The increasing stability of the user plane within the CCITT recommendations for B-ISDN and the wide applicability of the B-ISDN `ATM-layer' specification to all types of ATM system enables the definition and implementation of ATM interface ASICs. The ever falling cost of VLSI implies that a variety of interface controllers for ATM end systems will become available.
Users of private ATM LANs can employ an approach, such as MSNA, where the simple semantics of an end-to-end virtual circuit enable users to insulate themselves from variations in B-ISDN specifications. Heterogeneous styles of ATM network, including B-ISDN, proprietary ATM LANs and mobile optical and radio ATM systems, may inter-operate provided each is able to offer the basic ATM layer service of shipping 48 byte cell payloads (plus the bit in the header) without miss-ordering, along a virtual circuit. For signalling, one requires entities which perform signalling adaptation, from one signalling domain or protocol to another. These entities have no in-band presence and so do not introduce a restriction for data throughput. Local islands of heterogeneous ATM technology will achieve wide-area interconnection using the empty adaptation layer offered by B-ISDN [8].