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     

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     

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.     

Recovery in multilayer optical networks

The integration of different network technologies into a multilayer network, as in Internet-based networks carried by optical transport networks (OTNs), creates new opportunities but also challenges with respect to network survivability. In different network layers, recovery mechanisms that are active can be exploited jointly to reach a more efficient or faster recovery from failures. This interworking is also indispensable in order to overcome the variety of failure scenarios that can occur in the multilayer-network environment. A well-considered coordination between the different layers and their recovery mechanisms is crucial in order to attain high performance recovery. This paper provides an overview of multilayer recovery issues and solutions in an Internet protocol (IP)-over-optical-network environment, which is illustrated by quantitative case studies.     

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     

Quantitative Survivability Analysis Using Probability Model Checking: A Study of Cluster-Based Vehicle Networks with Dual Cluster Heads

As an important part of future 5G wireless networks,a vehicular network demands safety,reliability and connectivity.In this context,networking survivability is usually considered an important metric to evaluate network performance.In this paper,we propose a survivability model for vehicle communication networking based on dual cluster heads,wherein a backup cluster head(CH)will be activated if the primary CH fails,thereby effectively enhancing the network lifetime.Additionally,we introduce a software rejuvenation strategy for the prime CH to further improve the survivability of the entire network.Using the Probabilistic Symbolic Model Checker(PRISM),we verify and discuss the proposed survivability model via numerical simulations.The results show that network survivability can be effectively improved by introducing an additional CH and further enhanced by adopting the software rejuvenation technique.     

WDM光网及多层网络生存性的研究

为了适应多层次网络发展的需要，在讨论WDM光层生存性机制的基础上，针对多层网络联合的生存性机制进行了仔细的分析，提出了一种多层协调的实现办法，并讨论了多层空闲资源设计中的共享问题。     

Management and control of transparent optical networks

Multiwavelength optical networking is expected to play a significant role in the next-generation transport networks providing capacity enhancements as well as built-in network survivability and reconfigurability. While advances have been made in the hardware technologies, considerable research effort is still required in the area of network management and control in order for optical networking to be proven commercially viable. This paper investigates key design issues concerning optical network management and control and examines how the networking architecture is influenced by the various management considerations     

Resilience in multilayer networks

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. Especially in the area of network survivability, much can be gained by a better alignment of the healing actions taken by different network layers in case of outages. Survivability issues encountered in a multilayer environment include, among others: how to identify the original failure cause, how to appoint for each failure a layer responsible for its healing, how to let different layers interwork, and how to provide spare resources in an efficient way     

Data-centric optical networks and their survivability

The explosive growth of data traffic-for example, due to the popularity of the Internet-poses important emerging network requirements on today's telecommunication networks. This paper describes how core networks will evolve to optical transport networks (OTNs), which are optimized for the transport of data traffic, resulting in an IP-directly-over-OTN paradigm. Special attention is paid to the survivability of such data-centric optical networks. This becomes increasingly crucial since more and more traffic is multiplexed onto a single fiber (e.g., 160×10 Gb/s), implying that a single cable cut can affect incredible large traffic volumes. In particular, this paper is tackling multilayer survivability problems, since a data-centric optical network consists of at least an IP and optical layer. In practice, this means that the questions "in which layer or layers should survivability be provided?" and "if multiple layers are chosen for this purpose, then how should this functionality in these layers be coordinated?" have to be answered. In addition to a theoretical study, some case studies are presented in order to illustrate the relevance of the described issues and to help in strategic planning decisions. Two case studies are studying the problem from a capacity viewpoint. Another case study presents simulations from a timing/throughput performance viewpoint     

Value optimization of survivable multilayer IP/MPLS-over-WSON networks

Network operators are willing to provide a range of services in the hope of maximizing their profits: from the highly available connectivity services for key business customers to the unprotected or even best effort services for residential customers. These services are being provided through IP/multiprotocol label switching (MPLS) over wavelength-switched optical networks (WSON) networks. Such multilayer network enables the application of optimal load balancing between the packet and the optical layer, optimizing both the cost of the packet layer and the utilization of the WSON. To provide highly available services, redundant network resources need to be added to the network providing survivability against failures; generally speaking, the higher the survivability degree, the higher both the capital and the operational expenditures (CAPEX and OPEX, respectively) of the network. In this work, we design networks to meet specific availability objectives considering single failures in optical links, IP/MPLS nodes, and optoelectronic ports. The benefits of the designed networks are evaluated from an economic perspective defining costs and revenues models and using Net Present Value as a metric to evaluate future cash flows after an investment. To this end, CAPEX and OPEX, including power consumption and maintenance, and penalties as a consequence of service level agreement breaches are considered. Exhaustive numerical results on several reference network scenarios demonstrate how the value of the network can be maximized by tuning availability objectives.     

