面向业务感知的共享链路保护策略研究

针对传统弹性光网络采用专用路径1+1保护策略存在资源浪费的问题,文章提出了一种共享链路保护策略.在检测到链路故障后,柔性光转发器切换至共享保护链路,并根据业务的优先级和请求频率重排业务权重,依据业务权重提供差异化的路由和频谱分配.此外,文章提出一种以物理网络拓扑结构、业务需求集合和优质业务量占比为约束条件,以最小化频谱...     

波长与路由分配的一种经济学模型

文章从经济学的角度出发，在相应的可操作条件下，将光网络资源按需求规律和利润模型，提出了一种RWA问题新的数学模型。分析和仿真表明提出的模型在很大程度上反映了现实网络中有限资源与利润最大化的关系。对网络运营和规划具有参考价值。     

静态P-Cycles双链路故障保护策略的研究

p-Cycles应用在WDM格网中可以得到高的容量利用平和快速保护倒换时间，本文给出了一种格网生存性有关客量问题的研究方法，即孤立节点分析法，提出了p-Cycles在双链路故障情况下的保护策略．并建立了以保护容量需求作为优化目标的p-Cycles优化设计模型。     

静态P-Cycles双链路故障保护策略的研究

p-Cycles应用在WDM格网中可以得到高的容量利用率和快速保护倒换时间,本文给出了一种格网生存性有关容量问题的 研究方法,即孤立节点分析法,提出了p-Cycles在双链路故障情况下的保护策略,并建立了以保护容量需求作为优化目 标的p-Cycles优化设计模型。     

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.     

光网络和光通道保护的设计工具

介绍了一种高效而可靠的光网络设计技术和软件工具(SPIDER)，它考虑了设计中的诸多方面，比如路由选择、波长的优化使用、断纤以及接口失效时的保护等等。该软件可以测试各种网络结构和保护机制效率。此外，它可以比较各种路由协议的效率和复原属性。     

ASON中的一种基于SRLG限制的通路保护路由与波长分配算法

网络的生存性技术是下一代智能光网络——ASON中的关键技术之一。其中，通路保护策略是一种有效的网络生存性策略。它通过为一个业务连接请求同时建立工作光通路和保护光通路，来确保业务传输的可靠性。这里路由选择与波长分配算法的设计是问题的关键。在ASON的生存性技术引入了共享风险链路组（SRLG）的概念，要求业务的工作光通路与保护光通路SRLG分离，不共担失效风险，从而可以有效地提高网络的生存性。本文首先分析了SRLG对ASON中通路保护RWA算法的限制，然后提出了一种考虑了SRLG限制的动态路由与波长分配算法。     

波带交换光网络中的保护机制

本论文主要对波带交换光网络中的保护机制进行了一定的研究,提出了基于波带通道的专用保护和共享保护机制和算法,其中在共享保护算法中考虑不同的策略提出了三种不同的算法,即只共享逐跳的保护波长通道的WSP算法,只共享嵌入到波带通道中的保护波长通道的BSP算法和能同时共享两者的BWSP算法.最后进行了相应的网络仿真,讨论并得出BWSP算法的性能是最优的.     

网状WDM网中双链路失效的共享路径保护设计

该文研究了WDM网状网中双链路失效问题,在假定所有链路共享风险链路组(Share Risk Link Group, SRLG)分离的条件下,提出了一种动态共享路径保护(Dynamic Shared-Path Protection,DSPP)算法。DSPP能根据网络状态动态调整链路代价,为每条业务请求选择一条最小代价的工作路由和两条最小代价且SRLG分离的保护路由。仿真表明,DSPP不仅能完全保护双链路失效,并且能在资源利用率、阻塞率和保护切换时间之间进行性能折衷。     

支持流量疏导弹性光网络的共享保护策略

针对支持流量疏导的EON(弹性光网络),提出了一种改进的共享保护策略。改进策略针对不同粒度级别(如光隧道级和低速子载波级)的路径进行分级的共享保护,以保证对网络中隧道级路径进行隧道级保护。仿真结果表明,文章所提保护算法比传统的共享保护算法在阻塞率及资源利用率方面都有明显改善,其中业务阻塞率最大降低了0.47;在保护带G为16个频隙的情况下,资源利用率可节约10.95%。     

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.     

