下一代光网络中光路的快速建立

文章针对下一代光网络中光路快速建立的问题,介绍了IP-over-optical的网络体系结构,并在此基础上介绍了动态RWA问题和综合解决RWA问题的动态和半动态寻路算法,讨论了这两种算法的容错性能。     

GMPLS网络中的混合共享光路保护算法

提出了一种混合共享光路保护(HSLP)算法,用以解决通路保护方法中备份路径建立成功率低的问题.在本算法中,首先执行通路保护方法,如果备份路径建立失败,则动态划分工作路径段.用户的服务请求,包括恢复时间和可靠性等,可以通过限制备份路径的跳数来满足.仿真结果表明,HSLP 算法不仅能够获得较低的保护失败率,而且可以使资源利用率与平均恢复时间获得更好的折中.     

基于拓扑信息挖掘的动态流量疏导算法

在迭加模型的IP over WDM 网络中,文章作者进一步利用饱和割集算法来提取IP层的有效拓扑信息,利用该信息优化建立光路的方法,降低了整个网络的阻塞率.仿真结果显示,应用了双重饱和割集算法的网络比只用一种饱和割集算法的网络的阻塞率更低.     

Bi-directional lightpath reconfiguration in regional IP-over-WDM networks by a centralized control system

Bi-directional lightpath reconfiguration performance has been evaluated experimentally for regional IP-over-wavelength-division multiplexing network applications, making the network scalable and stable when traffic changes occur. The reconfiguration performance was examined in an experimental network with reconfigurable optical add/drop multiplexers (ROADMs) to connect four nodes with bi-directional dual-fibers. The experiment was conducted by controlling the ROADMs. The control signals were sent by a developed system. The lightpaths were added or deleted by the control system in the experimental network, and IP packets were monitored. The results clarified that lightpaths could be reconfigured by controlling the ROADMs, and IP packets could be routed dynamically by Open Shortest Path First so as to adapt the lightpath changes. The reconfiguration functions of the system together with the ROADMs provide network administrators with easy management of the network in a skill-less, centralized and remotely controlled way. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Priority-based Dynamic Lightpath Allocation for Survivable WDM Networks

In recent years, there has been considerable research interest in the design of survivable wavelength division multiplexing (WDM) networks. Many papers have proposed mixed-integer linear program (MILP) formulations as well as heuristics to optimally allocate lightpaths, using protection based schemes. Such schemes provide quick and guaranteed recovery, but do not use resources efficiently. About 50% of allocated resources remain idle, under fault-free conditions. If these “idle” resources were used for low-priority connections (which could be pre-empted if necessary), the resource utilization would improve significantly. This paper introduces two MILP formulations for priority-based dynamic lightpath allocation in survivable WDM networks. We define three different levels of service and allocate resources based on the requested service level. An important advantage of our approach is that while we can handle multiple levels of service, the traditional (single level) shared and dedicated path protection schemes can be treated simply as a special case of the proposed formulations. The first formulation solves the problem optimally, but is quite time consuming. The second formulation makes some simplifications, and is more efficient. The results demonstrate that our approach can significantly improve resource utilization and is feasible for practical sized networks, particularly under low- to medium-traffic load. For large networks and high traffic conditions, simpler heurtistic algorithms are more appropriate. In such cases, the proposed MILP formulation can be a useful tool to validate the performance of the heuristics.     

Task transmission control with dynamic lightpath setup for constant processing delay in an optical grid

This paper proposes a task transmission control with dynamic lightpath setup in an optical grid. In our proposed method, a job manager changes the number of tasks in a resource manager dynamically so as to maintain a constant processing delay. It leads to effective utilization of computing resource. I‐PD control is applied to maintain efficient network management. Furthermore, in order to avoid frequent lightpath setup process, multiple lightpaths are established simultaneously by our proposed algorithm. Numerical results show the effectiveness of the proposed task transmission method. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

一种基于OBGP协议的光网络域间路由的新型机制

本文提出一种采用光边界网关协议(OBGP)实现WDM光格状网的域间路由的新型机制;该机制基于最小跳选择策略建立最优化路径的思想,同时引进"迂回路由"策略和"并行信令"方式,实现了动态、分布式的光通道确立过程.在OPNet平台上针对两种网络拓扑进行仿真实验,结果表明:该机制能够在网络繁忙时期降低阻塞率,提高网络性能;同时发现:网络规模、单信道波长数以及网络负载等网络参数对于网络性能具有一定的影响.     

Connection Establishment of Label Switched Paths in IP/MPLS over Optical Networks

We propose and investigate three connection admission control policies for the establishment of label switched paths (LSPs) in IP/MPLS over optical networks. We show that the policy of establishing LSPs first in the optical layer achieves a better blocking performance. We examine the effect of the number of add/drop ports of optical cross-connects (OXCs) on the LSP blocking performance. We show that there exists a lower bound for the number of add/drop ports of OXCs for the network to achieve almost the best LSP blocking performance.     

Topological Design and Lightpath Routing in WDM Mesh Networks: A Combined Approach

Multicommodity flow models are commonly used to formulate the logical topology design (LTD) problem and the lightpath routing (LR) problem as mixed integer linear programming (MILP) problems. In general, MILP formulations are intractable even for relatively small networks due to the combinatorial complexity of the problem. In this paper we propose improvements to these models and a method to solve the LTD and the LR problems in a combined manner. The interest is two fold: firstly, by tackling the two problems with separate models, problem instances of realistic size (up to 14 nodes in this paper) can be dealt with. Furthermore, different combinations of optimization models and objective functions can be investigated in a modular manner. Secondly, the mechanisms proposed to combine the problems allow to keep track of the global design problem when solving each individual step.     

Reconfiguration of Logical Topologies with Minimum Traffic Disruptions in Reliable WDM-Based Mesh Networks

A wavelength division multiplexing (WDM) network offers a flexible networking infrastructure by assigning the route and wavelength of lightpaths. We can construct an optimal logical topology, by properly setting up the lightpaths. Furthermore, setting up a backup lightpath for each lightpath improves network reliability. When traffic demand changes, a new optimal (or sub-optimal) topology should be obtained by again applying the formulation. Then, we can reconfigure the running topology to the logical topology obtained. However, during this reconfiguration, traffic loss may occur due to the deletion of older lightpaths. In this paper, we consider reconfiguring the logical topology in reliable WDM-based mesh networks, and we propose five procedures that can be used to reconfigure a running lightpath to a new one. Applying the procedures one by one produces a new logical topology. The procedures mainly focus on utilizing free wavelength resources and the resources of backup lightpaths, which are not used usually for transporting traffic. The results of computer simulations indicate that the traffic loss is remarkably reduced in the 14-node network we used as an example.