帧中继承载业务的ATM传输技术

在帧中继网络协议模型的基础上,对继帧中继承载业务的ＡＴＭ传输中关网络互通,虚连接复用,参数映射等技术问题进行了讨论,并对帧中继业务与ＡＴＭ宽带业务互通问题进行了简要介绍。     

ATM与帧中继互连技术

ＡＴＭ技术是ＩＴＵ－Ｔ推荐的Ｂ－ＩＳＤＮ交换技术，而帧中继在提供广域网业务方面很成功。因此，在ＡＴＭ发展的初期不可避免地会与帧中继技术并存。本文阐述了ＡＴＭ与帧中继网络互加和业务互连的相关技术及其存在的问题。     

Service convergence using MPLS multiservice networks

Enterprises are increasingly using virtual private networks to interconnect remote sites. Traditionally, service providers have used ATM core networks to deliver layer 2 services such as frame relay, ATM, or TDM private lines, which enterprise customers have then used to build their corporate network infrastructure. Such services account for the majority of data service revenues today. However, pressure has increased on service providers to combine increased flexibility with reduced costs in the context of a highly dynamic telecommunications market. Service providers also need to generate new revenues from their IP network infrastructure, through new opportunities such as IP VPNs and virtual private LAN services, while simultaneously achieving operational efficiencies through the convergence of all of their services on a common MPLS backbone. New access and metro network technologies, such as Ethernet, are also emerging that can be used to deliver these new services to enterprise customers alongside ATM and frame relay access. This must be achieved while also supporting existing technologies such as ATM, which continue to deliver highly profitable services. This article discusses the technical challenges in meeting the often conflicting requirements of delivering both traditional layer 2 services and new layer 3 services on a converged MPLS network. We show how both network and service interworking are required, and how these must operate at the user, control, and management planes to enable profitable services to be delivered over the new converged network. The different solutions being defined in the standards bodies are described, and the distinct scenarios they address are explained.     

Network management considerations for interworking ATM networkswith non-ATM services

Rapid progress has been made on standards and implementation agreements for interworking ATM networks with frame relay, DS1/DS3 circuits, and SMDS. This article examines ATM network management issues in these interworking environments, with an emphasis on how each interworking environment has unique requirements for network management     

ATM for narrowband services

ATM is a broadband fast-packet technology, but its modern technological base should make it less expensive than existing circuit switching systems once economies of scale are reached. The article examines the use of ATM to address the growth of emerging narrowband services such as frame relay. ATM's flexibility in supporting variable rates and levels of service make it an ideal network technology to carry multiple services. While B-ISDN services promise many benefits to users, major issues must be addressed before such services can be available on a large scale. Utilizing ATM as a backbone technology to support the growing capacity needs of emerging narrowband services could facilitate more rapid introduction of ATM into the network infrastructure and speed delivery of future BISDN services     

Narrowband and broadband infrastructure design for wirelessnetworks

There has been an explosion in the number of wireless subscribers. A number of air interface technologies, such as GSM, TDMA and CDMA, are available to wireless service providers for offering wireless services. In addition, a variety of networking technologies, such as STM, ATM and frame relay, are available to the wireless services provider for designing their infrastructure networks. The abundant choice of technologies, and their associated capabilities and costs, creates a need for network design tools which can help vendors and wireless service providers to understand the economics of investing in different technologies. This article is concerned with the design of narrowband and broadband infrastructure networks for wireless access. The article first describes the different technology alternatives and tariff structures and their impact on wireless infrastructure network design. The general infrastructure design problem is then stated and a solution methodology outlined. Examples of the economic trade-offs involved in narrowband and broadband networking technologies are also presented     

Frame relay in public networks

Frame relay is a significant networking technology in the current data networking environment. Given its inherent advantages, it is particularly well-suited to LAN interconnection. In a public network, frame relay has key advantages for end users in terms of performance and cost efficiency. The effectiveness of frame relay in public networks, the management of public frame relay networks, the evolution from frame to cell services, and product implementations are discussed. The advantages frame relay has over existing technologies are described     

