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     

Network design sensitivity studies for use of digital cross-connectsystems in survivable network architectures

Provides the results of an economic study on the use of SONET digital cross-connect systems (DCS) to provide survivable transmission network architectures in local exchange networks. Three fundamental survivable transmission technologies are considered: (1) a SONET self-healing ring, (2) a SONET point-to-point fiber system with 1:1 automatic protection switching and diverse routing of protection facilities, and (3) a DCS mesh with automatic DCS restoration (rerouting) protection. These three technologies are used in various combinations to form six survivable network alternatives for evaluation. Two local exchange carrier (LEC) networks are used (a 15 node network and a 53 node network) and demand, network connectivity, and unit equipment cost sensitivities are evaluated on these alternatives. In addition, the survivability of each alternative in the event of a major node failure is calculated. The motivation for the study is to determine the viability of DCS-based survivable network architectures and, in particular, the viability of SONET DCS with integrated optical terminations. The study has two objectives: (1) given a specific survivable network technology, under what conditions is it economical to place a broadband DCS (B-DCS) in a central office as opposed add-drop multiplexers (ADM); and (2) which survivable technologies with B-DCS are economical, and under what conditions. The authors conclude that the most cost-effective networks consist of “hybrids” of SONET point-to-point, ring, and mesh technologies, and that the B-DCS is economically viable for interconnection between these technologies     

Service applications for SONET DCS distributed restoration

This paper determines the scope of network applications and services that could be offered using a SONET DCS-based self-recovering mesh architecture with distributed control. The study includes an outage impact analysis on network services and a determination of how network restoration time objectives will affect the applicability for the distributed controlled DCS network architecture. It is concluded that using SONET DCS distributed control architectures to provide more complete survivability of a network would support numerous applications. Future services will demand a fault-tolerant network with complete survivability; this may only be reached through integration of SONET DCS distributed control architectures with other survivable architectures such as cell relay networks (e.g., supporting SMDS) and self-healing rings     

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.     

SONET ring applications for survivable fiber loop networks

Synchronous optical network (SONET) self-healing rings (SHR) are studied in the loop environment. SONET SHR architectures for loop feeder networks are discussed, focusing on three possible dual central office (CO) architectures for fiber loop networks, using SONET SHRs to reduce network costs and provide network service survivability. These architectures reflect an integrated planning concept for SONET networks that eliminates the boundary between the access network and the inter-office network. It is shown that the use of SONET SHRs makes it easy to evolve to a protected dual CO access architecture. Economic and survivability studies are discussed. The economic studies show that using the ring approach yields significant advantages over the traditional diverse protection approach in terms of cost and survivability, especially for the dual CO architectures     

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。     

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 SONET networks-design methodology

A prototype software system that implements a methodology for the strategic planning of survivable interoffice networks is presented. The software system determines strategic locations and ring types for synchronous optical network ring placement. Two types of survivable network architectures are considered-1:1 diverse protection and SONET self-healing rings. The software considers three types of SONET self-healing rings-unidirectional, 2-fiber bidirectional, and 4-fiber bidirectional. Hubbing is assumed in all architectures. Inputs include nodes, links, connectivity, facility hierarchy, and multiyear point-to-point demands, together with the costs of fiber material and splicing, route mileage (installation), and multiplexors and regenerators of different rates. The outputs are a set of near-optimal rings based on cost, specifying the ring types and rates, fiber span sizes and counts, regenerator locations and speeds, the topology (set of links to be used), and the network cost. In addition, the software outputs the time in the planning period that each ring and fiber span should be installed     

Internetworking connectionless and connection oriented networks

The use of connection-oriented (CO) networks for the transport of IP traffic is seen to have value to both users and service providers. Given the expectation that most endpoint-generated traffic will be in the form of connectionless (CL) IP datagrams, we address the problem of how to internetwork a CL (IP) network with a CO network. CO networks can be packet-switched or circuit-switched. Examples of packet-switched CO networks include ATM and MPLS networks, in which resource reservations are made at the ATM or shim layer, and IP-switch-based networks, in which resource reservations are made at the IP layer. Examples of circuit-switched networks include SONET/SDH and WDM networks that consist of programmable optical crossconnects. We consider the internetworking problem for two modes of operation of CO networks: provisioned, in which connections are set up a priori, and switched, in which connections are set up on demand. The main focus of this article is on the more complex problem: the internetworking of CL IP networks with CO networks operated in a switched mode. Our solution consists of (i) interworking user plane protocols with protocol conversion in some cases instead of always using protocol encapsulation, (ii) interworking routing protocols by either simply having gateways know routing information of both networks or having all nodes know routing information of both networks, and (iii) interworking signaling protocols by using application- or transport-layer end-to-end handshakes to trigger connection setups through the CO network. We demonstrate throughput improvements with our integrated routing interworking scheme over the MPOA IP-ATM internetworking solution for two example networks     

