光突发交换环网中多接收机情况下的性能分析

因特网应用技术和光通信技术的飞速发展使现在网络的现状发生了翻天覆地的变化.最近,光突发交换技术的出现掀开了光通信技术的新篇章,它是光电路交换和光分组交换的折中方案.研究了光突发交换环网的性能,提出了为每个节点配备多个接收机的方法来降低竞争的发生,仿真结果表明,只要为每个节点配备少量的接收机就能达到很好的性能,不必将每个节点的接收机满配,从而可以降低硬件投入.     

光突发交换网络中多优先级业务冲突性能分析

对在光突发交换网络核心节点中发生的多优先级业务冲突问题进行了性能分析,与以往同类研究不同的是,不仅给出了不同优先级业务在核心节点产生的阻塞率情况,而且还给出了各优先级业务平均进入系统的数据量以及占用系统的均值等性能,研究结果对设定网络流量以及业务优先级等问题提供了理论参考价值.     

Performance comparisons of restoration techniques in optical burst switching networks

This paper describes restoration techniques for OBS networks. First, we introduce the design issues to be essentially considered, when restoration techniques will be built into OBS networks. Second, considering the design issues, we propose a novel restoration model named “Recover-Then-Reserve,” which can enhance the restoration performance. Third, we develop a simulator using the NS-2 platform to verify the performance of the restoration techniques (path, link, and sub-path) designed by each restoration model (GMPLS-based OBS restoration and our proposal). Performance is evaluated on the following metrics: restoration success rate, restoration time, connection availability, and burst loss probability. The effects of the failure frequency and the number of the restoration attempts on the restoration performance are also investigated. Our experiments show that the proposal can reduce the restoration time by about 25 ms compared to the GMPLS-based OBS restoration model. Also, path restoration technique has better performance than link and sub-path restoration techniques because it has the highest restoration success rate, allowing similar restoration time. Our experiments also show that the more the restoration attempts made and the less the failure frequency becomes, the better the restoration performance obtained.

Techniques for optical packet switching and optical burst switching

Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several different technologies have been developed so far for the transfer of data over WDM. We survey two new technologies which are still in the experimental stage-optical packet switching and optical burst switching-and comment on their suitability for transporting IP traffic     

基于PSO的OBS路由优化选择算法研究

光突发交换(OBS)被认为是下一代光交换技术.利用粒子群优化算法(PSO)对OBS网络路由优化选择问题进行了研究和分析,仿真结果表明,基于PSO的OBS路由算法在计算代价方面要优于传统的最短路径算法,结论对改进OBS的路由选择协议有一定的理论指导意义.     

定长光突发交换节点的QoS性能分析

分析了光突发交换网络中基于附加偏移时间(EOT,extra offset time)的业务优先等级区分服务的变长突发方案的不足，提出了一种定长光突发方案。它能在较小附加延迟的情况下保证高优先级的业务完全不受低优先级业务的阻塞，即使每个优先级的附加等待时间都减小到变长突发方案的1/3，同时使最高优先级业务的阻塞率更小，而且具有现实可行性。     

Hierarchical time-sliced optical burst switching

To overcome the need for large buffers to store contending bursts in optical burst switched (OBS) networks, a recent variant called time-sliced OBS (TSOBS) suggested that bursts be sliced and spread across multiple frames of fixed-length time-slots. Since TSOBS is rigid in its frame structure, this paper generalises TSOBS to allow a hierarchy of frames. Termed hierarchical TSOBS (HiTSOBS), this scheme supports several granularities of rates, and permits multiple traffic classes with different loss-delay requirements to efficiently share the network. Our contributions are as follows: first, we present an architecture for HiTSOBS and offer it as a viable option for the realisation of flexible and cost-effective OBS networks. Second, we develop mathematical analysis to study the loss and delay performance of the proposed HiTSOBS system. Finally, we present simulation results that captures these loss-delay tradeoff values. Our HiTSOBS architecture gives network operators the freedom to choose the right mix of traffic with desired loss-delay requirements to coexist in the network.     

