WDM网络恢复算法性能的比较

随着波分复用(WDM)技术的迅速商用化,骨干网络传输带宽呈现爆炸式增长的趋势,这使得网络生存性变得越来越重要.传统的网络生存性包括保护和恢复两种机制,而恢复机制直接影响着网络失效以后其承载业务的可靠性.文章综合前人的研究成果,从3个角度出发,提出了3种不同的恢复算法,并通过仿真数据对这3种算法性能进行了分析.     

Routing scalability in multi-domain DWDM networks

This paper studies routing scalability in multi-domain DWDM networks. Although inter-domain provisioning has been well studied for packet/cell-switching networks, the wavelength dimension (along with wavelength conversion) poses many challenges in multi-domain DWDM settings. To address these concerns a detailed GMPLS-based hierarchical routing framework is proposed for multi-domain DWDM networks with wavelength conversion. This solution uses mesh topology abstraction schemes to hide domain-internal state. However related inter-domain routing loads can be significant here, growing by the square of the number of border nodes. To address these scalability limitations, improved inter-domain routing update strategies are also proposed and the associated performance of inter-domain lightpath RWA and signaling schemes studied.

一种适用于mesh网络的分布式恢复算法

文章简要介绍了传统的基于链路的恢复技术,并在此基础上提出一种改进的分布式恢复算法,这种新的算法不仅可以恢复链路故障,而且也可以解决节点故障。通过仿真分析可看出,它在故障恢复速度和资源利用率等方面都表现出优越的性能。     

一种改进的多域光网络保护机制

生存性是保证业务服务质量的关键,多域光网络生存性问题中,由于存在多域间拓扑和路由信息不可见等约束,导致生存性实现较为困难.提出了将多域光网络进行逻辑聚合的思路,在此基础上分别针对域内和域间提出了非等值负载保护和M∶1保护机制.域内的非等值负载保护机制可以根据节点数以及业务量动态地分配保护路径,从而有效地提高资源利用率.     

多域光网络生存性的关键技术研究

多域光网络的生存性作为衡量网络性能优劣的关键指标,与实际网络应用的关系最为密切,是当前迫切需要解决的关键问题;聚焦高速化、多业务化驱动的多域光网络环境下的生存性技术.基于光网络的多业务、分布式控制的特性,分析了多域光网络生存性机制的研究现状及面临的挑战;给出了一种针对多域光网络生存性问题的分类方法;结合多域光网络对生存性的需求,对相关关键技术进行了归类和研究,并指明了进一步研究的方向和重点.     

WDM疏导网络中基于光路的动态恢复

针对波分复用(WDM)网络中单链路出错的生存性流量疏导问题,文章提出了一种基于光路的动态恢复机制(DRAL).DRAL不预留任何资源,当链路出错时,通过在网络中动态地发现资源来对错误链路进行恢复,将一个出错的光路转发到一条新建立的光路或其他可用的光路上.仿真结果显示,DRAL拥有很高的恢复概率.     

Hybrid protection algorithms based on game theory in multi-domain optical networks

With the network size increasing, the optical backbone is divided into multiple domains and each domain has its own network operator and management policy. At the same time, the failures in optical network may lead to a huge data loss since each wavelength carries a lot of traffic. Therefore, the survivability in multi-domain optical network is very important. However, existing survivable algorithms can achieve only the unilateral optimization for profit of either users or network operators. Then, they cannot well find the double-win optimal solution with considering economic factors for both users and network operators. Thus, in this paper we develop the multi-domain network model with involving multiple Quality of Service (QoS) parameters. After presenting the link evaluation approach based on fuzzy mathematics, we propose the game model to find the optimal solution to maximize the user’s utility, the network operator’s utility, and the joint utility of user and network operator. Since the problem of finding double-win optimal solution is NP-complete, we propose two new hybrid protection algorithms, Intra-domain Sub-path Protection (ISP) algorithm and Inter-domain End-to-end Protection (IEP) algorithm. In ISP and IEP, the hybrid protection means that the intelligent algorithm based on Bacterial Colony Optimization (BCO) and the heuristic algorithm are used to solve the survivability in intra-domain routing and inter-domain routing, respectively. Simulation results show that ISP and IEP have the similar comprehensive utility. In addition, ISP has better resource utilization efficiency, lower blocking probability, and higher network operator’s utility, while IEP has better user’s utility.     

