Data processing system and method for pacing information transfers in a communications network

• US 5,918,020 A
• Filed: 02/28/1997
• Issued: 06/29/1999
• Est. Priority Date: 02/28/1997
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Blackard, Joe Wayne, Petersen, Lynn Erich, Gillaspy, Richard Adams, Henthorn, William John, Russell, Lance W., Shippy, Gary Roy
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): TITCOMB, WILLIAM D
• Application Number:
  US08/808,930
• Time in Patent Office: 851 Days
• Field of Search: 370/232, 370/389, 370/395, 395/200.57, 395/200.58, 395/200.54
• US Class Current: 709/228
• CPC Class Codes: H04L 47/10 Flow control; Congestion control

Abstract

A data processing system and a method implement a unique push, or streaming, model for communicating time sensitive encoded data, such as video and audio data, in a communication network. A pacing mechanism is implemented in the data processing system to allow a client to pace a streaming server in a stable way such that a fill level of a client buffer will oscillate around a single threshold value. A simple protocol is implemented to protect pacing primitives, allow recovery for pacing primitives, and to keep a client and a server synchronized during the pacing operation. To implement the pacing mechanism, the streaming server transmits data at a slightly faster rate than it was encoded. Subsequently, a decoder circuit at the client, or receiver, uses the transmitted data at the encoded rate. Thus, the utilization of buffers in the client will gradually increase. When the utilization of buffers reaches a threshold level, the client provides a pacing message to the server. When the pacing message is received, the server withholds sending data for a period of time sufficient to drop the client buffer utilization to a level below a threshold level.

Claims

1. A communication network, comprising:

a server for transmitting a plurality of information values at a first rate until a pacing message is received by the server;

a client computer system coupled to the server for decoding the plurality of information values at a second rate and for providing the pacing message, said client computer system further comprising;

input means for receiving the plurality of information values at the first rate;

buffer means for storing the plurality of information values, the buffer means being coupled to the input means for receiving the plurality of information values;

decoder coupled to the buffer means for decoding each of the plurality of information values at the second rate; and

central processing unit coupled to the buffer means for detecting when the buffer means stores a predetermined number of values and asserting the pacing message when the buffer means stores more than thee predetermined number of values.

2. The communication network of claim 1 wherein the second rate is less than the first rate.

3. The communication network of claim 1 wherein the first rate is a relatively fixed rate.

4. The communication network of claim 1 wherein the pacing message indicates an amount of time the server is to wait until resuming transmission of the plurality of information values.

5. The communication network of claim 4 wherein the amount of time is calculated by the client computer system.

6. The communication network of claim 1, wherein the server withholds transmitting the plurality of information values for a period of time required to remove a portion of a plurality of stored information values from the buffer means such that the buffer means stores less than the predetermined number of values.

7. The communication network of claim 1 wherein the client computer system and the server perform independently during the period of time required to remove the portion of the plurality of stored information values form the buffer means.

8. The communication network of claim 1 wherein the plurality of information values is video information.

9. The communication network of claim 1 wherein the pacing message is provided from the client computer system to the server using a receiver report packet of a real time protocol (RTP) standard.

10. The communication network of claim 1 wherein the server is placed in a wait state for a first time period when the pacing message is received by the server.

11. The communication network of claim 10 wherein the server remains in the wait state for the first time period when a subsequent pacing message is received by the server.

12. The communication network of claim 10 wherein the server ignores a subsequent pacing message when the first time period expires and the subsequent pacing message is a retransmitted pacing message.

13. The communication network of claim 1 wherein the client computer system detects when an operation executed in response to the pacing message is complete.

14. The communication network of claim 13 wherein the operation is a pacing operation.

15. A method for operating a server while the server is communicating a plurality of information values with a client computer system, comprising the steps of:

enabling a server to transmit the plurality of information values at a first rate;

receiving a transmission variable value from the client computer system at an input circuit of the server;

comparing the transmission variable value with a pacing coordination variable value stored in a memory of the server; and

initiating a pacing operation in which the server withholds communicating the plurality of information values for a time period.

16. The method of claim 15, wherein a step of initiating a pacing operation, further comprises the step of:

accessing a wait interval value to determine the time period in which the server withholds communicating the plurality of information values.

17. The method of claim 16 wherein the wait interval is provided to the server in a pacing message provided by the client computer system.

18. The method of claim 16 wherein the pacing message comprises the wait interval value and the transmission variable value.

19. The method of claim 16, wherein the step of initiating the pacing operation, further comprises the step of:

enabling the server to enter a suspend state in which the server ignores a subsequent pacing operation from the client computer system.

20. The method of claim 15, further comprising the step of:

modifying a state of the pacing coordination variable value to have a current pacing coordination variable value after the time period has passed.

21. The method of claim 20, further comprising the step of:

transmitting a transmission variable value from the server to the client computer system, wherein a state of the transmission variable value corresponds to the state of the current pacing coordination variable value.

22. The method of claim 21, further comprising the step of:

recommencing transmission of the plurality of information values from the server to the client computer system when the transmission variable value is transmitted from the server to the client.

23. A method for operating a client computer system while a server is communicating a plurality of information values with the client computer system, comprising the steps of:

i. receiving the plurality of information values from the server;

ii. storing the plurality of information values in a buffer pool of the client computer system;

iii. determining a first number of data values stored in the buffer pool of the client computer system;

iv. repeating steps i. through iii. when the first number of data values stored in the buffer pool is below a buffer threshold level; and

v. transmitting a pacing message to the server when the first number of data values stored in the buffer pool is above the buffer threshold level.

24. The method of claim 23, further comprising the steps of:

vi. calculating a wait period to indicate a period of time the server should wait before commencing to transmit the plurality of information values after the pacing message is received by the server; and

vii. transmitting the wait period to the server in the pacing message.