OBS网络中的虚拟突发交换技术

针对由于网络复杂度提高,突发数据在预留时冲突可能性增大,导致OBS网络性能下降的情况,提出OBS网络中的虚拟突发交换技术和相应的实现技术。其汇聚机制是基于服务类别的虚拟汇聚,调度策略对应有两种：非抢占调度策略和抢占调度策略。利用虚拟突发交换技术有利于减少信道碎片,提高链路利用率,提供可靠的QOS保证。用OPNET系统仿真工具进行验证,结果表明：虚拟突发交换与OBS传统交换方式相比有较高网络链路的利用率,较少的控制分组和数据突发的丢包率,增加了整个网络的吞吐量。     

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。     

An introduction to optical burst switching

Optical burst switching is a promising solution for all-optical WDM networks. It combines the benefits of optical packet switching and wavelength routing while taking into account the limitations of the current all-optical technology. In OBS, the user data is collected at the edge of the network, sorted based on a destination address, and grouped into variable sized bursts. Prior to transmitting a burst, a control packet is created and immediately sent toward the destination in order to set up a bufferless optical path for its corresponding burst. After an offset delay time, the data burst itself is transmitted without waiting for a positive acknowledgment from the destination node. The OBS framework has been widely studied in the past few years because it achieves high traffic throughput and high resource utilization. However, despite the OBS trademarks such as dynamic connection setup or strong separation between data and control, there are many differences in the published OBS architectures. In this article we summarize in a systematic way the main OBS design parameters and the solutions that have been proposed in the open literature.     

Buffering-deflection tradeoffs in optical burst switching

A very important issue in optical burst switching (OBS) networks is the excessive burst drop when no suitable network resources are found during path reservation. In this study, a network scenario is evaluated in which AWG-based optical nodes are used as burst router nodes within the optical network. The two classical solutions to solve the burst contentions on the channels outgoing from the node are considered, that is, either based on buffering within the node, or by exploiting deflection routing. A performance evaluation is carried out to evaluate and compare these solutions for different network topologies with different node and traffic parameters. Our main contribution is to set numerical tradeoffs between burst deflection through the network and buffering in the node, so that a guidance in optical network design is provided where node buffering is inherently technologically limited.     

光突发交换中的竞争解决

在过去的几年里,全球互联网上的IP业务量呈爆炸式增长,快速增长的业务量使人们把很大一部分精力放在了发掘光纤巨大的带宽资源上面,密集波分复用(DWDM)传输技术的出现及成熟使光纤所能承载的信息量成倍增长。目前,单一光纤已能够传输Tb/s以上容量的信息,DWDM已经成为各种网络升级扩容的首选方式;另一方面,如此高速增长的业务量又给信息处理交换带来了巨大的压力。由于目前各个网络交换节点都是采用电交换方式,速率远低于信息在光域中的传输速率,这就造成了一个“电子瓶颈”。为解决这一问题,光交换成为必然的发展趋势,但是由于目前光存…     

Hybrid switching and p-routing for optical burst switching networks

One promising switching technology for wavelength-division multiplexing optical networks is optical burst switching (OBS). However, there are major deficiencies of OBS. (1) The delay offset between a control message and its corresponding data burst is based on the diameter of a network. This affects network efficiency, quality-of-service, and network scalability.( 2) OBS adopts one-way resource reservation scheme, which causes frequent burst collision and, thus, burst loss. We address the above two important issues in OBS. In particular, we study how to improve the performance of delay and loss in OBS. To reduce the end-to-end delay, we propose a hybrid switching scheme. The hybrid switching is a combination of lightpath switching and OBS switching. A virtual topology design algorithm based on simulated annealing to minimize the longest shortest path through the virtual topology is presented. To minimize burst collision and loss, we propose a new routing algorithm, namely, p-routing, for OBS network. The p-routing is based on the wavelength available probability. A path that has higher available probability is less likely to drop bursts due to collision. The probability-based p-routing can reduce the volatility, randomness, and uncertainty of one-way resource reservation. Our studies show that hybrid switching and p-routing are complementary and both can dramatically improve the performance of OBS networks.     

