【作者】 张亮；

【导师】 张连芳；

【作者基本信息】 天津大学 ， 计算机应用技术， 2004， 硕士

【摘要】 摘要目前 Internet 只提供尽力而为的服务，在这种不支持 QoS 的网络中实时多媒体业务和电信服务会产生严重的性能下降。为获得对业务流的 QoS 保证，ISP 需要一种能够支持 QoS 的动态路由算法。MPLS 技术有望解决这个问题。为了达到这一目标，需要对支持 QoS 的框架和路由算法进行研究。本文提出了一种新的框架和算法来动态地建立有带宽保证的路径。受最小干扰路由（MIRA）和基于特征的路由（PBR）启发，在我们的工作中利用了预先了解的网络业务知识，称为“业务 Profile”。业务 Profile 可以通过测量得到，或者由服务级别约定（SLA）得到。它粗略地反映了网络中未来业务的分布。本文提出的框架有三个主要部分：离线（off-line）阶段，基于网络运行的统计数据，计算每个预先定义的业务类所需链路能力的预分配，用作在线（on-line）路由阶段用到的准入控制阈值；在线路由阶段，基于离线路由和当前的网络状态，进行路径选择，并在 MPLS 网络中建立 LSP；以及相应的链路状态路由协议，将链路状态信息在整个网络上发布。在线算法被设计为足够简单，来尽可能减小为每个流进行路由的计算要求。而离线计算阶段需要对一个多物品网络流问题求解，它是一个计算量很大的过程，但可以离线进行。链路状态路由协议的作用是保持网络中每个路由器上的链路状态数据库随时更新。在 NS-2 仿真软件中我们实现了这个 QoS 框架，并进行了大量仿真实验。仿真结果表明这个新的 QoS 框架和路由算法在路由的流数和准入的带宽数等度量上，比传统的最短路径优先（SPF）路由算法有比较大的性能提高。我们工作的主要贡献在于提供了在基于 MPLS 的 ISP 网络中动态建立有带宽保证的 LSP 的一种可靠的机制。更多还原

【Abstract】 ABSTRACT Real-time multimedia traffic and telecommunication services can experiencesevere quality degradation in QoS-unaware networks such as the Internet, whichprovides best-effort services only. ISPs need a QoS-aware dynamic routing algorithmto overcome this problem. MPLS is a promising technology that has the potential toprovide such solution. However, QoS-aware framework and routing algorithm are tobe developed to achieve this goal. In this thesis, we present a new framework andalgorithm for dynamically setting up paths with bandwidth guarantees. Inspired by theMinimum Interference Routing (MIRA) and Profile-Based Routing, our work uses apriori knowledge of the network, which is called “traffic profile”. The traffic profilecan be obtained by measurement or service level agreements (SLAs). It roughlyrepresents the future traffic distribution in the network. Our framework has three major components: offline routing, based on thenetwork running statistics, which calculates the admission thresholds for eachpre-defined traffic class and the pre-allocation of link capacities for the online routingphase; online routing, based on offline routing and the current network state, whichperforms path selection and then sets up LSPs in MPLS network; and thecorresponding link state advertisement protocol, which distributes the link stateinformation throughout the whole network. The online algorithm is designed simpleenough to keep the computational requirement per flow setup as low as possible,while the offline calculation part is to solve a multi-commodity flow problem, whichis a time-consuming process but can be executed offline. And the link stateadvertisement protocol keeps the link state database on each of the routers in thewhole network up-to-date. We have implemented our QoS framework in Network Simulator2 (NS-2) andcarried out extensive simulations. The simulation results show that the new QoSframework and routing algorithm significantly outperforms the conventional routingalgorithms like shortest path first on the metrics such as the fraction of requests routedand the fraction of requested bandwidth routed. Moreover, the major contribution ofour work is that it provides a reliable mechanism to dynamically set up bandwidthguaranteed LSPs in a MPLS-based ISP network.更多还原