固定选路的波分复用全光网中的波长分配算法

该文研究了动态业务下,无波长变换的波分复用光传送网采用固定选路时的波长分配问题,提出了一种中心式的波长分配算法-最小影响算法。该算法能精确地描述某个波长的分配对全网状态的影响,因而能够更有效地使用网络资源。计算机仿真表明,如果用阻塞概率来衡量,该波长分配算法优于文献中已有的典型算法。     

一种波分复用全光网波长分配算法

研究了动态业务下 ,无波长变换的波分复用全光网采用固定选路时的波长分配问题 ,提出了一种中心式的波长分配算法—最小影响算法。该算法能精确地描述某个波长的分配对全网状态的影响 ,因而能够更有效地使用网络资源。计算机仿真表明 ,如果用阻塞概率来衡量 ,该波长分配算法优于文献中已有的典型算法     

WDM网络中的一种波长分配算法

本文研究了动态业务下，采用固定选路和备用选路的波分复用光传送网中的波长分配问题，提出了一种波长分配算法-相对最小影响算法。与己朋的利用全网信息分配波长的算法相比，该算法能更精确地描述波长分配对全网状态的影响，使网络资源的充分利用成为可能。计算机仿真表明，该波长分配算法性能较好。     

波分复用全光网中的一种新的波长分配算法

研究了动态业务下，采用固定选路和备用选路的波分复用光传送网中的波长分配问题．提出了一种新的波长分配算法，新算法在已市算法的基础上进行了改进，与已有算法相比，该算法能更精确地描述波长分配对全厨状态的影响。计算机仿真表明，如果用阻塞率来衡量，该波长分配算法优于文献中已有的波长分配算法。     

一种波分复用全光网波长分配算法

研究了动态业务下，无波长变换的波分复用全光风采用固定选路时的波长分配问题，提出了一种中心式的波长分配算法－最小影响算法。该算法能精确地描述某个波长的分配对全网状态的影响，因而能够更有效地使用网络资源。计算机仿真表明，如果用阻塞概率来衡量，该波长分配算法优于文献中已有的典型算法。     

光网络中基于SRLG约束的动态RWA算法

在IPoverWDM光网络中,需要为每条工作光路提供光通路保护,即提供一条保护光路。光网络中引入了共享风险链路组(SRLG)的概念,要求工作光路与保护光路不共享风险链路组。不考虑波长分配提出一种新的启发式算法,该算法同时计算两条SRLG分离且总费用低;在此算法基础上利用分层图的思想,提出WDM网络中的一种在SRLG约束条件下的动态选路波长分配算法。     

基于蚁群系统的分布式RWA算法研究

针对波分复用(WDM)光网络中动态选路和波长分配(RWA)问题，提出了一种基于蚁群算法的分布式动态RWA方法。将蚁群算法与分层图模型结合，实现了RWA的并行计算。仿真结果表明，与现有最短路径法相比，该算法能有效地降低光路阻塞率，促进波长资源的合理分配，同时分布式的计算方式也降低了现代频繁变化的大型光网络的通信开销。     

WDM光传送网的选路和波长分配算法

文章综述了波分复用(WDM)光传送网的选路和波长分配(RWA)算法;考虑了两种需求情况一种是从建立光路的需求出发,另一种是从运送分组业务的需求出发;还概述了RWA设计中要考虑的附加问题,包括波长变换、抗毁和服务策略.     

Hose不确定模型下一种新的动态选路算法研究

该文讨论了全连接结构的光交换网络在Hose不确定模型下的动态选路问题,并基于Valiant负载平衡机制,提出了一种新的动态选路算法.分配系数可调的负载平衡选路算法(Load Balancing with Adjustable Distribution Fraction, LBADF)。LBADF算法根据网络中各条链路上空闲光路的数目对Valiant负载平衡机制中的分配系数进行动态的调整,从而达到优化网络性能的目的。计算机仿真表明LBADF算法相对于分配系数恒定的VLB算法具有更小的全网呼损率,同时也相应地降低了全网中所有节点对的最大呼损率。     

下一代光网络选路策略研究

简述了下一代光网络选路的基本问题;综述了有关方面近年来的研究状况,包括支持优先级的选路及波长分配(RWA)算法、IP业务在光网络中的选路策略及业务量疏导问题.根据各种方法的性能和实际网络建设优化的需要,指出了下一代光网络选路策略领域还需进一步研究的问题.     

Adaptive alternate routing in WDM networks and its performance tradeoffs in the presence of wavelength converters

Routing in wavelength-routed all-optical WDM networks has received much attention in the past decade, for which fixed and dynamic routing methods have been proposed. Taking into account the observation that wavelength-routed all-optical WDM networks are similar to circuit-switched voice networks, except with regard to wavelength conversion, we propose an adaptive alternate routing (AAR) scheme for wavelength-routed all-optical WDM networks. A major benefit of AAR is that it can operate and adapt without requiring an exchange of network status, i.e., it is an information-less adaptive routing scheme. The scope of this work is to understand this scheme in its own right since no other dynamic routing schemes are known to have the information-less property. In this paper, we conduct a systematic study of AAR with regard to factors such as the number of converters, load conditions, traffic patterns, network topologies, and the number of alternate paths considered. We observe that the routing scheme with multiple alternate routes provides more gain at a lower load instead of requiring any nodes to be equipped with wavelength converters. On the other hand, the availability of wavelength converters at some nodes, along with adaptive routing, is beneficial at a moderate to high load without requiring all nodes to be equipped with wavelength converters. We also observed that a small number of alternate routes considered in a network without wavelength converters gives a much better performance than a network with full wavelength converters and fewer alternate routes. Throughout this study, we observed that the proposed adaptive alternate routing scheme adapts well to the network traffic condition.     

