Method for improving TCP performance over wireless links

• US 7,020,083 B2
• Filed: 10/29/2001
• Issued: 03/28/2006
• Est. Priority Date: 08/31/2000
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Garcia-Luna-Aceves, Jose Joaquin, Parsa, Christina
• Primary Examiner(s): Rao, Seema S.
• Assistant Examiner(s): Bhandari, Puneet
• Application Number:
  US10/021,318
• Publication Number:
  US 20020154602A1
• Time in Patent Office: 1,611 Days
• Field of Search: 370/252, 370/394, 370229-2351, 370/236
• US Class Current: 370/230
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 1/1832 Details of sliding window management
• CPC Class Codes: H04L 1/187 Details of sliding window management
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/12 Avoiding congestion; Recovering from congestion
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• 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 69/168 specially adapted for link layer protocols, e.g. asynchronous transfer mode [ATM], synchronous optical network [SONET] or point-to-point protocol [PPP]
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/0242 Determining whether packet losses are due to overload or to deterioration of radio communication conditions
• CPC Class Codes: H04W 28/0273 adapting protocols for flow control or congestion control to wireless environment, e.g. adapting transmission control protocol [TCP] wireless network protocols or protocol adaptations to wireless operation, e.g. wireless application protocol H04W80/00
• CPC Class Codes: H04W 28/0289 Congestion control load shedding arrangements in network planning H04W16/08; performing reselection for handling the traffic H04W36/22; wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]
• CPC Class Codes: H04W 80/06 Transport layer protocols, e.g. TCP [Transport Control Protocol] over wireless transmission control protocol/Internet protocol [TCP/IP] or user datagram protocol [UDP] H04L69/16

Abstract

A protocol for differentiating congestion-related packet loss versus random packet loss in a wireless data connection. The protocol monitors changes in the length of a transmission queue in a wireless data connection over an interval substantially equal to the amount of time it takes to transmit a window of data packets and receive acknowledgements corresponding to all data packets transmitted in the window. If packet loss is preceded by an increase in the queue length over two consecutive intervals, the packet loss is designated as being due to congestion and a congestion avoidance algorithm is initiated. Otherwise, the packet loss is designated as random loss and the transmission window is maintained at its current size. The protocol reduces the transmission rate only when congestion is identified as the cause of lost packets; otherwise wireless losses can simply be quickly retransmitted without a reduction in the data transmission rate.

Claims

1. A method of improving congestion control of data packets transmitted over a communication network employing transmission control protocol (TCP), said data packets transmitted from a source to a destination, said method comprising:

detecting an initial stage of congestion;

determining direction of said congestion by estimating relative delay that one data packet experiences with respect to another data packet as said data packets are transmitted over said network;

determining whether congestion is developing in a forward path;

isolating forward throughput from congestion occurring on a reverse path; and

in the absence of congestion in the reverse path, avoiding retransmission of data packets as a result of a timeout when there are a plurality of packet losses in a time window.

2. A method as recited in claim 1 or 8:

wherein said relative delay comprises increases and decreases in delay that said data packets experience with respect to each other; and

further comprising calculating said relative delay from a timestamp returned by a receiver of a data packet in an acknowledgment packet;

said timestamp specifying arrival time of a data packet at the receiver.

3. A method as recited in claim 2, further comprising determining the presence of multiple paths to a destination by timestamps returned from receivers of said data packets.

4. A method as recited in claim 1 or 8, further comprising determining whether congestion is increasing or decreasing in either a forward or reverse path.

5. A method as recited in claim 1 or 8, wherein determination of congestion direction allows that portion of the forward path to be isolated from events, or congestion, that may occur on the reverse path.

6. A method as recited in claim 1 or 8, wherein said TCP has an options field, and further comprising using said options field to detect the initial stage of congestion and determine the direction of congestion.

7. A method as recited in claim 1, wherein said source has a congestion window, and further comprising:

estimating the number of packets which reside in a bottleneck queue from said relative delay; and

keeping the number of packets in said bottleneck queue at a desired minimum by adjusting the congestion window of the source.

8. A method of improving congestion control of data packets transmitted over a communication network employing transmission control protocol (TCP), said packets transmitted from a source to a destination, said method comprising:

detecting an initial stage of congestion;

determining direction of said congestion by estimating relative delay that one data packet experiences with respect to another data packet as said data packets are transmitted over sold network;

wherein said source has a congestion window;

estimating the number of packets which reside in a bottleneck queue from said relative delay; and

keeping the number of packets in said bottleneck queue at a desired minimum by adjusting the congestion window of the source.

