1.1 Introduction

Spiraling demand for transparent, affordable, and dependable access to media-rich Web-based voice, data, and video services contributes to persistent usage of Integrated Services Digital Network (ISDN) applications in the present-day networking environment. Also known as Narrowband ISDN (N-ISDN), ISDN supports digital transmission over ordinary twisted copper wire pair traditionally used for telephone service.

Distinguished by its projected ability to facilitate worldwide connectivity via the in-place twisted copper wireline infrastructure, ISDN technology was widely promoted by the communications industry as a universal global transport solution during the 1970s and 1980s. At that time, however, affordable, dependable, compatible, and easily implemented ISDN services for small business and residential networks were not readily available from telecommunications carriers, vendors, and equipment manufacturers.

By the 1990s, competitive residential and small business solutions based on DSL (Digital Subscriber Line) and wireline and wireless cable network technologies outpaced ISDN implementations at SOHO (Small Office/Home Office) venues and small-sized business establishments. In addition, ISDN implementations were also overshadowed by multiservice, high-capacity, high-performance broadband solutions based on ATM (Asynchronous Transfer Mode) technology.

As a consequence, ISDN is not currently viewed as a worldwide platform for provisioning access to voice, video, and data services over the local loop. Nonetheless, commitment to ISDN utilization in residential venues and in sectors that include education, medicine, and business is reflected in continued ISDN deployments. The primary attraction of ISDN in the present-day marketplace is its ability to provision affordable video, audio, and data services and dependable throughput over the same twisted...