An Optical Packet Addressing Scheme for Optical Packet Switched Networks Using RF Frequency Carrier Assignment

We propose an efficient optical packet addressing technique for optical packet-switched networks, where the pre-assigned RF frequency carriers are used to represent the packet addresses. It can simplify the control process of optical packet switching so that it results in reduced address processing time and smaller complexity of the packet address processor due to simple extraction of address information. We also analyze the performance of the proposed packet addressing scheme in the transmission aspect taking into account packet address wavelength beating and laser nonlinearity.     

Quality of Service in Asynchronous Bufferless Optical Packet Switched Networks

Optical Packet Switching (OPS) is a promising technology for future core networks due to the ability to handle bursty traffic, adaptability to changes in the network infrastructure and good network utilization. In order to provide sufficient Quality of Service (QoS) to the emerging range of real-time and critical business applications, service differentiation should be present in future OPS. This paper presents the Preemptive Drop Policy (PDP), which provides service differentiation in asynchronous bufferless OPS. Based on time-continuous Markov chains, we introduce an analytical model of the PDP for switches with and without wavelength conversion. We extend the PDP into the Adaptive PDP (APDP), which provides absolute QoS guarantees in OPS. Simulations performed validate our analytical model and show that the APDP operates properly in a dynamic changing system load scenario.     

A Genetic Algorithm for Routing in Packet—Switched Communication Networks

ＡＧｅｎｅｔｉｃＡｌｇｏｒｉｔｈｍｆｏｒＲｏｕｔｉｎｇｉｎＰａｃｋｅｔ┐ＳｗｉｔｃｈｅｄＣｏｍｍｕｎｉｃａｔｉｏｎＮｅｔｗｏｒｋｓＨｅＣｕｉｈｏｎｇＯｕＹｉｓｈａｎＬｉＸｉａｎｊｉ（ＧｕａｎｇｄｏｎｇＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏｌｏｇｙ，Ｇｕａ...     

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。     

可用于光分组交换网的一种新型2×1节点接收机

提出了一种可用于光分组交换的2×1节点接收机,其特征在于,缓存是由前馈和反馈形式的光纤延迟线(FDLs)组合实现的。理论分析和仿真结果表明:当前馈和反馈形式的FDLs均可使用时,尽量使用前馈FDL的BCS控制策略更有利于改善接收机的分组丢弃性能,结构能很好地应用于突发业务和非突发业务环境,而且控制复杂度也较低。     

采用偏射路由算法的全光分组网络的性能分析

本文提出采用统一的马尔可夫链方法分析存储转发路由和偏射路由算法的网络，并在具体计算偏射概率时，采用了递推的算法。着重分析了偏射路由算法在无存储器、有单个存储器及有两个存储器的情况下，ＭａｎｈａｔｔａｎＳｔｒｅｅｔＮｅｔｗｏｒｋ和ＳｈｕｆｌｅＮｅｔ网络的性能，包括网络吞吐量、数据包的平均跳转次数和数据包跳转次数的概率分布，并对ＭａｎｈａｔａｎＳｔｒｅｅｔＮｅｔｗｏｒｋ和Ｓｈｕｆ－ｆｌｅＮｅｔ两种网络进行了简单的比较。     

光开关在自动交换光网络中的研究与检测技术

作为自动交换光网络中的核心器件,光开关将在未来全光网中发挥着重要作用,并成为未来光联网的关键技术。本文总结光开关实现方法的最新进展,重点介绍电光效应开关和超高速光控开关的工作原理和实际应用。最后阐述我实验室在光开关性能检测方面所做的研究工作.     

分组网络中同步标准的进展及分析

如何解决同步信号地面链路传递问题,是目前分组传送网络中研究的一个重要课题。传统同步体系中的标准仅适用基于电路交叉技术的网络,并不适用于指导分组传送网络中面临的问题。目前虽已有运营商应用1588v2,满足移动回传网络中的时间同步需求,但随着网络复杂性的逐步增强,以及对设备时间(时钟)能力要求的不断提高,亟待相关标准的出台及完善。文章对分组网络中的同步标准进行了讨论,并就当前包交换技术实现频率和时间同步的热点应用给出了建议。     

自动交换光网络中全光波长转换器的应用和实现

作为自动交换光网络中的核心器件,全光波长转换器在网络中发挥着重要作用.总结了全光波长变换的实现方法,并重点介绍基于半导体光放大器交叉相位调制和利用可调谐光纤光栅外腔半导体激光器实现全光波长变换的最新进展、工作原理,最后简单介绍本实验室目前所做工作以及取得的成果.     

Havana: Supporting Application and Channel Dependent QoS in Wireless Packet Networks

For wireless channels, interference mitigation techniques are typically applied at the packet transmission level. In this paper, we present the Havana framework which supports integrated adaptive-QoS in wireless packet networks by responding to impairments over multiple time scales that are present at the flow/session level. The Havana framework is based on three different control mechanisms that operate over distinct adaptation time scales. At the packet transmission time scale, a packet-based channel predictor determines whether to transmit a packet or not depending on the state of the wireless channel. At the packet scheduling time scale, a compensator credits and compensates flows that experience bad link quality. Over even longer time scales an adaptor regulates flows taking into account the ability of wireless applications to adapt to changes in the available bandwidth and channel conditions. We present the design and implementation of our framework and evaluate each of the proposed control mechanisms using the ns-2 simulator.     

