大规模异构光网络智能组网技术与实验演示环境(英文)

A novel routing architecture named DREAMSCAPE is presented to solve the problem of path computation in multi-layer, multi-domain and multi-constraints scenarios, which includes Group Engine (GE) and Unit Engine (UE). GE, UE and their cooperation relationship form the main feature of DREAMSCAPE, i.e. Dual Routing Engine (DRE). Based on DRE, two routing schemes are proposed, which are DRE Forward Path Computation (DRE-FPC) and Hierarchical DRE Backward Recursive PCE-based Computation (HDRE-BRPC). In order to ...     

多域光网络中一种支持区分可靠性的通路保护算法

区分可靠性的通路保护方案既能为光网络中具有不同可靠性需求的业务提供有效的故障保护,又能优化网络资源的利用,是一种高效的生存性机制。但目前此类问题的研究主要是集中于传统的单域光网络中,所得的研究成果无法直接运用于具有多域特点的下一代光网络中。针对这一问题,在对以往通路保护算法进行改进的基础上提出了一种适用于多域光网络中的支持区分可靠性的通路保护算法,并对其性能进行了计算机仿真研究。仿真结果表明,该算法不仅能满足多域光网络中不同业务的可靠性需求,而且能提高网络资源的利用率、降低业务连接的阻塞率。     

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。     

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。     

一种新的WDM光传送网保护设计算法

在WDM网络中,由于光路之间存在的依赖性,物理网络的单链路失效可能会造成虚拓扑不连通而使上层网络(SDH、ATM或IP)无法使用自身的恢复机制来恢复受影响的业务,因此虚拓扑在嵌入物理拓扑时必须避免发生这种情况.已有的分离备用路径(Disjoint Alternate Path,DAP)算法总是假设网络所有波长路由节点都具有全波长转换能力.本文提出的LG_-VTMDP保护设计算法利用分层图同时解决路由和波长分配两个子问题,并考虑了负载均衡和物理链路的容量限制.实验结果表明LG_-VTMDP算法优于DAP算法和已有波长分配算法组合后的性能.本文还在此基础上提出了一种有效的波长转换器放置算法WCP算法.     

On the Maximum Protection Problem in IP-over-WDM Networks Using IP LSP Protection

In dynamic IP-over-WDM networks efficient fault-management techniques become more difficult since as demands change with time the optimal logical topology varies as well. Changes in the virtual topology should be done with care because working IP LSPs routed on top of a virtual topology should not be interrupted. Reconfiguration of the virtual topology may also affect precomputed backup IP LSPs to be activated in case of failure meaning that backup IP LSPs would need to be recomputed after any change in the virtual topology. A good sense solution can be the dimensioning of the virtual topology for a worst case traffic scenario, having as goal the minimization of the network cost, for example, and then route dynamic IP LSPs on this virtual topology. The virtual topology would remain unchanged as long as possible, that is, until changes in the virtual topology are considered to bring considerable benefits. Since data services over IP are essentially of a best-effort nature, protection could be provided, using IP LSP protection, only when bandwidth is available in the virtual topology. The computation of backup IP LSPs does not interfere with working IP LSPs meaning that no service interruption will exist. Such a strategy, considered in this paper, allows resources to be used efficiently, since free bandwidth is used for backup purposes, while the normal delivery of traffic is guaranteed in peak traffic situations although having no protection guarantees. Our main objective is to quantify the spare capacity, which can be used for restoration (backup) purposes, over a virtual topology designed and optimized to carry a traffic scenario with no survivability and QoS requirements. We analyse the maximum protection (MP) problem in such IP-over-WDM network environment. Protection is provided to IP LSP requests whenever possible through bandwidth reservation in a backup IP LSP on the virtual topology. Besides the mathematical formalization of the MP problem, an upper bound and heuristic algorithms are proposed and evaluated. The traffic considered includes IP LSPs of different granularities and is the worst case traffic scenario for which the network should be dimensioned.     

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.     

A Kind of Topology Aggregation Algorithm in Hierarchical Wavelength-Routed Optical Networks

In large scale networks composed of several hierarchical subnetworks, topology aggregation is implemented for both scalability and security consideration. However, due to the special characteristic of optical wavelength-routed networks, existing topology aggregation algorithms cannot be applied directly for topology compression. In this paper, we propose a kind of topology aggregation algorithm suitable for hierarchical wavelength-routed optical networks, thereby considering information of residual wavelengths on network links. Basically, our topology aggregation algorithm is based on a transition matrix technique for constructing a full mesh topology and asymmetric star approach for a more compact topology. Simulations with randomly-generated networks show that topology information compression can be achieved with a little loss of its accuracy: the ratio of border node pairs with representation deviation being well below 10%. Results also indicate that the advantage of our algorithm is also behaved on reducing the amount of link-state-advertisement messages and making networks less vulnerable to propagation delay of these messages over communication links. This work is supported by National 863 Program 2003AA122220.     

