突发分片技术在OBS网络中的应用及其性能分析

对基于光突发分片技术的光突发竞争解决机制进行了研究,重点分析了基于突发分片技术的光突发交换网络性能,理论分析和仿真结果均表明,相比于恰量时间模型,突发分片技术具有低阻塞率和高信道利用率等优点,能够有效地减少网络数据丢失。     

光突发交换网络中TCP Reno 的性能分析

该文在分析光突发交换(OBS)网络对TCP性能影响的基础上,研究了单个突发所包含的属于同一TCP/ IP连接的分组数对TCP Reno吞吐量性能的影响,得到了一个吞吐量与突发丢失率、单个突发所包含分组数以及往返时延(RTT)的闭合表达式;并通过仿真验证了分析的正确性;分析和仿真结果表明,在接入链路带宽较大时,突发所包含的分组数存在一个最佳值,使TCP吞吐量达到最大。     

A Data Burst Assembly Algorithm in Optical Burst Switching Networks

Presently, optical burst switching (OBS) technology is under study as a promising solution for the backbone of the optical Internet in the near future because OBS eliminates the optical buffer problem at the switching node with the help of no optical/electro/optical conversion and guarantees class of service without any buffering. To implement the OBS network, there are a lot of challenging issues to be solved. The edge router, burst offset time management, and burst assembly mechanism are critical issues. In addition, the core router needs data burst and control header packet scheduling, a protection and restoration mechanism, and a contention resolution scheme. In this paper, we focus on the burst assembly mechanism. We present a novel data burst generation algorithm that uses hysteresis characteristics in the queueing model for the ingress edge node in optical burst switching networks. Simulation with Poisson and self‐similar traffic models shows that this algorithm adaptively changes the data burst size according to the offered load and offers high average data burst utilization with a lower timer operation. It also reduces the possibility of a continuous blocking problem in the bandwidth reservation request, limits the maximum queueing delay, and minimizes the required burst size by lifting up data burst utilization for bursty input IP traffic.     

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。     

Burst Assembly Schemes and Performance Evaluation in Optical Burst Switching Networks

1　Introduction　TheopticalInternethasbeenemergedasanefficientsolutionforsupportingever increasingInternettrafficbytakingadvantageofpotentiallyhugebandwidthofWavelength DivisionMultiplex (WDM )opticalnet works.Tomeettheincreasingbandwidthdemandsandreducecosts ,severalopticalnetwork paradigmshavebeenunderintensiveresearch .Ofalltheseparadigms,OpticalCircuitSwitching (OCS[1～ 3] )isrelativelyeasytoimplementbutlacksflexibilitytocopewiththefluc tuatingtrafficandthechanginglinkstate ,andrequi…     

Data Performance in Burst Switching When the Voice Silence Periods Have a Hyperexponential Distribution

The performance of data in burst switching has been analyzed in previous work with a fluid approximation of the data traffic. This study extends the previous model to the case where the silence interval between talkspurts has a hyperexponential, rather than an exponential, distribution. It is shown that data performance is extremely sensitive to the variance of the silence interval, and that, for empirical talkspurt and silence distributions, this model provides a vast improvement on models which assume that both types of intervals are exponentially distributed.     

业务自相似性对光突发交换调度算法影响分析

使用泊松业务流模型对光突发交换网络进行性能分析不能准确地反映网络状态。该文从理论上对突发包长度进行了推导,对基于时间门限汇聚机制下突发包数据流自相似程度进行了计算机仿真测量,并利用自相似业务流模型对光突发交换网络中比较常用的LAUC和LAUC-VF调度算法进行了性能仿真。仿真结果表明：基于时间门限的汇聚机制能够有效地降低数据流自相似程度,数据流的自相似特性对LAUC算法的影响并不非常明显,但对LAUC-VF算法的性能则产生了比较严重的影响,其突发包丢失率较泊松流平均增加了近3个百分点。     

Analysis of Burst Segmentation in Optical Burst Switching Networks Considering Path Correlation

One of the key problems hindering the realization of optical burst switching (OBS) technology in the core networks is the losses due to contention among the bursts at the core nodes. Such contention losses do not necessarily indicate a situation of congestion. Burst segmentation is an effective contention resolution technique used to reduce the number of packets lost due to the burst losses. In this work, we propose a method of analyzing the benefit of burst segmentation considering the effect of correlation in traffic across multiple paths. Starting with the cumulative distribution function (cdf) of the length of the bursts at the ingress node destined to a particular egress node, we evaluate the cdf of the burst length at each node along the path considering the probability of segmentation and the traffic on the adjoining paths. Comparing the burst length at the egress node with that at the ingress node, we evaluate the byte loss probability (ByLP) along the path and also the network-wide average ByLP. The proposed analytical framework studies the impact of segmentation on packet loss rate considering the effect of the length of a path, the number of paths adjoining a path (extent of path correlation), the effect of load on a path and other correlated paths, and the burst assembly algorithm. Analytical and simulation results in this work show that the proposed method of analysis gives a good understanding of the influence of aforementioned factors on the benefit of segmentation in OBS networks.      

基于阈值的光突发交换网络数据信道调度算法

光突发交换(OBS)是实现下一代光互联网中的一种极具前景的方案。该文提出了一种基于阈值的OBS网络数据信道调度算法,对于长度大于阈值的光突发数据包采用LAUC算法进行调度,对于长度小于阈值的光突发数据包采用LAUC-VF算法进行调度。仿真结果表明,该算法在调度时间方面与已有的LAUC算法很接近;而在光突发数据包丢失率性能方面要优于LAUC-VF算法。     

光突发交换试验网的可行性分析

文章对光突发交换网络的产生背景、光突发交换网络模型及技术实现的可行性,以及进一步发展光突发交换网络需要关注的核心技术予以分析,最后对建设中国下一代高速光因特网提出一些建议与思考。     

Performance Analysis of IEEE 802.11 DCF with Data Rate Switching

In this letter, we propose a novel Markov chain model for IEEE 802.11 WLAN, considering a commonly used data rate switching mechanism. In the proposed model, both collision and transmission errors are considered. The performance of IEEE 802.11 DCF (distributed coordination function) is analyzed using the proposed model. The accuracy of the proposed model is verified by simulation.     