Optical Interconnection Networks for Terabit Packet Switches

The challenge of building packet switches with terabit capacity is being met by wavelength division multiplexing (WDM) where the benefits of optical fiber are exploited. Two kinds of WDM-based bufferless optical interconnection networks are proposed in this paper to interconnect multiple electronic packet switch modules. One is based on 3-stage Clos principle and the other is based on broadcast-and-select principle. The proposed optical interconnection networks are implemented with small modular structures to provide capacities in the range of terabit per second. Their architectures, component and interconnection complexity, and power budget analyzes are presented. In addition, the crosstalk caused by the finite ON-OFF ratio of semiconductor optical amplifier is discussed. Bit error rates with respect to different ON-OFF ratios and extinction ratios are also evaluated. It is concluded that it is feasible to implement optical interconnection networks by using state-of-the-art WDM technology, and they are excellent candidates for future terabit packet switching systems.     

Routing Strategies to Minimize Packet Loss in an Optical Packet Switched Network 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. We study optical packet switches with recirculating fiber delay line (FDL) buffers. Through simulation, we have assessed the logical performance of a single optical packet router (OPR), focusing on packet loss rate (PLR). By verifying that our scheduling algorithm does not alter the traffic profile characteristics from in- to output, we illustrate how the single node results can be used to assess network-wide performance. We use the capability of assessing end-to-end PLRs to develop network-wide routing algorithms designed to minimize the maximal PLR occurring in the network. In case studies on pan-European networks, we first compare two algorithm variants and thereafter we compare the PLR-based routing algorithm with both load balancing and shortest path routing. While load balancing achieves PLRs that are multiple orders of magnitude lower than shortest path routing, the PLR-based algorithm can reach PLRs up to two orders of magnitude better. The improvement in PLR comes at the price of only a small increase in used bandwidth (a few percent). Subsequently we show that the discussed PLR-based routing algorithm can be easily extended to multiple priorities. By introducing multiple priorities we can keep the loss rates for high priority traffic very low. However, it may lead to an increase of the obtained minimal max-PLR value for low priority traffic. But as we prove this increase to be limited, the cost of introducing multiple priorities is small.     

光突发交换网络中QoS方案的研究

光突发交换是构建下一代光网络的有效交换技术,在OBS网络中如何有效地支持QoS已成为一个重要的研究课题.介绍了光突发交换网络中基于偏置时间的QoS方案和波长分组QoS方案,最后提出了一种基于波长分组技术,结合突发分片技术和Min-Sv算法的QoS的解决方案,通过建立相应的模型时其进行了仿真,仿真结果表明所提出的方案可以更好地提供区分服务,同时有效地提高了信道的利用率,降低了整体的丢失率.     

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.     

适用于Pbit/s光分组交换网络的丢包率下限模型

文章针对通过优化路由来改善光分组交换网络性能这一方法进行了深入地分析。文章认为在输出光缓存结构下可以计算出网络丢包率下限的理论模型,通过将该模型得到的丢包率下限与在已有路由算法下由仿真得到的丢包率进行比较,能够预测出最佳路由算法下的丢包率,从而进一步预测通过优化路由所能获得的最大性能提升。     

Packet Scheduling with QoS Differentiation

This article focuses on the Quality of Service (QoS) achieved by packet scheduling. A packet scheduling algorithm, which can differentiate the QoS among user and service classes, is presented. The algorithm can be tuned from signal to interference ratio (C/I) based scheduling to Round Robin and beyond. Thus, an operator can choose between optimizing the spectral efficiency or giving a fair QoS distribution among the users within a user and traffic class. By combining the two effects, different strategies can be used for different user and service classes. Simulation results for the downlink shared channel (DSCH) are presented and implementation issues are also discussed.     

A Novel All-Optical Routing Architecture for Optical Packet Switched Networks

Increasing bandwidth demand, mostly driven by the Internet Protocol (IP), has made researchers consider to deploy all-optical devices into packet switched networks. Despite huge bandwidth of the optical communication links (optical fiber) the usable capacity is limited due to bottlenecks (congestions) at the switching nodes. In this paper, a novel all-optical routing architecture is proposed for optical packet switched networks. In the design, practical optical devices (gratings, threshold elements, optical delays, and couplers) have been improved and exploited in order to integrate into an all-optical routing device. The system has been implemented and simulated by using an photonics simulation package (VPI-Virtual Photonics). The packets conveying a three-bit routing information tag at the bit rate of 10 Gbps have been successfully routed between two links. Some of the components are standard tools of the simulation package and some needed to be designed using the transfer function or theory developed in the literature. Noise and losses associated to the nonideal nature of the components are considered in the simulation as well.     

QoS Based Survivable Logical Topology Design in WDM Optical Networks

The need to establish wavelength-routed connections in a service differentiated manner is becoming increasingly important. In the backbone network, support of quality of service (QoS) capabilities at the lightpath level will have to be addressed in the optical domain. Providing a service differentiated connection on an arbitrary virtual topology which does not support any differentiated services will lead to the misuse of network resources. We address the virtual topology design and routing problem, where we minimize congestion in the network. In our work, the service differentiating parameter is bit error rate (BER) in the optical domain. We present a mixed integer linear programming (MILP) formulation for the above problem. We also propose a heuristic based approach to minimize the congestion in the network while satisfying the QoS constraints. These QoS constraints in our case are the differing BER requirements for each connection between each (source, destination) pair. We then present different methods of providing survivability for the virtual topology and compare the performance of these methods.     

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.      

Connection Establishment of Label Switched Paths in IP/MPLS over Optical Networks

We propose and investigate three connection admission control policies for the establishment of label switched paths (LSPs) in IP/MPLS over optical networks. We show that the policy of establishing LSPs first in the optical layer achieves a better blocking performance. We examine the effect of the number of add/drop ports of optical cross-connects (OXCs) on the LSP blocking performance. We show that there exists a lower bound for the number of add/drop ports of OXCs for the network to achieve almost the best LSP blocking performance.