BISDN is an extension of ISDN, that is, it has narrowband capability of ISDN but also the broadband capability.
The purpose of BISDN is to achieve complete integration of services, ranging from low-bit- rate burst signals to high-bit-rate continuous real-time signals.
There are two types of B-ISDN services which are as follows −
Interactive Services − Two-way exchange of information (other than control signalling information) between two subscribers or between a subscriber and a service provider.
Distribution Services − Primarily one way transfer of information, from service provider to B-ISDN subscriber.
These services are shown in the diagram format below −
The key technology developments for B-ISDN are as follows −
Optical fiber transmission systems that can offer low-cost, high-data rate transmission channels for network trunks and subscriber lines.
The Microelectronic circuits which offer high-speed, low-cost building blocks for switching, transmission, and subscriber equipment.
High-quality video monitors and cameras that have sufficient production quantities are offered at low cost.
The B-ISDN architecture is shown in the diagram below −
The architecture of the B-ISDN includes low Layer capabilities and high Layer capabilities. These capabilities support the services within the B-ISDN and other networks by means of interworking B-ISDN with those networks.
The low layer capabilities of B-ISDN architecture are explained below −
From the functional capabilities of the B-ISDN, as shown in Figure, the information transfer capabilities require further description.
Broadband information transfer is provided by an ATM at the B-ISDN user-network interface (UNI) and at switching entities inside the network.
The high layer capabilities of B-ISDN architecture are explained below −
Normally, the high Layer functional capabilities are involved only in the terminal equipment.
The support of some services, provision of high layer functions could be made through special nodes in the B-ISDN belonging to the public network or to centres operated by other organizations and accessed via B-ISDN user-network or network node interfaces (NNIs).