Network switching apparatus and method for congestion control

• US 20020181396A1
• Filed: 05/30/2002
• Published: 12/05/2002
• Est. Priority Date: 05/31/2001
• Status: Active Grant

• Current Assignee: VIA Technologies Incorporated (VIA Technologies)
• Original Assignee: VIA Technologies Incorporated (VIA Technologies)
• Inventors: Chen, Jen-Kai, Huang, Hsiang-Yi
• Granted Patent: US 7,382,728 B2
• Time in Patent Office: Days
• US Class Current: 370/229
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2433 Allocation of priorities to traffic types
• CPC Class Codes: H04L 47/50 Queue scheduling
• CPC Class Codes: H04L 47/6215 Individual queue per QOS, rate or priority

Abstract

A network switching apparatus and method for congestion control. Each one of the connection ports of the switching apparatus includes a low priority queue and a high priority queue. When a data packet enters a switching apparatus, the switching apparatus according to the type of the data packet enqueues the data packet to the low priority queue or the high priority queue. When congestion occurs at the switching apparatus, the low priority queue and the high priority queue can respectively perform the different ways of the congestion control, according to the input congestion mode. Also, when the switching apparatus receives a pause frame, response flow control can be performed, according to the output congestion mode. Since the different ways of the congestion control are performed according to the different types of the data packet, the congestion control can be optimized.

Claims

1. A network switching apparatus with congestion control, the network switching apparatus controller comprising:

a share buffer;

a plurality of connection ports;

a buffer control device, coupled to the share buffer;

a plurality of connection port control devices, coupled to the buffer control device, wherein the connection port control devices correspond to the connection ports one by one, when the corresponding one of the connection port control devices to a source one of the connection ports receives a data packet, the corresponding one of the connection port control device makes a request to the buffer control device, according to a size of the data packet, for allocating at least one segment needed by the data packet, thereby the data packet is stored in the at least one segment;

a forwarding device, coupled to the connection port control devices, and determining a target connection port, for the data packet, according to a type of the data packet; and

a queue control device, which is coupled to the buffer control device and the forwarding device, wherein the queue control device comprises a plurality of high priority queues and a plurality of low priority queues, one of the high priority queues and one of the low priority queues correspond to one of the connection port control device, wherein the queue control device associates said at least one segment, to one of the priority queues, according to the type of the data packet.

2. The network switching apparatus in accordance with claim 1, wherein the buffer control device takes segment as a unit, and makes a request to the share buffer to allocate memory and free allocated memory.

3. The network switching apparatus in accordance with claim 1, wherein each one of the queues reserves a number of segments.

4. The network switching apparatus in accordance with claim 1, wherein each one of the connection port control devices respectively includes:

a receiving media access control (RMAC) unit, coupled to one workstation or one LAN, so as to receive the data packet;

a receiving control unit, coupled to the receiving media access control unit, the queue control device, and the buffer control device, wherein when the receiving media access control unit receives the data packet, the receiving control unit then makes a request to the buffer control device to allocate said at least one segment, so as to store the data packet, and also makes a request to the queue control device to associate said at least one segment with an associated one of the queues;

a transmitting control unit, coupled to the queue control device and the buffer control device, so as to export the data packet from the associated one of the queues, and cause the buffer control device to free the at least one segment, originally occupied by the data packet; and

a transmitting media access control (TMAC) unit, coupled to the transmitting control unit and said workstation or LAN, so as to export the data packet to the corresponding one of the connection ports.

5. A method for a congestion control, the method comprising:

(a) determining whether or not a target connection port is under a situation of congestion;

(b) according to a type of the data packet, enqueuing the data packet to a high priority queue or a low priority queue corresponding to the target connection port if the target connection port is under the situation of congestion;

(c) performing backpressure control if the one of the workstations or LANs connected to the target connection port is not full duplex;

(d) performing drop control if the one of the workstations or LANs does not carry a function of flow control; and

(e) performing congestion control, according to an input congestion mode of the queue on which the data packet is enqueued if the one of the workstations or LANs does carry a function of flow control.

6. The method in accordance with claim 5, wherein the input congestion mode represents the flow control or the drop control.

7. The method in accordance with claim 5, wherein a parameter C is defined as a minimum threshold for congestion, which uses segment as an unit, and is used to prevent a buffer starvation during the worst situation;

a parameter Φ

is defined as a total number of the segments in the share buffer but having not been used yet, wherein the step (a) comprises;

when the total number of the segments not been used Φ

is less than the minimum value of a threshold for congestion C, then the target connection port is judged as a situation of congestion.

8. The method in accordance with claim 5, wherein a parameter Ψ

is defined as the summation of the reserved number of the segments R for each one of the queues;

a parameter Φ

is defined as a total number of the segments in the share buffer but having not been used yet, wherein the step (a) comprises;

if the reserved number of the segments R of the one of the queues for the target connection port to store the data packet is zero, and a situation of congestion has occurred on anyone of the other connection ports, then a situation of congestion is determined for the target connection port.

9. The method in accordance with claim 5, wherein a parameter D is defined as the minimum of the total reserved number of the segments;

a parameter T is defined as the summation of the reserved number of the segments R for each one of the queues;

a parameter Φ

is defined as a total number of the segments in the share buffer but having not been used yet, wherein the step (a) comprises;

if the reserved number of the segments R of the one of the queues for the target connection port to store the data packet is zero, and the total number of the segments Φ

in the share buffer but having not been used is less than or equal to a maximum between the minimum of the total reserved number of the segments D and the summation of the reserved number of the segments R for each one of the queues Ψ

, then a situation of congestion is determined for the target connection port.

10. A method of response flow control, the method comprising:

performing a congestion control according to an output congestion mode of a high priority queue of a source connection port if one data packet is exported from the high priority queue of the source connection port; and

performing the congestion control according to an output congestion mode of a low priority queue of the source connection port if one data packet is exported from the low priority queue of the source connection port.

11. The method of response flow control in accordance with claim 10, wherein the output congestion mode of the high priority queue represents continuously exporting the data packets.

12. The method of response flow control in accordance with claim 10, wherein the output congestion mode of the high priority queue represents temporarily pausing for exporting the data packets.

13. The method of response flow control in accordance with claim 10, wherein the output congestion mode of the low priority queue represents continuously exporting the data packets.

14. The method of response flow control in accordance with claim 10, wherein the output congestion mode of the low priority queue represents temporarily pausing for exporting the data packets.

15. The method of response flow control in accordance with claims 11, wherein when the source connection port continuously exports the data packets to a target connection port, on which a situation of congestion has occurred, the target connection port performs drop control.

16. The method of response flow control in accordance with claims 13, wherein when the source connection port continuously exports the data packets to a target connection port, on which a situation of congestion has occurred, the target connection port performs drop control.