BACKWARD CONGESTION NOTIFICATION

• US 20090052326A1
• Filed: 08/21/2007
• Published: 02/26/2009
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Bergamasco, Davide, Dutt, Dinesh
• Granted Patent: US 8,121,038 B2
• Time in Patent Office: Days
• US Class Current: 370/236
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/17 Interaction among intermediate nodes, e.g. hop by hop
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/33 using forward 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.

Claims

1. A method, comprising:

receiving a frame at an ingress port of a first network device;

determining a source address and a destination address of the frame;

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.

2. The method of claim 1, further comprising determining a virtual local area network value of the frame, wherein the calculating step comprises calculating the flow hash based upon the source address, the destination address and the virtual local area network value.

3. The method of claim 1, further comprising determining whether a backwards congestion notification (“

BCN”

) frame has recently been received for the identified flow.

4. The method of claim 1, wherein the forming further comprises including a backwards congestion notification (“

BCN”

) address in the CM tag, wherein the BCN address comprises an address of the ingress port.

5. The method of claim 1, wherein the ingress port is not configured to provide backwards congestion notification (“

BCN”

) reaction point functionality and wherein an egress port of the first network device is configured to provide BCN reaction point functionality, further comprising forming, by the egress port, an indication for an ingress port of a second network device to add a BCN address in the CM tag.

6. The method of claim 3, wherein it is determined that a recent indication of congestion has been received for the identified flow, further comprising determining congestion point information, wherein the forming further comprises including the congestion point information in the CM tag.

7. The method of claim 4, wherein the forming further comprises including an indication of whether the BCN address comprises a hierarchical address.

8. The method of claim 6, wherein determining congestion point information comprises retrieving a stored congestion point identification hash value.

9. A method, comprising:

receiving, at an ingress port of a core switch of a first Data Center Ethernet portion of a network, a frame from an Ethernet portion of the network, the frame having a congestion management (“

CM”

) tag;

determining that the CM tag indicates a source hierarchical media access control (“

MAC”

) address of a device in a second Data Center Ethernet portion of the network;

determining that the source hierarchical MAC address matches a hierarchical MAC address of the ingress port;

modifying the CM tag to indicate that a backwards congestion notification frame indicating the source hierarchical MAC address as a destination address should be forwarded to the device in the second Data Center Ethernet portion of the network; and

forwarding the frame to a destination address of the frame.

10. The method of claim 9, wherein the modifying comprises modifying the CM tag to indicate that a BCN frame indicating the source hierarchical MAC address as a destination address should not be terminated by the core switch.

11. The method of claim 9, wherein the modifying comprises setting a bit in the CM tag.

12. An apparatus, comprising:

a network interface system comprising at least one input port configured for receiving frames; and

a logic system comprising at least one logic device 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.

13. The apparatus of claim 12, wherein the logic system is further configured to determine a virtual local area network value of the frame and wherein the calculating function comprises calculating the flow hash based upon the source address, the destination address and the virtual local area network value.

14. The apparatus of claim 12, wherein the logic system is further configured to determine whether a backwards congestion notification (“

BCN”

) frame has recently been received for the identified flow.

15. The apparatus of claim 12, wherein the forming function further comprises including a backwards congestion notification (“

BCN”

) address in the CM tag, wherein the BCN address comprises an address of the ingress port.

16. The apparatus of claim 12, wherein the ingress port is not configured to provide backwards congestion notification (“

BCN”

) reaction point functionality and wherein an egress port of the apparatus is configured to provide BCN reaction point functionality, further comprising forming, by the egress port, an indication for an ingress port of another apparatus to add a BCN address in the CM tag.

17. The apparatus of claim 14, wherein the logic system determines that a recent indication of congestion has been received for the identified flow, wherein the logic system is further configured to determine congestion point information, wherein the forming function further comprises including the congestion point information in the CM tag.

18. The apparatus of claim 15, wherein the forming function further comprises including an indication of whether the BCN address comprises a hierarchical address.

19. The apparatus of claim 17, further comprising a memory, wherein determining congestion point information comprises retrieving a stored congestion point identification hash value from the memory.

20. An apparatus, comprising:

means for receiving a frame at an ingress port of a first network device;

means for determining a source address and a destination address of the frame;

means for calculating a flow hash based at least upon the source address and the destination address;

means for forming a congestion management (“

CM”

) tag that includes the flow hash;

means for inserting the CM tag in the frame; and

means for forwarding the frame to the destination address.