Feasibility study of a high-speed SONET self-healing ringarchitecture in future interoffice networks

The economic feasibility of using SONET self-healing-ring (SHR) architecture in survivable interoffice fiber networks is studied. The model used is discussed, and the selection criterion for the candidate area in this study, the SHR cost model, the hubbing network cost model, the network survivability measure, and the network growth model are described. Results of two case studies based on a metropolitan local access and transport area (LATA) network are discussed. One involves a single- and the other a dual-homing interoffice network. Sensitivity analysis and network impact results are highlighted     

On IP-over-WDM integration

Expanding Internet-based services are driving the need for evermore bandwidth in the network backbone. These needs will grow further as new real-time multimedia applications become more feasible and pervasive. Currently, there is no other technology on the horizon that can effectively meet such a demand for bandwidth in the transport infrastructure other than WDM technology. This technology enables incremental and quick provisioning up to and beyond two orders of magnitude of today's fiber bandwidth levels. This precludes the need to deploy additional cabling and having to contend with right-of-way issues, a key advantage. Hence, it is only natural that over time optical/WDM technology will migrate closer to the end users, from core to regional, metropolitan, and ultimately access networks. At present, WDM deployment is mostly point-to-point and uses SONET/SDH as the standard layer for interfacing to the higher layers of the protocol stack. However, large-scale efforts are underway to develop standards and products that will eliminate one or more of these intermediate layers (e.g., SONET/SDH, ATM) and run IP directly over the WDM layer. IP over WDM has been envisioned as the winning combination due to the ability of the IP to be the common revenue-generating convergence sublayer and WDM as a bandwidth-rich transport sublayer. Various important concerns still need to be addressed regarding IP-WDM integration. These include lightpath routing coupled with tighter interworkings with IP routing and resource management protocols, survivability provisioning, framing/monitoring solutions, and others     

利用DWDM实现核心网络的光网络互联

光网络互联实现了综合ＩＰ、ＡＴＭ、ＳＯＮＥＴ／ＳＤＨ和ＤＷＤＭ技术的低成本网络。ＤＷＤＭ技术彻底改变了核心网络,在ＤＷＤＭ配置的第二阶段,ＩＰ路由器和ＡＴＭ设备直接连接到ＤＷＤＭ,省去了ＳＯＮＥＴ／ＤＳＨ和ＡＴＭ,降低了成本,简化了扩容。光网络互联多数利用了现有标准,但新技术、新网络元素的引入同多带来了互操作问题,因此必须建立开放的ＤＷＤＭ系统,这也将推动光网络互联标准的发展。     

ATM local area networks: a survey of requirements, architectures,and standards

There is increasing interest in deploying ATM technology in local or campus networks. ATM is an ideal technology to overcome many of the limitations of today's LAN technologies. This article focuses on the application of ATM in the LAN environment to interconnect high-end host computers, and on the interworking of ATM-based LANs with legacy LANs. The authors introduce ATM LAN requirements, followed by a discussion of possible ATM LAN architectures to support these requirements. The article then covers current standards and their relation to the possible architectures, and concludes with a discussion of current ATM LAN issues and directions     

Frame relay and ATM interworking

Frame relay has proven to be a very successful wide area networking service, and ATM is gaining momentum in the industry to become the preferred common backbone technology for supporting a wide variety of network services, including native ATM cell relay service and frame relay service. In the years ahead, ATM is poised to become the dominant networking technology. Since frame relay and cell relay services will coexist for a long time to come, it is imperative that the network and service interworking specifications be defined and implemented. This article focuses on the topic of frame relay and ATM cell relay service and network interworking. The authors provide the rationale, the standards-based methodology, the major open issues, and a likely evolution scenario for the interworking of frame relay and ATM cell relay networks and services     

