Switching device utilizing flow-control management

• US 20070047535A1
• Filed: 08/31/2005
• Published: 03/01/2007
• Est. Priority Date: 08/31/2005
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Varma, Anujan
• Granted Patent: US 7,719,982 B2
• Time in Patent Office: Days
• US Class Current: 370/360
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/12 Avoiding congestion; Recovering from congestion
• CPC Class Codes: H04L 47/26 using explicit feedback to the source, e.g. choke packets
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 49/3018 Input queuing
• CPC Class Codes: H04L 49/3027 Output queuing
• CPC Class Codes: H04L 49/506 Backpressure

Abstract

In some embodiments a switching device is disclosed that includes one or more ingress queues to queue data received from external sources while waiting to forward the data to one or more egress queues. The egress queues queue the data while waiting to transmit the data to external sources. The switching device also includes a switch fabric to provide connectivity between the one or more ingress queues and the one or more egress queues. The switching device further includes an ingress flow-control manager to monitor flow-control state of the one or more ingress queues, and to detect and recover from loss of ON flow-control messages. Other embodiments are otherwise disclosed herein.

Claims

1. A switching device comprising:

one or more ingress queues to queue data received from external sources while waiting to forward the data to one or more egress queues, wherein the egress queues queue the data while waiting to transmit the data to external sources;

a switch fabric to provide connectivity between said one or more ingress queues and the one or more egress queues; and

an ingress flow-control manager to monitor flow-control state of said one or more ingress queues, and to detect and recover from loss of ON flow-control messages.

2. The device of claim 1, wherein said ingress flow-control manager tracks amount of time that an ingress queue has had an off status and ascertains congestion state of an associated egress queue if an ingress queue has had an off status for longer than a given amount of time.

3. The device of claim 2, wherein said ingress flow-control manager ascertains the congestion state of the associated egress queue by sending a query to an egress flow-control manager that monitors congestion state of the egress queues.

4. The device of claim 3, wherein the query is transported through said switch fabric.

5. The device of claim 3, wherein the query is transported through a control path separate from said switch fabric.

6. A switching device comprising:

one or more egress queues to queue data received from one or more ingress queues while waiting to transmit the data to external sources, wherein the ingress queues queue the data received from external sources;

a switch fabric to provide connectivity between the one or more ingress queues and said one or more egress queues; and

an egress flow-control manager to monitor congestion state of said egress queues and to generate and forward a flow-control message to at least a subset of the one or more ingress queues that are associated with an egress queue that had a change in the congestion state.

7. The device of claim 6, wherein the flow-control message is an on/off message.

8. The device of claim 6, wherein the flow-control message indicates a rate of flow.

9. The device of claim 6, wherein said egress flow-control manager generates an off flow-control message to turn off flow of data if the congestion state of the egress queue becomes congested.

10. The device of claim 9, wherein said egress flow-control manager forwards another off flow-control message if the egress queue receives a given amount of data after forwarding a previous off flow-control message.

11. The device of claim 6, wherein said egress flow-control manager generates an on flow-control message to turn on flow of data if the congestion state of the egress queue becomes free.

12. A method comprising:

queuing data received from external sources in one or more ingress queues;

queuing data to be transmitted to external sources in one or more egress queues;

providing connectivity between the one or more of ingress queues and the one or more egress queues;

monitoring flow-control state of the one or more ingress queues;

monitoring congestion state of the one or more egress queues; and

detecting and recovering lost flow-control messages.

13. The method of claim 12, wherein said detecting includes

tracking amount of time that the flow-control state of an ingress queue has been identified in an off state;

and

ascertaining the congestion state for an associated egress queue if an ingress queue has had an off state for longer than a given amount of time.

14. The method of claim 13, wherein the ascertaining includes sending a query to the associated egress queue.

15. The method of claim 14, further comprising generating and forwarding an on flow-control message to the ingress queue in response to the query if the congestion state of the associated egress queue is determined to be free.

16. The method of claim 12, further comprising generating and forwarding flow-control messages to at least a subset of the one or more ingress queues that are associated with an egress queue that had a change in the congestion state.

17. The method of claim 16, wherein an off flow-control message is generated to turn off flow of data if the congestion state of the egress queue becomes congested.

18. The method of claim 17, wherein said detecting includes

determining amount of data received by the egress queue after forwarding the off flow-control message;

determining if the amount of data received by the egress queue is greater than or equal to a given amount of data; and

forwarding another off flow-control message if the data received is greater than or equal to the given amount of data.

19. The method of claim 16, wherein an on flow-control message is generated to turn on flow of data if the congestion state of the egress queue becomes free.

20. A store and forward device comprising

a plurality of line cards to receive and transmit data to external sources, wherein the plurality of line cards include dynamic random access memory responsive to said store-and-forward device, the dynamic random access memory providing a plurality of ingress queues to queue data received from the external sources and a plurality of egress queues to queue data to be transmitted to the external sources;

a switch fabric to provide selective connectivity between the plurality of ingress queues and the plurality of egress queues;

an egress flow-control manager to monitor congestion state of the plurality of egress queues and to generate and forward a flow-control message to at least a subset of the plurality ingress queues that are associated with an egress queue that had a change in the congestion state; and

an ingress flow-control manager to monitor flow-control state of the plurality of ingress queues, and to detect and recover from loss of ON flow-control messages.

21. The device of claim 20, wherein

the ingress flow-control manager monitors amount of time an ingress queue has been identified in an off state;

the ingress flow-control manager generates and forwards a query to the egress flow-control manager if flow for an ingress queue has been identified in the off state for at least some given time frame; and

the egress flow-control manager forwards an on flow-control message to the ingress queue in response to the query if the congestion state of an associated egress queue is determined to be free.

22. The device of claim 20, wherein

the egress flow-control manager generates an off flow-control message to turn off flow of data if the congestion state of the egress queue becomes congested;

the egress flow-control manager monitors amount of data received by the egress queue after forwarding the off flow-control message; and

the egress flow-control manager forwards another off flow-control message if the egress queue receives at least a given amount of data after forwarding previous off flow-control message.

23. A machine-accessible medium comprising content, which, when executed by a machine causes the machine to:

queue data received from external sources in one or more ingress queues;

queue data to be transmitted to external sources in one or more egress queues;

provide connectivity between the one or more of ingress queues and the one or more egress queues;

monitor flow-control state of the one or more ingress queues;

monitor congestion state of the one or more egress queues; and

detect and recovering lost flow-control messages.

24. The machine-accessible medium of claim 23, wherein when executed by the machine further causes the machine to:

track amount of time that the flow-control state of an ingress queue has been identified in an off state;

send a query to determine the congestion state of an associated egress queue if an ingress queue has had an off state for longer than a given amount of time; and

generate and forwarding an on flow-control message to the ingress queue in response to the query if the congestion state of the associated egress queue is determined to be free.

25. The machine-accessible medium of claim 23, wherein when executed by the machine further causes the machine to:

generate and forwarding an off flow-control message to at least a subset of the one or more ingress queues that are associated with an egress queue that becomes congested;

determine amount of data received by the egress queue after forwarding the off flow-control message;

determine if the amount of data received by the egress queue is greater than or equal to a given amount of data; and

forward another off flow-control message if the data received is greater than or equal to the given amount of data.