基于多种性能约束的光突发交换网络动态组装算法

在综合分析光突发交换网络中组装算法对控制平面处理时延、数据平面资源利用效率和数据平面突发丢失率等多种性能指标的影响的基础上,提出了一种能够同时满足多种网络性能指标约束的边缘节点动态组装算法。该算法根据全网目标性能指标的约束,动态调整组装输出的突发长度和突发时间门限,从而实现同时满足全网链路资源利用率和控制平面突发丢失概率的双重性能约束。     

基于NS的光突发交换仿真平台设计

光突发交换（OBS）是一种可行的构建下一代光网络的交换技术，它可以在现有光交换技术基础上较好地支持网络中的突发性业务。由于业务的突发性强，所以路由和波长分配的设计是OBS网络需要解决的一个关键问题。仿真是设计网络协议和验证算法的重要手段之一，但对于OBS，目前还缺乏一种通用仿真模型。该文在NS-2网络仿真软件的基础上，实现了一个光突发交换的仿真平台OBSns。仿真数据表明，OBSns得到的仿真结果和理论分析结果相符，可以用来设计并验证光突发交换网络中的波长和路由分配算法。     

卫星CICQ交换系统调度算法研究

联合输入交叉点排队(CICQ)交换结构由于在交叉点引入少量缓存,可以将输入端口和输出端口进行有效隔离,降低调度算法的复杂度,并适用于大容量交换。为此,研究基于交叉点缓存的各种调度算法和基于CICQ的交换结构,提出一种基于流量控制的FCSA算法,通过OPNET仿真分析表明该算法在均匀分布和突发业务源的情况下具有较好的时延性能,并且复杂度低,吞吐量大。将该算法应用于星载交换机,结果表明,该算法可以满足星载交换机多业务突发传输的特点,易于硬件实施。     

一种改进的光突发交换数据包竞争解决算法

光突发交换技术是近年出现的一种新型交换技术,偏射路由在解决突发数据包竞争具有自己独特的优点.对光突发竞争机制进行了分析比较,针对目前数据包竞争算法存在的问题,研究一种改进的偏射路由算法和实现机制,相比未改进的算法,模拟仿真结果表明在业务流量负栽增加的情况下具有更好的性能.     

基于异步光分组交换的高性能计算机系统

基于异步光分组交换及光组播技术,提出一种新型高性能计算机系统（HPCS）。采用分布式控制结构进行系统的分级管理,有利于处理大批量突发业务及系统的全光多级扩展。基于循环光纤延时线（Rec-FDL）,提出一种紧凑、大容量的异步全光分组冲突解决机制,并与传统的分组重传冲突解决算法（PRA）进行了性能比较;建立了系统的稳定性、丢包率及时延分析模型。仿真结果表明,对于一个能够实现40 320个CPU互连的两级系统,Rec-FDL机制的平均分组等待时延TRec-FDL约为0.004 ns,而PRA算法的平均分组等待时延Trerans随分组传输距离D增加而增加,在D为10 m和20 m时,Trerans分别等于0.006 ns和0.01 ns。因此,对于分布式HPCS而言,Rec-FDL机制具有更优秀的时延特性。     

战术Ad hoc网业务量突发特性下的退避算法研究

战术Ad hoc网是一种以突发数据业务为主的分组无线网络,业务流实际上具有着一种自相似特性,与以往研究中所使用的泊松业务模型区别很大。自相似业务突发产生成批到达,使得节点缓存队列更加拥塞,排队时延增长。在研究多路重尾ON/OFF源生成自相似业务的基础上,通过对各源的突发情况进行定量分析,提出了一种适用于自相似业务的退避算法。该算法为节点引入适当的竞争系数,使得对于信道的访问可以根据当前网络的突发状态合理分派。实验在OPNET下进行,通过调整网络节点数和突发程度,仿真得到各项统计结果。不论网络时延还是吞吐量,改进后的协议都具有较好的性能。这对战术Ad hoc网络的协议设计、资源的优化配置具有参考价值。     

NS2在光突发交换仿真中的应用

通过对网络模拟仿真软件NS2的扩展，建立光突发交换仿真平台；并且利用该仿真平台对作者提出的一种新的调度算法的性能进行了验证，新算法综合考虑信道上空闲间隙的利用率以及资源预约后生成的前后间隙的影响。仿真结果表明，新算法的性能比传统算法LAUC-VF算法的性能更好，改善率最大可以达到11％。     

