How Integrated Services Digital Network Works?
ISDN is a broadband service provides end to end digital communication for high speed data supporting voice, video and multimedia applications. Broadband as compare to Baseband is a type of service that supports logical channels. ISDN BRI and ISDN PRI are two services of ISDN technology used worldwide. The ISDN BRI (Basic Rate Interface) offers two B channels and one D channel (2B+D). BRI B-channel service operates at 64 kbps and is meant to carry user data; BRI D-channel service operates at 16 kbps and is meant to carry control and signalling information, although it can support user data transmission under certain circumstances. The D channel signalling protocol comprises Layers 1 through 3 of the OSI reference model. BRI also provides for framing control and other overhead, bringing its total bit rate to 192 kbps called isdn 2. The BRI physical-layer specification is ITU-T formerly the CCITT 1.430. ISDN PRI (Primary Rate Interface) service offers 23 B channels and one D channel in so
