基于虚拟突发的OBS数据信道重调度算法研究

基于虚拟突发的概念,提出了一种新的光突发交换(OBS)数据信道重调度算法,即(WCRA-VB).新算法一方面有效地克服了传统OBS网络中数据突发(DB)与控制分组(BHP)到达顺序不一致带来的问题,另一方面极大地增强了数据块重调度的灵活性.仿真结果表明:与传统OBS重调度算法(其重调度粒度为常规突发)和原虚拟突发调度方案相比较,本文的WCRA-VB算法具有以下优势:既能有效改善网络总的丢包率,也能提高链路利用率,同时具有很强的灵活性.     

一种基于虚拟突发的OBS网络业务疏导机制

提出了一种基于虚拟突发光突发交换的(OBS)网络业务疏导机制TG-VB(traffic grooming based on virtual burst)。作为一种多粒度动态业务疏导机制,TG-VB将常规突发通过"逻辑汇聚"组成虚拟突发,增大核心网中业务传输粒度;同时,TG-VB根据虚拟突发整体传输、整体调度的特点,为汇聚的常规突发动态地选择最优的共用传输路径。仿真结果表明,与采用传统疏导机制的OBS网络相比,TG-VB能够有效地减轻核心节点的通信处理开销,降低对网络节点端口数量的需求;在相同负载条件下,TG-VB可极大地提高波长信道利用率。     

OBS网络数据信道调度算法性能比较

光突发交换(OBS)网络中数据信道的调度算法是提高OBS网络性能的关键技术之一.文章给出了LAUC、LAUC-VF、BR和LAUC-VF-BS等几种数据信道调度算法的基本原理,通过仿真对这些调度算法进行了性能比较,结果表明LAUC-VF-BS算法能够更有效地降低突发丢失率,提高信道利用率,从而改善网络性能.     

光突发交换网络中的闭环竞争解析

为改善光突发交换网络(OBS)的性能,深入探讨了光突发交换网络中的闭环竞争解析,提出了OBS网络中的主动资源预留方案OBS—RED和显式竞争通知方案OBS—ECN。OBS—RED采用随机早期丢弃策略,即根据数据信道拥塞情况,随机早期地丢弃控制分组。OBS—ECN的实现需要OBS—RED的支持。在OBS—ECN中,不是随机丢弃控制分组,而是将这一信息显式地通知边缘节点,边缘节点再作相应的处理。OBS—RED与OBS—ECN的应用,有利于提高网络吞吐量和链路带宽资源利用率,大大减少数据突发的阻塞概率。     

OBS网络中改进汇聚算法的研究

WDM技术的迅速发展使网络传输带宽大幅提升,由此出现了节点瓶颈问题.由于光器件技术的不成熟,出现了相对简单的过渡技术--光突发交换(OBS),成为当前最具应用前景和技术优势的交换方式.OBS中的突发汇聚技术是边缘节点的关键技术之一,文中在基本汇聚算法的基础上介绍了四种改进算法,分析说明合理的汇聚算法不仅可以减轻交换节点的处理负担,还可以实现流量整形及OoS区分功能,提高OBS网络的整体性能.     

光突发交换网络中的传输控制协议性能

光突发交换(OBS)是IP over WDM核心网络采用的交换技术。在OBS网络中,送往同一边缘节点的IP分组汇聚成传输和交换的基本单元———数据突发(DB),DB丢弃会导致大量IP分组丢失,显著影响传输层的性能。文中分析OBS网络的参数对传输控制协议(TCP)吞吐量和时延的影响。仿真结果表明,DB丢包率越高,TCP性能越差。在低丢包率情况下,随着DB长度的增加,TCP吞吐量和端到端时延明显增加,高丢包率情况下则不明显;随着汇聚周期的增加,TCP吞吐量逐渐下降,端到端时延逐渐增加。     

光突发交换网络数据信道调度算法的研究

在OBS网络中,核心节点的调度算法是影响网络交换性能的重要因素。如何有效地对数据突发(Data Burst)分组进行合理调度,提高信道利用率,减少丢包率是关键问题所在。在讨论了几种数据信道调度算法的基础上提出了一种BHP收集调度算法,该算法在一个收集周期内对到达的多个BHP所对应的突发数据,按照一定的方式对它们进行集中调度,从而达到合理调度。仿真结果表明BHP收集调度算法比其他几种算法的突发丢失率性能都要好。     

