【作者】 袁巍；

【导师】 李津生；

【作者基本信息】 中国科学技术大学 ， 通信与信息系统， 2006， 博士

【摘要】 因特网的飞速发展对数据传输技术提出了更高要求。密集波分复用(DWDM)技术能充分利用光纤巨大的传输容量，基本满足了对带宽的需求。为了有效利用原始带宽，应该直接在光层透明地传输和交换IP分组。光突发交换(optical burst switching，OBS)作为一种新的光交换技术，具备了波长路由和光分组交换的优点，有着很好的应用前景。在OBS网络中，具有相同出口地址(和相同服务质量参数)的多个IP分组被汇聚成一个数据突发(Burst)，作为一个整体在网络中传输。OBS的一个重要特点是Burst的数据信息和控制信息分开传送和交换。这方便了光核心路由器对控制信息的电处理，也为实现数据信息的端到端全光透明传输奠定了基础。 在OBS网络中支持区分服务(differentiated services，DiffServ)是一个非常重要的研究课题。区分服务模型可以分为两种：相对区分服务模型和绝对区分服务模型。在OBS网络中支持区分服务可以通过以下两种方法来实现：使用额外偏移时间(extra offset time)和使用具有区分服务功能的数据信道调度机制。 本文着重阐述了在OBS网络中支持区分服务的方法，其主要内容包括：光交换网络的背景，OBS网络的介绍，基于额外偏移时间的区分服务机制和区分服务数据信道调度机制等。论文的主要研究工作和创新如下： 论文的第二章介绍了OBS网络的体系结构和诸如数据信道调度、资源预留协议等重要研究课题。这一章提出了一种新的数据信道调度算法——最少波长转换(minimalwavelength convening times，MWCT)算法。它能有效地降低网络中波长转换操作的频率，从而减轻核心路由器的负担，并削弱波长转换操作给光信号带来的不良影响。 现有的资源预留协议JET(just enough time)会导致延时冗余，与偏转路由(deflectingrouting，DR)兼容也有一定难度。本文的第四章提出了一种新的资源预留协议JLT(just little time)。JLT协议只需很小的初始偏移时间，并使用光缓存来补偿偏移时间的不足。它能有效地减小Burst端到端的延时，并能无修改地兼容偏转路由。为在基于JLT的OBS网络中支持相对区分服务，第四章提出了PJLT(prioritized JLT)协议。PJLT协议使用额外偏移时间，它能减少高优先级Burst的资源请求被低优先级Burst阻塞的概率，从而显著降低高优先级业务的数据丢失率。第四章还提出了一种结合使用额外偏移时间和Burst抢占／Burst主动分段丢弃技术的支持绝对区分服务的新方法。该方法可以用于基于JET的或者基于JLT的OBS网络中，分别称为PSPJET(supporting preemption and segment PJLT)机制和PSPJLT(supporting preemption and segment PJET)机制。PSPJET／PSPJLT机制的数据丢失率比PJET／PJLT低，而且对高业务负载的承受能力比APJET(absolute PJET)机制更强。此外，PSPJET机制不要求使用光缓存，可以用于无光缓存的OBS网络中，降低网络的建设成本。 另外一种在OBS网络中支持区分服务的方法是使用具有区分服务功能的数据信道调度机制。论文的第五章提出了一种SD(service differentiation)数据信道算法。该算法能为更多还原

【Abstract】 The explosive growth of Internet is driving the demand for a high-speed transmission technology. DWDM (dense wavelength division multiplexing) technology has exploited the huge potential bandwidth of optical fibers to meet the bandwidth requirement. In order to efficiently utilize the raw bandwidth, IP packets should be transmitted and switched directly at the optical layer. Optical burst switching (OBS) has been proposed as a new optical switching technology combining the advantages of optical wavelength routing and optical packets switching. OBS is considered as a promising solution for optical Internet backbone in the near future. In OBS networks, several IP packets with the same egress router address and some common attributes like quality of service (QoS) are assembled into a burst which is to be forwarded through the network as one entity. An intrinsic feature of the OBS is the physical separation of transmission and switching of burst payloads and their headers, which helps to facilitate the electronic processing of headers at optical core routers and provide end-to-end transparent optical paths for transporting burst payloads.Differentiated Services (DiffServ) support in OBS networks is a very important issue. DiffServ models consist of relative DiffServ model and absolute Diffserv model. There are two main approaches to support DiffServ in OBS networks: using extra offset times and using special data channel scheduling.This dissertation focuses on DiffServ support in OBS networks and its content includes: the background of optical switching networks, the introduction of OBS networks, extra offset time based DiffServ mechanism and data channel scheduling based DiffServ mechanism. The research topics and our contributions are as follows.The architecture of OBS networks and some important issues including data channel scheduling algorithms and resource reservation schemes are introduced in Chapter 2. A new data channel scheduling algorithm called minimal wavelength converting times (MWCT) is proposed in this chapter to reduce the times of wavelength converting and consequently reduce the burden of core routers and negative influence on optical signal of the wavelength converting operation.Since the existing resource reservation scheme for OBS networks called just-enough-time (JET) can result in delay time redundancy and is not compatible with Deflecting Routing (DR) easily, a new resource reservation scheme called just-little-time (JLT) is put forwarded in Chapter 4. JLT scheme need only a small initial offset time and use optical buffers in core routers to compensate the offset time. JLT can reduce the end-to-end delay time of bursts and cooperate with DR without any modification. To support relative DiffServ in JLT-based OBS networks, PJLT (prioritized JLT) scheme is proposed in this chapter. The extra offset time is used in PJLT更多还原