Chapter9.ISDN Technology Background

Chapter 9. ISDN Technology Background

ISDN was developed by telephone companies (telcos) as an end-to-end out-of- band digital technology well suited for data, voice, and video streams. Connectivity over ISDN offers end users increased bandwidth, reduced call setup time, reduced latency, and gave a lower signal-to-noise ratio (SNR). Being a dialup service (fast dial is another name for ISDN), the technology carries digital signaling. In the United States, the ISDN definitions are described in National ISDN standards (NI) to ensure interoperability between a variety of services and providers. The standard defines architecture layers , services, protocols, channels, reference points, and devices. The main topics of this chapter are as follows :

• ISDN standards, ISDN channels, and ISDN layered architecture

• Layer 1, Basic Rate Interface (BRI)

• ISDN devices, reference points, and interfaces

• Layer 2 in D channel Link Access Procedure on the D channel (LAPD)

• Layer 3 in D channel Q.931

• ISDN switch types