTS-AR is beneficial to allocate transmission bandwidth and other network resources from macro perspectives.(2) For the topological organization problem of relay overlay network, this dissertation presented a two-level topology model of relay overlay network based on application-level traffic optimization and application awareness. Using underlying network information provided by network operators, relay servers were organized effectively according to the underlying network topology information. And through the performance detection process among relay servers, a number of transmission performance metrics of overlay network were obtained. This topology model has the characteristics of physical network awareness, application awareness, and the high scalability. For high-quality relay path assignment problem, this dissertation presented a relay path assignment scheme based on the application layer traffic optimization and application awareness, on the basis of the presented overlay network topology model. This scheme includes a relay path cost evaluation method, which combines multiple factors such as routing overhead, transmission performance and relay server processing power, and an optimal relay path generation algorithm. This scheme not only has a better performance in choosing high-quality relay path, but also provides the flexibility to balance loads among provider-defined domains and among relay servers.(3) For load distribution problem in multipath transmission, this dissertation presented a kind of load distribution mechanism supporting a variety of application types. A new partition granularity, flow block, was introduced. The partition method and size of flow blocks are related to the application type, which is used to meet the transport needs of a variety of application types. For reliable and non-real-time application type, an earliest free path preference reliable multipath transport load distribution algorithm was presented to maximize the data throughput of end users. For real-time application type, a packet reordering-controlled realtime multipath transport load distribution algorithm was presented for the purpose of minimizing the packet reordering risk. In the data plane of the multipath transmission general framework, this dissertation designed a multipath transmission protocol suite supporting a variety of transmission demands and being easily extensible. Each concrete multipath transport protocol is aimed to meet the transmission requirements of a specific category of upper applications.(4) In view of the lack of value-added services in IMS and the shortage of control and quality assurance mechanism in the cloud computing, this dissertation presented a cloud computing service model supporting IMS signaling access control, which is named IMSCloud. Cloud computing services are effectively controlled by the signaling system, QoS policy decision and charging strategy in IMS. For telecom operators, IMSCloud is able to quickly deploy content-rich and commercially valuable cloud computing services without changing the existing IMS architecture. And IMSCloud is able to provde users with quality-quaranteed cloud computing services using policy and charging control framework. IMSCloud will be able to promote the popularity and growth of IMS. For cloud computing service providers, IMSCloud can make full use of the existing perfect authentication and policy and charging control framework in IMS to implement the commercial operations of cloud computing services and the standardization of cloud computing service management interfaces.更多还原