一种高速crossbar调度算法及其性能分析

分析了高速crossbar调度算法iSLIP在处理突发业务时性能严重恶化的原因。结合LQF/iLQF算法的思想,提出了又一种输入排队crossbar调度算法iPGQM。仿真结果表明:该调度算法在均匀业务流量下和iSLIP算法的性能基本相同;在突发业务的条件下,iPGQM算法具有更好的抗突发特性;特别在重负载的条件下,与iSLIP算法相比,不仅具有更高的吞吐量,而且平均延迟降低了10%左右。     

DiffServ中基于优先级的队列调度算法

为了提高DWRR算法的时延性能及应对突发流的能力,文中结合比例时延区分服务模型,在DWRR算法的基础上提出了一种能够体现优先级的队列调度算法-PDDRR。该算法的控制目标是保证各业务流的平均排队时延在无突发业务流时维持在给定的比率,而在应对突发流时忽略时延的比例公平原则,根据网络实时负载动态地调整各队列的权值,合理地分配资源。仿真结果表明,算法不仅能实现不同优先级业务的时延区分,而且在业务流突发时为各等级业务提供服务质量保证。     

一种支持比例区分服务的OBS数据信道调度算法

光突发交换（OBS）是实现IP／DWDM网络的一种极有前途的方案,该文提出了一种用于OBS网络的PDF数据信道调度算法,此算法能支持比例区分服务，保证高优先级业务数据比低优先级业务数据得到更可靠的传输．计算机仿真验证了PDF调度算法的性能．     

Provision of differentiated performance in Optical Burst Switching networks based on burst assembly processes

Optical Burst Switching (OBS) has been designed as a practical solution for the high-speed transport network using enabling optical technologies, which can work without optical buffering or pure optical signal processing in the intermediate nodes. As a collection of many packets, optical bursts exhibit different traffic characteristics in the bufferless optical core networks compared to the packet-level traffic in the conventional electronic switching systems. However, many OBS studies often neglect this issue by assuming the inputs to be optical bursts when analyzing the system performance. This paper demonstrates that the loss performance of optical bursts is dramatically different when considering burst assembly process at the edge nodes and the connectivity of the core nodes. We develop some analytical models which can model the loss performance more accurately than the traditional methods. Based on our observations, we propose a scheme to support differentiated loss performances for optical bursts by modifying the burst assembly parameters at the source edge nodes. Our scheme is implemented at the edge nodes and there is no specific requirement to the core nodes. Thus, our design provides good flexibility and scalability in the heterogeneous Internet.     

On ordered scheduling for optical burst switching

Optical burst switching (OBS) is a promising optical networking paradigm for efficient transport of bursty IP traffic over wavelength division multiplexing (WDM) optical Internet networks. In OBS, the header of a burst is sent in advance of the data burst to reserve a wavelength channel at each optical switching node along the path. The nodes use a scheduling algorithm to assign wavelengths to incoming bursts. Our work is motivated from the observation that existing scheduling algorithms assign a wavelength to a burst when its header arrives at the node. Thus, information about other bursts whose headers arrive later is not available when the scheduling decision is made. This leads to suboptimal scheduling decisions and unnecessary burst dropping. The key idea in our proposed algorithm, Ordered Scheduling, is to defer making the scheduling decision until just before the burst arrival in order to have full knowledge about other bursts. The effectiveness of the proposed algorithm is studied through simulation and the computational complexity and signalling overhead are analysed.     

A Novel Framework for IP DiffServ over Optical Burst Switching Networks

This paper presents a novel framework for IP Differentiated Services (DiffServ) over optical bursts witching (OBS), namely, DS-OBS. The network architecture, functional model of edge nodes and core nodes,the control packet format, a novel burst assembly scheme at ingress nodes and scheduling algorithm of core nodes are presented. The basic idea is to apply DiffServ capable burst assembly at ingress nodes and perform different per hop behavior (PHB) electronic treatments for control packets of different QoS class services at core nodes. Simulation results show that the proposed schemes can provide the best differentiated service for expedited forwarding (EF), assured forwarding (AF) and best effort (BE) services in terms of end-to-end delay, throughput and IP packet loss probability.     

Performance analysis of timer-based burst assembly with slotted scheduling for optical burst switching networks

In this paper, we analyze the performance of a timer-based burst assembly for optical burst switching (OBS) networks. In our analytical model, an ingress edge node has multiple buffers where IP packets are stored depending on their egress edge nodes, and bursts are assembled at the buffers in round-robin manner. Moreover, bursts are transmitted in accordance with slotted scheduling where each burst transmission starts at the slot boundary. We construct a loss model with two independent arrival streams, and explicitly derive the burst loss probability, burst throughput, and data throughput. In numerical examples, we show the effectiveness of our analysis in comparison with the Erlang loss system. It is shown that our model is quite useful for an OBS network with a large number of input and output links.     

