ATM网的非连接业务支持方式

ＡＴＭ技术能否在数据通信网中广泛采用取决于其是否能高效地支持现有业务，其中主要为非连接业务。本文介绍了几种基于ＡＴＭ网的非连接业务支持方式和协议体系结构，并分别进行了分析评述。     

ATM局域网仿真技术

ＡＴＭ局域网仿真技术是由ＡＴＭ论坛提出的一种利用ＡＴＭ网络支持数据通信业务的方法。本文首先简介了引入此项技术的背景，继而分析了ＡＴＭ局域网仿真的基本思想以及仿真局域网的协议体系，网络配置，功能单元与连接种类等基本概念，并详细分析了ＡＴＭ局域网仿真中各项协议规程的工作机制。     

ATM业务量管理及其对ATM交换机设计的影响

ＡＴＭ网络允诺为各种通信业务在同一个通信网络中提供满足各自服务质量的要求的服务。为此，ＡＴＭ网络体系应能提供业务量管理（ｕｔａｆｆｉｃ ｍａｎａｇｅｍｅｎｔ）功能以支持网络业务千差万别的服务质量要求。本文首先阐述了ＡＴＭ论坛（ＡＴＭ Ｆｏｒｍ）中所定义的ＡＴＭ业务种类，它们各自的服务质量要求，以及为保证服务质量所应采用的管理策略。ＡＴＭ交换机是网络中的关键部件，其不同的设计思想对网络中不同业务服务     

话音ATM交换的实现——ATM论坛电路仿真系列建议

近年来，随着ＡＴＭ主干网络的建设和发展，研究ＡＴＭ对现有通信业务的支持方式和适配技术是目前ＡＴＭ技术研究的热点之一。话音ＡＴＭ交换在降低话音通信成本和简化网络操作环境等方面提供了大量的技术手段，并且支持在单一网络环境中的多种综合业务传输。ＡＴＭ论坛制定了电路仿真系列建议，话音ＡＴＭ交换的技术已经基本成熟。文章通过对话音ＡＴＭ交换的实现和优化方面的技术进行分析，并提出一种基于ＮａｔｉｖｅＭｏｄｅＡＴ     

ATM业务流控制技术

业务流控制是ＡＴＭ的关键技术之一。业务警管和连接接纳控制构成了ＡＴＭ的业务流控制通过网络和用户共同签订并承诺履许的业务合约实现连接接纳控制，对于不同的业务类型其业务合约参数不同，具有相应的控制机制。业务流控制的国际标准化工作正在积极开展，１－ＴＵ－Ｔ建议的标准为１．３７１。     

接入型ATM交换机中局域网仿真系统的研制

接入型ＡＴＭ交换机广泛应用于校园网或企业网等专网环境中，因而支持局域网数据通信业务是其应具备的主要功能之一。ＡＴＭ论坛提出的局域网仿真技术是目前广泛采用的一种利用ＡＴＭ网络支持数据通信业务的方式。     

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。     

一种利用ABR业务支持多媒体传输的机制

ＡＴＭ 是一种基于信元交换、面向连接的高速技术,其特点就是能够传送任何业务,不管这些业务有什么样的特征（诸如比特率、质量要求、突发特性等）。多媒体是使用ＡＴＭ 提供的高速宽带业务的重要应用。利用可用比特率（ＡＢＲ）业务传输多媒体通讯,可以在保证较高的服务质量同时还能获得较高的网络带宽的利用率。从利用ＡＢＲ业务保证多媒体通讯的服务质量、支持点到多点通讯和多点对点通讯三方面分析了ＡＢＲ业务支持多媒体传输的机制,并给出相应的支持算法     

ATM网支持IP协议的研究

ＡＴＭ网络是面向连接的，而ＩＰ是采用数据报方式的无连接协议。讨论ＩＰ协议数据格式与ＡＴＭ信元格式之间转换方法、ＡＴＭ地址与ＩＰ地址映射方法及利用信令系统建立虚通路连接传输ＩＰ业务的方法。     

ATM在非均匀业务模式下的性能分析

本文通过对各种基于不同缓存结构和技术的ＡＴＭ交换结构在非均匀业务模式下的性能进行分析，揭示了它们在不同业务模式下的性能差别，同时还给出了一种高性能的ＡＴＭ交换网络的设计方法。     

