【作者】 张伟；

【导师】 林金桐；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 光突发交换(OBS：Optical Burst Switching)由于充分结合了电的灵活处理技术和光的高速传输交换技术，被认为是未来IP／DWDM全光网络的可行性方案，成为了学术界和产业界的研究热点。但是，OBS网络距离真正的实用化，还有许多关键技术需要解决，尤其是如何灵活有效地支持上层TCP业务，降低业务的传输时延等。另外，现有OBS研究多集中于协议算法等理论研究，而试验网络的研究只是刚刚起步。为此，本论文首先在国内外现有研究的基础之上，对OBS网络承载上层业务中涉及到的突发组装及全网的资源调度等若干技术进行了研究，并提出了几种可行的解决方案。然后，本论文介绍了一个基于标签交换的LOBS试验网络，并讨论了该试验网络中的关键技术以及最新的实验结果。具体可以总结如下：1．讨论了TCP业务在OBS网络中的传输性能。分析了在OBS网络中分别丢弃TCP业务数据突发包和ACK突发包时的网络性能，并就此设计方案对其进行仿真模拟和试验验证。结果表明，在传输过程中出现冲突竞争时，通过赋予数据突发包和ACK突发包不同的QoS优先级，可以避免TCP业务在OBS网络发生丢包时的性能过度恶化。2．提出了一种基于延迟机制的批量调度算法，并就同等优先级的突发数据在窗口内部发生冲突时，提出一种将较短的突发包丢弃的方案，以此保证网络的带宽利用率。其后，分析了当前智能调度算法普遍存在的问题。即随着调度算法的功能愈发强大，其实现复杂度也随之提高，并由此导致在网络核心节点处的时间消耗进一步增大。为了在OBS网络核心节点处运行复杂的调度算法的同时，将由此造成的系统延时消耗控制在较低的水平，我们提出一种新型的基于控制包复制的调度算法(DS：Duplicate Scheduling)。DS-JET协议利用核心路由器强大的电处理技术，对进入节点的控制包进行直接转发，同时复制一份控制包到本地节点进行处理。利用该调度方法，在实现复杂的调度算法的同时，不仅可以有效的减少控制包在核心节点处的系统延时消耗，还可以有效的避免控制包传输过程中由于经过多跳而造成的多径效应。最后通过网络仿真表明，DS-JET协议在突发包阻塞率、网络吞吐量和QoS性能方面要优于传统JET协议。3．基于对OBS网络协议和算法的研究以及现有的硬件技术水平，提出了一个可扩展的结合标签交换的LOBS网络核心路由器的实现方案，并重点讨论了其中的突发资源调度模块、系统控制模块和光交叉矩阵，最终实现了一个Mesh结构的LOBS试验网络。该试验网络的各项性能和第一期OBS试验平台相比都有所提高。该试验网络不仅有助于研究OBS网络的协议算法，也为今后的光网络研究提供了一个通用的可扩展平台。4．针对OBS试验网络进行了一系列的实验。通过实验首先分析验证了该试验网络中各个关键模块的功能，如光开关、突发组装、突发资源调度、突发接收等。其次，测试了该试验网络的时延性能，并进行了多QoS业务(如数据、语音和图像)的承载实验，简单分析了OBS试验网络的业务传输性能。最后报道了在OBS平台上运行的LOBS&GMPLS网络互联实验。更多还原

【Abstract】 Optical Burst Switching (OBS), combining high-speed optical transmission/switching technology and flexible electronic processing, has attracted considerable research attention from both academic and industrial fields. Although OBS is a promising solution for future IP/DWDM all-optical network, a lot of key issues such as TCP transmission and end to end delay are still under studied. Moreover, most of current researches focus on theoretical topics such as network protocols and algorithms in OBS, while few experimental activities are reported.In this dissertation, some key issues such as burst assembly, resource scheduling and end-to-end QoS are investigated, and some feasible solutions are proposed. Then a testbed based on Label switching method for OBS network is demonstrated, and some key technologies in this testbed are discussed, finally some latest experimental results are presented. Following are details.1) The performance of TCP traffic over OBS network is discussed. The transmission performance of TCP traffic is investigated at the situation when Data burst and ACK burst are dropped individually. Simulation models have been constructed and experiments on OBS testbed have been carried out to evaluate the discussed issues. It turns out that Data burst losing result in worse network performance than ACK burst losing. Based on this result, high class of QoS can be assigned to Data burst when network contention happens to maintain TCP transmission at a comparable high level at bad network situation.2) A group-based scheduling (GS) algorithm with features of simplicity, high bandwidth efficiency and QoS capability is proposed. GS-scheduling algorithm schedule multi-bursts after a delay window time, by doing so it can better utilize the burst voids and achieve high bandwidth efficiency. Moreover, a contention resolution is proposed to handle the problem about contentions happening between bursts with the same class of QoS. Simulation results show that GS-scheduling demonstrate a better performance than LAUC scheduling algorithm.3) A novel DS-JET algorithm based on control packet duplication is proposed. DS-JET algorithm achieve powerful capability by coupling with current JET scheduling algorithms while features on low time consuming during the processing on network intermediate node, which result in lower network end to end latency than JET algorithms. Furthermore, the influence of path length priority effect can be reduced in DS-JET mechanism. Simulation results show that DS-JET demonstrates better performance in burst blocking probability, network throughput and end to end QoS provision.4) A testbed based on label switching for OBS network is demonstrated for the first time in China, and its network architecture and especially core router architecture are discussed, with emphasis on resource scheduler, optical cross-connect and system control/management module which provide a research platform for assembly algorithm, scheduling algorithm and routing/signaling protocols respectively. Finally, some corresponding experimental results are presented, in which various modules such as optical switch, burst assembler, resource scheduler and burst receiver are verified and network latency in the testbed is evaluated. Moreover, a multi-QoS traffic transmission experiment over the testbed is discussed which will be helpful for future research on up-layer application in optical network.更多还原