WDM网络光层保护整数线性规划算法的探讨

针对WDM(波分复用)光网络光层保护问题，提出了两种新的保护算法。这两种保护方法都属于ILP(整数线性规划)，所处理的是通道失效问题，而不是链路失效问题，分别列出两种算法的步骤和计算结果。     

WDM网络设计保护优化分析

WDM网络的物理保护由于需要大量冗余光资料而难以实现，而设计保护利用了层次结构网络中业务网络的生存能力，可以恢复光层故障中断的业务。为了消除业务网络的虚链路关联效应，文章提出了虚链路与光链路映射的优化模型并使用模拟退火算法进行了求解，仿真结果表明设计保护提供的业务恢复能力远远高于普通的最短路由算法。     

IP over WDM光网络联合保护策略

随着Internet和网络技术的发展,IP over WDM光网络成为下一代通信网最理想的解决方案。因此,IP over WDM光网络的生存性是下一代通信网成功与否的关键。在传统的保护策略中,IP层和WDM层之间不交换网络的状态信息。探讨了IP层和WDM层保护机制互相协作的必要性,并在通用多协议标签交换GMPLS的基础上,提出了联合保护策略的思想。     

中兴通讯WDM设备光层保护技术分析

随着采用波分复用(WDM)技术的光传输网络的广泛应用，WDM设备承载业务的特点越来越朝着多类型、大容量的方向发展，由此所引发的网络生存性需求就倍加引起重视，加之与传统的电层保护技术相比较，WDM设备的光层保护技术具备快速、高效、透明的特点，目前针对WDM光网络建立完善的光层保护机制已经成为业界的普遍共识。     

WDM网状网中基于光连接抗毁业务量疏导保护算法

研究了WDM网状网中基于光连接(connection)的抗毁业务量疏导通道(path)保护问题,以最大化网络的吞吐量为目标,提出了新的基于共享风险链路组(Shared Risk Link Group,SRL G)的共享保护算法和专用保护算法.并以NSFNET为仿真网络,比较说明了这两种算法在网络拥塞率和波长利用率方面的性能优劣.     

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光环形网络保护及实现方法

提出了WDM环形网络的几种保护方案,分析了利用1:1环路配置方式进行WDM光环形网络保护的实现方法,简单介绍APS在环保护中的应用。     

波分复用网络的保护方式

首先介绍了在WDM网络中常用的光通道保护、光复用段保护方式及其实际使用方案,然后对WDM网络中采用不同保护方式的优缺点进行了分析,并对WDM网络中保护方案的设计提出了建议.     

IP over WDM网络中能耗自感知的混合疏导专有保护算法

针对绿色生存性IP over WDM网络中资源开销大、网络阻塞率高的问题,提出一种能耗自感知的混合疏导专有保护(HG-PA-DPP)算法。首先在IP层的核心路由器对低粒度业务请求集中疏导;然后通过实时感知WDM层的链路负载和双层器件带来的链路能耗状态定义链路权值,基于分层图在不同波长平面上为各业务请求寻找权值小且链路分离的工作路径和保护路径,同时在业务的中间节点处对不需要光-电-光转换的光路进行光旁路处理;最后,将空闲或保护资源设置为休眠模式以实现节能。仿真结果表明,所提算法在高负载时有着更好的节能效果,且在大网络拓扑下资源开销(RO)为传统算法的76.5%,阻塞率(BP)仅为传统算法的61.1%。     

WDM光环网的几种保护倒换方案

WDM光网络技术的应用正迅速地提升传输速率与带宽,不断地促进着电信业的发展。WDM光网络的可靠性与生存性变得日益重要。目前的研究热点是在网络的生存性和可重构性方面开发类似于SONET/SDH环网保护的WDM光环网结构,使之具备在经受各种网络故障后能够维持可接受的业务质量的能力。与SDH光环网相比,WDM光环网具有自身的特点：光层的保护与恢复时间比SDH电层快,光层恢复可靠性高,光层恢复成本低,光层保护支持多协议、多业务恢复等等。WDM光网络在传统的传送网络的电通道层和物理层之间引入光层。光层由光通道层、光复用段层…     

Capacity Optimization for Surviving Double-Link Failures in Mesh-Restorable Optical Networks