Performance Assessment of Optical Burst Switching Ring and Chordal Ring Networks

This paper presents a performance analysis of optical burst switching (OBS) networks with ring and chordal ring topologies. The performance analysis considers signaling protocols with one-way reservation schemes, being focused on the following protocols: just-in-time (JIT), Jumpstart, JIT⁺, just-enough-time (JET) and Horizon. It is shown that for a network with 20 nodes, the nodal degree gain due to the increase of nodal degree from two (ring) to three (chordal ring) is about three orders of magnitude in the first hop of both topologies, and is between two and three orders of magnitude in the last hop of each topology. It is also shown that the largest chord length gain, in a 20-node OBS network with a chordal ring topology, is slightly less than two orders of magnitude.     

A New Performance Measurement for Voice Transmission in Burst and Packet Switching

Voice transmission in burst switching is characterized by the process of talkspurt clipping, while in packet switching, it is characterized by the process of packet delay. In most analyses, the talkspurt clipping has been measured by the clipping probability averaged over all bits, and the packet delay has been measured by the delay performance averaged over all packets. The resulting measures overlook the duration of clipping in a talkspurt and the significant difference of delay in packets arriving at different times. Because of the nature of voice, different effects of these may result in substantially different degrees of voice distortion. This paper studies the worst case performance of both processes. The voice traffic is modeled as a process alternating between overload and underload periods. Statistically, more clipping and delay will be incurred while in the overload period. By worst case we mean that, in burst switching, we measure the worst case of talkspurt clipping duration in an overload period, while in packet switching, we measure the worst case of packet delay in an overload period. Furthermore, a simple closed form equation is derived which gives a very good approximation of the worst case mean packet delay performance. This equation can be more generally applied when the packet service time is to be geometrically distributed or when voice and data are to be integrated. The voice performances in burst switching and packet switching are also compared.     

基于GMPLSD的光突发交换网络组播性能仿真

在通用多协议标记交换协议(GMPLS)控制面体系结构下,OBS网络组播的实现面临着一些技术问题.首先分析并解决了其中两个关键问题,即IP组播树与组播标记交换路径(LSP),以及组播LSP与光树间的映射问题;然后提出了支持组播的OBS边缘节点与核心节点的功能模型;并在OPNET仿真环境下,设计和开发了节点仿真模块,验证了OBS组播功能.仿真结果表明:在基于GMPLS的OBS网络体系结构下,光组播树建立时间普遍较短,而且在实现方式上,与光路相比,光树型方式具有较高的链路利用率.     

光突发交换技术

光突发换是近几年出现的一种光交换技术 ,它交换的单元粒度介于电路交换和分组交换之间 ,比电路交换灵活 ,带宽利用率高 ,又比光分组交换易于实现 ;全面介绍了这种交换技术 ,并对它与电路交换和光分组交换性能进行了比较。另外 ,还对光突发交换的关键技术进行了讨论 ,结合下一代互联网的技术趋势 ,对光突发交换的前景进行了评价。     

光突发交换技术

文章介绍了光子交换的发展情况,着重介绍了光突发交换的原理、网络和节点的结构、突发封装技术、协议以及发展方向.     

Optical Burst Switching With Large Switching Overhead

To date, optical burst switching (OBS) schemes assume the switch reconfiguration time to be negligible, a part of the processing delay of the control packet, or a fixed value added to the data burst length, regardless of the switch status. In this paper, we show that the switching overhead can have a significant impact on the performance of some OBS channel scheduling schemes. We have also proposed methods to alleviate the problem     

光通信网对数据信息的Burst交换

说明通信网交换方式从电路交换至分组交换和Burst交换的演变以适应全光通信网的发展趋势。解释了通信网利用Burst交换所需的网络边缘设备和核心结点设备。     

光突发交换网络边缘节点突发装配方案

介绍了光突发交换网络边缘节点突发装配的关键技术，详细论述了IP分组到达入口边缘节点后进入缓存的不同排队策略，重点研究了目前已经提出的各种突发装配策略，并对不同的突发装配策略进行分类比较。     

On Delay Performance and Burst Assembly for Wireless Mesh and Optical Burst Switching Converged Metro Area Network

Wireless Mesh Networks (WMN) have attracted increasing attention from the research community as a high-performance and low-cost solution to last-mile broadband Internet access. On the other side, Optical Burst Switching (OBS) is a promising access technology that uses optical fiber with burst switching paradigm. In this paper, we propose a novel Metropolitan Area Network (MAN) architecture, called Optical Burst Wireless Mesh Architecture (OBWMA) which integrates WMN at the user access side and OBS at the core of the MAN. OBWMA aims to combine advantages of both WMNs and OBS networks, such as large coverage at low cost and bandwidth availability. We specify the details of the interconnection and the internetworking of WMNs and the OBS network in OBWMA. Moreover, we develop an analytical model to compute the end-to-end delay in OBWMA in order to support flow requests with delay constraints. Furthermore, we propose a Control Bridge (CB) that ensures Quality of Service (QoS) mapping at the border between the WMN and the OBS parts. Also, we propose a burst assembly scheme, called Adaptive Hybrid Burst Assembly scheme (AHBA). Simulation results using ns-2 demonstrate the feasibility of OBWMA and the validity of our analytical model.