Multimedia service interworking over heterogeneous networkingenvironments

This article discusses technical issues related to delivery of multimedia services, such as video-on-demand, over heterogeneous networking environments. In particular, it describes the design and implementation of an experimental system for multimedia service interworking between a DAVIC (Digital Audio Visual Council) domain and an Internet domain. The system, called MIDDLEMEN (middlemen for multimedia environment), consists of the broker and the interworking unit, which work together to provide multimedia services across different types of networks in a seamless manner. The broker acts as a guide to multimedia services, and complements servers or clients that are not equipped with full functionality. The broker also controls the resources in MIDDLEMEN. The interworking unit performs various translation functions under the control of the broker, including stream transport protocol conversion, traffic monitoring and bit-rate control, service gateway conversion, and stream control conversion. Current implementation supports the delivery of a DAVIC-compliant VOD service from an ATM network to an IP network     

Wireless ATM—an overview

This paper sketches the requirements and possibilities of wireless ATM in local area networks. Because of the wide range of services supported by ATM networks, ATM technology is expected to become the dominant networking technology in the medium term for both public infrastructure networks and for local area networks. ATM infrastructure can support all types of services, from time-sensitive voice communications and desk-top multi-media conferencing, to bursty transaction processing and LAN traffic. Extending the ATM infrastructure with a wireless access mechanism meets the needs of those users and customers that want a unified, end-to-end networking infrastructure with high-performance, consistent service characteristics. The paper introduces ATM concepts, discusses the requirements for wireless ATM, in particular for data link control and radio functions. It closes with some notes on development of wireless ATM research systems standardization and spectrum allocations.     

全域联网技术─—帧中继SMDS和ATM

在全域联网中，帧中继、交换多兆比特数据业务和异步转移模式正成为一个灵活的宽带通信的重要新技术。本文扼要地叙述全域联网这些新技术的协议、体系结构和潜在的应用。     

QoS and service interworking using constraint route labeldistribution protocol (CR-LDP)

Introducing quality of service features to the IP/TCP protocol suite has become a hot topic of research in both industry and academia. Several architectures have been proposed for QoS support at the network layer (layer 3 in the OSI model). Both integrated services and differentiated services architectures are examples of QoS models that are implementable at the IP layer. Another development at the IETF is the work related to traffic engineering using multiprotocol label switching. While traffic engineering covers a wide range of topics, QoS support is recognized as one of its necessary features. This article describes the QoS features of the constraint-route label distribution protocol and how they can be efficiently utilized to achieve service interworking between a number of different networking technologies     

Cells-In-Frames: a system overview

Cells-In-Frames provides an efficient mechanism for integrating both voice and data traffic on an existing campus network that is currently supporting legacy LAN workstations. The solution suggested by this article is to export ATM services within standard LAN frames. Each frame will carry the traffic from one or more ATM cells, but any given LAN frame is associated with only one ATM virtual circuit. The widely different qualities of service required for voice and data traffic is achieved rough the use of AAL1 and AAL5 services. The AAL functions are split appropriately between the workstation and the LAN switch that interfaces to an ATM backbone network. With the use of the Q.2931 signalling protocols defined for ATM, Cells-in-Frames achieves a long-sought-after goal of providing switched networking services to LAN-attached workstations     

宽带数据通信网的演进

尽管ＩＰ化已成为宽带数据网络的演进方向,但电信运营商在选择融合网络解决方案时比较现实的选择是优化现有传送网基础设施,同时要兼顾公司目前或将要提供的业务。在光联网方案讨论中,文章对ＩＰ ｏｖｅｒ ＳＤＨ和ＩＰ ｏｖｅｒ ＡＴＭ进行了比较,认为集成型ＩＰｏＡ被看好。但由于ＡＴＭ的局限性,未来的联网方案将是基于ＤＷＤＭ的光互联网,而ＡＴＭ将演变为一种边缘技术,网络智能也将随之转移至网络边缘。     

充满活力的下一代网络技术--RSVP

近年来，随着经济的发展和计算机的普及，Internet业务出现了爆炸性的增长，并且出现了许多新兴的业务，如IP电、话、视频点播、视频会议等，现有Internet只提供传统单一尽力传送（best—effort）业务，因而急需新的网络协议以支持未来分类业务所需的不同带宽和服务质量（QoS）保障，现有网络虽然可以通过ATM（Asynchronous Transfer Mode）来解决QoS问题。但由于ATM信元的开销在整个帧中占了30％，严重降低了网络的传输效率，故未来网络不可能使用它。新出现的RSVP（资源预留协议）根据其自身的特点，必然会替代ATM，成为下一代网络保证QoS的关键网络技术。下面详细介绍RSVP的特点以及它如何有效的与未来的IPv6相结合。     

