可编程光缓存器在OBS中的应用

对之前报道的两种可编程光缓存器结构在光突发交换网中的应用进行了仿真研究.构建了仿真平台,选取支持QoS的JET协议,提出了一种简单的资源调度算法,在相同网络流量的情况下,对比研究了采用两种可编程光缓存器和固定时间光缓存器时,OBS网络在丢包率和时延等方面的差异.仿真结果表明,两种可编程光缓存器在以上性能方面有良好的优越性.因此该可编程光缓存器可较好地解决光突发交换网突发包的冲突问题.     

基于同波长光纤延迟线集光突发交换结构及其性能分析

由于光突发交换机制本身就避免了光缓存的使用，但是现实中，光突发包之间竞争以及提供优先级服务又依靠光纤延迟线来解决。为此，我们设计了应用光纤延迟线的光突发交换网络核心节点结构。为了避免光纤延迟线色散引起的突发包输入排队缓存偏移，在该结构中设计了同波长光纤延迟线集。采用了空分交换矩阵，避免了波长转换的需要。为了有效运行该交换结构，我们提出了输入排队与自适应光缓存调度算法，而该算法不仅仅适用于光突发交换，也适合于光纤延迟线得到普遍应用的光分组交换。该调度算法能够提供优先级服务，避免队头阻塞，对该调度算法建立了严格的理论分析模型，并进行了仿真。仿真结果表明，与传统的延迟线竞争解决方案相比，这一调度算法能够改善交换性能1到2个数量级，是利用光纤延迟线解决光突发交换中竞争问题的一个较佳方案。     

定长光突发下的FDL缓存和调度

为了改善光突发交换的阻塞性能,分析了定长光突发交换在FDL光缓存的排队和调度,提出了基于中间共享FDL光缓存结构的长队列优先(LQP)调度方案,该方案使交换端口充分共享FDL缓存单元,调度时间短,在模拟仿真中得到较好的阻塞性能结果。     

光突发交换网络中一种基于LAUC的批调度算法

为了降低突发丢失率和调度复杂度,提出了一种基于LAUC的批调度算法.该算法首先缓存多个突发控制包,当最大缓存时间到达时,根据突发到达顺序批调度处理缓存中的突发控制包,并采用LAUC算法来为突发预留信道资源.其优势在于:计算复杂度与LAUC一样低,因为它只增加了突发控制包缓存和改变了LAUC算法的调度顺序;突发丢失率比较低,仿真结果表明它的突发丢失率比LAUC算法要低,当最大缓存时间大于偏置时间的最大差值时,它的突发丢失率比LAUC-VF算法还要低.     

光突发交换网络中基于突发包分段的联合冲突解决方法研究

光突发交换(OBS)技术由于结合了电的灵活处理和光的高速传输,成为构建下一代全光互联干线网最具前景的交换方式,其单向资源预留方式导致的突发包冲突是限制OBS走向实用的关键。基于突发包分段的光缓存冲突解决方法和基于突发包分段的波长转换冲突解决方法,首先通过对低优先级突发包进行分段解决冲突,然后对分段后冲突部分突发包进行光缓存或波长转换降低丢包率。对基于突发包分段的光缓存和基于突发包分段的波长转换两种冲突解决机制的性能进行了比较研究,仿真结果显示:两种机制都能够有效地降低整个网络的丢包率。当网络负荷较高时,采用基于突发包分段的光缓存方法对降低突发包的丢失率效果比较明显;当网络负荷较低时,采用基于突发包分段的波长转换方法能够更加有效地降低突发包的丢失率。     

光突发交换网络新型偏射路由方案研究

光突发交换(OBS)被认为是下一代光网络中的有效核心交换技术之一,设计OBS网络的最初目的之一是减小突发包丢失率.解决突发竞争的方法主要包括光缓存、波长变换、偏射路由和突发分段.提出一种改进偏射路由方案,并建立了数学模型,对改进方案的性能进行了仿真分析,结果表明改进方案能更好的提高网络整体性能.     

配备光缓存的OBS核心路由器性能分析

光突发交换(Optical Burst Switching,OBS)网络是下一代IP over WDM全光网络的发展趋势.文章主要研究并分析了OBS网络中配备有光缓存的核心路由器性能,给出了突发数据分组阻塞率、输出端口占用率、排队时延等性能参数.所得结果对0BS网络理论研究进行了一定的补充.     