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.     

基于业务的智能光网络生存性研究

目前对于智能光网络（ION）生存性方面的研究主要是针对光网络本身，基于静态的资源配置和管理机制对于快速变化的业务需求而言缺乏灵活性，难以满足未来智能光网络中复杂业务的需求。基于业务的智能光网络生存性策略，可以解决现有网络生存性策略与业务侧的生存性需求之间的差异。通过将对生存性需求的描述和定义从网络侧转移到业务侧，以业务对生存性的需求为核心，能很好地实现智能光网络中对生存性策略的控制和实现。     

光传送网的生存技术

 生存技术作为光传送网体系演进中最为重要的组成部件,受到学术界和工业界广泛而持久的关注.论文回顾和总结光传送网生存技术的重要研究成果及若干最新进展,内容包括:光网络的连接恢复技术、可生存光网络的资源优化与服务质量、两层网络的连接恢复技术以及透明光网络的故障定位技术.     

光网络选路和波长分配研究

文章在叙述了光网络中选路和波长分配(RWA)要解决的基本问题后,对有关方面的近年研究作了综述,主要包括:虚拓扑重构、业务量疏导的RWA、多播RWA、抗毁网络的RWA.抗毁问题涉及WDM网络的抗毁选路、区分可靠性、网状网的快速恢复、多故障下的抗毁.     

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.     

基于联合故障概率的频谱灵活光网络生存性业务认知算法

This paper addresses the problem of survivable traffic assignment with failure probability requirement in flexible bandwidth optical networks. We describe a Survivable Traffic Cognition (STC) algorithm with joint failure probability. Survivable Traffic Assign-ment (STA) algorithm and Conventional Traf-fic Assignment (CTA) algorithm are added to illustrate the effectiveness of our proposed STC. We investigate the effect of joint failure probability on blocking probability, spectral utilization ratio, average joint failure probabil-ity, and the average hops. Simulation results show that our proposed STC not only achieves better performance in terms of blocking probability and spectral utilization ratio than CTA and STA, but also does not cause higher average joint failure probability or larger average hops compared with STA. As a result, STC makes the best use of spectral resources and does not cause large average joint failure probability.     

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.     

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.     

新型大尺寸电磁驱动MEMS光学扫描镜的研制

设计并制作了一种结构新颖的镜面尺寸为6mm×4mm的电磁驱动MEMS光学扫描镜.这种背面为微型铜驱动线圈的MEMS硅基扭转镜面沉浸在由包含永磁体的磁回路产生的磁场中,当电流信号通过驱动线圈时,MEMS光学扫描镜绕着扭转梁发生了大角度的扫描运动.采用MEMS体硅加工工艺和电镀技术制作的器件显示出了优良的性能,实验获得的扫描镜静态转角斜率为0.03°/mA,当器件进行动态扫描时,在381Hz的谐振频率下获得了最大±10.2°的光学扭转角度,空气中的Q因子为221,相应的功耗为13μW,与此同时MEMS光学扫描镜具备了出色的镜面粗糙度、光学反射率和镜面平整度.实验证明该器件完全适合于微型光谱仪和可调光滤波器的应用.     

新型大尺寸电磁驱动MEMS光学扫描镜的研制

设计并制作了一种结构新颖的镜面尺寸为6mm×4mm的电磁驱动MEMS光学扫描镜.这种背面为微型铜驱动线圈的MEMS硅基扭转镜面沉浸在由包含永磁体的磁回路产生的磁场中,当电流信号通过驱动线圈时,MEMS光学扫描镜绕着扭转梁发生了大角度的扫描运动.采用MEMS体硅加工工艺和电镀技术制作的器件显示出了优良的性能,实验获得的扫描镜静态转角斜率为0.03°/mA,当器件进行动态扫描时,在381Hz的谐振频率下获得了最大±10.2°的光学扭转角度,空气中的Q因子为221,相应的功耗为13μW,与此同时MEMS光学扫描镜具备了出色的镜面粗糙度、光学反射率和镜面平整度.实验证明该器件完全适合于微型光谱仪和可调光滤波器的应用.     

EPON系统光路保护方案的研究与应用

以EPON技术为基础的有线电视宽带网,面临着数据和图像的多业务发展需求,对网络的可靠性提出了更高的要求,因此迫切需求一种经济高效的系统保护方案。主要介绍了两种光纤保护技术,并在实际的网络构建方式中衍生出多种构建方案,适用于不同场景的需求。     

基于多波长光传送网的网络保护与恢复

介绍了传送网的发展趋势和结构变化 ,分析了原有传送网的一些保护与恢复方式 ,然后着重分析了多层传送网保护与恢复方面的一些问题 ,提出了在基于多波长的多层融合光传送网中如何更好地实现保护与恢复的几种方法及原则 ,并进行了相应的对比和分析。