抗毁WDM网络中支持多优先级的波长分配算法

WDM网络将在未来的骨干网中扮演重要的角色,具备抗毁能力和支持多优先级都很必要.本文提出了两种基于优先级的波长分配算法——波长编号法和分配限额法,并研究了动态业务下,抗毁WDM网络使用这两种波长分配方法后网络的阻塞率性能.研究的内容包括业务量负载、光纤链路的波长通道数和每条链路包含的光纤数对网络性能的影响.本文还给出了仿真结果.     

影响波长转换器改善WDM网络性能的因素

分析了影响波长转换器改善WDM网络性能的各种因素,并且给出了多种衡量波长转换器改善WDM网络性能的重要参数。     

一种波长转换受限WDM网络的动态路由和波长分配算法

本文基于分层图模型,提出了在节点波长转换范围受限和波长转换器数目受限情况下,解决WDM网络的动态路由和波长分配问题的一种算法.通过计算机仿真,研究了本算法的性能以及这两种波长转换受限情况对网络阻塞率的影响.     

WDM网络中稀疏多纤及波长配置算法

由于成本及技术的原因, WDM光网络中的波长变换设备资源和单纤波长数有限,但在网络 建设时,会预留富裕的光纤,如何依据动态业务有效利用这些光纤降低网络阻塞率,并优化单纤波长配置以 满足网络性能,具有现实意义。该文提出了一种WDM网络的稀疏多纤及波长配置算法,该算法基于动态 业务。仿真结果表明,利用稀疏多纤的网络配置,只需要较少的单纤波长即可满足网络阻塞性能要求。     

波长变换器均匀放置的Mesh-Torus的性能分析

本文主要研究了在WDM的Mesh Torus中 ,部分网络节点使用波长转换器能给网络带来的好处 .文中比较了在非泊松业务下 ,波长转换器按二项式分布和均匀分布放置时在阻塞率、转换增益和公平性方面能带来的好处 ,证明了波长转换器均匀放置在链路负荷均匀的情况下的Mesh Torus中是一种优化配置     

稀疏波长变换网络性能分析与研究

文章对动态业务模型下的稀疏波长变换网络性能进行了分析与研究，对波分复用（WDM）网络中引入波长变换器后的网络性能进行了系统的仿真，分析了波长变换器数量、波长变换器位置、波长变换范围以及路由波长算法等因素对网络性能的影响。     

波长变换器均匀旋转的Mesh—Torus的性能分析

本文主要研究了在WDM的Mesh-Torus中,部分网络节点使用波长转换器能给网络带来的好处。文中比较了在非泊松业务下,波长转换器按二项式分布和均匀分布旋转时在阻塞率、转换增益和公平性方面能带来的好处,证明了波长转换器均匀旋转在链路负荷均匀的情况下的Mesh-Torus中是一种优化配置。     

带有负载均衡机制的网状WDM网络抗毁策略研究

研究了带有负载均衡机制的抗毁网状WDM网络,旨在保证网络具有抗毁能力的同时尽量减少全网光域所使用的资源,即在选择工作路径和保护路径时尽量保证全网的负载均衡。以波长数量最小化为优化目标,建立规划模型分别对多纤网状WDM网络中的共享路径保护和共享链路保护策略进行了研究,同时辅以负载均衡机制对网络资源利用率进一步优化。仿真结果表明,该结构在保证网络抗毁性的同时,能够有效地减少全网总体所需的波长数,降低网络成本。     

稀疏多光纤光网配置算法对波长连续性限制的影响

针对波分复用（WDM）光网络在实现端到端业务链接时的波长连续性限制问题,提出了对光网络进行稀疏多光纤配置的方法。通过分析发现：稀疏多光纤配置能够使整个网络的性能受波长连续性限制的影响得到明显改善;具有稀疏多光纤配置的光网络长链路建链阻塞概率在全网阻塞率中的比例要高于使用相同数目波长转换器的光网络,这说明,波长转换器对于光网络的长链建链仍具有一定的优势。     

多光纤WDM网中支持QoS的波长重路由算法

在WDM网上，波长连续性限制会降低网络的信道利用率，增加光路建立请求的阻塞率。采用波长重路由技术可以减少波长连续性限制对网络性能的影响。该文采用波长图模型，对多光纤WDM网中支持QoS的波长重路由算法进行了探讨，提出一种支持QoS的波长重路由算法－－动态选择法，并采用两种网络模型，在不同负载的动态业务下对所提算法进行了仿真研究；仿真结果表明所提算法既满足了上层业务不同的QoS要求，同时又充分利用了有限的网络资源，使全网的平均阻塞率降低。     

Performance analysis of multi-fiber WDM network with limited-range wavelength conversion

