A data communication system such as a local area network or a wide area network capable of transmitting isochronous data. The system conveys both isochronous data and non-isochronous data by time multiplexing data into a recurring frame structure on a 4-bit nibble basis. The arriving data is de-multiplexed at a hub into separate channels which are forwarded to separate hardware appropriate for handling the particular data stream. The data is passed hierarchically from a source, through a node, and to a hub. The hub places the data into an internal connection memory for switching onto a high bandwidth bus for distribution to other destination hubs, nodes, or sinks, except, where the source node and destination node are attached to the same hub, the hub provides a local loopback to the destination node, thus avoiding the need to place the transmitted data onto the bus. This system conserves room on the bus for other isochronous and non-isochronous data.