Flow control technique for traffic in a high speed packet switching network

• US 6,388,992 B2
• Filed: 12/22/2000
• Issued: 05/14/2002
• Est. Priority Date: 09/09/1997
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Legoll, Jean-Jacques, Chabannet, Anne, Mariotti, Rene, Plattier, Edmond, Szczap, Michel, Aubert, Denis
• Primary Examiner(s): Jung, Min
• Application Number:
  US09/748,593
• Publication Number:
  US 20010012272A1
• Time in Patent Office: 508 Days
• Field of Search: 370/230, 370/232, 370/235, 370/236, 370/237, 370/389
• US Class Current: 370/232
• CPC Class Codes: H04L 12/2854 Wide area networks, e.g. public data networks
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/29 using a combination of thresholds

Abstract

A flow control mechanism for use in a high speed packet switching network where calls are multiplexed on network trunks with each connection using a reserved amount of the total bandwidth. Data terminal equipments access the network via access nodes. Each access node includes a Leaky Bucket component which maintains a refillable token pool. Each time an incoming packet is received by the leaky bucket component, the number of available tokens is compared to two predetermined threshold values. If the number of tokens is less than the low threshold, acknowledgments of received packets are stopped, inducing an interruption of packets transmitted by the emitting terminals. Interrupting packet transmission will lead to a regeneration of the number of tokens in the token pool. If the number of tokens reaches the high threshold, acknowledgments are again generated to restore packet transmissions. The first and second thresholds are greater than zero, reducing the chances that a packet will be marked as being discardable.

Claims

1. A method for controlling data traffic at an access node of a packet switching network, said data traffic being provided from sources which continue to transmit traffic only where acknowledgments of previously-transmitted traffic are received on a predetermined basis, said access node implementing a leaky bucket admission control mechanism in which tokens are added to the pool at a predetermined rate, said method comprising the steps of:

receiving and temporarily storing each incoming packet;

testing the number of tokens available in the token pool against first and second thresholds having values greater than zero;

discontinuing acknowledgements of received packets where the test reveals the number of available tokens is less than the first threshold and packet acknowledgments are currently being provided to the packet source;

resuming acknowledgments of received packets where the number of available tokens is greater than a second threshold and acknowledgments are currently not being provided to the packet source; and

transmitting the stored packet and decrementing the token pool.

2. A computer readable memory device, comprising:

said computer readable memory device containing computer instructions and data to execute in a computer for practice of the method of claim 1.

3. Electromagnetic signals propagating over a computer network, comprising:

said electromagnetic signals having computer instructions and data to execute in a node for practice of the method of claim 1.

4. The method of claim 1 further comprising:

setting the second threshold greater than the first threshold.

5. The method of claim 1 further comprising:

setting the first threshold to a value less than 50% of the maximum number of tokens in the token pool; and

,

setting the second threshold to a value greater then 50% of the maximum number of tokens in the token pool.

6. The method of claim 1 further comprising:

setting the first threshold to a value of 25% of the maximum number of tokens in the token pool; and

,

setting the second threshold to a value of 75% of the maximum number of tokens in the token pool.

7. A node to execute computer instructions for carrying out the method according to claim 1.

8. A communications network comprising at least one node to execute computer instructions according to claim 1.

9. A system for controlling data traffic at an access node of a packet switching network, said data traffic being provided from sources which continue to transmit traffic only where acknowledgments of previously-transmitted traffic are received on a predetermined basis, said access node implementing a leaky bucket admission control mechanism in which tokens are added to the pool at a predetermined rate, said system comprising:

a packet buffer for receiving and temporarily storing each incoming packet;

a comparator for testing the number of tokens available in the token pool against first and second thresholds having values greater than zero;

acknowledgment controlling logic to discontinue generating packet acknowledgments when the test reveals the number of available tokens is less than the first threshold and the packet acknowledgments are being provided to the packet source, and for resuming generation of such acknowledgments when the number of available tokens is greater than a second threshold and acknowledgments are not being provided to the packet source;

a network interface to transmit the packet stored in the buffer; and

token pool logic responsive to transmission of the packet for decrementing the token pool.

10. The system of claim 9 further comprising:

the second threshold is set to a value greater than the first threshold.

11. The system of claim 9 further comprising:

the first threshold is set to a value less than 50% of the maximum number of tokens in the token pool; and

,

the second threshold is set to a value greater then 50% of the maximum number of tokens in the token pool.

12. The system of claim 9 further comprising:

the first threshold is set to a value of 25% of the maximum number of tokens in the token pool; and

,

the second threshold is set to a value of 75% of the maximum number of tokens in the token pool.

13. A system for controlling data traffic at an access node of a packet switching network, said data traffic being provided from sources which continue to transmit traffic only where acknowledgments of previously-transmitted traffic are received, said access node implementing a leaky bucket admission control mechanism in which tokens are added to the pool at a predetermined rate, said system comprising:

a packet buffer to receive and temporarily store each incoming packet;

means for testing the number of tokens available in the token pool against first and second thresholds;

means for discontinuing acknowledgements of received packets where the test reveals the number of available tokens is less than the first threshold and packet acknowledgments are currently being provided to the packet source;

means for resuming acknowledgments of received packets where the number of available tokens is greater than a second threshold and acknowledgments are currently not being provided to the packet source; and

means for transmitting the stored packet and decrementing the token pool.

14. The system of claim 13 further comprising:

means for setting the second threshold greater than the first threshold.

15. The system of claim 13 further comprising:

means for setting the first threshold to a value less than 50% of the maximum number of tokens in the token pool; and

,

means for setting the second threshold to a value greater then 50% of the maximum number of tokens in the token pool.

16. The system of claim 13 further comprising:

means for setting the first threshold to a value of 25% of the maximum number of tokens in the token pool; and

,

means for setting the second threshold to a value of 75% of the maximum number of tokens in the token pool.