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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. 相似文献
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Ning-Hai Bao Zhi-Zhong Zhang Le-Min Li Hong-Fang Yu Hong-Bin Luo 《Photonic Network Communications》2011,22(1):13-22
As the size and the complexity of optical mesh networks are continuing to grow and the severe natural disasters are occurring
more frequently in recent years, multiple failures (link failures or node failures) become increasing probable. Protection
strategies against these failures generally provision backup paths for working paths based on link-disjointness or node-disjointness.
Compared with link-disjoint protection, node-disjoint protection means higher degree of risk isolation and can accommodate
both link failures and node failures. This motivates us to propose a hybrid node-disjoint protection, named Segment and Path
Shared Protection (SPSP), to provide 100% protection against arbitrary simultaneous double-node failures (the worst double-failure
case). For each service connection request, SPSP first provisions backup segments for the working segments, respectively,
as the primary backup resources, then provisions a single backup path for the whole working path as the second backup resource.
In addition to its complete protection capability and flexible scalability for double failures, SPSP can also obtain better
network load balance and resource sharing degree by dynamic link-cost adjustment and reserved backup resource sharing. Simulation
results show that SPSP can achieve a shorter average recovery time than path shared protection (PSP) and higher resource utilization
and lower blocking probability than segment shared protection (SSP). 相似文献
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Networks employ link protection to achieve fast recovery from link failures. While the first link failure can be protected using link protection, there are several alternatives for protecting against the second failure. This paper formally classifies the approaches to dual-link failure resiliency. One of the strategies to recover from dual-link failures is to employ link protection for the two failed links independently, which requires that two links may not use each other in their backup paths if they may fail simultaneously. Such a requirement is referred to as backup link mutual exclusion (BLME) constraint and the problem of identifying a backup path for every link that satisfies the above requirement is referred to as the BLME problem. This paper develops the necessary theory to establish the sufficient conditions for existence of a solution to the BLME problem. Solution methodologies for the BLME problem is developed using two approaches by: 1) formulating the backup path selection as an integer linear program; 2)developing a polynomial time heuristic based on minimum cost path routing. The ILP formulation and heuristic are applied to six networks and their performance is compared with approaches that assume precise knowledge of dual-link failure. It is observed that a solution exists for all of the six networks considered. The heuristic approach is shown to obtain feasible solutions that are resilient to most dual-link failures, although the backup path lengths may be significantly higher than optimal. In addition, the paper illustrates the significance of the knowledge of failure location by illustrating that network with higher connectivity may require lesser capacity than one with a lower connectivity to recover from dual-link failures. 相似文献
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On the complexity of and algorithms for finding the shortest path with a disjoint counterpart 总被引:4,自引:0,他引:4
Dahai Xu Yang Chen Yizhi Xiong Chunming Qiao Xin He 《Networking, IEEE/ACM Transactions on》2006,14(1):147-158
Finding a disjoint path pair is an important component in survivable networks. Since the traffic is carried on the active (working) path most of the time, it is useful to find a disjoint path pair such that the length of the shorter path (to be used as the active path) is minimized. In this paper, we first address such a Min-Min problem. We prove that this problem is NP-complete in either single link cost (e.g., dedicated backup bandwidth) or dual link cost (e.g., shared backup bandwidth) networks. In addition, it is NP-hard to obtain a K-approximation to the optimal solution for any K>1. Our proof is extended to another open question regarding the computational complexity of a restricted version of the Min-Sum problem in an undirected network with ordered dual cost links (called the MSOD problem). To solve the Min-Min problem efficiently, we introduce a novel concept called conflicting link set which provides insights into the so-called trap problem, and develop a divide-and-conquer strategy. The result is an effective heuristic for the Min-Min problem called COnflicting Link Exclusion (COLE), which can outperform other approaches in terms of both the optimality and running time. We also apply COLE to the MSOD problem to efficiently provide shared path protection and conduct comprehensive performance evaluation as well as comparison of various schemes for shared path protection. We show that COLE not only processes connection requests much faster than existing integer linear programming (ILP)-based approaches but also achieves a good balance among the active path length, bandwidth efficiency, and recovery time. 相似文献
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传统的通道保护倒换采用软件方式进行,但对于大容量设备来说,软件方式无法满足ITU-T的倒换时间要求,尤其是对于TUG3或TU12颗粒的低阶通道保护.信息辅助保护倒换将通道的告警信息编成一定的码字,再将其插入到本通道空闲的开销字节中,以实现全硬件的自动保护倒换.这种倒换不仅可以保证满足系统50 ms的倒换时间要求,而且可以大大降低微处理器的负荷. 相似文献
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Protected Working Capacity Envelope (PWCE) has been proposed to simplify resource management and traffic control for survivable
WDM networks. In a PWCE-based network, part of the link capacity is reserved for accommodating working routes, and the remaining
capacity is reserved for backup routes. The shortest path routing is applied in PWCE-based networks. An arrival call is accepted
only when each link along the shortest path has a free working channel. Such a working path routing scheme greatly simplifies
the call admission control process for dynamic traffic, and it is especially suitable for implementation in a distributed
manner among network nodes. In this article, we investigate two protection strategies: Bundle Protection (BP) and Individual
Protection (IDP). In BP, only one backup path can be used to protect a failure component, whereas multiple backup paths can
be used in IDP. We formulate four mixed integer non-linear programming (MINLP) problems using BP and IDP strategies for single
link and single node failure protection. Each model is designed to determine link metrics for shortest working path routing,
working and backup channel assignments, and backup path planning. Our objective is to minimize call-blocking probability on
the bottleneck link. Since these models are highly non-linear and non-convex, it is difficult to obtain exact global optimal
solutions. We propose a Simulated Annealing-based Heuristic (SAH) algorithm to obtain near optimal solutions. This SAH adopts
the concepts of simulated annealing as well as the bi-section technique to minimize call-blocking probabilities. To evaluate
the performance, we made simulation comparisons between SAH and the unity link weight assignment scheme. The results indicate
that SAH can greatly reduce call-blocking probabilities on benchmark and the randomly generated networks. 相似文献