Abstract: A service multiplexer (2) for connecting a plurality of signal sources to a public switched communication network transfers data in the form of a synchronously transferred data cells from a plurality of inputs (4) to an output (6) for connection to the network. The multiplexer (2) includes a bandwidth control unit which receives a bandwidth control signal from the network representative of available bandwidth for transmission of cells to the network and generates feedback control signals for transmission to the signal sources to cause them to alter their data transmission rates in accordance with the available bandwidth. An activity detector coupled to the bandwidth control unit monitors the bandwidth of data received at the inputs. The multiplexer allows ABR (available bit rate)—commandable signal sources to be linked to a single port of a public network operating on an ABR basis to provide an efficient and fair allocation of bandwidth for each source.

Abstract: A network for ATM signals includes source end systems SES1, SES3 connected by a permanent virtual connection PVC1 through switch SW1 . . . SWN. Dynamic bandwidth controllers DBC1, DBC2 operate as virtual source/virtual destinations. The individual switches, such as switch SW2 have associated rate controllers RC1 which determine the available bandwidth for the signal path PVC1. Dynamic bandwidth controller DBC1 interrogates the rate controller RC1, RC2 using resource management RM signals which cascade from switching node to switching node along the path in a forward direction and then in a backward direction. The DBC's communicate with the SES's using RM signals which may be of a different format to the RM signals which pass from switching node to switching node.