On Finding the Multicast Protection Tree Considering SRLG in WDM Optical Networks

In this letter, a new sharing mechanism, SRLG sharing, is proposed, which allows the links of the same shared risk link group (SRLG) in a primary light tree to share protections in WDM optical networks. In previous studies, how to share spare resources with SRLG constraints has not been studied in multicast optical networks. In this letter, considering SRLG sharing, we propose a novel algorithm –multicast with SRLG sharing (MSS)– to establish a protection light tree. Finally, the algorithm MSS and the algorithm multicast with no SRLG sharing (MNSS) are compared through a simulation to show that our new sharing scheme of SRLG sharing is more efficient than that of no SRLG sharing in terms of spare resource utilization and blocking probability.     

Dynamic Survivability in WDM Mesh Networks Under Dynamic Traffic

Network survivability is a crucial requirement in WDM mesh networks. In this paper, we systematically consider the problem of dynamic survivability with dynamic single link failure in WDM networks under dynamic traffic demands. Specifically, we investigate various protection schemes, such as dedicated path protection (DPP), shared path protection (SPP), dedicated link protection (DLP), shared link protection (SLP), and two restoration schemes, path restoration (PR) and link restoration (LR). Moreover, two new shared protection methods are proposed, i.e., SRLG-based shared link protection (SRLG-SLP) and SRLG-based shared path protection (SRLG-SPP). The SRLG (shared risk link group) constraint defines the availability of protection resources to a working path, which requires that any two working paths sharing the same risk of failure (or in the same SRLG) cannot share the same protection resources. Furthermore, in our study, we consider a more practical dynamic single-link failure model, in which the link-failure-interarrival time and link-failure-holding time are considered as two independent parameters. Based on this link-failure model, extensive simulations are done to analyze and compare the dynamic survivable performance of various protection and restoration schemes. Resource utilization, protection efficiency, restoration efficiency, and service disruption ratio are employed as survivable performance metrics versus traffic load, link-failure frequency, and link-failure reparation time to evaluate the survivable performance. Many meaningful results are given. In addition, we show that the developed SRLG-SLP and SRLG-SPP protection schemes perform very well in terms of protection efficiency and service disruption ratio, while sacrificing some performance in terms of resource utilization.     

Realization strategies of dedicated path protection: A bandwidth cost perspective

Communication networks have to provide a high level of availability and instantaneous recovery after failures in order to ensure sufficient survivability for mission-critical services. Currently, dedicated path protection (or 1 + 1) is implemented in backbone networks to provide the necessary resilience and instantaneous recovery against single link failures with remarkable simplicity. However, in order to satisfy strict availability requirements, connections also have to be resilient against Shared Risk Link Group (SRLG) failures. In addition, switching matrix reconfigurations have to be avoided after a failure in order to guarantee instantaneous recovery. For this purpose, there are several possible realization strategies improving the characteristics of traditional 1 + 1 path protection by lowering reserved bandwidth while conserving all its favorable properties. These methods either utilize diversity coding, network coding, or generalize the disjoint-path constraint of 1 + 1.In this paper, we consider the cost aspect of the traditional and the alternative 1 + 1 realization strategies. We evaluate the bandwidth cost of different schemes both analytically and empirically in realistic network topologies. As the more complex realizations lead to NP-complete problems even in the single link failure case, we propose both Integer Linear Programming (ILP) based optimal methods, as well as heuristic and meta-heuristic approaches to solve them. Our findings provide a tool and guidelines for service providers for selecting the path protection method with the lowest bandwidth cost for their network corresponding to a given level of reliability.     

WDM光网络中一种基SRLG限制的动态共享保护算法研究

WDM光网络中引入了共享风险链路组(SRLG)的概念,要求工作通道与保护通道不能处于同一个SRLG之中.文章提出了一种基于SRLG限制的动态共享通道保护算法,即满足K对业务的动态链路权重配置(K-Dynamic Link weight Configuration,K-DLWC)算法,该算法的关键在于为链路定义了两个动态权重.在计算工作通道和保护通道时,它能综合解决SRLG限制、局部最优等关键问题.     

