Abstract: A plurality of terminals, each responsive to RR (receive ready) and RNR (receive not ready) messages for respectively enabling and inhibiting the transmission of data packets by the terminal, are coupled to a packet handler via a multiplexed path. In order to limit each terminal to an allocated bandwidth, for each terminal a number is stored representing a number of data bytes which the respective terminal is permitted to transmit within a timed period at its allocated bandwidth, and in each timed period a counter counts down from this number in accordance with the number of data bytes transmitted by the terminal. An RNR message is transmitted to the terminal if and when a zero count is reached, and following such an RNR message na RR message is transmitted to the terminal to enable it for the next time period. The arrangement provides a relatively instantaneous limiting of the bandwidth of each terminal to its allocated bandwidth, and can be applied independently for each direction of transmission.