异步光分组交换网的流量建模

研究了异步光分组交换网的流量特性，提出了网络流量的解析模型和近似模型。研究表明，在采用计时门限光分组组装算法的情况下，如输入IP流具有短程相关特性(ShortRangeDependent)，则光分组的到达间隔时间呈负指数分布，光分组的长度趋于高斯分布。     

考虑光开关稳定响应时间的光分组组装性能分析

在光分组交换中,光分组的组装算法将对交换的性能产生重要的影响.由于当前技术水平的限制,光分组的长度与光开关的稳定响应时间粒度相近,因此光开关的稳定响应时间对光分组组装算法的影响必须加以考虑.为此,提出两种考虑光开关稳定响应时间的光分组组装算法,即Threshold-Based-ST算法和Timer-Based-ST算法.采用仿真实验的方法对所提出的组装算法性能进行评估.仿真结果表明,Threshold-Based-ST算法和Timer-Based-ST算法都存在一个最优的组装参数.     

光分组交换节点技术

文章首先介绍了光分组交换网络的分类和光分组交换节点的基本结构,接着详细讨论了全光分组交换节点设计和实现中的关键问题:交换结构的设计、光存储的实现以及分组拥塞问题的解决方案。     

光分组交换网络结构

光分组交换技术日益成为世界各国研究的重点 ,光交换的结构设计是光分组交换技术的关键。文中详细介绍了目前正在研究的空间光开关、广播选择和波长路由三种光分组交换结构。随着光网络、光器件和光系统技术的发展 ,光分组交换必会走向实用化     

光分组交换节点技术

文章首先介绍了光分组交换网络的分类和光分组交换节点的基本结构，接着详细讨论了全光分组交换节点设计和实现中的关键问题，交换结构的设计，光存储的实现以及分组拥塞问题的解决方案。     

光分组交换网

本文介绍了全光分组交换网的国内外研究状况，讨论了光分组交换节点的功能和结构及其实现光分组交换网的关键技术，对光分组交换网的研究具有重要的参考价值。     

光分组交换网络结构

光分组交换技术日益成为世界各国研究的重点，光交换的结构设计是光分组交换技术的关键。文中详细介绍了目前正在研究的空间光开关、广播选择和波长路由三种光分组交换结构。随着光网络、光器件和光系统技术的发展，光分组交换必会走向实用化。     

光分组交换与光IP路由器技术

文章介绍了光分组交换的概念 ,对其进行了分类与比较 ,并全面总结了光分组交换与光IP路由器的关键技术 ,最后介绍了光分组交换的最新发展———光突发交换     

光分组交换技术的研究

光分组交换技术的引入，改善了带宽的利用率和网络的灵活性，延伸了光的透明性。在光分组交换层中光分组的产生、同步、缓存、再生，分组头重写及分光组之间挑功率的均衡成为实现光分组产换的基本技术，而多波长方案并不是光分组交换的唯一模式，光时分分组交换、光标签交换、波分及混合分组交换、多协议标签交换、光突发分组交换等交换方式的出现必将对未来的通信网产生重要的影响。     

核心网中的光分组交换

文章分析了光分组交换提出的原因。介绍了光分组交换节点的组成，给出了与光分组交换相关的使用技术的进展情况，最后对光分组交换的前景做了分析。     

一种新型的光分组交换环网体系结构

提出了一种以波长为标签的新型全光变长分组交换环网的体系结构、网络节点的光分组数据包收发模型,以及防止光分组冲突的多令牌协议。使用多令牌协议的环网在进行光分组交换时,不需要高速的光子器件,无需使用延迟线、电中继以及解决光分组的冲突问题。通过数值仿真,分析了4节点、8节点和16节点环网巾光分组各种的时延特性以及网络的吞吐量特性。结果表明,当网络负载增大时,数据包的平均时延增大,同时网络节点的吞吐量和资源利用率也随之增大;网络节点数目越多,网络的吞吐率也越大。     

Probabilistic Analysis of Cyclic Packet Transmission Scheduling in WDM Optical Networks

We study the packet transmission scheduling problem with tuning delay in wavelength-division multiplexed (WDM) optical communication networks with tunable transmitters and fixed-tuned receivers. By treating the numbers of packets as random variables, we conduct probabilistic analysis of the average-case performance ratio for the cyclic packet transmission scheduling algorithm. Our numerical data as well as simulation results demonstrate that the average-case performance ratio of cyclic schedules is very close to one for reasonable system configurations and probability distributions of the numbers of packets. In particular, when the number of receivers that share a channel and/or the granularity of packet transmission are large, the average-case performance ratio approaches one. Better performance can be achieved by overlapping tuning delays with packet transmission. We derive a bound for the normalized tuning delay Δ such that tuning delay can be completely masked with high probability. Our study implies that by using currently available tunable optical transceivers, it is possible to build single-hop WDM networks that efficiently utilize all the wavelengths.     