P-cycle Protection in multi-domain optical networks

Providing resilient inter-domain connections in multi-domain optical GMPLS networks is a challenge. On the one hand, the integration of different GMPLS domains to run traffic engineering operations requires the development of a framework for inter-domain routing and control of connections, while keeping the internal structure and available resources of the domains undisclosed to the other operators. On the other hand, the definition of mechanisms to take advantage of such automatically switched inter-domain connectivity is still an open issue. This article focuses on the analysis of applicability of one of these mechanisms: P-cycle-based protection. The proposed solution is based on the decomposition of the multi-domain resilience problem into two sub-problems, namely, the higher level inter-domain protection and the lower level intra-domain protection. Building a P-cycle at the higher level is accomplished by certain tasks at the lower level, including straddling link connection, capacity allocation and path selection. In this article, we present several methods to realize inter-domain P-cycle protection at both levels and we evaluate their performance in terms of availability and spent resources. A discussion on a proposal of implementation of signalling based on extensions of existing protocols such as RSVP-TE and the PCE architecture illustrates the practical viability of the approach.

智能光网络的多域生存性技术研究

自动交换光网络是传送网的发展趋势,而快速高效的生存性是其重要特点.介绍了光网络生存性,重点分析了多域网络和域间路由问题,并且提出了具体的实现多域网络的生存性方法.     

A novel Topology Aggregation approach for shared protection in multi-domain networks

Routing for shared protection in multi-domain networks is more difficult than that in single-domain networks because of the scalability requirements. We propose a novel approach for shared protection routing in multi-domain networks where the key feature is a special Topology Aggregation. In this Topology Aggregation, only some potential intra-domain paths (intra-paths for short) are selected for carrying working and backup traffic between domain border nodes. The abstraction of each intra-path to a virtual edge makes the original multi-domain network to become an aggregated network. On the aggregated network, a single-domain routing algorithm for shared protection can be applied for obtaining the complete routing solutions. The experiments show that the proposed approach is scalable. Moreover it is close to the optimal solution in single-domain networks and outperforms the previously proposed scalable solutions in multi-domain networks.     

多域光网络中采用条件风险分离度的生存性策略

为了克服多域光网络中可扩展性约束的缺点,在多域光网络中提供区分业务的服务,提出一种采用条件风险分离度的多域光网络生存性策略.该策略给出条件风险分离度的概念,应用条件风险分离度实现域内虚链路映射,计算区分业务可靠性的端到端工作,保护路由对.仿真结果表明,所提生存性策略不仅能够区分业务可靠性,降低业务阻塞率,而且能够为业务提供平均高于其请求6.5%的可靠度.     

A concurrent two-layer restoration scheme for GMPLS WDM networks

Next generation backbone networks will likely consist of IP routers as well as optical cross connects (OXCs) and will deploy an optical control plane protocol. Generalized Multi Protocol Label Switching (GMPLS) has been proposed as the candidate of choice for the control plane. Optical fibers may carry large volumes of traffic and therefore adequate mechanisms must exist to enable the network to automatically recover from failures of fiber. In mission critical networks survivability becomes very important. We investigate the problem of autonomous recovery in such networks. The literature contains work in this area that investigates the problem of multilayer recovery. Such recovery had only been sequential in the sense that the published work recovers first in the optical domain, assuming the availability of redundant resources, and then proceeds to recover packet label switched paths. We report a recovery procedure for recovering packet label switch paths (packet LSPs) and lambda label switch paths (λLSP) concurrently. We have conducted an OPNET-based simulation study that compares the performance of the concurrent scheme with the previously published sequential two-layer recovery scheme. The study shows that the concurrent two-layer recovery scheme performs as much as forty-four percent faster than the sequential two-layer recovery scheme.     