时隙可变长分组缓存调度算法

提出了一种采用时隙处理光分组竞争冲突的基于光纤延迟线的光分组交换缓存算法——时隙可变长分组缓存调度算法SVPB(slotted variable-length-packet-capable buffer)。该算法根据先到先服务的排队原则,通过对到来的光分组进行时间轴分段处理,解决了FDLs作为缓存器的不足。从仿真结果得到,在网络负载较高时所提出的调度算法SVPB比已有的调度算法分组丢失率有明显的降低。     

OBS网络中基于优先级的先分割后缓存冲突解决方法

为了有效地降低突发包的丢失率和保证OBS网络中不同优先级业务的服务质量,提出了一种基于优先级的先分割后缓存冲突解决方法。该方法通过在多波长信道系统的输出数据信道上设置光纤延迟线组来缓存被分割的冲突突发包。当冲突发生时,首先基于突发包的优先级和处理完毕时间进行"竞争突发包头部分割或者原突发包尾部分割"处理;无冲突部分进行交换或者直接在事先预留的输出数据信道上处理,冲突部分的分割突发包进行光缓存。仿真结果表明,多波长信道系统中,高优先级突发包的丢失率低于低优先级突发包的丢失率。同时该方法在一定程度上可以有效地减少端到端的传输时延和整个网络的丢包率,从而提高整个OBS网络的性能。     

异步光分组交换的光电混合队列及调度

研究了以光纤延迟线作为主要的常规缓存,以电存储器作为辅助缓存的光电混合缓存的光电混合缓存结构,并用改进的FF-VF算法调度冲突的分组,达到改善长度可变光分组交换的分组丢失率目的.分析和仿真结果都表明,光电混合缓存和改进的FF-VF算法能改善可变长光分组交换在负载较高时的分组丢失率性能,并减少光纤延迟线的数目.     

A burst loss probability model with impatient customer feature for optical burst switching networks

We consider optical delay line buffer as a solution to reduce the number of lost burst in optical burst switching, one of the promising candidates for future networks. Such network takes burst loss as an important performance criteria in the design step. Network performance, however, cannot be captured efficiently using traditional queueing models, because they often ignore the impatience of messages traveling through optical switches which is one of the popular issues in communication networks. In this paper, we develop an analytic model for this system using queueing theory and considering special impatience features. Simulation results show that (i) the developed model with impatience features can decrease burst loss probability ( ? 10%) compared with other approaches, and (ii) applying that model, we demonstrate that shared buffer architecture in optical burst switching network with optical buffer often achieves lower burst loss probability than dedicated buffer way in several different scenarios. Copyright © 2014 John Wiley & Sons, Ltd.     

光突发交换网络基于优先级与突发包分割的光缓存方法

为了保证光突发交换(OBS)网络中不同优先级业务的服务质量(Qos)和有效地降低突发包的丢失率,提出了一种基于优先级与突发包分割的光缓存方法.该方法通过在输出数据信道上设置光纤延迟线组来缓存被分割的冲突突发包.当冲突发生时,基于突发包的优先级进行"竞争突发包头部分割或者原突发包尾部分割,,处理;无冲突部分进行交换或者直...     

未来光因特网中的光交换方式及其发展趋势

Internet的业务流量正以每六个月翻一番的速度快速增长,未来网络中,数据业务超过话音业务只是时间问题,因此,基于电路交换的电信网升级到支持基于分组交换的数据业务是不可避免的,但是对因特网来说,由于光逻辑与光存储等器件不成熟,发展全光分组交换,技术上异常困难。另一方面,近来新提出的光突发交换,技术上相对简单,性能特点优异,因而成为更理想的选择,本文介绍了全光分组交换和光突发交换的研究现状,比较了两者的优缺点,最后指出改进光突发交换性能的两种方式。     

Scheduling Algorithms for a Slotted Packet Switch with either Fixed or Variable Length Packets

We address the problem of congestion resolution in optical packet switching (OPS). We consider a fairly generic all-optical packet switch architecture with a feedback optical buffer constituted of fiber delay lines (FDL). Two alternatives of switching granularity are addressed for a switch operating in a slotted transfer mode: switching at the slot level (i.e., fixed length packets of a single slot) or at the burst level (variable length packets that are integer multiples of the slot length). For both cases, we show that in spite of the limited queuing resources, acceptable performance in terms of packet loss can be achieved for reasonable hardware resources with an appropriate design of the time/wavelength scheduling algorithms. Depending on the switching units (slots or bursts), an adapted scheduling algorithm needs to be deployed to exploit the bandwidth and buffer resources most efficiently.     

