Switching via an interconnection network
The switching techniques overcome the bandwidth limitation of a single shared bus. This technique use a more sophisticated interconnection network such as those that have been used in the past to inter connect processor in a multiprocessor computer architecture.
A crossbar switch is an interconnection network consisting of 2 N buses that connect N input ports to N output ports as shown in figure. A packet arriving at an input port travels along the horizontal bus attached to the input port until it intersects with the vertical bus leading to the desired output port. If the vertical bus leading to the bus output port is free the packet is transferred to the output port. If the vertical bus is being is used to transfer a packet from another port to this same output port. The arriving packet is blocked and must be queued at the input port.