9. A method of improving congestion control of data packets transmitted over a communication network employing transmission control protocol (TCP), said packets transmitted from a source to a destination, said method comprising:

detecting an initial stage of congestion;

determining direction of said congestion by estimating relative delay that one data packet experiences with respect to another data packet as said data packets are transmitted over said network;

determining whether congestion is developing in a forward path;

isolating forward throughput from congestion occurring on a reverse path;

wherein said source has a congestion window,

estimating the number of packets which reside in a bottleneck queue from said relative delay; and

keeping the number of packets in said bottleneck queue at a desired minimum by adjusting the congestion window of the source.

10. A method as recited in claim 9:

wherein said relative delay comprises increases and decreases in delay that said data packets experience with respect to each other; and

further comprising calculating said relative delay from a timestamp returned by a receiver of a data packet in an acknowledgment packet;

said timestamp specifying arrival time of a data packet at the receiver.

11. A method as recited in claim 10, further comprising determining the presence of multiple paths to a destination by timestamps returned from receivers of said data packets.

12. A method as recited in claim 9, further comprising determining whether congestion is increasing or decreasing in either a forward or reverse path.

13. A method as recited in claim 9, wherein said TCP has an options field, and further comprising using said options field to detect the initial stage of congestion and determine the direction of congestion.

14. A method of improving congestion control of data packets transmitted over a communication network employing transmission control protocol (TCP), said packets transmitted from a source to a destination, said method comprising:

detecting an initial stage of congestion;

determining the direction of said congestion by estimating the relative delay that one data packet experiences with respect to another data packet as said data packets are transmitted over said network;

said relative delay comprising increases and decreases in delay that said data packets experience with respect to each other; and

calculating said relative delay from a timestamp returned by a receiver of a data packet in an acknowledgment packet;

said timestamp specifying arrival time of a data packet at the receiver;

determining whether congestion is developing in a forward path;

isolating forward throughput from congestion occurring on a reverse path; and

in the absence of congestion in the reverse path, avoiding retransmission of data packets as a result of a timeout when there are a plurality of packet losses in a time window.

15. A method as recited in claim 14 or 18, further comprising determining the presence of multiple paths to a destination by timestamps returned from receivers of said data packets.

16. A method as recited in claim 14 or 18, further comprising determining whether congestion is increasing or decreasing in either a forward or reverse path.

17. A method as recited in claim 14 or 18, wherein determination of congestion direction allows that portion of the forward path to be isolated from events, or congestion, that may occur on the reverse path.

18. A method of improving congestion control of data packets transmitted over a communication network employing transmission control protocol (TCP), said packets transmitted from a source to a destination, said method comprising:

detecting an initial stage of congestion;

determining direction of said congestion by estimating relative delay that one data packet experiences with respect to another data packet as said data packets are transmitted over said network;

said relative delay comprising increases and decreases in delay that said data packets experience with respect to each other;

calculating said relative delay from a timestamp returned by a receiver of a data packet in an acknowledgment packet;

said timestamp specifying arrival time of a data packet at the receiver;

wherein said source has a congestion window,

estimating the number of packets which reside in a bottleneck queue from said relative delay; and

keeping the number of packets in said bottleneck queue at a desired minimum by adjusting the congestion window of the source.

19. A method of improving congestion control of data packets transmitted over a communication network employing transmission control protocol (TCP), said packets transmitted from a source to a destination, said method comprising:

detecting an initial stage of congestion;

determining the direction of said congestion by estimating the relative delay that one data packet experiences with respect to another data packet as said data packets are transmitted over said network;

determining whether congestion is developing in a forward path;

isolating forward throughput from congestion that may occur on a reverse path;

in the absence of congestion in the reverse path, avoiding retransmission of data packets as a result of a timeout when there are a plurality of packet losses in a time window;

wherein said relative delay comprises increases and decreases in delay that said data packets experience with respect to each other; and

calculating said relative delay from a timestamp returned by a receiver of a data packet in an acknowledgment packet;

said timestamp specifying arrival time of a data packet at the receiver.

20. A method as recited in claim 19, further comprising determining the presence of multiple paths to a destination by timestamps returned from receivers of said data packets.

21. A method as recited in claim 19, further comprising determining whether congestion is increasing or decreasing in either a forward or reverse path.

22. A method as recited in claim 19, wherein said source has a congestion window, and further comprising:

estimating the number of packets which reside in a bottleneck queue from said relative delay; and

keeping the number of packets in said bottleneck queue at a desired minimum by adjusting the congestion window of the source.

23. A method as recited in claim 19, wherein said TCP has an options field, and further comprising using said options field to detect the initial stage of congestion and determine the direction of congestion.