共查询到20条相似文献,搜索用时 15 毫秒
1.
本文研究了WDM网状网中双链路失效的动态共享链路保护设计问题,提出了一种新的启发式算法TBP (Two Backup Paths) 和一种改进的启发式算法OBP (One Backup Path).两种保护算法都能根据当前网络状态动态地动态调整链路代价,所选路由都是最小代价的路径.文本还研究了双链路失效的保护切换时间,详细描述了保护切换过程.仿真表明,(1)两种算法都能有效地保护双链路失效;(2)TBP的性能优于OBP;(3)与其他算法相比,TBP具有最快的保护切换时间. 相似文献
2.
该文研究了WDM网状网中双链路失效问题,在假定所有链路共享风险链路组(Share Risk Link Group, SRLG)分离的条件下,提出了一种动态共享路径保护(Dynamic Shared-Path Protection,DSPP)算法。DSPP能根据网络状态动态调整链路代价,为每条业务请求选择一条最小代价的工作路由和两条最小代价且SRLG分离的保护路由。仿真表明,DSPP不仅能完全保护双链路失效,并且能在资源利用率、阻塞率和保护切换时间之间进行性能折衷。 相似文献
3.
Resilient optical networks are predominately designed to protect against single failures of fiber links. But in larger networks, operators also see dual failures. As the capacity was planned for single failures, disconnections can occur by dual failures even if enough topological connectivity is provided. In our approach the design of the network minimizes the average loss caused by dual failures, while single failures are still fully survived. High dual failure restorability is the primary aim, capacity is optimized in a second step. For WDM networks with full wavelength conversion, we formulate mixed integer linear programming models for dedicated path protection, shared (backup) path protection, and path rerouting with and without stub-release. For larger problem instances in path rerouting, we propose two heuristics. Computational results indicate that the connectivity is of much more importance for high restorability values than the overall protection capacity. Shared protection has similar restorability levels as dedicated protection while the capacity is comparable to rerouting. Rerouting surpasses the protection mechanisms in restorability and comes close to 100% dual failure survivability. Compared to single failure planning, both shared path protection and rerouting need significantly more capacity in dual failure planning. 相似文献
4.
刘祺 《电信工程技术与标准化》2004,(6):50-53
光突发交换拥有光电路交换和光分组交换两种方式的主要特征,是未来光网络的一种有希望的实现形式,本文对wDM光突发交换网络的实现做了简要的介绍,主要从wDM光突发交换网络的生存性出发对相关问题进行了分析研究,并提出了相应的解决方案. 相似文献
5.
在WDM网络中,由于光路之间存在的依赖性,物理网络的单链路失效可能会造成虚拓扑不连通而使上层网络(SDH、ATM或IP)无法使用自身的恢复机制来恢复受影响的业务,因此虚拓扑在嵌入物理拓扑时必须避免发生这种情况.已有的分离备用路径(Disjoint Alternate Path,DAP)算法总是假设网络所有波长路由节点都具有全波长转换能力.本文提出的LG-VTMDP保护设计算法利用分层图同时解决路由和波长分配两个子问题,并考虑了负载均衡和物理链路的容量限制.实验结果表明LG-VTMDP算法优于DAP算法和已有波长分配算法组合后的性能.本文还在此基础上提出了一种有效的波长转换器放置算法WCP算法. 相似文献
6.
7.
8.
9.
针对WDM(波分复用)光网络光层保护问题,提出了两种新的保护算法。这两种保护方法都属于ILP(整数线性规划),所处理的是通道失效问题,而不是链路失效问题,分别列出两种算法的步骤和计算结果。 相似文献
10.
A Novel Fast Multicast Algorithm with Enhanced Survivability in WDM Optical Networks 总被引:3,自引:1,他引:2
WDM optical networking technology is expected to facilitate bandwidth-intensive multicast application by establishing a light-tree which regards the source node as the root and all the destination nodes as the leaves. However, the existing multicast routing algorithms are time-consuming and the generated light-trees are very sensitive to failures, e.g., a single fiber cut can disrupt the information from transmitting to several terminals. In this paper, we propose a novel fast multicast algorithm with enhanced survivability (FMES), which applies a two-stage multicast routing approach, and employs a path protection scheme for each segment of the first stage tree. Analysis and experimental results show that FMES has the significant advantage of a much shorter running time than that in existing schemes, and this advantage can be enlarged in the distributed routing and signaling system of the coming intelligent optical networks. We also compare FMES with non-protection and full-protection schemes. It shows that the FMES scheme achieves the best trade-off between network survivability and resource-utilization. We illustrate our study with numerical experiments based on the real-life ChinaNet topology. 相似文献
11.
We consider extensions of the most common mesh-restorable network capacity design formulation that enhance the dual-failure restorability of the designs. A significant finding is that while design for complete dual-failure restorability can require up to triple the spare capacity, dual failure restorability can be provided for a fairly large set of priority paths with little or no more spare capacity than required for single-failure restorability. As a reference case we first study the capacity needs under complete dual-failure restorability. This shows extremely high spare capacity penalties. A second design model allows a user to specify a total capacity (or budget) limit and obtain the highest average dual-failure restorability possible for that investment limit. This formulation, and a relationship between dual-failure restorability and availability, can be used to trace-out the capacity-versus-availability trade-off curve for a mesh network. A third design strategy supports multiple-restorability service class definitions ranging from best-efforts-only to an assurance of complete single and dual-failure restorability on a per-demand basis. This lets a network operator tailor the investment in protection capacity to provide ultra-high availability on a service-selective basis, while avoiding the very high investment that would be required to support complete dual-failure restorability of the network as a whole. 相似文献
12.
