Abstract: A broadband telecommunications switch (1), for switching packets of data received on a plurality of input ports (5) to plurality of bandwidth limited output ports (10), comprising for each input port (5) a control processor (22) which operates to send request data for each of a plurality of switching periods to each output port (10), which request data is representative of a requirement for communications bandwidth from said output ports (10) sufficient to accommodate packets of data received at said input ports (5) for switching to said output ports (10) for the switching period. Each of said bandwidth allocators (24) responds to said request data by generating bandwidth allocation data appertaining to an allocation of a share of the bandwidth of the output port (10) to the input port (5), which share of bandwidth said input port (5) uses to switch data from said input ports to said output ports during said switching period.

Abstract: A broadband telecommunications system comprises at least one broadband telecommunications switch, and a data transmitter coupled to the broadband telecommunications switch and to each of a plurality of data sources. The system operates to communicate date from the data sources to destinations in the form of a plurality of cells, the communication being arranged to satisfy predetermined transmission parameters. The transmission parameters include an initial cell rate representative of a maximum rate at which data from the data sources may be initially communicated to the telecommunications switch, when the sources become active.

Abstract: An apparatus for queuing and scheduling ATM cells across an ATM switch comprises sustainable cell rate calendar connected in series with a peak cell rate calendar wherein cells are scheduled independently in each. The sustainable cell rate calendar guarantees the maximum ATM cell delay is not exceeded. The ATM cells are not placed on the peak cell rate calendar unless the peak cell rate threshold might be exceeded. In this case the cell is scheduled on the peak cell rate calendar and it is this that determines when the cell is sent. In this way, it is possible to guarantee absolute minimum and maximum cell rates of a connection.

Abstract: AN ATM communication system having both dynamic bandwidth allocation capability comprising storage mechanism for DBA traffic, the storage mechanism further including dedicated storage mechanism for ABR traffic. The system being such that ABR bandwidth requests are allocated after all other DBA bandwidth allocations have been satisfied. A device for interrupting an ABR transmission, before a bandwidth allocation within which the said ABR transmission is included has been fully used, for the transmission of other higher priority DBA traffic is provided.