INQIRE: a software approach to monitoring QoS in ATM networks

Unlike traditional best-effort packet networks, ATM networks support a wide range of services by providing a specified QoS on each ATM connection. Currently, QoS can be measured with specialized high-speed testing equipment but their complexity and cost prevent them from wide field use. This article describes the INQIRE project approach based on software for enabling common personal computers (with an ATM network interface card) to function as QoS monitoring stations at the edges of an ATM network. The main objective is to develop a low-cost, off-the-shelf alternative to broadband testing equipment. An INQIRE station, consisting of a PC running the INQIRE application, can actively probe any selected connection and collect sample measurements of the QoS. The monitoring approach is intended to be non-intrusive and work with any ATM network without requiring any modifications to existing ATM switch equipment or interruptions to active services     

Mobility management in wireless ATM networks

Mobile ATM offers a common wired network infrastructure to support mobility of wireless terminals, independent of the wireless access protocol. In addition, it allows seamless migration to future wireless broadband services, such as wireless ATM, by enabling mobility of end-to-end ATM connections. In spite of the diversity in mobile networking technologies (e.g., cellular telephony, mobile-IP, packet data services, PCS), all of them require two fundamental mechanisms: location management and handoff. This article describes different schemes for augmenting a wired ATM network to support location management of mobile terminals and handoff protocols for rerouting a connection data path when the endpoint moves. A prototype implementation of mobile ATM integrating mobility support with ATM signaling and connection setup, is presented. It shows how mobile ATM may be used to provide mobility support to an IP terminal using non-ATM wireless access     

Connection splitting: an efficient way of reducing call blocking inATM

In this paper, we propose a technique for reducing asynchronous transfer mode (ATM) call blocking which is achieved by splitting wide-band connections into multiple low-bandwidth subconnections and routing them independently through the network. The essence of the mechanism is to use fragmented network bandwidth for supporting calls which are otherwise blocked by conventional routing. ATM bandwidth fragmentation may take place in a situation when a connection occupies a part of a link bandwidth and the rest of it is not sufficient for another connection. The unused bandwidth becomes fragmented. We provide a detailed cell-level design for the split-scheduling algorithms, which use a special type of ATM resource management cell for maintaining cell ordering. The analysis and simulation of the scheduling algorithms show that connection splitting is capable of delivering acceptable cell-level quality of service to multiple traffic classes. We also deliver a solution for implementing splitting without requiring any protocol changes within the network. We show that it is sufficient to modify the data and control plane protocols only within the end stations. Finally, a set of routing-level simulations for splitting demonstrates that splitting can reduce blocking by up to 45% for high-bandwidth calls in a moderately loaded network. Considering that it does not incur any network expenses or protocol changes, we propose splitting as an efficient means for reducing connection blocking     

Architecture design for ATM statistical multiplexers

Both high-speed packet switches and statistical multiplexers are critical elements in the ATM (asynchronous transfer mode) network. Many switch architectures have been proposed and some of them have been built, but relatively fewer statistical multiplexer architectures have been investigated to date. It has been considered that multiplexers are a special kind of switches which can be implemented with similar approaches. The main function of a statistical multiplexer, however, is to concentrate traffic from a number of input ports to a comparatively smaller number of output ports; ‘switching’ in the sense that a cell must be delivered to a specific output port is often not required. This implies that the channel grouping design principle, in which more than one path is available for each virtual circuit connection, can be applied in the multiplexer. We show that this technique reduces the required buffer memory and increases the system performance significantly. The performances of three general approaches for implementing an ATM statistical multiplexer are studied through simulations with various bursty traffic assumptions. Based on the best performing approach (sharing output channels and buffers), we propose two architecture designs to implement a scalable statistical multiplexer that is modularly decomposed into many smaller multiplexers by using a novel grouping network.     