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength conversion technology and wavelength converters play an important role in enhancing fiber utilization and in reducing the overall call blocking probability of the network. In this paper, we develop a new analytical model to calculate the average blocking probability in multi-fiber link networks using limited-range wavelength conversion. Based on the results obtained, we conclude that the proposed analytical model is simple and yet can effectively analyze the impact of wavelength conversion ranges and number of fibers on network performance. Also a new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Finally, we analyze network performance with the proposed scheme. It can be observed from numerical simulations that limited-range converters placed at a few nodes can provide almost the same blocking probability as full range wavelength converters placed at all the nodes. We also show that being equipped with a multi-fiber per-link has the same effect as being equipped with the capability of limited-range wavelength conversion. So a multi-fiber per-link network using limited-range wavelength conversion has similar blocking performance as a full wavelength convertible network. Since a multi-fiber network using limited-range wavelength conversion could use fewer converters than a single-fiber network using limited range wavelength conversion and because wavelength converters are today more expensive than fiber equipment, a multi-fiber network in condition with limited-range wavelength conversion is less costly than a single-fiber network using only limited-range wavelength conversion. Thus, multi-fiber per-link network using limited-range wavelength conversion is currently a more practical method for all optical WDM networks. Simulation studies carried out on a 14-node NSFNET, a 10-node CERNET (China Education and Research Network), and a 9-node regular mesh network validate the analysis.     

An effective model to evaluate blocking probability of time-slotted optical burst switched networks

Time-slotted optical burst switched network is a potential technique to support IP over Wavelength Division Multiplexing （WDM） by introduce Time Division Multiplexing （TDM） channel to Optical Burst Switching （OBS） technology. This paper presents a framework to evaluate blocking performance of time-slotted OBS networks with multi-fiber wavelength channels. The proposed model is efficient for not only single class traffic such as individual circuit switch traffics or best-effort traffics but also mixed multi-class traffics. The effectiveness of the proposed model is validated by simulation results. The study shows that blocking performance of multi-fiber TS-OBS network is acceptable for future Internet services.     

Reconfiguration of Logical Topologies with Minimum Traffic Disruptions in Reliable WDM-Based Mesh Networks

A wavelength division multiplexing (WDM) network offers a flexible networking infrastructure by assigning the route and wavelength of lightpaths. We can construct an optimal logical topology, by properly setting up the lightpaths. Furthermore, setting up a backup lightpath for each lightpath improves network reliability. When traffic demand changes, a new optimal (or sub-optimal) topology should be obtained by again applying the formulation. Then, we can reconfigure the running topology to the logical topology obtained. However, during this reconfiguration, traffic loss may occur due to the deletion of older lightpaths. In this paper, we consider reconfiguring the logical topology in reliable WDM-based mesh networks, and we propose five procedures that can be used to reconfigure a running lightpath to a new one. Applying the procedures one by one produces a new logical topology. The procedures mainly focus on utilizing free wavelength resources and the resources of backup lightpaths, which are not used usually for transporting traffic. The results of computer simulations indicate that the traffic loss is remarkably reduced in the 14-node network we used as an example.     

一种WDM网状网中基于共享保护的业务量疏导算法

在WDM网络中业务的带宽需求远低于一个波长所提供的带宽,业务量疏导可以聚集低速业务到大容量的光路中从而有效地利用波长带宽资源.目前大多数业务量疏导的研究限于环形网,考虑对WDM网状网中低速业务可靠疏导的文献更少.该文综合考虑WDM网状网生存性及业务量疏导,提出了基于波长分层图的共享保护业务量疏导算法(SPTG-LG,Shared Protection Traffic Grooming algorithm ba,sed on wavelength Layered-Graph),并对算法进行了仿真和分析.     

A Lagrangian-Relaxation Based Network Profit Optimization For Mesh SONET-Over-WDM Networks

In Wavelength Division Multiplexing (WDM) networks, the huge capacity of wavelength channels is generally much larger than the bandwidth requirement of individual traffic streams from network users. Traffic grooming techniques aggregate low-bandwidth traffic streams onto high-bandwidth wavelength channels. In this paper, we study the optimization problem of grooming the static traffic in mesh Synchronous Optical Network (SONET) over WDM networks. The problem is formulated as a constrained integer linear programming problem and an innovative optimization objective is developed as network profit optimization. The routing cost in the SONET and WDM layers as well as the revenue generated by accepting SONET traffic demands are modelled. Through the optimization process, SONET traffic demands will be selectively accepted based on the profit (i.e., the excess of revenue over network cost) they generate. Consiering the complexity of the network optimization problem, a decomposition approach using Lagrangian relaxation is proposed. The overall relaxed dual problem is decomposed into routing and wavelength assignment and SONET traffic routing sub-problems. The subgradient approach is used to optimize the derived dual function by updating the Lagrange multipliers. To generate a feasible network routing scheme, a heuristic algorithm is proposed based on the dual solution. A systematic approach to obtain theoretical performance bounds is presented for an arbitrary topology mesh network. This is the first time that such theoretical performance bounds are obtained for SONET traffic grooming in mesh topology networks. The optimization results of sample networks indicate that the roposed algorithm achieves good sub-optimal solutions. Finally, the influence of various network parameters is studied.     