光突发交换网络中基于标记可抢占的调度算法

根据光突发交换(OBS)网络核心节点的结构和功能 特点,分析了OBS网络核心节点的数据信道 调度算法,提出了一种新的基于标记可抢占调度算法(LPSA),并讨论和分析了算法的实 现过程。本文算法根据到达核心节点的控制包所属业务等级的突发数据(OB)包占用的网络带 宽决定 数据信道调度的方法,实现了合理的使用数据信道和各业务类别间的业务区分,最终达到改 善OBS网络性能的目的。     

多态OBS网络中基于信道整理的调度算法

多态光突发交换(POBS)网络能够有效地支持多种同步和异步业务的传输,但是其异步突发业务的丢失率较相同网络环境下的传统OBS丢失率要高。如何有效地对多态OBS中异步突发进行合理调度,是降低异步突发丢失率的关键所在。提出了一种基于信道整理的调度算法,将已经成功调度的突发重新调度到最合适的数据信道,使得信道资源得到充分的利用,从而降低了异步突发的丢失率。仿真结果表明,该算法能很好地降低多态OBS网络中异步突发的丢失率。     

自适应混合光交换

当前的混合光交换只是简单地把光电路交换和光突发交换叠加在一起,其复杂度高.并且不能有效支持突发性强的业务.针对这种缺陷,本文提出了一种自适应混合光交换方式.自适应混合光交换的入口边缘节点监测一对入口边缘节点和出口边缘节点之间的业务流量的大小,自适应地调整光交换方式.在最小突发长度最大汇聚时间算法的基础上,提出了自适应混合光交换的汇聚算法,以提高光路的利用率和有效支持突发性强的业务.同时提出了数据信道调度算法,它能统一为光路和数据突发预留资源,并降低了混合光交换的复杂度,提高了网络性能.仿真结果表明,与光突发交换相比,自适应光交换能有效降低IP包丢失率和端对端时延.     

光突发交换中的突发包组装技术研究

光突发交换是近几年出现的一种很有前途的光交换技术，比电路交换灵活，带宽利用率高，又比光分组交换易于实现，突发包的组装是光突发交换的关键技术，在很大程度上影响到光突发交换网络的性能。文中介绍了光突发包的格式，描述了交换网络中突发包组装所需的层次结构和功能结构，并给出了一种典型的生成算法。最后，对选择突发包组装时间应考虑的各种因素进行了系统的分析。     

Meteor burst communications. I. Meteor burst propagation

Meteor burst communication systems are introduced with emphasis placed on the unusual propagation mode which they employ. The origin of meteors and their trails is reviewed and the trail characteristics relevant to communication systems described. The restriction on scattering geometries for viable transmission paths is explained and the related footprint and hot-spot properties of meteor burst systems outlined. Meteor burst transmission loss is formulated in the conventional way as a modified bistatic radar equation and the origins of the modifying factor qualitatively explained. Meteor burst equipment, operating principles and applications are also briefly discussed. Finally, important quantities for assessing the performance of meteor burst systems are defined and typical values quoted     

光突发交换网络中突发组装机制的性能分析

研究了光突发交换网络中关键技术之一的突发组装机制,介绍了基于时间门限组装、基于长度门限组装和混合门限组装3种典型的突发组装机制,并对比分析了三种组装机制对网络汇聚性能（突发大小、组装时延）的影响以及自相似性能的改善情况,得出混合门限组装机制能获得更好的网络汇聚性能和自相似性能的改善的结论。     

