TCP selective acknowledgements for communicating delivered and missed data packets

• US 20050063303A1
• Filed: 07/28/2004
• Published: 03/24/2005
• Est. Priority Date: 07/29/2003
• Status: Active Grant

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Orbital Data Corporation (Cloud Software Group)
• Inventors: Samuels, Allen R., Sutter, Paul G.
• Granted Patent: US 7,630,305 B2
• Time in Patent Office: Days
• US Class Current: 370/229
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 1/1621 Group acknowledgement, i.e. the acknowledgement message defining a range of identifiers, e.g. of sequence numbers
• CPC Class Codes: H04L 1/1671 the supervisory signal being transmitted together with control information
• CPC Class Codes: H04L 1/1874 Buffer management
• CPC Class Codes: H04L 2001/0097 Relays
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 67/2876 Pairs of inter-processing entities at each side of the network, e.g. split proxies
• CPC Class Codes: H04L 67/56 Provisioning of proxy services store-and-forward switching systems in data switching networks H04L12/54
• 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 69/166 IP fragmentation; TCP segmentation

Abstract

One or more flow control modules, implemented on various types of network topologies, provide a number of functionalities for controlling the flow of IP packets (such as TCP/IP packets) over a network connection. The flow control modules may be implemented within a sender and/or receiver or may be deployed into a network as a separate device without requiring significant additional resources.

Claims

1. A method for acknowledging data packets received over a network from a sender, the method comprising:

tracking data packets received over the network;

generating a plurality of selection acknowledgment (SACK) packets, each SACK packet responsive to a landing data packet and identifying a plurality of ranges of data packets that had been received when the landing data packet was received, at least two of the ranges being consecutive to imply that a set of data packets between the consecutive ranges have not been received; and

transmitting the SACK packet to the receiver.

2. The method of claim 1, wherein the consecutive ranges identified in a first SACK packet overlap the consecutive ranges identified in a next SACK packet.

3. The method of claim 1, wherein each SACK packet further identifies a range of received data packets that includes the landing data packet associated with the SACK packet.

4. The method of claim 1, wherein tracking comprises maintaining a list of ranges of received data packets.

5. The method of claim 4, wherein the list of ranges is ordered.

6. The method of claim 5, further comprising:

maintaining a reference into the list of ranges of received data packets, wherein the consecutive ranges identified in a generated SACK packet are chosen according to the reference; and

responsive to the generation of a SACK packet, advancing the reference to a subsequent range in the list.

7. The method of claim 6, wherein advancing the reference comprises wrapping to a beginning of the list upon reaching an end of the list.

8. The method of claim 1, wherein the ranges are of sequence numbers for the data packets.

9. The method of claim 1, wherein the method complies with TCP/IP.

10. The method of claim 1, wherein the method is performed in a proxy device coupled to a receiver.

11. A method for retransmitting packets based on acknowledgements received from a receiver over a network, the method comprising:

receiving a selection acknowledgement (SACK) packet, the SACK packet identifying a plurality of ranges of data packets that had been received when a landing data packet that triggered the SACK packet was received, at least two of the ranges being consecutive to imply that a set of data packets between the consecutive ranges have not been received;

inferring that a set of data packets between the consecutive ranges have not been received; and

retransmit data packets based on the inferring.

12. The method of claim 11, wherein each SACK packet further identifies a range of received data packets that includes the landing data packet.

13. The method of claim 11, wherein the retransmitting comprises retransmitting the set of data packets between the consecutive ranges of the SACK packet unless the data packets were retransmitted after the landing data packet.

14. The method of claim 11, further comprising:

adding unacknowledged data packets to a presumed lost list upon receiving an acknowledgement for a later-transmitted data packet;

wherein the retransmitting comprises retransmitting any data packets that are (1) in the presumed lost list, and (2) between the consecutive ranges of the SACK packet.

15. The method of claim 14, wherein the retransmitting a data packet further comprises waiting for a predetermined number of acknowledgements, and retransmitting the data packet only if the data packet has not been acknowledged.

