智能光网络的多层生存性技术

文章对多层网络生存性问题、独立的网络生存性配置方案和多层网络生存性配置方案进行了概括和分析,对基于IP,GMPLS/Optical智能光网络多层结构的调整策略进行了研究,并讨论了基于智能光网络的统一控制平面、利用层间信令协调机制的集成多层网络生存性方案。     

IP／MPLS-over—WDM的网络生存性

Internet的发展和数据业务的爆炸性增长对当前网络提出了更高的要求。网络将演变为IP，MPLS-over—WDM。对于这种以光网络为基础的网络构架，网络的生存性问题变得尤为重要。本文首先介绍了MPLS网络的生存性机制。由于以数据业务为中心的光网络至少包含IP层和光层，本文提出了几个在多层网络生存性面临的问题，并给出了几种方案。最后，讨论了IP／MPLS-over-WDM特有的生存性思考。     

智能光网络多层生存性技术

分析了现有网络中独立的和层间协调的生存性机制,并且对基于GMPLS的智能光网络的多层生存性进行分析,可以看到智能光网络为多层网络生存性提供了更好的保证.     

IP/MPLS-over-WDM的网络生存性

Internet的发展和数据业务的爆炸性增长对当前网络提出了更高的要求。网络将演变为IP/MPLS—over—WDM。对于这种以光网络为基础的网络构架,网络的生存性问题变得尤为重要。本文首先介绍了MPLS网络的生存性机制。由于以数据业务为中心的光网络至少包含IP层和光层,本文提出了几个在多层网络生存性面临的问题,并给出了几种方案。最后,讨论了IP/MPLS—over—WDM特有的生存性思考。     

智能光网络中基于DRS的多层生存性策略的研究

近年来,基于区分生存性业务(DRS)的多层生存性问题在智能光网络生存性技术的研究中愈发受到关注.本文在分析现有多层生存性机制存在问题的基础上,结合DRS模型,设计了一种基于DRS的多层生存性策略,并对层间协调机制中的关键问题进行了研究.该策略不仅考虑了业务的可靠性需求差异,而且平衡了网络资源分配,有重要的实际应用价值.     

多层网络中的生存性策略

多种不同层次技术的融合是现代通信网络的一大特点,同时也它带来了多层网络中故障恢复机制的协调问题。首先对多层网络中涉及到的各种生存性问题进行了概述,然后在IP/optical网络结构下,详细介绍分析了多层网络中的各种生存性策略。最后,给出了在多层网络中如何选择相应的生存性策略的指导方针。     

IP voer WDM光网络及其生存性问题讨论

本文介绍了IP voer WDM光网络的演进过程与发展趋势；讨论了其生存性问题，包括光层生存性有关概念、分类及各自的优缺点，IP/MPLS层与WDM层联合生存机制的必要性以及这种联合机制需要解决的竞争问题=带宽资源共享问题和失效扩散问题等。     

IP over DWDM网络的生存性研究

探讨了IP over DWDM生存性的机制，研究了各个网络层的恢复特点以及不同层间相互作用对生存性的影响，明确了多层网络生存性的优点，从而得出光层能够提供最快的保护，较高的层能够提供智能恢复。最后提出了一种在光层的自动保护倒换的结构，这种保护能够优先考虑来自较高层的告警信息，使IP over DWDM网络做到智能化的快速恢复，为IP over DWDM网络的研究和建设提供了一定基础。     

多层网络中的生存性

未来传输网络中,不同的网络技术(如IP、SDH和WDM技术)的融合需要不同网络层次之间进行有效地配合,特别是网络生存性领域更是如此。首先对多层网络生存性机制的框架以及在多层网络环境下实现网络生存性的技术进行了概述,同时以IP over WDM为例,说明了这些方法的应用方式。     

动态多层恢复在IP—over—OTN网络中的应用

近几年来，Internet的迅猛发展和数据业务的快速增长极大地推动了电信传送网络向多业务和高带宽的方向发展。为了保证业务的正常提供，网络生存性的问题显得越来越重要。而多层传输网络中不同网络技术的集成（如IP和OTN），给多层网络的生存性带来了机遇和挑战。主要表现在多层网络中，不同网络层间的可相互协调性，使网络故障的恢复速度更快。当然，这同时也给不同网络层间恢复机制的协调运作带来了挑战。     

IP/MPLS-Over-WDM网络的生存性

Internet的发展和数据业务的爆炸性增长对当前网络提出了更高的要求。网络将演变为IP/MPLS-over-WDM。对于这种以光网络为基础的网络构架,网络生存性问题变得尤为重要。由于以数据业务为中心的光网络至少包含IP层和光层,笔者提出了几个在多层网络生存性面临的问题,并给出了几种方案。最后,讨论了IP/MPLS--Over-WDM特有的生存性思考。     

Providing fault tolerance in wireless access networks

Research and development on network survivability has largely focused on public switched telecommunications networks and high-speed data networks with little attention on the survivability of wireless access networks supporting cellular and PCS communications. This article discusses the effects of failures and survivability issues in PCS networks with emphasis on the unique difficulties presented by user mobility and the wireless channel environment. A simulation model to study a variety of failure scenarios on a PCS network is described, and the results show that user mobility significantly worsens network performance after failures, as disconnected users move among adjacent cells and attempt to reconnect to the network. Thus, survivability strategies must be designed to contend with spatial as well as temporal network behavior. A multilayer framework for the study of PCS network survivability is presented. Metrics for quantifying network survivability are identified at each layer. Possible survivability strategies and restoration techniques for each layer in the framework are also discussed     

