【作者】 谢久雨；

【导师】 陈雪； 叶培大；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2011， 博士

【摘要】 随着数据业务的不断增长,光通信网络经历了从基于SDH的点到点传输系统向网状网的发展,并且网络规模日益增大,节点更多,拓扑更加复杂。支持多粒度业务传送和可大规模扩展的多层多域体系结构,已成为光网络发展的必然趋势。在大规模多层多域光网络中,针对数量庞大的路径计算及复杂的约束条件,需要大量的CPU资源来运行复杂的算法,这对网络设备构成了一定的挑战,为此互联网工程任务组(IETF)提出了路径计算单元(PCE)的概念,它是将路由计算功能独立了出来,由专门的资源来承担。如何充分利用PCE的技术优势,使其与其它网络技术有效结合,为网络提供高速、准确、可靠的选路功能,已成为业界的研究热点之一。论文主要围绕作者所参加的国家863计划目标导向课题“可大规模扩展的多层多域智能光网络关键技术与实验系统”而展开。结合PCE以及自动交换光网络(ASON)和广义多协议标签交换(GMPLS)技术,论文对多层多域智能光网络的网络体系结构、跨域路由、资源预留和流量疏导等方面进行了研究并取得了若干具有创新性的研究成果。论文主要的创新工作如下：第一,针对PCE故障可能对网络造成的风险,提出了一种PCE冗余备份方案,在此方案中,通过相邻PCE间的相互合作,使得当单个PCE发生故障时,系统能够立即将其工作转交给合适的PCE接管,从而保证网络的正常运行。第二,针对多层多域光网络的跨域路由问题,提出了一种基于层次化PCE的跨域路由方案,该方案利用多PCE的并行计算能力,同时考虑各域的流量工程信息,从而能够保证路径的最优性及较短的建路时延。理论分析与实验测试结果表明,该方案能够明显减小建路时延并降低网络阻塞率。第三,针对光网络中分布式后向资源预留情况下产生的波长预留冲突问题,提出了以PCE协助选择和备份预留为特征的解决方案,具体包括三种方法：前两种方法通过主要通过PCE的协助进行波长预留冲突的避免；第三种方法主要通过在网络资源比较充裕的情况下加入备用波长预留的方式降低冲突的概率。仿真结果表明,所提三种方法均对分布式后向资源预留冲突引起的阻塞起到了很好的抑制作用,和传统方案相比,全网阻塞率得到了明显的降低。第四,在多层光网络的流量疏导方面,提出了一种结合PCE技术的跨层路由方案,该方案通过对新建路径的跳数进行约束,并采取拓扑融合机制,使得网络能够根据资源占用情况、负载均衡需求实现进行跨层路径的选择。仿真结果表明,该方案能够有效提高网络资源的利用效率并降低标签交换路径(LSP)的请求阻塞率。第五,对课题组提出的多层多域多约束GMPLS/ASON光网络的新型路由体系结构—DREAMSCAPE进行了研究分析,参与了DREAMSCAPE的协议与机制的研究设计,组织开发了网络实验平台的网管系统,参与提出并共同实现了网络实验平台上双路由前向路径计算方案(DRE-FPC)和层次化双路由反向回溯方案(HDRE-BRPC),并对分层跨域的路由方案的性能进行了实际测试与比较分析。更多还原

【Abstract】 With the growing of data service, the optical networks have experienced the change of the peer-to-peer SDH transport system to mesh networks, and there are lager network scale, more network nodes and more complicated network topologies. It is the future development trend for the optical networks to provide a scalable multi-layer/multi-domain network structure supporting the transport of multi-granularity services. In the large-scale multi-layer/multi-domain optical networks, high performance CPU resources are needed to process complicated algorithms as there are always huge path computation tasks with complicated constraints, which is a huge challenge to the network devices. Thus the IETF workgroup proposed the concept of PCE, which realize the path computation function by arrange specific resource. It is now a hot research field that combine the advantages of PCE with other network technologies to provide rapid, right and reliable routing function for the network services.The research work of this paper is based on an 863 project named DREAMSCAPE, and combined with the PCE technology, mainly focuses on such research fields as network structure, multi-domain routing, resource reservation, traffic grooming and etc. The main work and innovative contributions of this paper can be summarized as follows:Firstly, an additional backup model for PCE is proposed in order to avoid the risk as the PCE does not work. In this model, the system can turn the function of PCE to other ones immediately as it is down, thus the network can work properly. Secondly, based on the research work on existing strategies for multi-domain routing, a hierarchical PCE-based multi-domain routing scheme is proposed. This scheme guarantees the optimal route and path setup delay considering TE information and utilizing multiple PCEs. Both the theoretical analysis and the test results show that the scheme can reduce the setup-delay and the network blocking probability obviously.Thirdly, three different wavelength assignment schemes are proposed to solve the reservation collision problem in the destination initialized reservation scenario. The first two are realized through an assistance unit located in PCE in the process of wavelength selection. The third one is realized through reserving an additional backup lambda for the connection requests to decrease the collision probability as there is enough resource. Simulation results show that, the three schemes have successfully avoided the collision between two or more concurrently connections that traverse the same link/links and performs much better than the two traditional schemes in decreasing total blocking probability.Fourthly, two PCE-based dynamic traffic grooming schemes are proposed, one of which is realized through setting a threshold for the hops of a path and the other is realized through integration of the physical topology and logical topology and considering the load balance on the physical topology to establish a LSP connection. Simulation results show that the proposed schemes have higher resource use rate and lower blocking probability than the traditional way.Lastly, the novel routing structure-DREAMSCAPE proposed by the 863 project that the author participated in is studied and analyzed. The experimental platform is constructed and a network management system is developed. Based on the platform, two proposed routing scheme namely DRE-FPC and HDRE-BRPC are tested compared to the traditional HR scheme and some of the testing results are given and analyzed.更多还原