AT&T DS1/DMi/ISDN-PRI manual Introduction

INTRODUCTION 1-5

Figure 1-1.System 85 R2V4 ISDN Configuration

Generic 2 provides a signaling method called nonfacility-associated signaling (NFAS). NFAS allows a D-channel on one PRI facility (sometimes called a PRI pipe) to provide signaling for B-channels on another PRI pipe. With NFAS, if two or more PRI pipes are present, an optional D-channel backup feature is available. One D-channel is administered as the primary D-channel on one DS1 and the secondary D-channel on another DS1. Only one D-channel per primary-secondary pair can be active at a time. If the primary D-channel fails, the signaling function is switched automatically to the secondary (sometimes called the backup) D-channel. Without D-channel backup, D-channel failure results in loss of service for all calls passing through a PRI pipe.

Generic 2 offers ISDN-BRI, however, some BRI capabilities are not initially available. Figure 1-2,Generic 2 ISDN Network Configuration, shows a Generic 2 switch in a sample network.