Integrity of public telecommunications networks

Provides an overview of the special issue of the IEEE Journal of Communications, Volume 12, Number 1 (January 1994) which addresses open questions in network integrity, reliability and survivability. Current progress in this area is discussed. The questions addressed include user survivability perspectives on standards, planning, and deployment; the analysis and quantification of network disasters; survivable and fault-tolerant network architectures and associated economic analyses; and techniques to handle network restoration as a result of physical damage or failures in software and control systems. Special interests are devoted to the survivability of broadband networks employing the new transport/switching techniques based on the synchronous optical network (SONET) and asynchronous transfer mode (ATM) standards due to their emerging role in future B-ISDN. Network integrity due to failures of common channel signaling (CCS) systems is also very critical. The present special issue includes 22 papers and is organized into the following sections: user perspectives and planning, software quality and reliability, network survivability characterization and standards, network restoration for SONET networks, network restoration for ATM networks, traffic effect and performance enhancement for computer networks, and survivable network design methods. Network restoration methods for SONET, ATM, and computer networks correspond to those for the physical layer (SONET), ATM layer, and the network layer, defined in the CCITT broadband ISDN layer structure     

Survivable MPLS Over Optical Transport Networks: Cost and Resource Usage Analysis

In this paper we study different options for the survivability implementation in MPLS over optical transport networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the offered traffic granularity and the physical network structure on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. On the other hand, sparse networks of low connectivity parameter use more wavelengths for optical path routing and increase the configuration cost, as compared with dense networks. We demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with different cost variations, and were obtained for networks targeted to a nationwide coverage     

Integrated Survivability Strategies of IP／GMPLS／Opticai Multi——layer Network

In last decade,due to that the popularity of the internet, data--central traffic kept growing, some emerging networking requirements have been posed on the today‘s telecommunication networks,especially in the area of network survivability. Obviously, as a key networking problem, network reliability will be more and more important. The integration of different technologies such as ATM, SDH, and WDM in multilayer transport networks raises many questions regarding the coordination of the individual network layers.This problem is referred as multilayer network survivability. The integrated multilayer network survivability is investingated as well as the representation of an interworking strategy between different single layer survivability schemes in IP via generalized multiprotocol label switching over ootical netwnrk     

Integrated Survivability Strategies of IP/GMPLS/Optical Multi-layer Network

In last decade,due to that the popularity of the internet, data-central traffic kept growing,some emerging networking requirements have been posed on the todays telecommunication networks,especially in the area of network survivability.Obviously,as a key networking problem,network reliability will be more and more important.The integration of different technologies such as ATM,SDH,and WDM in multilayer transport networks raises many questions regarding the coordination of the individual network layers.This problem is referred as multilayer network survivability.The integrated multilayer network survivability is investingated as well as the representation of an interworking strategy between different single layer survivability schemes in IP via generalized multi-protocol label switching over optical network.     

Optimized design of survivable MPLS over optical transport networks

In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTNs) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single-layer survivability, where some recovery mechanism (e.g. protection or restoration) is implemented in a single network layer and multilayer survivability, where recovery is implemented in multiple network layers. The survivable MPLS over OTN design is implemented as a static network optimization problem and incorporates various methods for spare capacity allocation (SCA) to reroute disrupted traffic.The comparative analysis between the single layer and the multilayer survivability shows the influence of the traffic granularity on the survivability cost: for high-bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low-bandwidth LSPs the single-layer survivability is more cost-efficient. For the multilayer survivability we demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9%) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one; however, this is at the increase in the optimization problem complexity. These results are based on a cost model with current technology pricing and were obtained for networks targeted to a nationwide coverage.     

Emerging technologies for fiber network survivability

Reducing network protection costs, while maintaining an acceptable level of survivability, has become an important challenge for network planners and engineers. This article will review technology and architectures that may be used to implement cost effective survivable fiber networks for each transport layer, and discuss the interworking system between survivability mechanisms across different layers and associated open issues. Standards development, product availability and the current status of deployment will also be reviewed. The first section reviews a class of survivable fiber network architectures that has been deployed or is scheduled to be deployed. Next is a review of emerging technologies for these survivable architecture implementations. These emerging technologies include SONET, ATM, and passive optical technology. Finally the issue of multiple layer interworking on SONET/ATM networks is discussed     

OTN——未来信息社会的承载平台

为实现高速、大容量、多业务、全透明的光传送网,目前人们正在集中研究光交叉、光放大、光电集成、光无源器件以及全光信号处理等方面课题。同时以 DWDM技术为基础的 OTN组网也从点到点形式发展到了具有OADM和OXC节点的网状网结构,而网络生存性的需要又衍生出各种网络自愈技术。文中还提到了OTN中存在的技术难点,指出了OTN技术发展中需要研究的课题。     

Impacts of Hierarchy in Ethernet Ring Networks on Service Resiliency

In transport networks, a multi‐ring architecture is very useful to facilitate network planning and to design and provide more resilient services for customers. Unlike traditional synchronous optical network multi‐rings, the service resiliency of Ethernet‐based multi‐rings is significantly impacted by the ring hierarchy because a link or node failure in a certain level ring triggers filtering database flush actions in all higher level rings as well as in the ring with the failure, and consequently a large amount of duplicated data frames may be flooded. In this paper, we investigate how the ring hierarchy impacts the service resiliency of multi‐ring networks. Based on extensive experiments on various single‐ and multiple‐link failures, we suggest two effective inter‐ring connection rules to minimize the transient traffic and to ensure more resilient multi‐ring networks. In addition, we consider a flush optimization technique called e‐ADV, and show that the combination of e‐ADV and multi‐ring structures satisfying our inter‐ring connection rules results in a more attractive survivability performance.