16. The method of claim 11, wherein the ranges are of sequence numbers for the data packets.

17. The method of claim 11, wherein the method complies with TCP/IP.

18. The method of claim 11, wherein the method is performed in a proxy device coupled to a sender.

19. A method for communicating data packets from a sender to a receiver over a network, the method comprising:

transmitting data packets from the sender to the receiver over the network;

responsive to receiving a data packet at the receiver, generating a SACK packet that includes at least two ranges of data packets, the data between the two ranges of data packets not received by the receiver;

transmitting the SACK packet from the receiver to the sender;

at the sender, inferring that the data between the two ranges of data packets in the SACK packet had not been received by the receiver when the SACK packet was generated; and

retransmitting data packets from the sender to the receiver based on the inferred lost packets.

20. A computer program product for acknowledging data packets received over a network from a sender, the computer program product comprising a computer-readable medium containing computer program code for performing the operations:

tracking data packets received over the network;

generating a plurality of selection acknowledgment (SACK) packets, each SACK packet responsive to a landing data packet and identifying a plurality of ranges of data packets that had been received when the landing data packet was received, at least two of the ranges being consecutive to imply that a set of data packets between the consecutive ranges have not been received; and

transmitting the SACK packet to the receiver.

21. The computer program product of claim 20, wherein the consecutive ranges identified in a first SACK packet overlap the consecutive ranges identified in a next SACK packet.

22. The computer program product of claim 20, wherein each SACK packet further identifies a range of received data packets that includes the landing data packet associated with the SACK packet.

23. The computer program product of claim 20, wherein tracking comprises maintaining a list of ranges of received data packets.

24. The computer program product of claim 23, wherein the list of ranges is ordered.

25. The computer program product of claim 24, further comprising:

maintaining a reference into the list of ranges of received data packets, wherein the consecutive ranges identified in a generated SACK packet are chosen according to the reference; and

responsive to the generation of a SACK packet, advancing the reference to a subsequent range in the list.

26. The computer program product of claim 25, wherein advancing the reference comprises wrapping to a beginning of the list upon reaching an end of the list.

27. The computer program product of claim 20, wherein the ranges are of sequence numbers for the data packets.

28. A computer program product for retransmitting packets based on acknowledgements received from a receiver over a network, the computer program product comprising a computer-readable medium containing computer program code for performing the operations:

receiving a selection acknowledgement (SACK) packet, the SACK packet identifying a plurality of ranges of data packets that had been received when a landing data packet that triggered the SACK packet was received, at least two of the ranges being consecutive to imply that a set of data packets between the consecutive ranges have not been received;

inferring that a set of data packets between the consecutive ranges have not been received; and

retransmit data packets based on the inferring.

29. The computer program product of claim 28, wherein each SACK packet further identifies a range of received data packets that includes the landing data packet.

30. The computer program product of claim 28, wherein the retransmitting comprises retransmitting the set of data packets between the consecutive ranges of the SACK packet unless the data packets were retransmitted after the landing data packet.

31. The computer program product of claim 28, further comprising:

adding unacknowledged data packets to a presumed lost list upon receiving an acknowledgement for a later-transmitted data packet;

wherein the retransmitting comprises retransmitting any data packets that are (1) in the presumed lost list, and (2) between the consecutive ranges of the SACK packet.

32. The computer program product of claim 31, wherein the retransmitting a data packet further comprises waiting for a predetermined number of acknowledgements, and retransmitting the data packet only if the data packet has not been acknowledged.

33. The computer program product of claim 28, wherein the ranges are of sequence numbers for the data packets.

34. A network communications system comprising:

a receiver-side flow module configured to generate a SACK packet responsive to receiving a data packet at the receiver, the SACK packet including at least two ranges of data packets, the data between the two ranges of data packets not received by the receiver; and

a sender-side flow module configured to received SACK packets from the receiver flow module and, responsive to receiving a SACK packet, infer that the data between the two ranges of data packets in the SACK packet had not been received by the receiver when the SACK packet was generated;

wherein a sender is coupled to the sender flow module for retransmitting data packets from the sender to the receiver based on the inferred lost packets.

35. The system of claim 34, wherein the sender-side flow control module is implemented within the sender.

36. The system of claim 34, wherein the receiver-side flow control module is implemented within a receiver.