ISDN made the first real attempt at bringing services such as voice/videoapplications to end subscriber premises. B-ISDN is directly related toAsynchronous Transfer Mode (ATM) and is discussed in Chapter 10, "ATM andB-ISDN." BRI and PRI are deployed overwhat are considered to be narrowband circuits, ranging from 16 kbps of a 64-kbpsdigital signal 0 (DS0), to a 2.048-Mbps circuit. The N-ISDN offerings are what this chapterfocuses on, and they include BRI and PRI services.
Originally, ISDN was developed as two separate types of service, N-ISDN(narrowband) and B-ISDN (broadband). Although manydigital services are available today, ISDN offers some unique features that willsolidify its place in telecommunication for years to come. Modern telecommunication technologies are based on digital principles forreasons of flexibility, efficiency, and feature capability. In today's market, these features havebecome more and more prevalent, and because of that something had to be designedthat could handle these functions. The analog infrastructure was never designed to provide voice, video, anddata integration for customers. This amplification also increases the noisecontent. Remember that when analog circuits become too attenuated,the signal is merely amplified. Analog services are acceptable in short distances,but they simply can't provide the quality of service (QoS) and bandwidthover the long haul. In the days of old, the service providers infrastructure was deployed as aseries of analog services. PRIThis section describes the operation of primary ratecircuits and how they are deployed around the world. It covers bothline-coding schemes and deployments. This section isintended to give you an in-depth view on how ISDN works.īRIThis section details how BRI circuits operate and howthey are deployed in North America, Europe, and Japan. ISDN specificationsThis section describes the different ISDNspecifications and how they operate in the ISDN network. ISDN networkThis section introduces you to the physicalattributes of the ISDN network and how ISDN circuits are typically deployed.Both Basic Rate Interfaces (BRIs) and Primary Rate Interfaces (PRIs) aredetailed and the associated ISDN reference points. Integrated Services Digital Network (ISDN) introductionTheintroduction is geared towards explaining the development and progress of ISDNas a digital network structure.
This chapter covers the following topics: