Optical Network Design and Implementation

ISDN

Integrated Services Digital Network (ISDN) is a digital system that allows voice and data to be transmitted simultaneously using end-to-end digital connectivity. ISDN allows multiple digital channels to be transmitted simultaneously over the same wiring infrastructure used for analog lines. Two kinds of channels are defined in ISDN. The B channel or bearer channel carries user traffic, whereas the D channel or data channel carries CCS signaling data. The bandwidths of B channels are 64 kbps. Some switches limit B channels to a capacity of 56 kbps. The D channel handles signaling at 16 kbps or 64 kbps, depending on the service type. Original recommendations of ISDN were in Consultative Committee for International Telegraph and Telephone (CCITT) ...