Implementing integrated and differentiated services for theInternet with ATM networks: a practical approach

This article reports on design, implementation, and preliminary experimentation of a network architecture that supports quality of service for Internet applications. It gives an overview of the various approaches toward communication networks that support application-specific degrees of QoS. Special emphasis is put on the integrated and differentiated services approaches and on combinations of them. A new architecture is described which aims to bring these concepts closer to practical realization in wide-area networks. The new architecture supports the integrated as well as differentiated services approaches in a smoothly integrated way, and uses the capabilities of an underlying ATM network to realize QoS. The enhancements to the existing network infrastructure are deliberately limited to the integration of a single new type of network element called an edge device. The potential benefits of such an architecture for various stakeholders are explained, and how the new architecture could be introduced smoothly in existing networks by small migration steps, also covering networks based on technologies other than ATM. It is shown that the approach can be scaled up to a very large QoS-aware overlay network for the Internet     

An evolvable ATM-based video network design supporting multipleaccess network technologies

This article describes an overall video network architecture with primary focus on the ATM subnetwork. The ATM subnetwork provides efficient switching capability for providing constant bit rate and variable bit rate video communication services. The ATM subnetwork can support multiple access networks like hybrid fiber coax (HFC), asymmetric digital subscriber line (ADSL), and fiber to the curb (FTTC). A broadband network controller is presented as the external controller for the ATM subnetwork which performs the functions of the session/network manager and the ATM-based connection management. The initial deployment of video is likely to be permanent virtual connection (PVC)-based, so a dynamic PVC-based scenario is described. The ATM switch architecture presented here has been optimized to support video applications. An evolution to the switched virtual connection environment and support of multiple services over the ATM subnetwork is also addressed. Traffic management schemes are discussed which provide the negotiated quality of service to the connections     

Asynchronous transfer mode security

It is envisioned that asynchronous transfer mode (ATM) will provide scalable and high-performance application-independent security services. The ATM Forum Security Working Group is currently developing its phase one security specification, which defines a number of security services for the ATM user plane and control plane. In addition, mechanisms for carrying security-related messages and required security infrastructure mechanisms are also being defined. These mechanisms will allow an organization to build an ATM network which not only meets its performance objectives, but also its information protection requirements as specified in its site security policy. This article provides an overview of ATM security as specified by the ATM Forum Security Working Group. First, the ATM user and control planes' security services and mechanisms are described. Then the security messaging mechanisms at connection establishment and during the connection lifetime phases are discussed     

ATM in MPLS-based converged core data networks

Services supported by asynchronous transfer mode account for the majority of data and Internet service revenues generated by carrier networks today. This is based on ATM's ability to support high availability services with quality of service. However, the influences of the Internet and a highly dynamic telecommunications market have raised demands for increased flexibility while controlling costs. Therefore, future carrier networks are likely to continue to be based on established technologies, such as ATM, as well as IP. In many cases, this is achieved through maintaining separate ATM and IP core networks, with the IP network supporting Internet services, while the ATM network continues to support guaranteed services such as private lines, broadband access, and video. In some cases, however, it can be advantageous for a carrier to transport segments of their ATM network over their IP network core; for example, to transport ATM traffic currently carried on leased facilities onto an IP network where the service provider owns the facilities. Developments in IP and MPLS-based traffic engineering and QoS may increase the ability of IP-based networks to support ATM services using MPLS. This article provides an overview of approaches enabling a network based on MPLS that naturally supports IP services to also support ATM services. The drivers and requirements for convergence on an IP/MPLS core network are presented, followed by an overview of the different approaches and associated challenges currently being debated in the standards bodies.     

Survey of switching techniques in high-speed networks and their performance

One of the most promising approaches for high speed networks for integrated service applications is fast packet switching, or ATM (asynchronous transfer mode). ATM can be characterized by very high speed transmission links and simple, hard-wired protocols within a network. To match the transmission speed of the network links, and to minimize the overhead due to the processing of network protocols, the switching of cells is done in hardware switching fabrics in ATM networks. A number of designs have been proposed for implementing ATM switches. Although many differences exist among the proposals, the vast majority of them are based on self-routeing multistage interconnection networks. This is because of the desirable features of multi-stage interconnection networks such as self-routeing capability and suitability for VLSI implementation. Existing ATM switch architectures can be classified into two major classes: blocking switches, where blockings of cells may occur within a switch when more than one cell contends for the same internal link, and non-blocking switches, where no internal blocking occurs. A large number of techniques have also been proposed to improve the performance of blocking and non-blocking switches. In this paper, we present an extensive survey of the existing proposals for ATM switch architectures, focusing on their performance issues.