Evolution of the North Carolina Information Highway

As the first information highway of its kind, the North Carolina Information Highway is likely to set an example for ATM broadband deployment not only in the BellSouth region but also in the rest of the country. The article outlines an evolutionary path for new network architectural features and additional video and data services that can be supported by the NCIH. These architectures will support the introduction of on-demand video services (e.g. the distance learning service), and other associated vertical services. As standard procedures are developed, users will be able to use data services like TCP/IP and frame relay over large-bandwidth ATM connections. In addition, they will have opportunities to use their existing applications in the legacy LANs, as well as with ATM endpoints. As ATM standards agreements are realized over the next few years, and the ATM technology cost curve continues to improve, the NCIH will prove to be a very cost-effective and high-performance alternative for all the high-speed communication needs of the North Carolina State Government     

Transport architecture evolution in UMTS/IMT‐2000 cellular networks

Mobile evolution from the second generation (2G) to the third generation (3G) raises several important questions for operators and manufacturers. How to ensure that the old and current investments can still be utilized in the future? What is the optimum architecture? ATM or IP? Voice or data? There is no single correct answer to these questions, as it all depends on individual cases. In this paper, we discuss the transport architecture evolution for the universal mobile telecommunications system (UMTS)/international mobile telecommunications—year 2000 (IMT‐2000), or 3G cellular networks and interworking aspects between 2G and 3G cellular networks. The interfaces between access nodes in a cellular network and the changes incorporated to support packet data services are described. Emerging services such as mobile data, virtual private networks (VPN) and location aware networking are described. Role of ATM and IP in this new transport architecture is presented. Control and data plane interworking issues between different transport technologies are described. The new ATM standard, ATM adaptation layer type 2 (AAL2) and its applicability for transporting compressed speech in an ATM based cellular network is described. A similar approach in IP, multiplexing in real‐time transport protocol (RTP) payload to transport compressed speech on selective interfaces of 3G network, is introduced. Transport network architecture evolution within four different scenarios is evaluated. Special interest is focused on the protocol stacks and flexible layered solutions that allow smooth migration from one transport technology to another. Copyright © 2000 John Wiley & Sons, Ltd.     

ATM Forum signalling protocols and their interworking

The ATM Forum is a key body which has been developing specifications for asynchronous transfer mode (ATM) technology over the past six years. It has produced a number of signalling specifications covering the user network interface, the inter-carrier interface and private networking environments. While work continues on 'fine-tuning' these agreements, there is still discussion about how they are used in large scale networks, and in particular on the interworking of public and private network environments.This paper reviews the current status of the relevant protocols and their scope. It then explores the issues related to their interworking and discusses the role of the proposed ATM internetwork interface (AINI) as an alternative internetwork or inter-carrier interface to its broadband intercarrier interface (B-ICI).     

Voice over ATM: an evaluation of network architecture alternatives

This article describes eight application scenarios in which there is a business case for voice over ATM. It then evaluates alternative network architectures for implementing the required network functionality. The article incorporates much of the ongoing work of the ATM Forum and the ITU, but does not restrict itself to standards and implementation agreements. In addition, it evaluates nonstandardized alternatives for ATM transport of voice traffic. There are two main areas: N×64 kb/s structured data transfer, also known as composite cell transport-a network operator may aggregate individual voice calls into N×64 kb/s blocks for transport to an intermediate point in the network. At that point the individual calls need to be remapped into new M×64 kb/s blocks for the next stage of their transport. Architectural alternatives and advantages of remapping are investigated. Interworking of signalling is of two types: network interworking, in which the end users are connected to non-ATM networks and an ATM network is used for backbone transport; and service interworking, in which an ATM user is connected to a non-ATM user. Functionality and architectural alternatives for network and service interworking are evaluated     

宽带综合业务数字网的ATM技术

目前宽带综合业务数字网(B—ISDN)已成为各国研究与开发的重要内容。本文简述了信息传输技术的发展趋势,着重介绍了ATM技术的概念、ATM信元结构和传输帧结构、ATM交换技术和ATM系统参考模型。