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.     

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.     

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     

Survivability function - a measure of disaster-based routing performance

The explosive growth of data traffic imposes critical requirements on core network survivability. Developments in wavelength-division multiplexing have strengthened this need. Survivability becomes increasingly crucial, since large traffic volumes are multiplexed onto a single fiber. A single cable cut can affect incredibly large groups of users, leading to catastrophic socioeconomic effects. This paper defines the network survivability function - the probability function of the percentage of total data flow delivered after failure and survivability attributes - the expected percentage of total data flow delivered after failure, the respective p-percentile values, the worst case survivability. Models for finding these survivability measures are described. The main goal in this paper is to investigate the survivability function for typical routing protocols used in the IP networks. Examples of survivability assessment of a typical wide area network employed in Poland illustrate the proposed approach.     

Traffic engineering in next-generation optical Networks

In this article traffic-engineering issues regarding network survivability, traffic grooming, impairment-aware routing, virtual-topology engineering, and coordination among multiple layers of network architecture will be reviewed for next-generation optical networks based on Wavelength-Division Multiplexing (WDM). Due to the recent progress and development of WDM technology, increasing traffic demands can be readily accommodated in the next-generation optical networks. In spite of the huge amount of capacity (e.g., OC-192) provided by a WDM channel, enhanced network services and network performance improvement can only be achieved with efficient traffic-engineering mechanisms. The fault-tolerant function is essential in order to provide seamless services to users by protecting their traffic against failures in the optical network because many connections can be carried on a fiber. Because the capacity of a WDM channel is very large, its bandwidth may not be efficiently utilized by a single connection. Hence, low-rate user connections need to be efficiently aggregated through the traffic-grooming scheme. An intelligent routing algorithm is especially necessary in the optical network where signal impairments due to device imperfections might degrade the signal quality. In addition, the virtual network connectivity (topology) should be flexibly maintained such that dynamic changes to the traffic demands can be easily absorbed, which can be implemented by the virtualtopology engineering method in a WDM network. As the dominant usage of Internet Protocol (IP) of the Internet is expected to reside directly above the WDM layer in the future network, the coordinated trafficengineering scheme should be deliberately designed for the multi-layer network by judiciously choosing where to put many overlapping functions in the different network layers.     

A novel domain-by-domain survivable mechanism in multi-domain wavelength-division-multiplexing optical networks

In multi-domain wavelength-division-multiplexing (WDM) optical networks, the inter-domain routing is a challenge since each single-domain cannot view the full network topology. At the same time, survivability is also an important issue in optical networks since the failures of fiber links or network nodes may lead to a lot of traffic being blocked. In this paper, we study the survivability in multi-domain WDM optical networks, and propose a new survivable mechanism called load balanced domain-by-domain routing (LBDDR). In LBDDR, in order to obtain the efficient inter-domain survivable routes, we present the domain-by-domain routing (DDR) method which can find the intra-domain sub-working path and sub-backup path in each single-domain to form the inter-domain working path and backup path for each demand. In order to reduce the blocking probability, we present the load balanced routing method which can encourage the traffic to be uniformly distributed on the links with more free wavelengths. Simulation results show that, compared with conventional mechanism, LBDDR can obtain better performances.     

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     

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。     

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.     

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。     

Study on a joint multiple layer restoration scheme for IP over WDM networks

In this article we investigate the problem of a restoration scheme for IP over WDM networks. Network reliability is gaining importance with the huge volume of traffic carried by such networks. Providing survivability at the optical layer is inherently attractive, but raises many questions and challenges, given the characteristic of optical aggregated lightpath and relatively coarse traffic granularity. The emergence of MPLS and its extension, MP/spl lambda/S, opens up new possibilities for developing simple integrated protection/restoration schemes that can be coordinated at both the IP and optical layers . This article first presents an overview of existing MPLS/MP/spl lambda/S recovery mechanisms. Then we propose a joint two-layer recovery scheme for IP-centric WDM-based optical networks where the optical layer takes the recovery actions first, and subsequently the upper IP layer initiates its own recovery mechanism, if the optical layer does not restore all affected services. A simulation-based analysis shows the benefits of the proposed two-layer recovery scheme over single-layer recovery schemes. We demonstrate the advantages of finer granularity in IP layer recovery and the effectiveness in speed on the optical layer. The impact of several network parameters on recovery performance is also studied in the paper.     

WDM光网络的保护和恢复技术

文章概述了IP、SDH和WDM层网络的生存性技术,重点介绍了光传送网的光层生存性技术与光网络恢复技术,还对故障定位、多层生存性机制的协调等问题进行了简单介绍,最后给出了一个业务配置RWA算法与恢复RWA算法的实际方案。     

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     

Logical topology design for IP rerouting: ASONs versus static OTNs

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures.     

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.     

Packet-format and network-traffic transparent optical signal processing

In this paper, we demonstrate optical transparency in packet formatting and network traffic offered by all-optical switching devices. Exploiting the bitwise processing capabilities of these "optical transistors," simple optical circuits are designed verifying the independency to packet length, synchronization and packet-to-packet power fluctuations. Devices with these attributes are key elements for achieving network flexibility, fine granularity and efficient bandwidth-on-demand use. To this end, a header/payload separation circuit operating with IP-like packets, a clock and data recovery circuit handling asynchronous packets and a burst-mode receiver for bursty traffic are presented. These network subsystems can find application in future high capacity data-centric photonic packet switched networks.     

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.     

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。