光分组交换网络中光纤延迟线缓存技术

光分组交换网是全光网络发展的必然趋势.然而,光分组交换网络发展的瓶颈是光缓存技术.目前,在光域比较现实的还是采用光纤延迟线(FDL)作光缓存.重点研究了光纤延迟线光缓存技术,对FDL光缓存技术进行了深入的分析和归纳,并对每一种光纤延迟线光缓存调度策略的优缺点都进行了细致的分析.最后指出了光纤延迟线光缓存技术的未来研究重点和发展方向.     

Blocking and Delay Analysis of Single Wavelength Optical Buffer With General Packet Size Distribution

Buffers are essential components of any packet switch for resolving contentions among arriving packets. Currently, optical buffers are composed of fiber delay lines (FDL), whose blocking and delay behavior differ drastically from that of conventional RAM at least two-fold: 1) only multiples of discrete time delays can be offered to arriving packets; 2) a packet must be dropped if the maximum delay provided by optical buffer is not sufficient to avoid contention, this property is called balking. As a result, optical buffers only have finite time resolution, which may lead to excess load and prolong the packet delay. In this paper, a novel queueing model of optical buffer is proposed, and the closed-form expressions of blocking probability and mean delay are derived to explore the tradeoff between buffer performance and system parameters, such as the length of the optical buffer, the time granularity of FDLs, and to evaluate the overall impact of packet length distribution on the buffer performance.     

Analytical MMAP-Based Bounds for Packet Loss in Optical Packet Switching with Recirculating FDL Buffers

The major goal of optical packet switching (OPS) is to match switching technology to the huge capacities provided by (D)WDM. A crucial issue in packet switched networks is the avoidance of packet losses stemming from contention. In OPS, contention can be solved using a combination of exploitation of the wavelength domain (through wavelength conversion) and buffering. To provide optical buffering, fiber delay lines (FDLs) are used. In this paper, we focus on an optical packet switch with recirculating FDL buffers and wavelength converters. We introduce the Markovian arrival process with marked transitions (MMAP), which has very desirable properties as a traffic model for OPS performance assessment. Using this model, we determine lower and upper bounds for the packet loss rate (PLR) achieved by the aforementioned switch. The calculation of the PLR bounds through matrix analytical methods is repeated for a wide range of traffic conditions, including highly non-uniform traffic, both in space (i.e., packet destinations) and time (bursty traffic). The quality of these bounds is verified through comparison with simulation results.     

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.     

异步光分组交换的缓存排序方案及性能

分析了简单的先到先服务(FCFS)光纤延迟线(FDL)循环占用方案性能,发现其分组丢失率(PLR)较高,提出3种输入分组按长度排序,寻找最小的FDL缓存优化分配方案.分析和仿真结果表明:约10%的分组排序后使3种方案都大大地能减小PLR,最小长度分组占用最小可用FDL缓存方案的性能最好.业务负载低于0.8时,排序的缓存方案对管理有限的FDL是有效的.     

Packet Pacing in Small Buffer Optical Packet Switched Networks

In the absence of a cost-effective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. To mitigate the performance degradation resulting from small buffers, this paper proposes that optical edge nodes “pace” the injection of traffic into the OPS core. Our contributions relating to pacing in OPS networks are three-fold: first, we develop real-time pacing algorithms of poly-logarithmic complexity that are feasible for practical implementation in emerging high-speed OPS networks. Second, we provide an analytical quantification of the benefits of pacing in reducing traffic burstiness and traffic loss at a link with very small buffers. Third, we show via simulations of realistic network topologies that pacing can significantly reduce network losses at the expense of a small and bounded increase in end-to-end delay for real-time traffic flows. We argue that the loss-delay tradeoff mechanism provided by pacing can be instrumental in overcoming the performance hurdle arising from the scarcity of buffers in OPS networks.      

End-to-End Delay Evaluation for an Optical Transparent Packet Network

In this paper an all optical packet switching network is considered to provide transparent transport of information. To this end the evaluation of the end-to-end packet delay is performed by means of analytical tools. Bounds are proposed for the maximum packet delay and calculated by means of a simple additive formula that can be used for approximate end-to-end delay evaluation. Packetization and multiplexing delay at the access interface and queuing delay inside the nodes are considered as contributions to the whole packet delay. The obtained results shown that time transparency can be reached within suitable network design.