Digital communication between computers and their users has until now been provided by exploiting the telephone network to carry digital data because of the wide coverage of the telephone network and the high capital cost of establishing any new, generally-available telecommunication service. In the long run it is expected that a specialized digital communication network will be required, designed around the requirements of computer services which interact in ‘real-time’ with their remote users. The system design of the proposed new network is outlined and some estimates of performance are given.