The Research for Optical Burst Switching Networks with Providing Service Differentiation

【作者】 张兴；

【导师】 孙小菡；

【作者基本信息】 东南大学 ， 物理电子学， 2005， 硕士

【摘要】 IP/WDM技术凭借其巨大的传输带宽和简洁高效的构架成为下一代光网络的基础。当光骨干网中采用WDM技术满足传输所需的带宽以后,目前在电域中交换数据的电子路由器就成为制约网络QoS保证的瓶颈。光突发交换(OBS)技术支持带宽统计复用,具有适中的光交换粒度,能够充分利用成熟的电域技术和先进的光域技术,称为目前可行的光交换方案。同时,随着基于互联网的业务类型的迅速扩展,为特殊业务提供较高的QoS保证,是运营商和研究人员必须考虑的问题。本文旨在研究OBS体系对网络QoS的支持,提出了能够提供服务区分的调度机制和算法。首先介绍和比较了两个保证QoS要求的服务模型:集成服务和区分服务。结果表明,区分服务模型扩展性较好,比集成服务能够提供更好的QoS,区分服务更易于在OBS网络体系中实现。通过将时延、时延抖动、带宽、阻塞率和误码率等更多的光层QoS参数考虑进来,建立了一个更加细化的区分服务映射模型,该模型可以针对各类业务的特点为其提供不同的服务,尤其对于一些特殊业务,对QoS的要求不再是单一的而是多方面的,该模型可以提供更好的服务。其次在OBS网络的边缘路由器中,提出了提供时延区分的基于时间和长度的突发汇聚机制和基于载荷区分的提前预留资源(LD-ARR)机制,给出了具体的算法和流程,分析了这两种机制的优点,数值仿真结果表明,突发汇聚机制可以实现不同业务的时延区分,对时延要求高的业务,突发汇聚时间和最大突发长度参数可以设置较小值;对时延要求低的业务突发汇聚时间和最大突发长度参数设置较大值。LD-ARR机制可以为不同业务提供时延区分,其在边缘路由器的总时延比采用传统的资源预留机制要小的多。最后在核心路由器中,本文提出了能够提供时延抖动区分的延时再调度(DSBD)算法模型,分析了该算法优点,数值仿真结果表明,采用DSBD调度算法的高优先级业务的抖动比低优先级的业务的抖动要减少40%左右,确实能严格保证业务对时延抖动的要求,能够有效减小端到端时延的抖动,支持对不同业务的时延抖动区分。更多还原

【Abstract】 IP over WDM technology with the advantages of enormous bandwidth and simplified configuration is the evolving trend of next generation optical internet. However, as the network capacity increases, electronic switching nodes seem unable to keep up. Optical burst switching technologies (OBS) have many virtues such as supporting bandwidth multiplexing, fine granularity and facilitating the better synergy of the mature electronic technologies and the advanced optical technologies. Meanwhile, it should be considered that providing QoS support for special applications.The focus of this dissertation is on the study of OBS network architecture supporting (QoS), at the same time, some schemes and algorithms which could provide service differentiation are proposed. Firstly, based on the characteristics of all kinds of applications and the analysis of QoS parameters in optical layer, a mapping model between applications and QoS parameters is built. It is show that providing QoS support in optical layer is necessary and important and OBS can support service differentiation. In edge routers, burst assemble scheme with time and length limit and advanced reserving resource scheme based on load differentiation to provide delay differentiation are proposed. Detailed flow charts and processes are also introduced. Finally, simulation results show that burst assemble scheme could provide delay differentiation for different applications, which burst assemble timer and burst length threshold is set to smaller value for delay-sensitive applications and vice versa. Applications which employ LD-ARR scheme also have less delay in edge routers than those use conventional reserving resource scheme. In core routers, a delay scheduling before deadline (DSBD) algorithm to provide jitter differentiation are proposed. The expressions for upper and lower bound of delay and the upper bound of delay jitter are also derived. Numerical results show that DSBD scheduling algorithm could strictly guarantee the requirements of delay jitter for jitter-sensitive applications, which can reduce delay jitter of about 40% comparing with that without using this algorithm. And DSBD scheduling algorithm could support jitter differentiation for different applications.更多还原