Broadband-ISDN standardization - state of the art

Abstract

Broadband-ISDN (B-ISDN) is the wide-area network of the future. Its Asynchronous Transfer Mode (ATM) supports both transmission and switching with a unique concept: the ‘cell’. The use of ATM is evolving in the public as well as in the private domain. It also more and more captures lower bit rate interfaces down to about 2 Mb/s. Right from the beginning, B-ISDN standardization has taken into account the portation of existing applications and protocols to B-ISDN. This is supported by a specific layer, the ‘ATM Adaptation Layer’, introduced in the B-ISDN Protocol Reference Model for the adaptation between ATM characteristics and the requirements of higher layer protocols. B-ISDN aims at the flexible and dynamic support of varying communication requirements. ATM is suited to transfer constant and variable bit rate data streams in a unique way. Additionally, this aim is reflected in the separate handling of calls - communication relationships - and connections - data streams with specific characteristics - within a call. Special connections are used for the management of calls and connections. The characteristics of these ‘signalling connections’ can also be adapted to the amount of signalling information transferred.