Methods, systems and computer program products for reliable data transmission over communications networks

• US 6,076,114 A
• Filed: 04/18/1997
• Issued: 06/13/2000
• Est. Priority Date: 04/18/1997
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wesley, Ajamu A.
• Primary Examiner(s): Rinehart, Mark H.
• Application Number:
  US08/844,392
• Time in Patent Office: 1,152 Days
• Field of Search: 709/224, 709/230, 709/235, 709/237, 370/229, 370/230, 370/231, 714/748, 714/749
• US Class Current: 709/235
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/161 Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
• CPC Class Codes: H04L 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: H04L 69/164 Adaptation or special uses of UDP protocol
• CPC Class Codes: H04L 69/166 IP fragmentation; TCP segmentation
• CPC Class Codes: H04L 69/326 in the transport layer [OSI layer 4] H04L69/16 takes precedence
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

Methods, systems and computer programs provide reliable transmission of data over a communications link in a communications network which otherwise may be unreliable. The transmission of the data packets in a communications link between a sending station and a receiving station is reliably managed by biasing the expected round trip time associated with the first sending station to accommodate relatively large fluctuations in the actual latency of transmissions in the data packets between the sending station and the receiving station whereby the number of retransmissions of data packets between the sending station and the receiving station is relatively minimized. The retransmission of data packets is controlled by first modifying the expected round trip time associated with the first computer causing the expected round trip time to approach the largest actual latency experienced by the sending station and also to account for the size of the data packets successfully transmitted between the sending station and the receiving station. The retransmission of the data packets may also be controlled by dynamically regrading the round trip time associated with the sending station based on an indication by the receiving station that the communications link can be trusted. The round trip timer is regraded by dynamically increasing the expected round trip time based on the successful transmission of a data packet on the first attempt and is dynamically decreased based on the unsuccessful transmission of the data packet on the first transmission attempt. The communications network may be a wired communications network, a wireless communications network, or a combination of wired and wireless communications networks.

Claims

1. A method for reliably managing the transmission of a plurality of data packets over a communications link between a first computer and a second computer, the method comprising the step of:

controlling retransmission of the data packets between the first computer and the second computer over the communications link based on a biased expected round trip time associated with the first computer, the biased expected round trip time being biased as a function of fluctuations in the latency of transmissions of the data packets between the first computer and the second computer, whereby data packets are reliably transmitted between the first computer and the second computer and the number of retransmissions of data packets is relatively minimized.

2. The method according to claim 1 wherein said controlling step comprises the steps of:

modifying the expected round trip time associated with the first computer based on the largest latency of the first computer corresponding to the transmitting step and the size of the data packets successfully transmitted between the first computer and the second computer; and

controlling the retransmission of data packets between the first computer and the second computer over the communications link based on the modified expected round trip time associated with the first computer.

3. The method according to claim 2 wherein said modifying the expected round trip time step comprises the steps of:

comparing the expected round trip time and an actual round trip time corresponding to the actual time between the transmitting of one of said data packets by the first computer and a determination by the first computer that the one of said data packets was transmitted successfully; and

modifying the expected round trip time in response to the comparing step and the size of the one data packet successfully transmitted between the first computer and the second computer.

4. The method according to claim 3 wherein said modifying step comprises the steps of:

expanding the expected round trip time if the actual round trip time is at least as great as the expected round trip time;

reducing the expected round trip time if the expected round trip time is greater than the actual round trip time.

5. The method according to claim 1 wherein said controlling step comprises the steps of:

dynamically regrading the expected round trip time associated with the first computer, the expected round trip time being dynamically regraded as a function of the successful transmission of a first data packet between the first computer and the second computer; and

controlling the retransmission of a second data packet between the first computer and the second computer over the communications link based on the dynamically regraded expected round trip time associated with the first computer.

6. The method according to claim 5 wherein said dynamically regrading step comprises the steps of:

determining that the communications link between the first computer and the second computer is reliable or unreliable;

dynamically increasing the expected round trip time associated with the first computer if the communications link between the first computer and the second computer is reliable; and

dynamically decreasing the expected round trip time associated with the first computer if the communications link between the first computer and the second computer is unreliable.

7. The method according to claim 1 wherein said first computer has an application comprising a web server and said second computer has an application comprising a web browser.

8. The method according to claim 1 wherein the communications link comprises at least one of a wireless communications link, a wired communication link, and the combination of a wired communications link and a wireless communications link.

9. The method according to claim 1 wherein said controlling step comprises the steps of:

acknowledging that data packets were received by the second computer;

determining the actual round trip time associated with each of said data packets transmitted to the second computer;

modifying the expected round trip time associated with the first computer as a function of the actual round trip time of the first computer and the size of the data packets successfully transmitted between the first computer and the second computer; and

controlling the retransmission of data packets between the first computer and the second computer over the communications link as a function of the modified expected round trip time associated with the first computer.

10. The method according to claim 9 wherein said modifying the expected round trip time step comprises the steps of:

comparing the expected round trip time and an actual round trip time corresponding to the actual time between transmitting of one of said data packets from the first computer to the second computer and a determination by the first computer that the one of said data packets was transmitted successfully; and

modifying the expected round trip time in response to the comparing step and the size of the one data packet successfully transmitted between the first computer and the second computer.

11. The method according to claim 10 wherein said modifying step comprises the steps of:

expanding the expected round trip time if the actual round trip time is at least as great as the expected round trip time; and

reducing the expected round trip time if the expected round trip time is greater than the actual round trip time.

12. The method according to claim 5 wherein said dynamically regrading step comprises the steps of:

determining that the communications link between the first computer and the second computer is reliable or unreliable; and

notifying the first computer that the communications link between the first computer and the second computer is one of reliable and unreliable in response to the determining step.

13. A computer program product for reliably managing the transmission of a plurality of data packets over a communications link between a first computer and a second computer, the computer program product comprising:

a computer readable storage medium having computer readable code means embodied in said medium, said computer readable code means comprising;

computer instruction means for controlling retransmission of the data packets between the first computer and the second computer over the communications link based on a biased expected round trip time associated with the first computer, the biased expected round trip time being biased as a function of fluctuations in the latency of transmissions of the data packets between the first computer and the second computer, whereby data packets are reliably transmitted between the first computer and the second computer and the number of retransmissions of data packets is relatively minimized.

14. A system for reliably managing the transmission of a plurality of data packets over a communications link between a first computer and a second computer, the system comprising:

means for controlling retransmission of the data packets between the first computer and the second computer over the communications link based on a biased expected round trip time associated with the first computer, the biased expected round trip time being biased as a function of fluctuations in the latency of transmissions of the data packets between the first computer and the second computer, whereby data packets are reliably transmitted between the first computer and the second computer and the number of retransmissions of data packets is relatively minimized.