Meteor burst communications

The characteristics of meteor burst communications are described and compared to those of HF and satellite systems. The two generic types of MB systems, broadcast and channel-probing systems, are explained. In systems using the broadcast protocol, the transmitter knows nothing about the occurrence of bursts or trails and transmits continuously for a sufficient duration to permit all recipients to receive the message/data with the desired probability. For practical purposes, the optimum burst or block duration for such systems is around 100-200 ms, based on the characteristics of the predominant trails. Channel-probing MB systems are more common and are commercially available in several versions. Here the transmitter repeatedly sends a short (typically 5-20 ms) probe signal until it receives a similarly short message response, indicating the availability of a suitable trail. A third, intermediate type of protocol with hybrid features does not probe the channel with a short signal, but starts repeatedly transmitting the first packet, in effect using it as a probe signal. Fundamental design issues and/or parameters of specific relevance to MB communication systems are discussed. Some historical and more recent MB systems are examined     

光突发交换技术

介绍了一种很有发展潜力的新交换模式－－光突发交换。对其基本概念、交换原理、网络结构、节点结构进行了简明的阐述,通过与另外两种典型交换模式－波长路由与光分组交换的比较,总结了光突发交换的优势,并指出了光突发交换尚待解决的问题。     

光突发交换中的突发业务流模型及其应用

提出了一种光突发交换中的突发业务流模型,采用该模型对光突发交换中的LAUC-VF输出调度算法在不同的突发业务强度和突发长度下的性能进行了模拟仿真,分析比较了该算法在此突发业务流和普通业务流模型下的性能,仿真结果表明,该突发业务流模型具有一定的合理性。     

A unified study of burst assembly in optical burst switching networks

This article presents a comprehensive study of burst assembly in optical burst switching (OBS) networks. This investigation aims to provide a unified study of burst assembly algorithms. After analyses of conventional assembly algorithms, we present an adaptive burst assembly algorithm: data-length time-lag product assembly algorithm. Numerical results show that the proposed algorithm takes the real-time traffic state into account to adapt burst length and its injected intervals. It obtains a more acceptable performance. Moreover, we investigated the impact of burst assembly applied at the edge of OBS networks. We analyze the Hurst parameter of the input traffic to the output traffic that results from the burst assembly. Two formulas are presented to describe changes of the Hurst parameter. Theoretical results are validated through extensive simulations in time-based, length-based, and adaptive assembly algorithms, respectively.     

Exploring node light-splitting capability for burst grooming in optical burst switched networks

Optical burst switching (OBS) is a switching concept which lies between optical circuit switching and optical packet switching. Both node switching time and burst size can impact the resource efficiency of an OBS network. To increase resource utilization, burst grooming has been proposed where numerous data bursts are coalesced to form a larger burst that will be switched as one unit in order to reduce the resource waste and switching penalty. In this article, assuming burst grooming can only be realized at edge nodes, we study the burst grooming problem where sub-bursts originating from the same source may be groomed together regardless of their destinations under certain conditions. We explore the capability that core nodes can split incoming light signals to support multicast to achieve more efficient burst grooming. Specifically, core nodes can transmit the groomed burst to multiple downstream nodes if the sub-bursts in the groomed burst have different destinations. The groomed burst will traverse a tree which spans the source and all the destinations of the sub-bursts in the groomed burst. The destination egress nodes recognize, de-burstify, and drop the sub-bursts destined to these nodes, i.e., the sub-bursts destined to these egress nodes are removed from the groomed burst. At the same time, the remaining sub-bursts may be groomed with sub-bursts at these egress nodes subject to burst grooming criteria. We propose two effective burst grooming algorithms, (1) a no over-routing waste approach (NoORW); and (2) a minimum relative total resource ratio approach (MinRTRR). Our simulation results have shown that the proposed algorithms are effective in terms of the burst blocking probability, the average burst end-to-end delay, the number of sub-bursts per groomed burst, as well as the resource waste.     

Impact of burst aggregation time on performance in optical burst switching networks

In this paper, we present the performance analysis of Just-In-Time Optical Burst Switching (JIT-OBS) under realistic web traffic. We demonstrate and explain the impact of Burst Aggregation Time (BAT) on performance under the short-lived TCP flows model. We consider both data and control planes. Our results show that BAT has an impact on TCP performance through packet losses and packet delay in the data plane. The results also show that the network has an optimal point of operation dependence upon BAT. We also incorporate BAT’s impact on the control plane’s congestion.