波长路由网络选路时的光信号质量限制研究

光网络中,路由与波长分配(RWA)算法是最优化网络性能的核心问题之一,传统的RWA算法都假设光网络的物理层状态是理想的,即不存在光信号传输损伤的问题.通过对这个缺陷的分析,将光信号的传输损伤问题充分考虑到路由与波长分配算法中,从算法的角度来实现对光信号的传输保护,这样做不仅能有效防止业务的物理损伤阻塞,还能极大地提高光网络的性能.     

静态波长路由光网络中路由和波长分配算法的统计修正

本文采用统计的方法对以网络最小所需波长数为优化目标的路由和波长分配算法进行了修正.数值模拟计算表明,经过统计方法修正之后,可以求得更接近波长下限的网络所需波长数.另外本文还首次提出用统计的方法对路由和波长分配算法进行比较,通过比较两个算法在经过统计修正之后求得的网络所需波长数的分布可以知道它们的优劣.     

光网络中的路由信息交换

分析了IP路由路和核心光网络之间 ,光子网内部以及光子网之间的路由信息交换。这种路由信息交换在自动建立穿越多个光子网的端到端光通道的过程中是非常重要的。UNI路由信息交换 ,分为三种类型 ,并对部分对等模型和完全对等模型做了详细分析 ,此外 ,对NNI路由信息交换以及端到端的光通道动态供给模型也做了粗略分析。     

Dynamic Deflection Routing with Virtual Wavelength Assignment in Optical Burst-Switched Networks

In optical burst-switched networks, one of the most significant issues is contention resolution. There have been several deflection routing techniques as contention resolution. While contention is resolved by traditional deflection routing, it cannot guarantee that the control packet will reserve all the wavelengths successfully to the destination on the alternate path, especially when traffic load in a network is high. Therefore, in this paper, we propose a Deflection Routing with Virtual Wavelength Assignment (DR-VWA) algorithm in order to provide a higher resource guarantee for loss-sensitive traffic bursts. The proposed DR-VWA scheme (1) dynamically decides the alternate path with the least traffic load and (2) allows high-priority bursts in terms of loss to be assigned available wavelengths over the path virtually. The proposed scheme is evaluated through simulation, and it is shown that significant improvement with regard to burst loss and wavelength conversion cost can be achieved.This work was supported in part by the Korea Science and Engineering Foundation (KOSEF) through OIRC project and by the US National Communications System (NCS).     

Routing and Wavelength Assignment in Optical Networks Using Logical Link Representation and Efficient Bitwise Computation

In this paper, we propose and evaluate a new approach for implementing efficient routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) optical networks. In our method, the state of a fiber is given by the set of free wavelengths in this fiber and is efficiently represented as a compact bitmap. The state of a multiple-fiber link is also represented by a compact bitmap computed as the logical union of the individual bitmaps of the fibers in this link. Likewise, the state of a lightpath is represented by a similar bitmap computed as the logical intersection of the individual bitmaps of the links in this path. The count of the number of 1-valued bits in the bitmap of the route from source to destination is used as the primary reward function in route selection. A modified Dijkstra algorithm is developed for dynamic routing based on the bitmap representation. The algorithm uses bitwise logical operations and is quite efficient. A first-fit channel assignment algorithm is developed using a simple computation on the bitmap of the selected route. The resulting bitwise routing algorithm combines the benefits of least loaded routing algorithms and shortest path routing algorithms. Our extensive simulation tests have shown that the bitwise RWA approach has small storage overhead, is computationally fast, and reduces the network-wide blocking probability. The blocking performance of our RWA method compares very favorably with three routing methods: fixed alternate routing, shortest path using flooding, and Dijkstra’s algorithm using mathematical operations. Our simulation experiments have also evaluated the performance gain obtained when the network access stations are equipped with finite buffers to temporarily hold blocked connection requests.     

