The Asynchronous Transfer Mode (ATM) and the switches and other network elements based on this principle have matured significantly over the past few years. Extensive field trials have been successfully performed all over the world and an increasing number of operators is starting to offer regular services based on ATM infrastructures. The general trend towards deregulation and liberalization resulting in an increasing competition among network providers world wide creates a strong push towards flexible, high-performance, cost effective infrastructures for data, voice, video and multimedia communication. ATM has the potential to provide the universal platform for this future B-ISDN because it combines the features of classical telecommunication networks with features required to cope with the increasing demand for computer based communication. Therefore, ATM allows a consolidation of all existing, dedicated networks for the various services onto a common network platform and at the same time provides a solid and future proof basis for new services and applications. To make this ATM-based multiservice platform a favorable option for large wide area networks, the reliability known from the classical voice networks has to be provided in addition to a virtually unlimited scaleability of the switching systems and of the network as a whole. Whereas the support of permanent connections, i. e. the application of simple VP-crossconnects, was adequate for the first trial networks, on-demand connections controlled by powerful signaling systems have to be provided in the future broadband networks. Moreover, the rather simple resource allocation and traffic management functions used in the first ATM networks have to be extended to be able to guarantee an application specific quality of service while optimizing the use of the available network resources and, thus, to be able to fully exploit the inherent capabilities of the ATM principle. Another crucial point for the success of the ATM multiservice platform is the efficient interworking with existing networks, especially with the narrowband ISDN, the Frame Relay or SMDS based public data networks and with TCP/IP based Internets. This paper describes a new generation ATM switch which fully exploits the capabilities of todays technology to implement the full functionality necessary to cope with these requirements. It introduces the basic architectural concepts, the functionality and some implementation aspects of this large, highly reliable ATM switch which has been specifically designed for application in the core of a future B-ISDN. Special emphasis is put on the concept and realization of the switch fabric which can be scaled from a few Gbit/s into the Tbit/s range.