OBS网络中基于优先级与概率的偏射路由算法*

摘 要：为了保证OBS网络中不同优先级业务的服务质量和解决偏射算法在偏射控制上的问题,提出了一种基于优先级与概率的偏射路由算法。该算法根据突发包的优先级和转发概率来控制突发包的偏射,并从网络突发阻塞概率的意义上寻找最佳偏射路由。当冲突发生时,分割优先级低的突发包,并将分割突发包偏射到空闲的链路上;节点根据链路上指定的权值,按概率为分割突发包选择一条可以使网络突发阻塞概率最小的最佳偏射路由。仿真结果表明,虽然网络中可选路由数目的增加对网络性能的改善非常有限,但是该算法能够有效的降低整个网络的丢包率,并且得到的高优先级突发包的丢失率低于低优先级突发包的丢失率,从而很好的保障了网络的服务质量。故这种方法能够有效的提高OBS网络的性能。     

Link scheduling state information based offset management for fairness improvement in WDM optical burst switching networks

In wavelength division multiplexed (WDM)-based optical burst switching (OBS) networks, bursts that traverse longer paths are more likely to be dropped compared to bursts that traverse shorter paths resulting in a fairness problem. Fairness here refers to having, for all ingress–egress node pairs in a network, a burst to have equal likelihood to get through independent of the hop length involved. In this paper, we develop a link scheduling state based fairness improvement method which can be used in a classless as well as a multi-class environment. The basic idea is to collect link scheduling state information and use it to determine the offset times for routes with different hop lengths. By using the online link state information, this method periodically computes and adapts the offset times needed, thus inherently accounting for the traffic loading patterns and network topological connectivity. It also ensures that the delay experienced by a burst is low and shorter-hop bursts are not over-penalized while improving the performance of longer-hop bursts. The effectiveness of the proposed method is evaluated through simulation experiments.     

GMPLS-based OBS光传输网络体系结构*

提出一种采用GMPLS协议作为控制面的光突发交换（OBS）网络体系结构,给出了网络结构、节点功能模型、控制包格式和新增控制信令交换接口的建议。提出的网络结构是在OBS的突发控制包用通用标签代替地址,并使用GMPLS协议栈完成路由和信令功能,实现流量工程和生存性研究。     

TCP over OBS的性能分析及改进

在光突发网络中，边缘路由器的FAP封装策略有减缓TCP流发送速率的趋势，这使得TCP流“相关受益”减小，导致其吞吐率也随之下降。对于这一问题，可以通过一种增大ACK封装时间的汇聚方案来解决。通过仿真验证，该方案的确大幅提高了TCP流的吞吐率。     

An integrated congestion control mechanism for optimized performance using two-step rate controller in optical burst switching networks

Optical burst switching (OBS) is a promising solution to implement the optical internet backbone. However, the lack of adequate congestion-control mechanisms may result in high burst loss. Schemes such as fiber delay line (FDL), wavelength conversion, and deflection routing to reduce burst collision are unable to prevent the network congestion effectively. To address this problem, we propose and investigate a global solution, called Integrated Congestion-Control Mechanism (ICCM), for OBS networks. ICCM, which combines congestion avoidance with recovery mechanism, restricts the amount of burst flows entering the network according to the feedback information from core routers to edge routers to prevent network congestion. Also, a flow-policing scheme is proposed to intentionally drop the overloaded traffic with a certain probability at a core router to support fairness among flows. Moreover, the transmission rate of each flow is controlled to achieve optimized performance such as maximizing throughput or minimizing loss probability using two-step rate controller at the edge router. Simulation results show that ICCM effectively eliminates congestion within the network and that, when combined with a flow-policing mechanism, the fairness for competing flows can be supported while maintaining effective network performance.     

构建网络的新方法：基于环路的混合交换光网络*

为了能够更好地支持突发性数据业务,提出了一种新型网络交换结构——基于环路的混合交换光网络（cyclebased hybrid switching optical networks,CHSON）。该网络结合了光电路交换（OCS）和光突发交换（OBS）两种交换技术,不仅可以有效地降低网络节点的分组转发压力,而且能够较好地承载突发性数据业务。首先介绍了CHSON的网络结构和虚拓扑设计,然后阐述了节点设计及其执行流程。仿真表明,CHSON具有比OCS网络更低的丢包率,而且在丢包率和平均分组延时方面,CHSON较