Apparatus and method for routing data in a switch

A method for routing data to be performed by a switch, the method comprising:

• receiving, by an input port of the switch, a data packet that is to be routed to a destination node;
• identifying, by route lookup circuitry of the switch, a first plurality of output ports that are available to route the data packet to the destination node;
• selecting, by the route lookup circuitry of the switch based on first congestion information associated with individual output ports of the first plurality of output ports at a first time point prior to the data packet being buffered in an input queue of the switch, a subset of the first plurality of output ports to be included in a second plurality of output ports;
• and
• selecting, by route selection circuitry of the switch based on second congestion information associated with individual output ports of the second plurality of output ports at a second time point after the data packet is buffered in the input queue, a destination output port to which the data packet is to be routed by the switch, wherein the second congestion information is different from the first congestion information.

A computing system comprising:

• a plurality of processors;
• a switch coupled to the plurality of processors to route data between the plurality of processors, the switch comprising:
• an input port to receive an adaptive data packet and an associated destination local identifier (DLID) to indicate a destination node for the data packet;
• route lookup circuitry coupled to the input port, the route lookup circuitry to:
• determine a first set of output ports including a plurality of output ports that are available to send the data packet to the destination node;
• obtain first congestion information associated with the output ports of the first set of output ports;
• and
• select, from the output ports of the first set of output ports, a plurality of output ports for a second set of output ports based on the first congestion information, the second set of output ports to include a subset of the output ports of the first set of output ports;
• an input queue coupled to the route lookup circuitry, the input queue to, after the selection of the plurality of output ports for the second set of output ports, store the data packet and route information to identify the output ports of the second set of output ports;
• and
• route selection circuitry coupled to the input queue, the route selection circuitry to:
• obtain, after storage of the data packet and route information by the input queue, second congestion information associated with the output ports of the second set of output ports, wherein the second congestion information is different than the first congestion information;
• and
• select, from the second set of output ports based on the second congestion information, a destination output port to which to route the data packet.