Backward congestion notification

Abstract

In one embodiment, an apparatus comprises a network interface system having at least one input port configured for receiving frames and a logic system comprising at least one logic device. The logic system may be configured to perform the following functions: determining a source address and a destination address of a frame received at an ingress port; calculating a flow hash based at least upon the source address and the destination address; forming a congestion management (“CM”) tag that includes the flow hash; inserting the CM tag in the frame; and forwarding the frame to the destination address.

We claim: 
     
         1 . An apparatus, comprising:
 a memory; and   a processor coupled to the memory, at least one of the processor or the memory being adapted for:   receiving a first frame at a first ingress port of a first network device;   calculating a flow hash based at least upon a source address of the first frame and a destination address of the first frame;   inserting a congestion management (“CM”) tag in the first frame, wherein the CM tag comprises the flow hash and an indication for a second ingress port of a second network device to add a backwards congestion notification (“BCN”) address in the CM tag; and   forwarding the first frame to the destination address.   
     
     
         2 . The apparatus of  claim 1 , at least one of the processor or the memory being further adapted for:
 determining a virtual local area network value of the first frame, wherein calculating the flow hash comprises calculating the flow hash based upon the source address, the destination address and the virtual local area network value.   
     
     
         3 . The apparatus of  claim 1 , at least one of the processor or the memory being further adapted for:
 determining whether a BCN frame has been received for a first flow associated with the first frame.   
     
     
         4 . The apparatus of  claim 1 , wherein the indication comprises a bit in the CM tag. 
     
     
         5 . The apparatus of  claim 1 , wherein the first ingress port is not configured to provide BCN reaction point functionality and wherein a first egress port of the first network device is configured to provide BCN reaction point functionality. 
     
     
         6 . The apparatus of  claim 3 , at least one of the processor or the memory being further adapted for:
 determining congestion point information when the BCN frame has been received for the flow associated with the first frame, wherein the CM tag further comprises the congestion point information.   
     
     
         7 . The apparatus of  claim 1 , wherein the BCN address comprises an address of the ingress port. 
     
     
         8 . The apparatus of  claim 6 , wherein determining congestion point information comprises:
 retrieving a stored congestion point identification hash value.   
     
     
         9 . A method, comprising:
 receiving a first frame at a first ingress port of a first network device;   calculating a flow hash based at least upon a source address of the first frame and a destination address of the first frame;   inserting a congestion management (“CM”) tag in the first frame, wherein the CM tag comprises the flow hash and an indication for a second ingress port of a second network device to add a backwards congestion notification (“BCN”) address in the CM tag; and   forwarding the first frame to the destination address.   
     
     
         10 . The method of  claim 9 , further comprising:
 determining a virtual local area network value of the first frame, wherein calculating the flow hash comprises calculating the flow hash based upon the source address, the destination address and the virtual local area network value.   
     
     
         11 . The method of  claim 9 , further comprising:
 determining whether a BCN frame has been received for a first flow associated with the first frame.   
     
     
         12 . The method of  claim 9 , wherein the indication comprises a bit in the CM tag. 
     
     
         13 . The method of  claim 9 , wherein the first ingress port is not configured to provide BCN reaction point functionality and wherein a first egress port of the first network device is configured to provide BCN reaction point functionality. 
     
     
         14 . The method of  claim 11 , further comprising:
 determining congestion point information when the BCN frame has been received for the flow associated with the first frame, wherein the CM tag further comprises the congestion point information.   
     
     
         15 . The method of  claim 9 , wherein the BCN address comprises an address of the ingress port. 
     
     
         16 . The method of  claim 14 , wherein determining congestion point information comprises:
 retrieving a stored congestion point identification hash value.