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。     

混合光波长转换在波分复用光网络中的应用

在全光网络中，如何合理利用波长转换来降低光网络的阻塞率是一个非常关键的问题。研究了最新的波长转换体系结构和波长转换手段，提出一种全新的混合波长转换方法，在减少网络中波长转换器个数的同时，维持拥塞概率类似于全波长转换。提出了5种不同的波长转换器使用策略，并利用数值模拟的方法，比较了这5种不同的波长转换器使用策略，分析结果，得出了最小化光网络的阻塞概率的波长转换使用策略。结合混合波长转换和波长转换器使用策略，进一步提出了光网络中优化波长转换器配置的遗传算法，通过对14个节点的美国自然科学基金网(NSF Net)的数值模拟，结果表明它是十分有效的，在减少光网络中波长转换器数量，且不增加光网络波长数量的情况下，基本保持原有网络性能。     

一种波长转换范围受限全光网中的波长分配算法

本文研究了波长转换范围受限全光网中的动态路由和波长分配问题,提出了一种固定备选路由条件下新的路由和波长分配算法.算法引入了波长相关性的概念,用波长关联权值定量描述了各路由的前后链路上不同波长之间的相互依赖关系.在建立连接时首先使用那些依赖性强,对其他路由影响小的波长,从全局的角度出发选择最优的路由和波长分配方案.计算机仿真表明,本文算法能够适用于稀疏网络和网状网,在均匀业务强度或者大部分业务量来自于长跳路由的情况下,本文算法能够显著降低网络阻塞概率和使用的波长转换器数目,有效提高系统性能.     

部分共享波长转换光网络动态路由的改进算法

提出了一种应用于部分共享波长转换（PWC）的波长路由光网络（WRON）中的基于节点阻塞的动态路由算法,它不需要共享复杂的波长转换信息,而是将各节点的阻塞特性考虑到路由过程中。为评价算法性能,在14节点的国家科学基金网（NSFNET）拓扑中进行了仿真。结果表明,新的路由算法显著改善了网络的阻塞性能和建路失败的概率,尤其是随着网络负载的降低,网络性能的改善更显著。     

智能光网中的联合路由

在IP/MPLS智能光网络中的LSP路由分为独立路由和联合路由两类。由于综合考虑了光层和IP层的可用资源信息和拓扑信息,联合路由能够提供比独立路由方案更高的资源利用率。文中提出了联合路由算法的设计目标,综述了联合路由算法的研究现状,并给出了下一步的研究方向。     

光网络选路和波长分配研究

文章在叙述了光网络中选路和波长分配(RWA)要解决的基本问题后,对有关方面的近年研究作了综述,主要包括:虚拓扑重构、业务量疏导的RWA、多播RWA、抗毁网络的RWA.抗毁问题涉及WDM网络的抗毁选路、区分可靠性、网状网的快速恢复、多故障下的抗毁.     

未来光核心网的体系结构与波长路由技术

概要介绍了未来光核心网体系结构和实现光核心网智能化节点-波长路由器的波长路由技术,重点讨论了思科系统公司提出的波长路由协议-WaRP,最后指出了光核心网进一步发展的两项关键技术。     

Sparse Wavelength Conversion in Wavelength-Routed WDM Optical Networks*

A wavelength-routed optical network can suffer inefficiencies due to the wavelength-continuity constraint (under which a signal has to remain on the same wavelength from the source to the destination). In order to eliminate or reduce the effects of this constraint, a device called a wavelength converter may be utilized. Due to the high cost of these wavelength converters, many studies have attempted to determine the exact benefits of wavelength conversion. However, most of these studies have focused on optical networks that implement full wavelength conversion capabilities. An alternative to full wavelength conversion is to employ only a sparse number of wavelength converters throughout the network, thereby reducing network costs. This study will focus on different versions of sparse wavelength conversion--namely, sparse nodal conversion, sparse switch-output conversion, and sparse (or limited) range conversion--to determine if most of the benefits of full conversion can be obtained using only sparse conversion. Simulation and analytical results on these three different classes of sparse wavelength conversion will be presented. In addition, this study will present heuristic techniques for the placement of sparse conversion facilities within an optical network.     

Sparse Regeneration in Translucent Wavelength-Routed Optical Networks: Architecture,Network Design and Wavelength Routing

In this paper we study an alternate network architecture, called translucent network, to the fully transparent and fully opaque network architectures. In a translucent wavelength-routed optical network, a technique called sparse regeneration is used to overcome the severe lightpath blocking due to signal quality degradation and wavelength contention in a fully transparent network while using much less regenerators than in a fully opaque network. In this paper, we present a node model and a network model that perform sparse regeneration. We address the problem of translucent network design by proposing several regenerator placement algorithms based on different knowledge of future network traffic patterns. We also address the problem of wavelength routing under sparse regeneration by incorporating two regenerator allocation strategies with heuristic wavelength routing algorithms. We compare the performance of different regenerator placement algorithms and wavelength routing schemes through simulation experiments. The benefit of sparse regeneration is quantitatively measured under different network settings.This work was supported by NSF grants (ANI-0074121 and EPS-0091900).Portions of this work have appeared in the Proceedings of the OSA Optical Fiber Communications (OFC 1999) Conference [6] and the Proceedings of the IEEE Global Telecommunications (GLOBECOM 2001) Conference [12].     