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.     

Dynamic Routing and Wavelength Assignment in Survivable WDM Networks

Dense wavelength division multiplexing (DWDM) networks are very attractive candidates for next generation optical Internet and intelligent long-haul core networks. In this paper we consider DWDM networks with wavelength routing switches enabling the dynamic establishment of lightpaths between each pair of nodes. The dynamic routing and wavelength assignment (RWA) problem is studied in multifiber networks, assuming both protection strategies: dedicated and shared. We solve the two subproblems of RWA simultaneously, in a combined way using joint methods for the wavelength selection (WS) and wavelength routing (WR) tasks. For the WS problem in contrast to existing strategies we propose a new, network state based selection method, which tries to route the demand on each wavelength, and selects the best one according to different network metrics (such as available channels, wavelengths per fiber and network load). For the WR problem we propose several weight functions for using in routing algorithms (Dijkstra or Suurballe), adapting dynamically to the load of the links and to the length of the path. The combination of different wavelength selection and routing (WS&WR) methods enables wide configuration opportunities of our proposed algorithm allowing good adaptation to any network state. We also propose the extension of the RWA algorithm for dedicated and shared protection and a new method for applying shared protection in dynamic WDM environment. The detailed analysis of the strategies demonstrate that our RWA algorithm provides significantly better performance than previous methods in terms of blocking probability whether with or without protection methods.     

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.     

WDM网络中基于负载平衡的动态波长路由算法

在WDM网络中，路由和波长分配（RWA）算法是一个焦点问题．当前的RWA算法多是考虑路径跳数或全网拥塞程度，并没有分析各个链路的具体情况．文中提出一种WDM网络中能实现负载平衡的路由算法——最大波长跳数比值（MWHR）算法。基本思想是：根据各备选路径的跳数和其经过的各链路上的可用波长数信息。计算该路径的优先选取权值，优先选取权值最大的路径．仿真表明，该算法在保证较低的阻塞率情况下，能有效的将业务负载均衡分布在网络中的所有链路上．     

An Ant-Based Approach for Dynamic RWA in Optical WDM Networks

In this paper, we propose a new ant-based algorithm for the dynamic routing and wavelength assignment (RWA) problem in optical WDM networks under the wavelength continuity constraint. Unlike conventional approaches, which usually require centralized global network information, our new RWA algorithm constructs the routing solution in a distributed manner by means of cooperative ants. To facilitate the ants’ foraging task, we adopt in our algorithm a probabilistic routing table structure for route selection. The new algorithm is highly adaptive in that it always keeps a suitable number of ants in the network to cooperatively explore the network states and continuously update the routing tables, so that the route for a connection request can be determined promptly by the current states of routing tables with only a small setup delay. Some new schemes for path scoring and path searching are also proposed to enhance the performance of our ant-based algorithm. Extensive simulation results upon three typical network topologies indicate that the proposed algorithm has a very good adaptability to traffic variations and it outperforms both the fixed routing algorithm and the promising fixed–alternate routing algorithm in terms of blocking probability. The ability to guarantee both a low blocking probability and a small setup delay makes the new ant-based routing algorithm very attractive for both the optical circuit switching networks and future optical burst switching networks     

Adaptive wavelength routing in all-optical networks

We consider routing and wavelength assignment in wavelength-routed all-optical networks (WAN) with circuit switching. The conventional approaches to address this issue consider the two aspects of the problem disjointly by first finding a route from a predetermined set of candidate paths and then searching for an appropriate wavelength assignment. We adopt a more general approach in which we consider all paths between a source-destination (s-d) pair and incorporate network state information into the routing decision. This approach performs routing and wavelength assignment jointly and adaptively, and outperforms fixed routing techniques. We present adaptive routing and wavelength assignment algorithms and evaluate their blocking performance. We obtain an analytical technique to compute approximate blocking probabilities for networks employing fixed and alternate routing. The analysis can also accommodate networks with multiple fibers per link. The blocking performance of the proposed adaptive routing algorithms are compared along with their computational complexity     

多光纤波分复用网的一种新的备用路由算法

基于经典的LLR算法,研究了波分复用光网络的路由问题,提出了一种用于多光纤网的新算法—LLHR,该算法综合考虑了链路负载和路由跳数两个因素。文章深入研究了网络光纤数、备用路由数和网络负载对算法性能的影响。计算机仿真结果表明,与LLR算法相比,该算法能有效降低网络的阻塞率,提高网络的性能。     

WDM全光网自适应路由和波长分配算法

研究了无波长转换WDM全光网的路由和波长分配算法（RWA）。通过对已有算法的分析和比较,提出了一种自适应最小跳数路由算法（ADMH）。此算法以最小跳数路由为基础,同时考虑网络状态的变化,因而不仅能尽量少使用网络资源,也能使网络资源的分布保持均衡。计算机模拟仿真的结果表明,这种算法性能在各种网络参数条件下优于或等于已有算法。