Shared partial path protection in WDM networks with shared risk link groups

For 100% shared risk link group (SRLG) failure protection, conventional full path protection has to satisfy SRLG-disjoint constraints, i.e., its working path and backup path cannot go though the same SRLG. With the increase of size and number of SRLGs, capacity efficiency of conventional shared full path protection becomes poorer due to SRLG-disjoint constraints and the blocking probability becomes much higher due to severe traps. To solve these problems, we present a partial path protection scheme where SRLG-disjoint backup paths may only cover part of the working path. Full path protection becomes a special case of partial path protection, in which the backup path covers the full working path. By choosing the most survivable partial backup path as backup path, we can make the impact of SRLG failures as low as possible and accept as many as possible connection requests. Assuming every SRLG has the same probability to fail, we present a heuristic algorithm to find the most survivable partial backup path by choosing full path protection first, iteratively computing partial backup paths and choosing the most survivable one. The benefit of this heuristic algorithm is that it can find the optimal results within less iteration. Analytical and simulation results show that, compared to conventional full path protection, our proposed scheme can significantly reduce blocking probability with little sacrifice on survivability. The proposed scheme is very useful particularly when the network contains a lot of SRLGs and the blocking probability of conventional full path protection becomes too high.

基于约束的智能光网络路由算法的实现

对智能光网络规划方法进行了较为全面的分析和阐述,提出了一种新的用于智能光网络仿真、规划的约束最短路径优先算法,能够有效均衡网络负载,提高网络资源利用率,降低链路失效时的风险.在此算法的基础上实现了智能光网络仿真规划软件,为运营商实际引入智能光网络后的研究设计和运行维护提供了有利工具.     

面向共享风险链路组故障恢复的多路径路由生成算法

为了在IP层恢复网络共享风险链路组(SRLG)故障,提出一种基于改进人工蜂群算法的网络多路径路由生成算法.针对SRLG故障特点建立多路径路由生成模型,最后通过改进人工蜂群算法求解.仿真验证该方法不仅可以生成满足SRLG约束的备用路径,还可以增强故障恢复能力、降低算法复杂度、缩短重路由的平均路径长度.     

IP/MPLSoverWDM网中基于共享风险链路组限制的共享通路保护算法

本文研究了IP/MPLS over WDM网中,如何建立两条共享风险链路组(SRLG)分离的标记交换路径(LSP)问题,提出一种新的基于SRLG分离的共享通路保护算法.该算法既可以保证用户业务的可靠性要求,同时又能够有效提高全网的资源利用率,从而大大降低全网LSP建立请求的阻塞率.本文还对所提算法进行了仿真研究,并给出了仿真结果.     

WDM网状网中基于共享风险链路组限制的业务量疏导算法

该文研究了业务量疏导WDM网状网中如何建立可靠的业务连接问题,提出一种新的基于共享风险链路组(SRLG)限制的共享通路保护算法。该算法既可以保证用户业务不同的可靠性要求,同时又能够有效提高全网的资源利用率,从而大大降低全网的业务阻塞率。该文还对所提算法进行了仿真研究,并给出了仿真结果。     

MSDP with ACO: A maximal SRLG disjoint routing algorithm based on ant colony optimization

Failure resilience is a desired feature in communication networks, and different methods can be considered in order to achieve this feature. One of these methods is diverse Routing. In this paper, we are going to suggest a sort of diverse routing algorithm, which can find two maximal shared risk link group (SRLG) disjoint paths between a source and a destination node. This algorithm is based on ant colony optimization algorithm, which consists of three parts. These parts are graph transformation technique, finding two maximal edge-disjoint routes and reverse transformation. The final routes are always maximal SRLG disjoint. Simulation results show the efficiency of the proposed method.