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.     

多域光网络联合路由保护算法

研究了多域光网络中的路由保护问题。为了避免多域光网络通路保护二步算法可能导致的多域陷阱问题,提出了一种基于Suurballe算法扩展的多域联合路由保护算法。仿真表明,相比传统的多域通路保护二步算法,该算法资源利用率高,阻塞率低,平均每连接跨域数小。     

多域光网络中考虑域间输出策略的分段共享保护算法

研究了多域光网络中的路由保护问题.在多域光网络中,域间路由的建立要遵从域间输出策略.在考虑域间输出策略的基础上提出了一种多域光网络中基于路径计算单元的分段共享保护算法.仿真表明,相比传统的基于路径计算单元的多域分段保护算法,该算法阻塞率低,平均保护切换时间短.     

光网络中的一种基于虚拟源的动态多播保护算法

随着各种多播业务的不断出现,如何在网络的光层实现多播业务的可靠性传输已成为光网络研究中的一个热点问题,而多播保护算法是这一问题的核心.目前多播保护算法的研究都是在假设网络所有节点具有多播功能的条件下进行的,然而由于成本的限制,实际光网络往往是一个稀疏多播光网络,即网络中只有部分节点具有多播功能.针对这一问题,提出了一种基于虚拟源的动态多播保护算法.仿真结果表明:该算法不仅能在稀疏多播光网络中满足多播业务可靠传输的要求,还具有较高的网络资源的利用率和较低的时间复杂度.     

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.     

多域光网络中抗破坏风险评估

为提高多域光网络抗破坏能力,拟改善对其进行风险评估的方法,通过构建多域光网络入侵风险评估模型,采用非线性维纳滤波检测方法进行多域光网络入侵的检测滤波,构建多域光网络抗破坏风险评估的检测统计量,结合分组样本回归分析方法进行多域光网络抗破坏风险的关联挖掘,采用自适应寻优方法求得多域光网络入侵风险的统计分布,利用模糊网格聚类方法发现多域光网络入侵集中的隐含模式,根据聚类分布情况实现多域光网络抗破坏风险评估。仿真结果表明,评估精度与信噪比呈正相关,而本文方法显示,在信噪比0. 5～3. 5的区间中,评估精度为0. 79～0. 986,高于时频分析方法的0. 522～0. 853与小波分析方法的0. 504～0. 807。耗时数据统计显示,在网络节点数100～500的区间中,本文方法耗时仅2. 46～9. 32 ms,低于时频分析方法的8. 66～26. 04 ms与小波分析方法的10. 21～45. 53 ms。采用该方法进行多域光网络抗破坏风险评估的效果较好,更具优越性。     

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.     

一种光网络中可用性的计算方法

光纤骨干通信网中,一条光纤的断裂会引起大量业务中断.因此,对于每一条工作光路可配置一条链路分离的保护光路.采用共享通路保护时光路连接的可用性计算是网络设计时的重要问题.现对共享通路保护方式下光路连接可用性的计算给出了推导过程和一种明显的计算公式.最后给出实例,通过与仿真结果的比较验证了计算方法的正确性.     

多域光网络中的动态RWA算法研究

随着光网络规模的不断增大,下一代智能光网络将被划分为多个路由域进行分布式管理.由于在这种具有分布式特点的多域光网络中,每个路由域只了解本地子网内的拓扑和资源信息,因此以往光网络中已有的基于全网信息的动态RWA算法将不在有效.文章首先分析了多域光网络中的动态RWA问题,然后针对多域网的特点对已有的RWA算法进行了修改,并在给定的多域光网络模型中对该算法进行了仿真研究.结果表明:在多域网络环境下,以往的动态RWA算法急需改进.     

光网络中一种考虑信号损伤限制和服务质量区分的动态RWA算法

在光网络中,光信号沿着路由与波长分配(RWA)算法选定的光通路传输的过程中会受到各种信号损伤的影响而导致信号质量的不断下降,严重影响着业务的服务质量(QoS).而光网络中多样化的客户层业务往往有着不同的QoS的需求,因此有必要根据不同的业务QoS需求对光信号损伤的影响进行不同程度的控制.针对这一问题,提出了一种能同时考虑信号损伤限制和服务质量区分的动态RWA算法,并通过计算机仿真的方法对其性能进行了分析和验证.结果表明:该算法既能克服光网络中信号损伤的影响又能为不同级别的业务提供不同的QoS保证,更贴近实际需求.     

Enhanced Dynamic Segment Protection in WDM Optical Networks under Reliability Constraints

In this letter, we study the protection problem in wavelength division multiplexing (WDM) optical networks, and propose a novel dynamic heuristic algorithm called differentiated reliable segment protection (DRSP). Differing from previous work, DRSP can effectively avoid the trap problem and is able to find a feasible solution for each connection request. Therefore, DRSP outperforms the previous work. Simulation results have shown to be promising.     

网状WDM网中支持区分可靠性的共享通路保护算法

光纤链路由于共享了某些物理资源(如光缆、管道、通路等),因此存在一定的故障相关性,术语“共享风险链路组(SRLG)”就是用于描述链路之间的这种风险共享关系的。SRLG分离成为保护设计的重要约束。该文研究了支持区分可靠性的SRLG分离共享通路保护设计问题。结合SRLG条件故障概率的概念,提出了部分SRLG分离的共享保护算法PSD-SPP(PartialSRLG-DisjointShared-PathProtection),有效地解决了SRLG分离约束下的区分可靠性设计问题。仿真结果表明该算法既满足了用户的区分可靠要求,又能有效利用资源。     

无向通信网端对端可靠性通用算法

针对无向通信网的节点和链路都存在失效的问题,提出了端到端可靠性的通用算法。对无向网络基于概率论的分解定理进行证明,介绍了无向网络的简化与分解算法及流程,并分析了端到端可靠度的计算准则,针对3种复杂程度无向网络进行了分析比较,最后提出一种无向通信网端对端可靠性通用算法。分析结果表明提出的通用算法适合节点和链路都不可靠的情...     