Performance analysis of burst switching for integrated voice/dataservices

The voice cutoff fraction and mean data waiting time of an integrated burst-switched system are analyzed. Several approximate approaches are proposed for the analysis. Comparison between simulation and approximate results shows that the accuracy of the approximations depends on the relationship between μ_d and μ_v where 1/μ_d and 1/μ_v are the mean lengths of data and voice packets (bursts), respectively. In general, the approximations give good accuracy for μ_d≲μ_v. For μ_d>μ_v, the approximations for the mean data waiting time give less accurate but adequate results. From the analysis, it is found that a burst-switched system can achieve a higher bandwidth efficiency when data traffic has a shorter burst length (e.g. interactive data). Furthermore, it is also observed that the relative burst lengths between voice and data can significantly affect the characteristic of the voice clipping process. The analysis shows that, under normal operating condition where voice traffic is predominant and the constraint that the voice cutoff fraction is less than 0.5%, the data queue is always stable     

时隙光突发交换网络调度问题研究

光突发交换（OBS）是构造下一代全光网络的潜在技术之一,但存在网络参数设计困难和阻塞性能有限等问题。文章介绍了一种新型基于时隙的OBS网络体系,简要阐明了其各部分功能,并将其与常规OBS网络进行了对比。提出了网络节点中关键的时隙分配与调度问题,并给出相应的在线调度策略,仿真结果表明BF算法性能较优。     

光标签突发包交换技术

光标签突发包交换是一种新出现的光交换技术。它把基于标签转发的速度优势、QoS(服务质量)保证及流量工程与光突发包交换控制机制(更长的转发数据单元、光网络边缘缓存、带外信令控制)结合起来。全面介绍了这种光交换技术，重点描述了其网络结构。另外，还对其所涉及到的关键技术进行了讨论，并结合下一代互联网的技术趋势，对光标签突发包交换的前景进行了评价。     

全新的光突发交换网络数据信道性能与故障监测机制

在首次提出探测突发概念的基础上,提出了一种全新的光突发交换网络数据信道性能与故障监测机制,即网元节点向数据信道周期性地或以某种特定方式发送探测突发,并在每个下一跳节点监测探测突发的误码情况,分析其误码特点,依此来评估每两个节点间的数据信道状态,判断被监测网络是否有故障发生.该机制能在很短时间内定位突然中断或恶化的故障信道,还可对所监视网络的老化等软故障进行有效的预警和评估,具有很高的实用价值和可操作性.     

On optical burst switching and self-similar traffic

In this letter we consider burst switching for very high speed routing in the next generation Internet backbone. In this scenario, Internet protocol (IP) packets to a given destination are collected in bursts at the network edges. We propose a burst assembly mechanism that can reduce the traffic autocorrelation or degree of self-similarity, and at the same time keep the delay due to burst formation limited at the network edges     

Node dimensioning in optical burst switching networks

Network dimensioning should be progressed for pursuing the ultimate efficiency of network system resources in order to satisfy target performance. This article studies node dimensioning as a method of resource optimization in optical burst switching (OBS) networks. OBS is a new switching technology for pursuing bufferless transparent optical networks by sending control packets prior to data burst in order to provision resources for the burst. However, the basic assumption of a bufferless node implies burst contention at a core node when more than two bursts attempt to move forward the same output simultaneously. Thus, burst contention is a critical performance metric and this article takes it into account as a constraint on node dimensioning and target performance. In this article, we first present node dimensioning issues for OBS networks. Two constraints from the transport plane and the control plane which affect burst contention are then introduced. The effect of the burst assembly process on node dimensioning is also presented. From numerical analysis, the optimal number of wavelengths in a link, which provides the lowest blocking probability, is obtained to suggest a guideline for node dimensioning.