In an optical transport network distinct logical groups of lightwave channels between neighboring OXC nodes (called spans) may sometimes be realized over a common physical resource such as a duct or conduit, and hence share a common cause of failure. This is closely related to the concept of shared risk on individual channels or links, called SRLGs, which is relevant to pre-planned path protection schemes with shared capacity on backup paths. But when considering span-restorable networks, shared risk over logical spans (not individual channels) is the corresponding issue of concern. This work considers several aspect of how such shared-risk span groups (SRSG) affect the protection capacity design and other aspects of span-restorable mesh networks. We provide a model for capacity planning any span-restorable network in the presence of a known set of such shared-risk spans and study the relationship between capacity requirements and the number and placement of such situations. This provides guidelines as to how many SRSGs can be sustained before the capacity penalty becomes severe and methods to diagnose which of them are the most limiting to overall protection efficiency. One finding of interest is that if a given percentage of all possible dual-failure combinations incident to a common node are allowed for in the design, then nearly the same percentage of other dual-span failure combinations (any two spans in the network) will also be restorable. We also show that designing a network to withstand even a small number of multi-span co-incident spared-risk span groups will yield a significant improvement in overall dual-failure restorability and hence also in network availability.Presented at Optical Networking and Communications Conference (Opti Comm 2002), Boston, MA, USA, July-August 2002. 相似文献
13.
The ever-increasing demand for network bandwidth makes network survivability an issue of great concern. Lightpath restoration is a valuable approach to guaranteeing an acceptable level of survivability in WDM optical networks with better resource utilization than that of its protection counterpart. Active restoration (AR) is a newly proposed lightpath restoration scheme [M. Mostafa et al. OSA Journal of Optical Networking, vol. 3, no. 4, pp. 247–260] that combines the best of protection and reactive restoration while avoiding their shortcomings. In this paper, we conduct detailed performance analysis on the restoration probability of AR-based WDM networks. In particular, analytical models of restoration probability are developed respectively for networks with full-wavelength conversion capability and for networks without wavelength conversion capability under different backup path searching schemes. Based on the new models, we investigate the effects of wavelength availability, wavelength conversion capability, path length as well as backup path seeking methods on the restoration probability. 相似文献
14.
15.
Maier Guido Pattavina Achille De Patre Simone Martinelli Mario 《Photonic Network Communications》2002,4(3-4):251-269
This paper is an introduction to survivability of WDM networks. All the main optical protection techniques proposed as far as now for the WDM layer are classified and reviewed. In particular, commonly adopted protection strategies for ring and mesh networks are explained. Moreover, off-line planning of WDM networks able to support path protection is briefly introduced. Finally, an example of heuristic network-capacity optimization is presented, discussing results obtained by considering a case-study network. 相似文献
16.
17.
随着网状网(Mesh)拓扑结构在下一代光传送网中的应用,基于Mesh的光传送网的生存性将成为研究热点。文章从光层生存性入手,首先分析Mesh生存性的主要特征,接着对Mesh网的保护与恢复策略进行归纳和总结,并介绍不同保护机制的应用特点,最后对Mesh网中的多层联合保护策略作了较为深入的探讨。 相似文献
18.
In dynamic IP-over-WDM networks efficient fault-management techniques become more difficult since as demands change with time the optimal logical topology varies as well. Changes in the virtual topology should be done with care because working IP LSPs routed on top of a virtual topology should not be interrupted. Reconfiguration of the virtual topology may also affect precomputed backup IP LSPs to be activated in case of failure meaning that backup IP LSPs would need to be recomputed after any change in the virtual topology. A good sense solution can be the dimensioning of the virtual topology for a worst case traffic scenario, having as goal the minimization of the network cost, for example, and then route dynamic IP LSPs on this virtual topology. The virtual topology would remain unchanged as long as possible, that is, until changes in the virtual topology are considered to bring considerable benefits. Since data services over IP are essentially of a best-effort nature, protection could be provided, using IP LSP protection, only when bandwidth is available in the virtual topology. The computation of backup IP LSPs does not interfere with working IP LSPs meaning that no service interruption will exist. Such a strategy, considered in this paper, allows resources to be used efficiently, since free bandwidth is used for backup purposes, while the normal delivery of traffic is guaranteed in peak traffic situations although having no protection guarantees. Our main objective is to quantify the spare capacity, which can be used for restoration (backup) purposes, over a virtual topology designed and optimized to carry a traffic scenario with no survivability and QoS requirements. We analyse the maximum protection (MP) problem in such IP-over-WDM network environment. Protection is provided to IP LSP requests whenever possible through bandwidth reservation in a backup IP LSP on the virtual topology. Besides the mathematical formalization of the MP problem, an upper bound and heuristic algorithms are proposed and evaluated. The traffic considered includes IP LSPs of different granularities and is the worst case traffic scenario for which the network should be dimensioned. 相似文献
19.