特殊场景的LTE覆盖技术

文章首先介绍了 LTE异构网和 LTE立体组网技术,在此基础上,重点研究高铁和密集城区的 LTE覆盖技术。讨论了如何应对高铁 LTE覆盖的多普勒频移效应问题,并给出了高铁沿线覆盖和隧道两种环境下的组网方式建议。最后,探讨了如何采用 LTE异构网和立体组网技术,通过合理的网络布局来解决密集城区的容量和深度覆盖问题。     

Incremental survivable network design against node failure in SDH/SONET mesh networks

Network survivability is becoming more and more important for the plenty of information each single fiber carries. Extra network resources are needed to increase network survivability level. In this paper, we investigate the problem of how to augment the network topology with adding new links and allocate spare capacity to maximize the service restorability against node failures in SDH/SONET mesh networks. A scheme called maximal node-disjoint backup paths provisioning with topology augmentation is proposed to tackle the problem, and another scheme called globally optimized path provisioning with topology augmentation, which allows adjusting the existing working paths of network flows, is investigated to optimize the augmented network globally. Both schemes are formulated as mixed integer linear programming models. Furthermore, heuristic algorithms are investigated to be implemented in software. Three algorithms, i.e., added links searching method, successive maximal survivable routing method, and random sequence routing convergence method, are designed and compared. Simulation results show the effectiveness of the algorithms.     

网络恢复机制可用性的定义及其应用

对于用户和业务提供者，网络生存性变得越来越重要。生存性是设计和规划新的电信网（如ＳＤＨ网和ＡＴＭ网）面临的一个根本的、亟待解决的问题。在过去的几年中，已提出几种应用于ＳＤＨ和ＡＴＭ网络中的不同的恢复机制。但在比较和评价恢复机制的性能时，以往只采用一种简单的方法。为克服该方法的缺陷，本文提出了面向用户和面向网络工程师的恢复机制可用性的定义。在后者的可用性分析中，考虑网络生存性对空闲容量的要求。由于一个网络的状态空间很大，进行可用性精确分析是不可行的，本文建议采用ＯＲＤＥＲ算法来近似测量可用性。同时还给出了恢复机制可用性定义的应用。一个应用是：网络工程师利用可用性定义，设计一个具有成本有效性的生存网络。另一个应用是：在ＡＴＭ生存网络的ＣＡＣ协商参数中，增加了一组新的参数—生存性性能参数。最后在计算机模拟中验证了：在评价恢复机制性能时，两个可用性的定义比传统方法更有效和更有意义     

The interface between IP and WDM and its effect on the cost of survivability

A summary of research on survivable IP networks overlaid over WDM networks is presented. The WDM networks are part of optical transport service providers, who lease lightpath services to institutions with IP networks. The lightpath services realize IP links for IP networks, and they have different protection grades such as unprotected and protected. The research included considering new network survivability requirements and incorporating them into network design problems. The cost of survivable IP over WDM networks is compared over three scenarios. Each succeeding scenario has the WDM network provide more flexible services, and the IP and WDM networks become more integrated. We consider the problem of setting up lightpaths for an IP network so that the network will remain connected after a fiber link fault. Algorithms to find the lightpaths and minimize cost are given. The network costs under the three scenarios are compared by simulations.     

采用多层恢复机制的IP over WDM网络生存性研究

IP over WDM网络是下一代网络的核心,生存性则是保证服务质量(QoS)的关键要素.当网络中出现故障时,选择在IP层还是光层进行保护和恢复是非常重要的课题.文章在论述IP层和光层的保护和恢复机制的基础上,提出了多层联合恢复机制的思想,针对多层联合恢复机制中各层之间如何协调进行了仔细的分析,并提出了自己的见解.     

多域光网络生存性的关键技术研究

多域光网络的生存性作为衡量网络性能优劣的关键指标,与实际网络应用的关系最为密切,是当前迫切需要解决的关键问题;聚焦高速化、多业务化驱动的多域光网络环境下的生存性技术.基于光网络的多业务、分布式控制的特性,分析了多域光网络生存性机制的研究现状及面临的挑战;给出了一种针对多域光网络生存性问题的分类方法;结合多域光网络对生存性的需求,对相关关键技术进行了归类和研究,并指明了进一步研究的方向和重点.     

ATM网络抗毁和自恢复技术研究

基于ATM/MPLS技术的通信网络是承载宽带多媒体业务的综合平台。为了对承载业务进行抗毁保护,对ATM的最基本的1+1、1∶1、m∶n抗毁保护结构进行了研究和总结。同时结合网络传输层,如:PDH、SDH、WDM、MPLS的保护和应用层业务,如:IP、电路交换、以太网和帧中继的抗毁迂回策略,提出了ATM的多层次抗毁自恢复组网结构,为ATM的应用研究提供了借鉴。     

抗毁WDM网中支持QoS的选路和波长分配算法

该文首先探讨了抗毁WDM网中支持QoS的分层图模型,在此基础上提出一种抗毁WDM网中支持QoS的选路和波长分配算法。该算法根据上层业务不同的QoS要求,对其光路建立请求区别对待,以满足它们不同的阻塞率和恢复率要求。计算机仿真结果表明该算法既满足了上层业务不同的QoS要求,同时又充分利用了有限的网络资源,使全网的平均阻塞率降低。     

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。