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网状网中双链路失效的保护设计

本文研究了WDM网状网中双链路失效的动态共享链路保护设计问题,提出了一种新的启发式算法TBP (Two Backup Paths) 和一种改进的启发式算法OBP (One Backup Path).两种保护算法都能根据当前网络状态动态地动态调整链路代价,所选路由都是最小代价的路径.文本还研究了双链路失效的保护切换时间,详细描述了保护切换过程.仿真表明,(1)两种算法都能有效地保护双链路失效;(2)TBP的性能优于OBP;(3)与其他算法相比,TBP具有最快的保护切换时间.     

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.     

Dynamic Establishment of Segmented Protection Paths in Single and Multi-Fiber WDM Mesh Networks

Wavelength division multiplexed (WDM) networks are matured to provide, scalable data centric infrastructure, capable of delivering flexible, value added, high speed and high bandwidth services directly from the optical (WDM) layer. But, providing fault-tolerance at an acceptable level of overhead in these networks has become a critical problem. This is due to the size of the current and future networks and diverse quality of service (QoS) requirements for multimedia and mission critical applications. Several distributed real-time applications require communication services with fault-tolerance apart from guaranteed timeliness at acceptable levels of overhead. Several methods exist in the literature which attempt to guarantee recovery in a timely and resource efficient manner. These methods are centered around a priori reservation of network resources called spare resources along a protection path. This protection path is usually routed from source to destination along a totally link disjoint path from primary path. This paper considers the problem of routing and wavelength assignment (RWA) in wavelength routed WDM optical networks. In particular, we propose an efficient algorithm to select routes and wavelengths to establish dependable connections (D-connections), called segmented protection paths. Our algorithm does not insist on the existence of totally disjoint paths to provide full protection. We present experimental results which suggest that our scheme is attractive enough in terms of average call acceptance ratio, spare wavelength utilization, and number of requests that can be satisfied for a given number of wavelengths assuming that the requests come one at time, and wavelengths are assigned according to fixed ordering. Furthermore, the results suggest that our scheme is practically applicable for medium and large sized networks, which improves number of requests that can be satisfied and helps in providing better QoS guarantees such as bounded failure recovery time and propagation delays without any compromise on the level of fault-tolerance for a given number of wavelengths and fibers. We conduct extensive simulation experiments to evaluate the effectiveness of the proposed scheme on different networks and compare with existing methods.This work was supported by the Department of Science and Technology, New Delhi, India. An earlier version of this paper was presented at Opticomm 2002 conference, July 29-August 2, Boston, USA.     

光传送网(OTN)基于ODUk的共享保护环

本文介绍了光传送网的基于ODUk的环网保护特性、APS协议要求、结构及内容、OTN环网结构及其保护的实现方法,并与SDH环形保护机制进行对比分析.     

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。     

An efficient network‐side path protection scheme in OFDM‐based elastic optical networks

Elastic optical networks (EONs) based on orthogonal frequency division multiplexing (OFDM) technologies are seen as a promising solution for next‐generation optical transport networks to support the rapidly growing and heterogeneous traffic. In EONs, the elastic bandwidth allocation and modulation format agilities combined with reconfiguration capabilities pave the new way for leveraging the network efficiency. In this paper, we recast the network‐side path protection in EONs considering the opportunities and challenges enabled by the flexible operation of OFDM technologies. For the first time, we propose to take advantages of the reconfiguration capabilities of OFDM transponders for adapting to transmission condition variations when switching from the working to protection path in network‐side protection. The idea is inspired by the observation that in reach‐diverse networks, the transmission margin between the working path and protection path of a connection might be large enough, and thus, the most spectrum‐efficient modulation format for each path could be separately tailored, rather than imposed by a common one based on the worse condition as with current fixed transmission technologies. We formulate survivable transparent network designs for both dedicated and shared path protection in the form of integer linear programming model taking into account our proposal for enabling different transmission operations between working and protection mode. Numerical results based on extensive simulations on a realistic network topology, COST239, are presented to highlight the benefits of our proposal compared to conventional approaches in terms of spectrum efficiency for un‐capacitated scenarios and improvements in blocking ratio for capacitated scenarios.     

WDM光网络中的共享通道保护方法

本文提出了全光网中提高资源利用率的共享保护方法,并把此方法与专用的预选路由保护方法做了比较,此外,从光纤数,波长数,业务强度,共享程度和拓朴结构对该保护方法做了详细的分析.结论表明共享保护通道可以极大提高网络的性能,使得网络阻塞率减低,提高网络资源利用率.