Efficient Online Algorithms for Dynamic Shared Path Protection in WDM Optical Networks

In this work, we have proposed and studied efficient online algorithms for shared path protection under dynamic traffic conditions in survivable WDM optical mesh networks. Given a connection request, routing and wavelength assignment of a working path and a protection path for the request is formulated as two integer linear programs based on shared and dedicated path protection, respectively. The objective is to minimize the total cost of additional resources used by the working path as well as the protection path to accommodate a new connection request. We then devise two resource efficient online algorithms using pre-computed candidate routes. The first algorithm uses one candidate working path and one candidate protection path for each newly arrived connection request while the second algorithm may use multiple candidate working paths and/or multiple candidate protection paths. The selection of a pair of paths from candidate routes as well as the assignment of appropriate wavelengths to accommodate a connection request is then jointly considered to minimize the total cost of additional resources. The solutions to the ILP formulations serve as the baseline for evaluating the performance of the proposed algorithms. We have evaluated the effectiveness of the proposed online algorithms via extensive simulations in terms of the connection blocking probability and the revenue earnings improved over the dedicated path protection approach. Our simulations indicate that our proposed computationally efficient online algorithms are able to provide 100% restorability against single failures with a resource efficiency comparable to that of the optimal shared path protection. The results also show that a small increase in the number of candidate working paths or protection paths (from 1 to 3) provides better performance, but a further increase does not improve the performance significantly. Therefore, a proper balance can be struck to achieve both satisfactory performance and efficient computation.The work reported in this paper was supported in part by AFRL, the U.S. Department of Energy Early Career Award DE-FG02-03ER25580, and a DAGSI graduate scholarship. Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the funding agencies.     

A Study of Path Protection in Large-Scale Optical Networks

We consider the problem of designing a network of optical cross-connects (OXCs) which provides end-to-end lightpath services to large numbers of client nodes, under the requirement that the network will survive any single-link failure. Our main objective is to quantify the additional resource requirements of implementing path protection schemes over a network with no survivability properties. To this end, we present heuristic routing and wavelength assignment algorithms for dedicated path protection and two variants of shared path protection, and integrate them into the physical and logical topology design framework we developed in an earlier study. We apply our heuristics to networks with up to 1000 client nodes, with a number of lightpaths that is an order of magnitude greater than the number of clients, and for a wide range of values for system parameters such as the number of wavelengths per fiber, the number of optical transceivers per client node, and the number of ports per OXC. Our results provide insight into the relative resource requirements of dedicated and shared path protection schemes. We also find that, using shared path protection schemes, it is possible to build cost-effective survivable networks that provide rich connectivity among client nodes with only a modest additional amount of resources over a network with no survivability properties.     

Cost Effective Shared Path Protection for WDM Optical Mesh Networks with Partial Wavelength Conversion

In this paper, we study routing and wavelength assignment of connection requests in survivable WDM optical mesh networks employing shared path protection with partial wavelength conversion while 100% restorability is guaranteed against any single failures. We formulate the problem as a linear integer program under a static traffic model. The objective is to minimize the total cost of wavelength-links and wavelength converters used by working paths and protection paths of all connections. A weight factor is used which is defined as the cost ratio of a wavelength converter and a wavelength-link. Depending on the relative cost of bandwidth and wavelength conversion, the optimization objective allows a proper tradeoff between the two. The proposed algorithm, the shortest-widest-path-first (SWPF) algorithm, uses a modified Dijkstra's algorithm to find a working path and a protection path for each connection request in the wavelength graph transformed from the original network topology. When there are multiple candidate paths that have the same minimum total cost, the path along which the maximum number of converters used at each node is minimized is chosen by the SWPF algorithm. We have evaluated the effectiveness of the proposed algorithm via extensive simulation. The results indicate that the performance of the proposed algorithm is very close to that of the optimal solutions obtained by solving the ILP formulation and outperforms existing heuristic algorithms in terms of total number of converters used and the maximum number of converters required at each node in the network. The proposed algorithm also achieves slightly better performance in terms of total cost of wavelength-links and converters used by all connections. We also investigated shared path protection employing converter sharing. The results show that the technique can reduce not only the total number of converters used in the network but also the maximum number of converters required at each node, especially when a large number of converters are needed in the network. In this study, although the ILP formulation is based on static traffic, the proposed algorithm is also applicable to routing dynamic connection requests.     

WDM网状网中支持业务量疏导的区分共享保护算法

该文综合考虑WDM网状网生存性及业务量疏导,采用部分光路共享保护机制为低速业务提供满足其可靠性和带宽需求的连接,提出了一种基于波长分层图的支持业务量疏导的区分共享保护算法—部分共享保护业务量疏导算法PSPTG(PartialShared-pathProtectionalgorithmsupportingTrafficGrooming)。仿真结果表明:该算法可以较好地利用资源。     

基于支撑树的光网络保护容量配置算法

本文提出了一种新的保护容量配置算法.该方法基于网络的支撑树概念,在支撑树树干和部分连枝上保留网络容量,保证网络上任何两个节点之间都有至少两条不同路由,为单一链路或节点故障提供良好的保护能力.