Optical signal processing for optical packet switching networks

Optical packet switching promises to bring the flexibility and efficiency of the Internet to transparent optical networking with bit rates extending beyond that currently available with electronic router technologies. New optical signal processing techniques have been demonstrated that enable routing at bit rates from 10 Gb/s to beyond 40 Gb/s. We review these signal processing techniques and how all-optical-wavelength converter technology can be used to implement packet switching functions. Specific approaches that utilize-ultra-fast all-optical nonlinear fiber wavelength converters and monolithically integrated optical wavelength converters are discussed and research results presented.     

光分组交换技术在未来通信网中的应用

随着带宽需求的日益增长,电信工业不得不把重心从传统的电话业务转向IP数据业务。在这种情形下,SDH/SONET的作用大大地减小了,而OTN（光传输网）将为IP数据业务提供一个全球的基础传输设施。采用了DWDM和OXC的光网络为传输IP业务提供了许多新的机会与挑战。该网络不仅可以在网络之间快速自动建立和拆除路由,而且还可以在路由上支持多种用户信号。因此,今天的光网络发展计划关键在于核心网络可以提供一个以快速OXC和适当的管理控制机制为基础的可重构的光传输层。在不久的将来,光传输网将能够支持大量的高容量的光信道,这…     

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。     

An in-band signaling protocol for optical packet switching networks

Advances in optical networking reveal that all optical networks offering a multigigabit rate per wavelength will soon become economical as the underlying backbone in wide-area networks, in which the optical switch plays a central role. One of the central issues is the design of efficient signaling protocols which can support diversified traffic types, in particular the bursty IP traffic. This paper introduces a novel signaling protocol called the sampling probe algorithm (or SPA) to be used in a class of optical packet switching systems based on wavelength division multiplexing (WDM). The proposed scheme takes a drastically different approach from all existing signaling protocols. The salient features are 1) the pretransmission coordination is using an in-band signaling protocol, and thus does not require separate control channel(s) for transmission coordination; 2) the protocol is based on a reservation (connection) scheme which is capable of supporting multimedia traffic; 3) a gated service is adopted in which each successful reservation allows multiple packets (train of packets) to be transmitted, which can significantly reduce the per packet overhead; 4) the scheduling algorithm is adaptive by allowing flexible assignment of bandwidth on-demand; 5) the channel status gathering is done in a distributed fashion, and uses a passive listening mechanism, which itself does not interfere with packet transmissions. The results demonstrate that the proposed in-band signaling protocol can achieve high throughput and stability under heavy traffic condition.     

An effective buffering architecture for optical packet switching networks

A novel optical buffering architecture for Optical Packet Switching (OPS) networks is proposed in this article. The architecture which adopts a fiber-sharing mechanism aims at solving the problem of using a large number of fiber delay lines that are used to solve resource contention in the core node in OPS networks. The new architecture employs fewer fiber delay lines compared to other simple architectures, but can achieve the same performance. Simulation results and analysis show that the new architecture can decrease packet loss probability effectively and achieve reasonable performance in average packet delay.

折射路由法在光分组交换网络中的运用

就OTDM(光时分复用)光分组交换网络的交换节点功能和关键技术进行了分析和探讨。对无缓冲折射路由法在街区网络上的应用和路由算法进行了深入研究，并根据概率分析模型，求得在稳定状态下吞吐量和平均时延的计算公式，最后与有缓冲区的存储转发网络的性能进行了比较。     

The European IST project DAVID: a viable approach toward optical packet switching

In this paper, promising technologies and a network architecture are presented for future optical packet switched networks. The overall network concept is presented and the major choices are highlighted and compared with alternative solutions. Both long and shorter term approaches are considered, as well as both the wide-area network and multiple-area networks parts of the network. The results presented in this paper were developed in the frame of the research project DAVID (Data And Voice Integration over DWDM) project, funded by the European Commission through the IST-framework.     

