System and method for supporting use of forward and backward congestion notifications in a private fabric in a high performance computing environment

A method for using multiple CE (congestion experienced) flags in both FECN (forward explicit congestion notification) and BECN (backward explicit congestion notification) in a high performance computing environment, comprising:

• providing, at one or more microprocessors, a first subnet, the first subnet comprising
• a plurality of switches, the plurality of switches comprising at least a leaf switch, wherein each of the plurality of switches comprise a plurality of switch ports,
• a plurality of host channel adapters, wherein each of the host channel adapters comprise at least one host channel adapter port, and wherein the plurality of host channel adapters is interconnected via the plurality of switches, and
• a plurality of end nodes, including a plurality of virtual machines;
• receiving, at an end node attached to a host channel adapter, an ingress packet from a remote end node, wherein the ingress packet traversed at least a portion of the first subnet along a path comprising a plurality of path stages prior to being received at the end node, wherein the ingress packet comprises a bit field, the bit field comprising a plurality of bits, indicating that the ingress packet experienced congestion at a first path stage of the plurality of path stages during the traversal of the at least a portion of the first subnet, wherein each bit of the bit field corresponds to a separate path stage the plurality of path stages, and wherein the indication of congestion at the first path stage is set within the bit field by a switch port associated with the first path stage;
• on receiving the ingress packet, determining, by the end node, by correlating an information of the path with the ingress packet, district switch ports at which the ingress packet experienced congestion, and sending a response message from the end node attached to the host channel adapter to the remote end node, the response message indicating that the ingress packet experienced congestion during the traversal of the at least a portion of the first subnet.

A non-transitory computer readable storage medium having instructions thereon for using multiple CE (congestion experienced) flags in both FECN (forward explicit congestion notification) and BECN (backward explicit congestion notification) in a high performance computing environment, which when read and executed cause a computer to perform steps comprising:

• providing, at one or more microprocessors, a first subnet, the first subnet comprising
• a plurality of switches, the plurality of switches comprising at least a leaf switch, wherein each of the plurality of switches comprise a plurality of switch ports,
• a plurality of host channel adapters, wherein each of the host channel adapters comprise at least one host channel adapter port, and wherein the plurality of host channel adapters is interconnected via the plurality of switches, and
• a plurality of end nodes, including a plurality of virtual machines;
• receiving, at an end node attached to a host channel adapter, an ingress packet from a remote end node, wherein the ingress packet traversed at least a portion of the first subnet along a path comprising a plurality of path stages prior to being received at the end node, wherein the ingress packet comprises a bit field, the bit field comprising a plurality of bits, indicating that the ingress packet experienced congestion at a first path stage of the plurality of path stages during the traversal of the at least a portion of the first subnet, wherein each bit of the bit filed corresponds to a separate path stage the plurality of path stages, and wherein the indication of congestion at the first path stage is set within the bit field by a switch port associated with the first path stage;
• on receiving the ingress packet, determining, by the end node, by correlating an information of the path with the ingress packet, district switch ports at which the ingress packet experienced congestion, and sending a response message from the end node attached to the host channel adapter to the remote end node, the response message indicating that the ingress packet experienced congestion during the traversal of the at least a portion of the first subnet.