British Telecommunications Plc’s efforts to expand beyond its telephone roots took a step forward last week when the company announced a pilot project for the UK’s first national Asynchronous Transfer Mode service. Entitled CellStream, the service is initially being tested by the Halifax Building Society Plc. CellStream, which British Telecom maintains has had most interest from the information technology, higher education, finance, manufacturing and media sectors, will be extended to the US later this year to interconnect with MCI Communications Corp’s HyperStream ATM service. CellStream is based on a series of ATM switches deployed in major business and commercial centers, to provide transport of ATM cells on a point-to-point virtual connection basis. Customers can choose between a 34Mbps or 155Mbps service, while retaining the ability to configure further virtual circuits within each access rate. CellStream can be tailored to match the bandwidth needs of individual applications. It offers two classes of service; Constant Bit Rate, CBR and Variable Bit Rate, VBR to cope with applications having differing synchronization and end-to-end timing. Constant Bit Rate is usually recommended for time-critical and bandwidth intensive applications such as full-time video, while Variable Bit Rate can be used for applications where timing is not critical, such as local network interconnect. British Telecom has also launched its international Switched Multi-Megabit Data service, SMDS offering connection between its national SMDS service and those of overseas carriers – initially with Telecom Eireann in Ireland, and MCI in the US. Through MCI, the British Telecom service will connect to other US SMDS networks operated by local exchange carriers.
