【作者】 张光胜；

【导师】 窦文华；

【作者基本信息】 国防科学技术大学 ， 计算机科学与技术， 2008， 博士

【摘要】 服务质量(QoS,Quality of Service)是网络研究的技术热点和难点。ITU-T、IETF等组织均对服务质量从不同角度和层面进行了研究,并提出了IntServ(综合服务模型, Integerated service)、DiffServ(区分服务模型,Differentiated Service)和MPLS(多协议标记交换,Multiple Protocols Label Switching) QoS体系结构。能够得到两大阵营从信令到架构完全支持的却只有MPLS QoS体系结构。这主要是因为MPLS具有以下特点:(1)MPLS技术将连接机制引入无连接的IP网络,一次路由,多次交换,既保留了路由的灵活性,又充分发挥了交换的高速度;(2)MPLS良好的扩展性和开放性使其不仅可以在物理层、多种数据链路层、IP层、TCP等多个层次上直接建构,还可以适应从数据链路层到应用层的多种使用要求。(3)MPLS可以对目前Internet的主要关键技术问题如QoS、VPN(虚拟专用网,Virtual Private Network)、流量工程、IPv4/IPv6的过渡、组播等技术均有全面而很好的支持和完整的解决方案。(4)边缘部署,核心可扩展,与Internet的发展方向一致。因此MPLS技术从出现以来便得到了迅速应用、普及和标准化,在无线网络、LAN/PAN/MAN/WAN、光网络、卫星网络、移动网络等众多领域得到了应用,网络设备厂商和科研院所纷纷投入巨资和众多人员进行研究和开发,具有MPLS功能的网络设备是目前中高端网络设备以及网络应用的基本要求。接纳控制(CAC,Connection Admission Control)是MPLS体系结构中LSP(标记交换路径,Label Switching Path)和TE(流量工程,Traffic Engineering)实现的基本功能组件。接纳控制一直是QoS实现和研究的热点问题。接纳控制可以同时实现两个目标:(1)保障所有连接的QoS;(2)有效地提高网络资源利用率,即在用户需求和网络效益最大化之间取得良好的折中。接纳控制的实现需要两个前提,只有同时满足了这两个前提条件,新连接请求才被接纳,否则被拒绝:(1)资源条件,即网络结点有足够的资源来满足新连接请求的服务质量;(2)不损害条件,即新连接的接入,不会影响已接纳分组流的QoS。目前主要的接纳控制技术主要分为分布式CAC技术、集中式CAC技术和基于策略的CAC技术。这些CAC技术可以根据需要在MPLS网络中进行应用,与其它技术一起构成完整的QoS实现解决方案。围绕MPLS LSP和MPLS TE的CAC实现机制,本文做出了以下具有创新性的工作:1.为了准确预测自相似网络流量,提出了基于测量的自相似网络流量预测算法(HSS-MBP)。近年来的研究表明,自相似特性是网络流量的基本特性,因此根据网络流量自相似特性开展相关的网络流量预测是网络研究的根本要求,论文后续章节的大部分相关工作均基于HSS-MBP开展。HSS-MBP算法以测量的方法对自相似流量进行了预测,理论分析和模拟表明HSS-MBP算法能在较少计算量的情况下较好地对自相似网络流量进行预测,更接近于实时预测网络流量的需要。2.为了在节点对流量进行调节,提出了基于测量的自相似接纳控制算法(HSS-MBAC)和基于测量的自相似自适应接纳控制算法(HSS-AMBAC)。算法通过预测和自适应地调节相关参数预测自相似网络流量,根据自相似流量的合成特性,使网络流量预测更为准确和及时,接纳控制更为有效,在保证带宽的情况下提高了接纳效率和带宽利用率。3.针对MPLS LSP本身固有特性和实现机制,提出了基于标记的LSP概率接纳控制算法(LB-PAC)。LB-PAC不会增加LSP建立的复杂度,有效避免了端点接纳控制和端到端接纳控制的局限性。针对时延敏感和带宽敏感两种不同应用分别提出了概率接纳控制算法,分析和仿真表明,算法进一步提高了LSP接纳效率和带宽利用率。4. QoS的效用问题是ISP(Internet服务提供商,Internet Service Provider)和用户都十分关心的问题,本文将效用机制引入MPLS DS-TE(区分服务感知的流量工程,DiffServ aware Traffic Engineering)实现其接纳控制,根据MPLS DS-TE技术要求提出了UB-MDTAC算法。算法较好地权衡了ISP关心的网络效率和用户价格方面的需求,从TE的角度提高了接纳效率和带宽利用率。5.针对CAC的柔性化部署要求,本文对MPLS中基于策略的接纳控制技术进行了研究和分析,提出了MPLS策略接纳控制模型(MPBMC)和多域MPLS策略接纳控制模型(MMPBMC),探讨了MPBMC/MMPBMC策略生成、策略冲突及消解方法,作为PBMC(基于策略的接纳控制,Policy based Admission Control)在MPLS网络中实施的基本参考依据。更多还原