Most research to date in survivable optical network design and operation, focused on the failure of a single component such as a link or a node. A double-link failure model in which any two links in the network may fail in an arbitrary order was proposed recently in literature [1]. Three loop-back methods of recovering from double-link failures were also presented. The basic idea behind these methods is to pre-compute two backup paths for each link on the primary paths and reserve resources on these paths. Compared to protection methods for single-link failure model, the protection methods for double-link failure model require much more spare capacity. Reserving dedicated resources on every backup path at the time of establishing primary path itself would consume excessive resources. Moreover, it may not be possible to allocate dedicated resources on each of two backup paths around each link, due to the wavelength continuous constraint. In M. Sridharan et al., [2,3] we captured the various operational phases in survivable WDM networks as a single integer programming based (ILP) optimization problem. In this work, we extend our optimization framework to include double-link failures. We use the double-link failure recovery methods available in literature, employ backup multiplexing schemes to optimize capacity utilization, and provide 100% protection guarantee for double-link failure recovery. We develop rules to identify scenarios when capacity sharing among interacting demand sets is possible. Our results indicate that for the double-link failure recovery methods, the shared-link protection scheme provides 10–15% savings in capacity utilization over the dedicated link protection scheme which reserves dedicated capacity on two backup paths for each link. We provide a way of adapting the heuristic based double-link failure recovery methods into a mathematical framework, and use techniques to improve wavelength utilization for optimal capacity usage.     

基于动态行为与网络流量分析技术的威胁检测研究

随着网络技术的快速发展,伴随而来的是愈来愈多的新型网络威胁,传统安全防护体系也濒临失效,基于全流量威胁检测逐渐成为新型威胁检测的有效途径。在实战过程中,依靠传统的分析方式,传统安全设备通常都无法对新型网络威胁的各个阶段进行有效的检测,换个角度来看攻防实战,真相往往隐藏在网络流量中,本文采用网络流量实时采集的思路,通过动态行为分析和网络流量分析技术实现新型网络威胁行为检测,有效解决了新型网络威胁的发现难题。     

E~2PROM工艺的ESD保护电路失效分析

ESD保护电路已经成为集成电路不可或缺的组成部分,如何避免由ESD应力导致的保护电路的击穿已经成为CMOSIC设计过程中一个棘手的问题。光发射显微镜利用了IC芯片失效点所产生的显微红外发光现象可以对失效部位进行定位,结合版图分析以及微分析技术,如扫描电子显微镜SEM、微红外发光显示设备EMMI等的应用可以揭示ESD保护电路的失效原因及机理。文章通过对一组击穿失效的E2PROM工艺的ESD保护电路实际案例的分析和研究,介绍了几种分析工具,并且在ESD失效机制的基础上,提出了改进ESD保护电路的设计途径。     

由版图引起的CMOS ESD保护电路失效的分析

ESD保护电路已经成为CMOS集成电路不可或缺的组成部分,在当前CMOS IC特征尺寸进入深亚微米时代后,如何避免由ESD应力导致的保护电路的击穿已经成为CMOS IC设计过程中一个棘手的问题.光发射显微镜利用了IC芯片失效点所产生的显微红外发光现象可以对失效部位进行定位,结合版图分析以及微分析技术,如扫描电子显微镜SEM、聚焦离子束FIB等的应用可以揭示ESD保护电路的失效原因及其机理.通过对两个击穿失效的CMOS功率ICESD保护电路实际案例的分析和研究,提出了改进ESD保护电路版图设计的途径.     

VMOS reliability

Whenever a new technology such as VMOS emerges, one key element to its success is the reliability of the products manufactured in that technology. The results of a reliability study to examine the fundamental VMOS device stability, high-temperature operating life (HTOL) failure rates, and electrostatic protection are presented for the VMOS technology. Experimental data for more than five (5) million device-hours of HTOL predict a reliability failure rate of less than 0.01 percent/1000 h at 70°C for products fabricated in the VMOS technology. In addition, an electrostatic protection capability greater than 1800 V is possible with specially designed VMOS input protection devices.     

