Broandband Integrated Services Digital Network (BISDN or Broadband ISDN) is designed to handle high-bandwidth applications. BISDN currently uses ATM technology over SONET-based transmission circuits to provide data rates from 155 to 622Mbps and beyond, contrast with the traditional narrowband ISDN (or N-ISDN), which is only 64 Kbps basically and up to 2 Mbps.
The designed Broadband ISDN (BISDN) services can be categorized as follows:
- Conversational services such as telephone-like services, which was also supported by N-ISDN. Also the additional bandwidth offered will allow such services as video telephony, video conferencing and high volume, high speed data transfer.
- Messaging services, which is mainly a store-and-forward type of service. Applications could include voice and video mail, as well as multi-media mail and traditional electronic mail.
- Retrieval services which provides access to (public) information stores, and information is sent to the user on demand only.
- No user control of presentation. This would be for instance, a TV broadcast, where the user can choose simply either to view or not.
- User controlled presentation. This would apply to broadcast information that the user can partially control.
The B-ISDN is designed to offer both connection oriented and connectionless services. The broadband information transfer is provided by the use of asynchronous transfer mode (ATM), in both cases, using end-to-end logical connections or virtual circuits. Broadband ISDN uses out-of-band signaling (as does N-ISDN). Instead of using a D Channel as in N-ISDN, a special virtual circuit channel can be used for signaling. However, B-ISDN was not widely deployed so far.
Protocol Structure
Broadband ISDN protocol reference model is based on the ATM reference model
Broadband ISDN: Broadband Integrated Services Digital Network (BISDN)
ATM adaptation layer (AAL). This layer is responsible for mapping the service offered by ATM to the service expected by the higher layers. It has two sublayers.
ATM Layer. This layer is independent of the physical medium over which transmission is to take place. It has those functions: Generic flow control (GFC) function, Cell header generation and extraction, Cell multiplex and demultiplex.
Physical layer. This consists of two sublayers: Transport Convergence (TC) and Physical medium (PM)
The management plane consists of two functions to perform layer management and plane management. The plane management is not layered as the other layers are. This is because it relies needs information on all aspects of the system to provide management facilities for the systems as a whole. The layer management provides information and control facilities for the protocol entities that exists in each individual layer. This includes operation and maintenance (OAM) functions for each layer.
The control plane is responsible for the supervision of connections, including call set-up, call release and maintenance.
The user plane provides for the transfer of user information. It also includes mechanisms to perform error recovery, flow control etc.
Related protocols: ISDN, ATM, B-ICI
Sponsor Source: ISDN protocol is defined by ITU-T.
Reference: http://www.cs.ucl.ac.uk/staff/S.Bhatti/D51-notes/node35.html: Broadband ISDN.