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     

Voice synchronization in packet switching networks

An algorithm for voice synchronization for packet switching networks is presented. The algorithm has been tested both in simulation and on a real network. The algorithm runs on the TRAME packet switching network for both the Vocoder and CELP DoD voice coding standards. Some results of these tests are presented. Some details of the algorithm development and implementation are given as well     

Architectures and performance of optical packet switching nodes for IP networks

As new bandwidth-hungry Internet protocol (IP) services are demanding more and more capacity, transport networks are evolving to provide a reconfigurable optical layer in order to allow fast dynamic allocation of wavelength-division-multiplexing (WDM) channels. To achieve this goal, optical packet-switched systems seem to be strong candidates as they allow a high degree of statistical resource sharing, which leads to an efficient bandwidth utilization. In this paper, we propose an architecture for optical packet-switched transport networks, together with an innovative switching node structure based on the concept of per-packet wavelength routing. The traffic performance of such node when loaded by a typical IP traffic is evaluated through computer simulation; packet loss probability and average delay performance are shown for various load conditions.     

The perspective of optical packet switching in IP dominant backboneand metropolitan networks

This article analyses the rationale and technical solutions for the use of optical packet switching techniques for both backbone and metropolitan applications. It also provides information on state-of-the-art technologies available for medium-term product development     

Impact of cumulative polarization-dependent gain on SOA-based optical packet switching networks

The physical layer scalability of multistage interconnection networks is determined by the maximum number of internal switching nodes that packets can traverse error-free. We show that for nodes based on commercial semiconductor optical amplifier switches with polarization-dependent gain of less than 0.35 dB, the maximum number of cascaded nodes could vary by as much as 20 nodes, depending both on the packet wavelength and its state of polarization. We explain such a dramatic effect by optical signal-to-noise ratio degradation due to accumulated amplified spontaneous emission noise with the number of nodes.     

Benchmarking and viability assessment of optical packet switching for metro networks

Optical packet switching (OPS) has been proposed as a strong candidate for future metro networks. This paper assesses the viability of an OPS-based ring architecture as proposed within the research project DAVID (Data And Voice Integration on DWDM), funded by the European Commission through the Information Society Technologies (IST) framework. Its feasibility is discussed from a physical-layer point of view, and its limitations in size are explored. Through dimensioning studies, we show that the proposed OPS architecture is competitive with respect to alternative metropolitan area network (MAN) approaches, including synchronous digital hierarchy, resilient packet rings (RPR), and star-based Ethernet. Finally, the proposed OPS architectures are discussed from a logical performance point of view, and a high-quality scheduling algorithm to control the packet-switching operations in the rings is explained.     

Wavelength conversion in optical packet switching

A detailed traffic analysis of optical packet switch design is performed. Special consideration is given to the complexity of the optical buffering and the overall switch block structure is considered in general. Wavelength converters are shown to improve the traffic performance of the switch blocks for both random and bursty traffic. Furthermore, the traffic performance of switch blocks with add-drop switches has been assessed in a Shufflenetwork showing the advantage of having converters at the inlets. Finally, the aspect of synchronization is discussed through a proposal to operate the packet switch block asynchronously, i.e. without packet alignment at the input     

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.     

Accuracy of traffic modeling in fast packet switching

Arrivals of calls, bursts, and packets to a fast packet switching system are governed by different time scales. This feature is used to break down the system performance analysis into layers. The impact of each layer on packet delay and blocking is investigated in isolation by assuming the global equilibrium in the next higher layer and deterministic flow of entities in all lower layers. The one-layer analytical model is developed and used to determine lower and upper estimates of a mean delay and blocking. Numerical results are compared with delays obtained from the multilayer simulation. Results of the analysis indicate that the channel utilization must be kept below a threshold value to avoid overload periods in the burst and call layers. Flow control techniques which can be used for that purpose are briefly discussed     

多粒度动态光交换结构及其波带疏导算法

针对提高交叉连接器端口效率问题,进行了线性规划探讨.采用了一种新型的多粒度光交换结构并提出了一种动态波带疏导算法,对波长资源进行动态分配,并选择NSFNet拓扑进行仿真,仿真结果表明,算法不仅可以减少多粒度交叉连接端口数,同时还可以有效地降低阻塞率,提高网络资源的利用率.