ATM technology: a backbone for high speed computer networking

Abstract

The use of data communication equipment in local environments is increasing rapidly. Applications such as electronic mail, file transfer, CAD/CAM, etc., currently result in the installation of more and more LANS in offices. Since the industry becomes more and more located at different places worldwide, the interconnection of these LANs becomes more and more a requirement. With the increasing number of applications, higher and higher bit rates are required at those interconnections. Different solutions exist to connect these LANs. Most of them are based on B-ISDN tecniques, using the ATM (Asynchronous Transfer Mode) cell relay principle. The first solution, which is initially applicable in a metropolitan area is based on the MAN (Metropolitan Area Network) technology as standardized by IEEE 802.6. It is based on the DQDB (Distributed Queue Dual Bus) principle, and offers to the customer both high speed data interconnectivity and isochronous services. To cover larger areas than metropolitan ones, MANs can be connected by high speed leased lines, or by an ATM backbone network. An alternative solution, but with some complementarity to MANs, is called an ATM crossconnect network. This solution offers to the customers semi-permanent high speed connectivity. This solution can also be used as an enhancement to MANs, to provide a backbone to connect multiple MANs. Such an ATM crossconnect network can be enhanced with a connectionless server, to offer to the customers full international high speed data connectivity. Both solutions use the ATM transfer mode of B-ISDN and thus allow a gradual evolution to the full B-ISDN, in which each service can demand dynamically its virtual connection (or multiple virtual circuits for multimedia services). To ensure a worldwide connectivity, all involved telecommunication operators have to plan the necessary coordination.