Reservation-based switching devices

A method of switching packets in a switching device, the switching device comprising a plurality of interconnected sub-switches forming an internal network of the switching device and each sub-switch comprising a switch controller, comprising:

• receiving a packet at a particular external input port of a first sub-switch of the plurality of interconnected sub-switches, wherein the first sub-switch is associated with and coupled to a first switch controller;
• determining, by the first switch controller, a particular external output port of a second sub-switch of the plurality of interconnected sub-switches to which the packet is to be routed, wherein the second sub-switch is associated with and coupled to a second switch controller, wherein the second sub-switch has an output queue corresponding to the particular external output port, wherein the first switch controller is coupled with the second switch controller via a reservation bus, and wherein the first sub-switch and second sub-switch are coupled via a data link that is different from the reservation bus;
• sending, by the first switch controller of the first sub-switch via the reservation bus to the second switch controller, a request to reserve a space for the packet in the output queue corresponding to the particular external output port;
• and
• routing, by the first switch controller of the first sub-switch, the packet to the particular external output to occupy the reserved space for the packet in the output queue.

A non-transitory machine readable storage medium having stored thereon machine readable instructions to cause a computer processor of a first switch controller of a first sub-switch of a plurality of interconnected sub-switches, to:

• in response to reception of a packet at an external input port of the first sub-switch, determine a particular external output port of a second sub-switch of the plurality of interconnected sub-switches to which the packet is to be routed, the plurality of interconnected sub-switches forming an internal network of the switching device, wherein the second sub-switch is associated with and coupled to a second switch controller, wherein the second sub-switch has an output queue corresponding to the particular external output port, wherein the first switch controller is coupled with the second switch controller via a reservation bus, and wherein the first sub-switch and second sub-switch are coupled via a data link that is different from the reservation bus;
• sending, by the first switch controller of the first sub-switch via the reservation bus to the second switch controller, a request to reserve a space for the packet in the output queue associated to the particular external output port;
• and
• in response to reception of an acknowledgement for the reservation from the second sub-switch, route the packet on the internal network to the particular external output to occupy the reserved space for the packet in the output queue.