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。     

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     

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.     

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…     

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。     

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.     

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.     

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.     

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.     

Performance evaluation of throughput in optical burst switching

Optical burst switching (OBS) provides a promising solution to utilize the huge terahertz bandwidth of optical wavelength division multiplexing (WDM) transmission technology. To exploit this bandwidth, several reservation schemes have been proposed that include just‐in‐time (JIT) signaling, just‐enough‐time (JET) signaling and burst segmentation (BS). It is necessary to investigate the performance of these schemes under the same constraints for a prescribed OBS application. Accordingly, in this paper, we analyzed and compared the performance of JIT, JET and BS techniques under various scenarios such as network size, delay variation and load variation in an OBS network using various performance metrics, such as the offset time and switch configuration time. Also, the performance of the network under various switching delays was also investigated. The modified BS reservation scheme has been found to yield significantly better performance and better throughput compared with the JIT and JET reservation schemes. Test results show that the effect of varying loads as well as delays significantly impacts the performance of the OBS network. The results presented in this paper are expected to lead further performance improvements in OBS networks using the BS reservation scheme. Copyright © 2010 John Wiley & Sons, Ltd.     

基于窗口的光突发交换调度算法

针对光突发交换网(OBS)中的资源竞争和QoS支持等问题，提出了一种新型的基于窗口的调度算法。该算法利用边缘节点的电缓存，对调度窗口中的突发数据包进行批量BORA调度，可以有效地降低网络中发生资源竞争的概率；同时调度窗口中的优先级策略还可以进一步增强QoS。网络仿真结果表明，通过选择合适的调度窗口和最大允许时延，该调度算法在0．8的网络负载下使得高优先级突发数据包的阻塞率下降一个量级，信道利用率提高3．5％。     

基于GMPLS的光突发交换网络的研究

文章基于通用多协议标签交换(GMPLS)的光突发交换(OBS)网络的体系结构,研究了如何将GMPLS引入OBS,并使两者能够高效协调地工作.重点讨论了GMPLS与OBS技术相结合的网络(GMPLS-based OBS)的各种关键技术和解决机制.特别在处理突发数据包(BDP)冲突竞争机制上提出了新的方法.最后,指出了GMPLS-based OBS进一步研究的方向.     

混合光突发交换网络的研究

提出了一种新的混合光突发交换（HOBS）网络，并且使用环网对网络进行了仿真比较研究。仿真结果表明HOBS的丢包率远低于OBS，并且下降的程度决定于拆分比例、缓存的大小以及节点的处理速率等参数。     

Performance analysis of optical composite burst switching

In this letter, we introduce a queueing model to study the performance enhancement in a so-called optical composite burst switching network (OCBS). Based on our model, we develop a simple analytical method to calculate the packet loss probability and we provide numerical results to compare the performance of OCBS versus the traditional optical burst switching (OBS) technique. We then provide explanations for the performance improvement of OCBS over that of OBS.     

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     

Labeled optical burst switching for IP-over-WDM integration

The rapid pace of development in both Internet applications and emerging optical technologies is bringing about fundamental changes in networking philosophies. Key trends are the emergence of dynamic wavelength provisioning and a corresponding reduction in wavelength provisioning timescales. As this transition continues, the current use of the wavelength-routing paradigm for carrying bursty Internet traffic will likely suffer from various shortcomings associated with circuit-switched networks. Meanwhile, optical packet switching technology is still facing significant cost and technological hurdles. Optical burst switching, or OBS, which represents a balance between circuit and packet switching, has opened up some exciting new dimensions in optical networking. This article describes the OBS paradigm, and also proposes the use of labeled OBS, or LOBS, as a natural control and provisioning solution under the ubiquitous IP multiprotocol label switching framework     

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。     

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.     

Dynamic burst discarding scheme for deflection routing in optical burst switching networks

This paper proposes a dynamic burst discarding scheme for deflection routing in optical burst switching networks. In general, deflection routing is effective in lightly loaded situations, whereas it has a contrary effect in congested networks because deflected bursts accelerate network congestion. Thus deflection routing should be employed in lightly loaded networks. Incoming traffic, however, varies in time and location, so that temporal and/or local congestion cannot be avoided. Our proposed scheme resolves this problem in the following way. Each node autonomously detects congestion with local information, and bursts to be deflected are discarded in a probabilistic manner, based on the degree of detected congestion and the numbers of elapsed and remaining hops of those bursts. Simulation experiments show that when congestion happens temporarily, the proposed scheme reduces the burst loss probability, and it utilizes network resources efficiently when local congestion happens.