Design of grooming architectures for optical WDM mesh networks: limited grooming with electronic wavelength conversion

In this article, we consider the problem of traffic grooming in optical wavelength division multiplexed (WDM) mesh networks under static traffic conditions. The objective of this work is to minimize the network cost and in particular, the electronic port costs incurred for meeting a given performance objective. In earlier work, we have shown the benefits of limited grooming switch architectures, where only a subset of wavelengths in a network are equipped with expensive SONET Add Drop Multiplexers (SADM) that provide the grooming functionality. In this work, we also consider the wavelength conversion capability of such groomers. This can be achieved using a digital cross-connect (DCS) in the grooming switch to switch low-speed connections between the SADMs (and hence, between wavelengths). The grooming switch thus avoids the need for expensive optical wavelength converters. Based on these observations, we propose a limited conversion-based grooming architecture for optical WDM mesh networks. The local ports at every node in this architecture can be one of three types: an add-drop port, a grooming port that allows wavelength conversion or a grooming port that does not allow wavelength conversion. The problem studied is: given a static traffic model, where should the different ports be placed in a network? We formulate this as an optimization problem using an Integer Linear Programing (ILP) and present numerical results for the same. We also present a heuristic-based approach to solve the problem for larger networks.     

Performance Analysis of Multi-Fiber WDM Network with Limited-Range Wavelength Conversion

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength conversion technology and wavelength converters play an important role in enhancing fiber utilization and in reducing the overall call blocking probability of the network. In this paper, we develop a new analytical model to calculate the average blocking probability in multi-fiber link networks using limited range wavelength conversion. Based on the results obtained, we conclude that the proposed analytical model is simple and yet can effectively analyze the impact of wavelength conversion ranges and number of fibers on network performance. Also a new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Finally, we analyze network performance with the proposed scheme. It can be observed from numerical simulations that limited range converters placed at a few nodes can provide almost the same blocking probability as full range wavelength converters placed at all the nodes. We also show that being equipped with a multi-fiber per-link has the same effect as being equipped with the capability of limited range wavelength conversion. So a multi-fiber per-link network using limited range wavelength conversion has similar blocking performance as a full wavelength convertible network. Since a multi-fiber network using limited range wavelength conversion could use fewer converters than a single-fiber network using limited range wavelength conversion and because wavelength converters are today more expensive than fiber equipment, a multi-fiber network in condition with limited range wavelength conversion is less costly than a single fiber network using only limited range wavelength conversion. Thus, multi-fiber per-link network using limited range wavelength conversion is currently a more practical method for all optical WDM networks. Simulation studies carried out on a 14-node NSFNET, a 10-node CERNET (China Education and Research Network), and a 9-node regular mesh network validate the analysis.     

Survivable traffic grooming with non‐service‐interruptive wavelength retuning in a WDM mesh network

This paper proposes a new survivable traffic grooming wavelength retuning (STGWR) scheme in an all‐optical wavelength division multiplexing (WDM) network. In a dynamic WDM network, a connection may require a bandwidth less than a wavelength capacity. In addition, a connection should be protected against any network failures. Survivable traffic grooming (STG) can protect connections at subwavelength granularities. Wavelength retuning is a promising approach in an all‐optical WDM network, where a signal must remain on the same wavelength from its source to the destination, to alleviate the wavelength continuity constraint and reduce the connection blocking probability. Although both STG and wavelength retuning have attracted extensive research attentions nowadays, no effort has been made to combine these two promising approaches in one network. In this paper, we propose a wavelength retuning scheme with no service interruption in an all‐optical network with STG capability. The scheme allocates two routes, one for the active path and other for the backup path, in a shared mesh restoration manner to each incoming connection request and conducts wavelength retuning only on the backup path. Both wavelength retuning and mesh protection are done at the connection level instead of at the lightpath level. The simulation results of the proposed schemes are also presented. Copyright © 2008 John Wiley & Sons, Ltd.     

多光纤WDM网中的QoS路由算法

利用区分光业务(DOS)模型可以将WDM光传送网中客户层(如IP)具有不同QoS要求的业务汇聚力较粗粒度的流,直接映射到光信道上,从而使客户层业务的不同QoS要求可以体现在DOS域的边缘光节点处的光路建立请求的不同优先级上。该文首先探讨了如何将多光纤WDM网转化为波长图,从而一次性解决选路和分配波长(RWA)问题,在此基础上,提出两种用于多光纤WDM网的QoS路由算法,对二者进行了比较,并进行了计算机仿真。     

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on‐demand provisioning of wavelength‐routed channels with service‐differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long‐reach transport and all‐optical switching, the deployment of all‐optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video‐on‐demand systems, real‐time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call‐blocking probability. The dynamic traffic‐grooming problem in wavelength‐routed networks is generally a two‐layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.