Technologies for efficiently determining a root of congestion with a multi-stage network switch

One or more machine-readable storage media comprising a plurality of instructions stored thereon that, in response to being executed, cause a network switch to:

• operate arbiter units in an upstream stage at a packet transfer rate that is greater than a packet transfer rate of an arbiter unit in an output stage;
• determine whether an input buffer of a remote network switch in communication with the arbiter unit in the output stage has sustained congestion indicative of an inability to transfer packets from the arbiter unit in the output stage over a first predefined time period;
• determine whether an output buffer of the arbiter unit in the output stage has sustained congestion indicative of an inability to transfer packets from one or more arbiter units in the upstream stage over a second predefined time period;
• determine, as a function of whether the input buffer of the remote network switch has sustained congestion and whether the output buffer of the arbiter unit in the output stage has sustained congestion, whether the network switch is a root of congestion;
• and
• request, in response to a determination that the network switch is the root of congestion, that one or more input sources to the network switch reduce a throughput to the network switch.

A network switch for determining a root of congestion, the network switch comprising:

• circuitry for operating, a plurality of arbiter units configured in a hierarchy of stages including an output stage and an upstream stage, the arbiter units in the upstream stage at a packet transfer rate that is greater than a packet transfer rate of the arbiter unit in the output stage;
• means for determining whether an input buffer of a remote network switch in communication with the arbiter unit in the output stage has sustained congestion indicative of an inability to transfer packets from the arbiter unit in the output stage over a first predefined time period;
• means for determining whether an output buffer of the arbiter unit in the output stage has sustained congestion indicative of an inability to transfer packets from one or more arbiter units in the upstream stage over a second predefined time period;
• and
• means for determining, as a function of whether the input buffer of the remote network switch has sustained congestion and whether the output buffer of the arbiter unit in the output stage has sustained congestion, whether the network switch is a root of congestion.

A method for determining a root of congestion, the method comprising:

• operating, by a network switch that includes a plurality of arbiter units configured in a hierarchy of stages including an output stage and an upstream stage, the arbiter units in the upstream stage at a packet transfer rate that is greater than a packet transfer rate of the arbiter unit in the output stage;
• determining, by the network switch, whether an input buffer of a remote network switch in communication with the arbiter unit in the output stage has sustained congestion indicative of an inability to transfer packets from the arbiter unit in the output stage over a first predefined time period;
• determining, by the network switch, whether an output buffer of the arbiter unit in the output stage has sustained congestion indicative of an inability to transfer packets from one or more arbiter units in the upstream stage over a second predefined time period;
• determining, by the network switch and as a function of whether the input buffer of the remote network switch has sustained congestion and whether the output buffer of the arbiter unit in the output stage has sustained congestion, whether the network switch is a root of congestion;
• and
• requesting, in response to a determination that the network switch is the root of congestion, that one or more input sources to the network switch reduce a throughput to the network switch.