Input/output of network switches and the like are improved by a system including a gearbox, an inverse-gearbox, and a Gigabit Ethernet link coupling them. The gearbox and inverse-gearbox interconnect data streams received through wider lower rate Gigabit Ethernet interfaces through narrower faster rate interfaces. The gearbox is configured to bit-multiplex physical-layer data streams received through input interfaces to generate bit-multiplexed data streams. The inverse-gearbox is configured to demultiplex the multiplexed data streams and to output the recovered data streams through output interfaces. One of the output interfaces is selected for each recovered data stream according to a respective embedded physical-layer data stream identifier.