A hierarchical extension to RSVP-TE for fast lightpath setup in dynamic optical networks

A dynamic optical network with a fast resource allocation ability is proposed to satisfy the increasing requirement of the fast developing services. The lightpath setup delay of the traditional serial signaling distribution method used by RSVP-TE and CR-LDP increases linearly with increasing scale of the network. When the network size becomes too large, the signaling delay may cause problems to real-time services and fast recovery. So, we propose a combined hierarchical signaling distribution (CHSD) method for fast lightpath setup and an extended RSVP-TE to support a hierarchical signaling distribution process. The simulation and theoretical analysis show that the lightpath setup delay by CHSD is reduced from O(N), which is the delay of the traditional serial distribution method, to in the best condition. The delay is also related to the hierarchical structure of the network and when the scale of the routing areas (RA) takes a uniform distribution and the RA number equals to , a minimum distribution delay is achieved. Thereafter, we extend RSVP-TE to support this hierarchical distribution method. By the simulation result, the extension is proved to be feasible.     

WDM疏导网络中的基于连接的动态恢复

针对WDM网络中单链路出错的生存性流量疏导问题,提出了一种基于连接的动态恢复机制(DRAC).DRAC不预留任何资源,当链路出错时,通过在网络中动态的发现资源来对错误进行恢复,将一个出错连接转发到一条新的多跳路径.仿真结果显示,提出的这种动态恢复机制拥有很高的恢复概率.     

Link-lifetime-based service restoration in optical datacenter network

Aiming at the correlated and cascading failures caused by large-scale disasters,a post-disaster service restoration scheme was proposed.This scheme utilized global service bandwidth concession and the limited lifetime of local links to mitigate resource crunch in the post-disaster network.According to their bandwidth and holding time requirements,the impacted services for restoration was prioritized firstly,then jointly employed anycast and manycast routing strategies to improve the service connectivity and bandwidth resource utilization.Simulation results show that the proposed scheme can significantly reduce the service loss ratio,effectively prolong the holding time of the impacted services and decrease the data flow loss ratio in the post-disaster network.     

基于遗传算法的WDM光传送网恢复优化算法

本文针对WDM光传送网的网络恢复问题,提出了一种基于遗传算法的恢复路由优化算法.在满足多重约束的条件下,该算法可处理不同故障情况下的多种最佳恢复路由的选取问题.通过对实际网络的计算,验证了该算法具有较强的实用性.     

光网络的保护恢复的研究

随着波分复用(WDM)技术的飞速发展,光网络的生存性要求也越来越高,文章阐述了光网络中通用的几种保护方法,给出了这几种保护方法的特点及使用范围,并且就资源利用率、造价、倒换时间、对节点的要求和对网络拓扑的要求这几方面做了比较和分析。最后得出在不同的网络,不同的生存性要求和不同的负载的情况下应采取不同的保护恢复方法。     

智能光网备份路径恢复问题研究

提出了智能光网中的备份路径的本地恢复、全局恢复和更为合理的两阶段恢复方案,并在GMPLs控制平面内设计了若干信令协议用于实现备份路径的建立与故障通知和恢复过程。该方案充分考虑了备份路径保护,能够提高预建立备份路径保护方案的可靠性。     

基于SDH的电力光纤通信网生存性探讨

文章结合当前电力光纤通信网的建设情况以及光纤网络技术的发展,阐述了基于同步数字体系(SDH)的网络主要的保护恢复方法及应用,网络互连时可采用的保护方式,并针对多层网络协同工作的问题,对基于SDH的多层网络生存性协调进行探讨,为网络拓扑的实际应用和网络结构的优化提供参考.     

Models of Restoration Probability in WDM Networks Employing Active Restoration

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.