光网络的保护策略

对光网络中的保护方法进行分类描述,结合当前的研究状况,对光网络保护算法的研究方向,提出相关见解.     

WDM光网络的恢复技术

文章介绍了光网络的生存技术，并重点介绍了Mesh网络中的恢复技术，分析了恢复技术的特点，策略，各种路由和波长分配算法选择，并进行了性能比较，同时给出了恢复的时间分析。     

WDM疏导网络的共享子通路保护算法

研究了WDM疏导网络中的生存性问题,提出一种支持多粒度业务的共享子通路保护算法(GSSP)。GSSP首先根据网络当前状态动态调整链路权值,在此基础上选择一条最短路作为工作通路;然后将该通路分为互不重叠的等长子通路,分别找出它们的保护通路,并且允许共享保护资源。GSSP可以保证业务连接的可靠性,又允许网络管理者根据不同的优化策略调整子通路长度,可以在恢复时间和资源利用率之间进行折中。最后对GSSP进行了仿真研究,给出了仿真结果。     

WDM光网络中基于SRLG的共享通道保护策略

研究了动态业务下,WDM光网络的生存性。提出了一种单链路故障模型,并在此单链路故障模型下,考察了基于共享风险链路组(SRLG)的共享通道保护策略SRLG-SPP的保护性能,并把它同共享通道保护SPP和专用通道保护DPP的性能做了比较。     

光网络生存性技术及其进展

随着光网络的不断普及,对光网络的稳定性和可靠性的要求越来越高,客观上促使生存性技术的不断改善和向前发展。就此主要从网络生存性策略、各层网络的生存性两个方面概述了各种网络的生存性技术以及网络生存性的最新进展。     

光网络生存性技术研究

光通信技术的发展使光纤的带宽资源得到充分利用,提供了极大的传输容量,其生存性对主干网络性能和服务至关重要。该文首先介绍了网络生存性定义,然后分析了保护和恢复的生存性技术,最后阐述了多层保护与恢复技术的协调问题。     

ASON中共享路径保护机制的实现方法

研究了自动交换光网络(ASON)中,保护资源可部分共享的共享路径保护机制(Shared Path Protection,SPP)如何实现的问题.设计了该机制在符合波长连续性限制条件的WDM光网络中的路由计算算法及在ASON上实现该机制的信令流程.在ASON实验平台上实现了该机制.     

WDM光网络中一种优先共享通路保护算法

为了提高波分复用光网络的可靠性,常采用分段共享通路保护算法,该方法通常要求保护通路要均匀分段并且应满足共享风险链路组约束,网络业务的阻塞率也就比较高,因此提出了用优先共享通路保护算法来降低业务阻塞率。通过计算机仿真进行了理论分析和实验验证,取得了两种保护算法下的业务阻塞率和资源预留比的数据。结果表明,优先共享保护通路算法能够有效地融合分段共享通路保护算法的优点,同时在业务的阻塞率和资源预留比方面优于分段共享保护通路算法。     

光网络P圈保护方法分析

在光网络中,节点和链路故障是光网络生存性的关键因素。P圈保护被认为是一种非常有前途的保护方式,有着高效、高速等特点。对光网络中的P圈保护单故障和多故障的策略和方式进行分析,并分析了基于树和基于段的光组播P圈保护策略。最后,指出P圈保护在未来光网络中的研究发展方向。     

WDM网络光层保护新算法的探讨

首先介绍了几种按照不同标准划分的WDM网络光层保护方法,然后提出了三种实现光层保护的新算法,对它们的内容和性能做了详细描述。按照提出的算法所求得的解,可以为WDM网络提供新的光层保护方式。     

Shared Sub-Path Protection Algorithm in Traffic-Grooming WDM Mesh Networks

In this paper, we investigate the problem of dynamically establishing dependable connections in wavelength division multiplexing (WDM) mesh networks with traffic-grooming capabilities. We first develop a new wavelength-plane graph (WPG) to represent the current state of the network. We then propose a dynamic shared sub-path protection (SSPP) scheme based on this WPG. To establish a dependable connection, SSPP first searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. If two sub-paths in SSPP are fiber-disjoint then their backup paths can share backup resources to obtain optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between resource utilization and restoration time.     

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.     

WDM光突发交换网中的生存性问题

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.     

WDM网基于混合共享和SRLG约束的通路保护

研究了网状波分复用（WDM）网中动态生存性路由配备问题，提出了一种新颖的基于共享风险链路组（SRLG）束的混合共享通路保护（MSPP）方案。MSPP为每个业务请求分配丁作通路和SRLG分离的保护通路，因此能完全保护单SRLG故障。与传统的共享通路保护（SPP）方案不同，在满足某些约束条件下，MSPP允许部分工作通路和保护通路共享资源。仿真结果表明，MSPP性能优于SPP。     

WDM光网络中基于链路的动态组播共享保护算法

针对WDM光网络中单链路失效的情况,提出了一种基于链路的保护动态组播业务的优化共享保护算法(Link-based optimized shared-protection algorithm for multicast sessions,LB-OSPM).该算法在对工作树任意光纤链路失效情况寻找保护路径时,允许组播内不同保护路径共享预留波长资源,同时通过引入预留波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,实现了不发生冲突的不同组播的保护链路间共享预留波长资源.研究采用欧洲光网络(European Optical Network,EON)的拓扑对不同波长资源配置和网络负载情况下LB-OSPM算法的网络连接阻塞率做了仿真.结果表明,通过引入共享机制,LB-OSPM算法在对单链路失效保证100％恢复率的同时可以获得更低的连接阻塞率,提高了波长资源利用效率.     

网状WDM网中多播业务的共享保护设计

研究网状波分复用(WDM)光网络中动态多播业务的保护方案,提出一种共享保护和重配置(SPR)算法.该算法根据网络状态动态调整链路代价,为每个多播业务请求建立最小代价工作树,并为光树上互不重叠的工作段提供链路分离的保护段.当网络中发生链路失效时,进行业务段保护切换和局部资源重配置.仿真表明,该算法可以合理共享波长资源、平衡网络负载,有效保护WDM网中任意单链路失效,并在多链路失效情况下大大提高业务恢复能力.     

WDM网络动态组播业务共享保护算法

该文研究了WDM网络中动态组播业务的保护.为提高网络资源的利用率,降低连接请求阻塞率,和单播业务的共享保护方案类似,组播连接之间也可以共享保护波长.本文提出了一种动态组播业务共享保护算法,并对算法的性能进行了仿真,同时和组播业务专有保护算法进行了比较.仿真结果表明,共享保护算法比专有保护算法使用了更少的波长资源,具有更低的连接阻塞率.     

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网中基于服务等级约定限制的动态共享通路保护算法

服务等级约定(SLA)是用户与服务提供者之间达成的有关服务内容、服务质量等方面的合约,它规定了服务提供者必须为用户提供的具体服务参数.连接可靠性和恢复时间是涉及生存性问题的两个重要SLA参数,如何保证用户请求的连接可靠性和恢复时间要求以避免违约而受到惩罚,同时又最大限度地降低成本是服务提供者最关心的问题之一.针对上述问题,本文提出一种动态约束共享通路保护算法(DCSP)加以解决.DCSP同时考虑用户提出的上述两个SLA参数要求,利用K路由和部分链路分离保护思想为它们动态提供区分服务.DCSP既能保证用户的服务要求,同时又有利于全网负载均衡和提高资源利用率.最后对所提算法进行了仿真研究,给出了仿真结果.