OBSns:一种OBS通用仿真平台的设计

光突发交换(OBS)是当前全光交换网络技术的研究热点之一,而仿真是OBS研究的一种重要手段。为了给研究者提供方便,同时实现各种研究结果的对比,开发了一种通用的OBS网络仿真平台--OBSns。OBSns以网络仿真工具NS-2为基础,对突发数据传输采用虚拟化的方法,实现了OBS网络的关键元素如突发组装、突发控制分组生成和传输、突发调度等等。同时OBSns是开放的,其各个元素都可以替换,从而为新算法和协议的研究提供了便利。     

Control architecture in optical burst-switched WDM networks

Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over WDM. In this paper, we describe the basic concept of OBS and present a general architecture of optical core routers and electronic edge routers in the OBS network. The key design issues related to the OBS are also discussed, namely, burst assembly (burstification), channel scheduling, burst offset-time management, and some dimensioning rules. A nonperiodic time-interval burst assembly mechanism is described. A class of data channel scheduling algorithms with void filling is proposed for optical routers using a fiber delay line buffer. The LAUC-VF (latest available unused channel with void filling) channel scheduling algorithm is studied in detail. Initial results on the burst traffic characteristics and on the performance of optical routers in the OBS network with self-similar traffic as inputs are reported in the paper.     

Modeling and Synthesis of Traffic in Optical Burst-Switched Networks

We analyze burst assembly process as the main building block of the optical burst switching (OBS) paradigm. The analysis is performed for time-based, volume-based, as well as hybrid burst assemblers. Under the assumption that the process of packet arrival to the assembly buffer is Poisson, exact analytical expressions are derived for length and interdeparture time of bursts that are generated by these three classes of assembly algorithms. Furthermore, we consider the issue of generating burst trace, which arises during the performance evaluation of OBS networks through discrete-event simulation. In such a simulation study, a significant part of the simulation time, particularly in the case of a network with a large number of ingress nodes, is used by the implementation of the burst assembly algorithms. This is due to the fact that each data burst is a result of aggregating several short-length packets, which-in a straightforward approach-have to be individually generated and, afterward, ldquomeltedrdquo into the burst. We present a novel approach to fast generation of bursts, which is based on the analytical models that are developed for burst length and burst interdeparture time distributions as well as an efficient generation technique (composition) supporting the generation of these distributions. The analysis is completed by numerical results that validate the accuracy of developed models and demonstrate the speedup gain of using proposed burst generation algorithms.     

光突发交换核心节点的缓存结构设计

提出了光突发交换（OBS）核心节点上缓存结构的合理而高效的设计方案。在建立核心节点的突发流与突发竞争模型的基础上,提出缓存结构设计应满足的基本条件,进而义提出将缓存结构和交换结构相结合的集成结构方案;同时,通过归纳和扩展,提出缓存结构的多角度综合分类规则。分析和仿真结果显示,集成结构方案满足所提出的缓存设计基本条件,在不受成本等限制时,尽量使用光纤共享型,而且在同样的共享范围,输出型要比输入型好,特别是光纤共享情况更为明显。     

OBS考虑优先级的突发包碎片可控合并重传算法

为了降低光突发交换网络中突发包的丢失率、降低网络路径的阻塞率、减小突发包冲突的概率,提出了考虑优先级的突发包碎片可控合并重传算法。当网络中数据通信发生冲突时,该算法能根据优先级进行突发包的分片,核心节点将这一信息反馈给边缘节点,边缘节点根据突发碎片的优先级以一定的概率重传被丢弃的突发包分片;同时,针对由于多次重传导致的突发包碎片过多的问题,该算法还按照突发包碎片的优先级顺序进行碎片重组,大大降低了网络的阻塞率。结果表明,相比以往的冲突解决算法,此算法在网络业务繁忙时的数据丢比特率和网络阻塞率方面的改善作用有比较明显的优势。这一结果对光突发交换网络的网络的性能改善方面是有帮助的。