【Abstract】 Quality of Service (QoS) is one of the most active research areas in networking. In an attempt to address the growing needs of applications, organizations such as ITU-T and IETF put forwarding into QoS research and proposed the structure of Integrated Service(IntServ), Differentiated Service(DiffServ) and Multiple Protocol Label Switching(MPLS) QoS. But the MPLS QoS is the only structure that was supported by the two organizations. This is mainly because MPLS have many special characteristics, including: (1) MPLS technology imports connection mechanism into non-connection IP network, realized one routing, multiple switching, remaining the routing flexibility and exerting the high speed of switching; (2) MPLS can be realized on diverse layers from physical layer to TCP layer and meets the use demands from Data Link Layer (DLL) to Application Layer (AL). The real scenario is anything over MPLS and MPLS over anything at present; (3)MPLS primely supports the key technologies such as QoS, VPN(Virtual Private Network), Traffic Engineering (TE), IPv4/IPv6 coexistence, multicast, etc. and provides integrated solving projects; (4)MPLS can be deployed at edge and can be expanded at core, according with the Internet developing. Therefore, MPLS was popular just from its appearance, and has been widely used in wireless network, LAN/PAN/MAN/WAN, optical network, satellite network and mobile network. Main network equipment providers and academic organizations research and develop the MPLS technology with huge capital and many people. Network equipments with MPLS function are the fundamental requirement of advanced network equipments and network applications.Call Admission Control or Connection Admission Control (CAC) technology is the basic function opponent of MPLS LSP and MPLS TE. CAC is the most active research areas in QoS at all times. CAC has two targets: (1) guaranteeing the all present QoS links; (2) effectively improving the usage of network resource. The main technologies of CAC can be classified to distributed CAC technology, centralized CAC technology and policy-based CAC technology. These CAC technologies can be realized in the MPLS network on demand, and can be integrated into other technologies to construct whole QoS settlement.The main research in this thesis surrounds the CAC realization mechanism of the MPLS LSP and MPLS TE, and the major contributions of this thesis include:1. To predict the network traffic precisely, we propose measure-based self-similar network traffic prediction algorithm (HSS-MBP). Self-similarity is the fundamental character of network traffic. The following of the thesis are mainly based on HSS-MBP. Through analysis and simulations, it shows that HSS-MBP has better prediction data with less computing. 2. To adjust the traffic at the node, we propose Measure-based Self-Similar CAC algorithm (HSS-MBAC) and Adaptive Measure-based Self-similar CAC algorithm (HSS-AMBAC).The algorithms predict the self-similar traffic and adjust it adaptively, traffic prediction is more precise and timely. Through analysis and simulations, they shows higher admission ratio under the same bandwidth.3. Referring to the inherent character and realization mechanism of MPLS LSP, we propose Label-based Probability Admission Control algorithm (LB-PAC). Avoiding the limitations of the End-point Admission Control algorithm and End-to-end Admission Control algorithm without increasing the complexity of LSP setup, LB-PAC utilizes MPLS LSP realization mechanism. According to the time sensitive application and bandwidth sensitive application, various probability admission control algorithm are proposed. Through analysis and simulation, the algorithms have higher admission ratio.4. The price of QoS is sensitive problem of ISP and users. Pricing mechanism is imported to the MPLS DS-TE and Price-based MPLS DS-TE algorithm (UB-MDTAC) is proposed. The algorithm balances the network usage of ISP focus and the price demand of users, and get better admission ratio under MPLS DS-TE.5. To meet the demand of flexible deployment of CAC, the policies of Policy-based Admission Control (PBAC) algorithm are analyzed and two models (MPBMC/MMPBMC) are proposed to meet the realization of PBMC in MPLS network.更多还原