Wavelength Routing Algorithm of All Optical Network Based on Traffic Engineering

General multi-protocol label switching （GMPLS） based on traffic engineering is one of the possible methods to implement all-optical network. This method implements the network with IP technique and guarantees the quality of service with traffic engineering. Based on the establishment of selecting schemes of optical path and methods of traffic calculation, the wavelength routing algorithm of all-optical network based on traffic engineering is presented by combining with prior route of shortest path and traffic engineering, the algorithm procedures are given, and the actual examples are introduced as well as the analysis on simulation calculation. This research results have certain significance for the achievement of optical switching technique of all-optical network.     

Link-State-Based Algorithms for Dynamic Routing in All-Optical Networks with Ring Topologies

The increased usage of large bandwidth in optical networks raises the problems of efficient routing to allow these networks to deliver fast data transmission with low blocking probabilities. Due to limited optical buffering in optical switches and constraints of high switching speeds, data transmitted over optical networks must be routed without waiting queues along a path from source to destination. Moreover, in optical networks deprived of wavelength converters, it is necessary for each established path to transfer data from source to destination by using only one wavelength. To solve this NP-hard problem, many algorithms have been proposed for dynamic optical routing like Fixed-Paths Least Congested (FPLC) routing or Least Loaded Path Routing (LLR). This paper proposes two heuristic algorithms based on former algorithms to improve network throughput and reduce blocking probabilities of data transmitted in all-optical networks with regard to connection costs. We also introduce new criteria to estimate network congestion and choose better routing paths. Experimental results in ring networks show that both new algorithms achieve promising performance.     

多域光网络联合路由保护算法

研究了多域光网络中的路由保护问题。为了避免多域光网络通路保护二步算法可能导致的多域陷阱问题,提出了一种基于Suurballe算法扩展的多域联合路由保护算法。仿真表明,相比传统的多域通路保护二步算法,该算法资源利用率高,阻塞率低,平均每连接跨域数小。     

全光网络中的波长选择器件

随着光通信技术的发展,特别是光波分复用（WDM）技术的广泛应用,光交叉连接技术（OXC）和光分插复用技术（OADM）受到了越来越多的关注。波长选择器件因具有对不同波长自由选取的功能而在以上两种技术中起到了十分重要的作用。本文介绍了目前研究的几种典型的波长选择器件,对它们的特点进行了分析和比较。     

Routing Mechanisms Employing Adaptive Weight Functions for Shortest Path Routing in Optical WDM Networks

Optical dense wavelength division multiplexed (DWDM) networks are an attractive candidate for the next generation Internet and beyond. In this paper, we consider routing and wavelength assignment in a wide area wavelength routed backbone network that employs circuit-switching. When a session request is received by the network, the routing and wavelength assignment (RWA) task is to establish a lightpath between the source and destination. That is, determine a suitable path and assign a set of wavelengths for the links on this path. We consider a link state protocol approach and use Dijkstras shortest path algorithm, suitably modified for DWDM networks, for computing the shortest paths. In [1] we proposed WDM aware weight functions that included factors such as available wavelengths per link, total wavelengths per link. In this paper, we present new weight functions that exploit the strong correlation between blocking probability and number of hops involved in connection setup to increase the performance of the network. We also consider alternate path routing that computes the alternate paths based on WDM aware weight functions. The impact of the weight functions on the blocking probability and delay is studied through discrete event simulation. The system parameters varied include number of network nodes, wavelengths, degree of wavelength conversion, and load. The results show that the weight function that incorporates both hop count and available wavelength provides the best performance in terms of blocking probability.     

多约束条件下WDM光网中多播选路和波长分配算法

在光层构建多播选路和波长分配时,必须考虑一些约束条件。主要的约束条件有以下4种：稀疏分光器配置约束、波长连续性约束、能量损伤约束及稀疏波长转换器约束。目前,研究人员只是针对其中一个或两个约束条件进行了算法研究。该文在详细分析各种约束条件之后,提出了一种基于多约束条件下多播选路和波长分配启发式算法。最后在CERNET和NSFNET两种网络拓扑上进行了仿真实验。根据算法仿真结果可以得出该算法可以有效地解决多约束条件下的多播路由及波长分配问题。