Chapter 9. Asynchronous Transfer Mode (ATM) Introduction

The following topics are covered in this chapter:

• ATM Wide Area Networks (WANs)

• ATM WAN Interfaces

• ATM Connections

• Virtual Paths

• Cell Transmission

• ATM Traffic Parameters

• ATM Service Classes

• Quality of Service (QoS) Parameters

• ATM WAN Architecture

• ATM Traffic Contract and Negotiation

Many enterprise customers and some service providers consider Asynchronous Transfer Mode (ATM) a mature, legacy technology. ATM supports the need for a low-cost wide-area networking (WAN) alternative to point-to-point, high-bandwidth, dedicated services. In addition to providing dedicated point-to-point services, ATM also enables switch-to-switch trunking, which supports legacy Time Division Multiplexed (TDM) Private Branch Exchange (PBX) networks, and public circuit switching networks used to support public switch telephone network (PSTN) voice services.

ATM is primarily used in the areas of a network service provider's (NSP's) WAN core and for inter-networking services provided to enterprise customers. Today, most service providers are migrating away from future deployments of ATM technologies or attempting to augment their existing ATM networks with incremental investments in related Edge, IP, and MPLS technologies.

There is much complexity and many concepts and acronyms to learn within ATM technologies. This chapter discusses these ATM concepts, acronyms, and technologies.

ATM is the most widely implemented network backbone technology in the NSP market. ATM is an Open System Interconnection (OSI) standards-based transport medium and is widely used within the core (network backbone) and the network access edge, enabling data, video, and voice communication at high (broadband) speeds. Although ATM WANs often are found in service provider backbones, with the rise in converged voice and data broadband applications, ATM also can be found in the large enterprise space.