End-to-end survivable broadband networks

Within the EC-sponsored RACE program, the IMMUNE project was established to analyze and specify appropriate strategies for introducing end-to-end survivability into corporate and public broadband networks to support these strategies by proper techniques and evaluation tools, and to demonstrate distributed restoration on PSN (public switched networks) and CPN (customer premises networks) laboratory models. The first objective was to define a set of survivability requirements and metrics to be used in the rest of the project. This has led to the identification of a range of survivability strategy options ann how they can be mapped onto user, service provider and operator requirements. The next step on the road to integral survivability is designing and planning survivable networks, and the evaluation of the restoration and protection mechanisms that will be applied in these networks. An overview is given of this part of the project. Most protection and restoration mechanisms operate within a single network layer and network part, autonomous from network management. The interaction of mechanisms in different network layers or in different network parts, and the role of network management, are discussed. For the demonstration lab models, two techniques have been selected for implementation: a distributed restoration mechanism for a meshed ATM PSN, and a CPN ATM ring protection switching mechanism. These techniques are described and an overview is given of the ongoing activities within the IMMUNE project, with a summary of the status of the demo models     

Dual-fiber optical burst switching network: A novel architecture for metropolitan area networks

Fiber optic rings are widely deployed in metropolitan area networks (MAN). These rings currently employ architectures and protocols that are neither optimized for nor scalable to the network demand. Therefore, emerging technologies are being pushed to replace the traditional architectures. Among these technologies, optical burst switching (OBS) is an effective and promising technology. In this study, a novel architecture, dual-fiber OBS (DOBS), is proposed. This architecture has similar functions to those of fiber delay lines, partial wavelength conversion and deflection routing. A theoretical model is developed to evaluate the performance of DOBS, which is compared with single-fiber and simple two-fiber schemes by introducing them into ring and mesh MAN in simulations. The results reveal that DOBS can exponentially reduce the burst dropping probability. Moreover, since DOBS can be implement using commercially available devices and dark fibers, it is commercially viable in metro networks.     

Architectures for ATM network survivability

This article surveys the restoration architectures for asynchronous transfer mode (ATM) network survivability that have been actively studied in this decade. Network reliability is critical for recent and future networks that will advance the information era. Moreover, it is one of the biggest factors in designing and managing networks. Since the early telecom network era, many restoration systems have been developed for plesiochronous digital hierarchy (PDH), synchronous digital hierarchy (SDH), synchronous optical network (SONET), leased lines and so on; and they were surveyed in many papers and books. This article focuses on new restoration techniques for ATM networks. First, the requirement studies are introduced. This includes the scant results published on the influence of failure and the state of failure analysis. Next, restoration schemes are categorized and briefly introduced. Examples include centralized control, automatic protection switch (APS), self-healing ring (SHR), self-healing network (SHN) and failure resistant virtual path (FRVP). In order to achieve adequate restoration probability with minimum cost, a network design scheme is necessary; thus, network design issues are introduced. Finally, this article focuses on the issues, future work, and problems that remain to be solved.     

Convergence of Protection and Restoration in Telecommunication Networks

This paper argues for the need for convergence of protection and restoration schemes in today's telecommunication networks. Such networks are presented both in a layered context and from an end-to-end perspective. Such convergence is both necessary to ensure inter-working amongst a multitude of technologies deployed and desirable to ensure simplified operations. This paper further identifies the issues and inter-working items that need resolution in today's telecommunication and data networks in order to achieve inter working amongst various existing and emerging restoration and protection schemes in a layered and end-to-end context. End-to-end context covers the access, metro, and long haul dimensions of the network. It also encompasses both the services and the transport layers of the network in the context of multi-domain, multi service provider networks. Layering issues arise from the mix of technologies at several layers for example: optical transmission and CWDM/DWDM at physical layer, SONET/SDH framing and management at layer-1, ATM, MPLS, Ethernet, and resilient packet rings at layer-2, and finally IP and routing protocols at layer-3. Given that some degree of routing and signaling intelligence is migrating down to the optical layer equipment, this whole layering concept is currently in transition. This paper shows the need for convergence in the form of a two level protection and restoration scheme. A service independent layer and a mesh restoration capability at the routing layer.     

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.     

The infrastructure for gigabit computer networks

The key features of the synchronous optical network (SONET) and asynchronous transfer mode (ATM) standards for the broadband integrated services digital network (B-ISDN) public network, which is expected to provide a powerful and ubiquitous infrastructure to support the emerging gigabit-per-second data and multimedia applications, are reviewed. The advantages of ATM, the ATM cell format, the B-ISDN protocol reference model and the ATM layer, the ATM adaptation layer, and ATM traffic management and signaling are discussed. An experimental high-performance parallel interface (HIPPI)-ATM-SONET interface is presented as an example to illustrate how the SONET and ATM techniques can be used to provide end-to-end transport for applications requiring a bandwidth of 800 Mb/s and possibly 1600 Mb/s