A high-speed data communication service such as inter-LAN is one of many services possible with ATM-based B-ISDN. Design objectives were to simplify the connection setup procedure, to ensure efficient utilization of network capacity, and to reduce delay in servers. These objectives were met in a B-ISDN service trial system featuring distributed connectionless servers connected by permanent virtual channels and cell-by-cell processing in the connectionless server. The system's eight connectionless servers accommodate up to 256 subscriber network interfaces. The authors discuss how multicast can be provided in ATM-based connectionless data networks for inter-LAN communications. Four possible configurations, distinguished by copy function (multicast/broadcast) and on functional arrangement in the inter-connectionless server network (centralized/distributed), are presented. The configurations are compared from perspectives of required hardware and network capacity. The distributed broadcast function is shown the most reasonable solution.

ATM's bandwidth flexibility and high switching speed advantages have made it the preeminent solution to the B-ISDN. However, networks based on ATM suffer from phenomena not encountered in the STM network, e.g., cell loss, and cell jitter. For ATM to support varied media, problems arising from these phenomena must be resolved. This paper discusses techniques which enable ATM to support CBR, VBR voice, VBR video, and connectionless services. We determine the problems to be resolved for each service and discuss solutions. We focus on dejittering and clock recovery for CBR service, on talk-spurt synchronization for VBR voice, and on video frame synchronization and lost-cell compensation for VBR video service. We show experimental results for a prototype HDTV codec and terminal adapter. For connectionless service, we show that connectionless service should be supplied by the B-ISDN itself using message handlers which support message routing and addressing, i.e., connectionless service functions (CLSF), as described by the CCITT. We propose a network topology of message handlers, which reduces the routing database and avoids transit message handler overload. We show an example of system configuration for connectionless service.