Failure protection methods for optical meshed-ring communications networks

We study the survivability of a meshed-ring communication network that employs cross-connect switches. For WDM networks, the cross-connect switches are implemented as wavelength routers. Nodes can also provide cross-connection at the ATM VP (virtual path) level. By meshing the ring, the nodal degree of connectivity is increased as compared to a ring topology, and thus more alternative (protection) paths are available. For routing purposes, wavelength subnetworks are embedded in the topology. Nodes communicate with each other across one of the subnetworks to which both belong. We consider two types of subnetwork topologies to simplify the routing in a normal (nonfailure) situation. For each type of subnetwork, different protection methods are proposed to protect against a single link and/or nodal failure. The throughput performance of such meshed-ring networks under failure conditions is clearly superior to that achieved by (SONET) ring networks. We show that certain protection methods even result in lower values of the protection capacity as well as the protection capacity ratio (i.e., the overall capacity used under a failure divided by the total capacity) as compared to ring networks. We also present methods for constructing wavelength subnetworks to achieve single-failure protection using the minimal number of wavelengths.     

MOS器件的ESD失效

静电放电(ESD)对半导体器件,尤其是金属氧化物半导体(MOS)器件的影响日趋凸显,而相关的研究也是备受关注.综述了静电放电机理和3种常用的放电模型,遭受ESD应力后的MOS器件失效机理,MOS器件的两种失效模式;总结了ESD潜在性失效灵敏表征参量及检测方法;并提出了相应的静电防护措施.     

A cognitive model‐based approach for autonomic fault management in OpenFlow networks

Autonomic network management is an approach to the management of complex networks and services that incorporates the detection, diagnosis and reconfiguration, as well as optimization, of their performance. A control loop is fundamental as it facilitates the capture of the current state of the networks and the reconfiguration of network elements without human intervention. For new networking architectures such as software‐defined networking and OpenFlow networks, in which the control plane is moved onto a centralized controller, an efficient control loop and decision making are more crucial. In this paper, we propose a cognitive control loop based on a cognitive model for efficient problem resolving and accurate decision making. In contrast to existing control loops, the proposed control loop provides reactive, deliberative and reflective loops for managing systems based on analysis of current status. In order to validate the proposed control loop, we applied it to fault management in OpenFlow networks and found that the protection mechanism provides fast recovery from single failures in OpenFlow networks, but it cannot cover multiple‐failure cases. We therefore also propose a fast flow setup (FFS) algorithm for our control loop to manage multiple‐failure scenarios. The proposed control loop adaptively uses protection and FFS based on analysis of failure situations. We evaluate the proposed control loop and the FFS algorithm by conducting failure recovery experiments and comparing its recovery time to those of existing methods. Copyright © 2013 John Wiley & Sons, Ltd.     

A New Shared Segment Protection Method for Survivable Networks with Guaranteed Recovery Time

Shared segment protection (SSP), compared with shared path protection (SPP), and shared link protection (SLP), provides an optimal protection configuration due to the ability of maximizing spare capacity sharing, and reducing the restoration time in cases of a single link failure. This paper provides a thorough study on SSP under the GMPLS-based recovery framework, where an effective survivable routing algorithm for SSP is proposed. The tradeoff between the price (i.e., cost representing the amount of resources, and the blocking probability), and the restoration time is extensively studied by simulations on three networks with highly dynamic traffic. We demonstrate that the proposed survivable routing algorithm can be a powerful solution for meeting stringent delay upper bounds for achieving high restorability of transport services. This can significantly improve the network reliability, and enable more advanced, mission critical services in the networks. The comparison among the three protection types further verifies that the proposed scheme can yield significant advantages over shared path protection, and shared link protection.     

Ellipse-underlay protection algorithm to deal with regional demolishments in mesh optical networks

For the abundant bandwidth, a malfunction in optical networks causes a great deal of loss to traffic, and hence the survivability of optical networks must be considered. Two technologies, protection and restoration, are used in general, and the former is investigated in this paper. The existing protection strategies mainly cope with a single link failure or a double-link failure in an optical network and not consider what causes these failures. In this paper, we study the reasons which lead to the network malfunctions, and pose a new concept named regional demolishment. A protection algorithm named Ellipse-underlay algorithm is also proposed. We compare the performance of the Ellipse-underlay algorithm to the Node-disjoint algorithm. Simulation results show that the Ellipse-underlay algorithm is more effective to the survivability of traffic than the Node-disjoint algorithm.