Wavefront detection and disambiguation of acknowledgments

• US 9,008,100 B2
• Filed: 10/03/2013
• Issued: 04/14/2015
• Est. Priority Date: 10/30/2002
• Status: Active Grant

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Inventors: Samuels, Allen R., Sutter, Paul G.
• Primary Examiner(s): Weidner, Timothy J
• Application Number:
  US14/045,543
• Publication Number:
  US 20140029430A1
• Time in Patent Office: 558 Days
• Field of Search: None
• US Class Current: 370/394
• CPC Class Codes: H04L 41/00 Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/34 ensuring sequence integrity, e.g. using sequence numbers
• 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 communicating with a remote system using Internet Protocol (IP) via a computer network, the method comprising:

transmitting, by a flow control module configured on a device, a first data packet from a sender to a remote system, the transmitted first data packet including a first transport layer sequence number;

transmitting, by the flow control module, a second data packet from the sender to the remote system, the second data packet including a second transport layer sequence number;

transmitting, by the flow control module, a third data packet from the sender to the remote system, the third data packet including a third transport layer sequence number;

retransmitting, by the flow control module, the first data packet from the sender to the remote system, the retransmitted first data packet including the first sequence number;

maintaining, by the flow control module, an ordered list of sequence numbers in order of transmission, the list comprising an entry for each of the transmission of the first, second, and third data packets and the retransmission of the first data packet;

receiving, by the flow control module from the remote system, a first acknowledgement packet, the first acknowledgement packet including one of;

(i) the second sequence number to indicate receipt by the remote system of the second data packet, or (ii) the third sequence number to indicate receipt by the remote system of the third data packet;

receiving, by the flow control module from the remote system, a second acknowledgement packet, the second acknowledgement packet including the first sequence number; and

determining, by the flow control module, whether the received second acknowledgement packet acknowledges receipt by the remote system of one of;

(i) the transmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the transmission of the first data packet, or (ii) the retransmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the retransmission of the first data packet.

2. The method of claim 1, further comprising adding, by the flow control module, an entry to the ordered list responsive to transmission or retransmission of a data packet, the entry comprising the transport layer sequence number of the transmission or retransmission of the data packet.

3. The method of claim 1, further comprising identifying as a last known received entry, by the flow control module and responsive to receiving the first acknowledgement packet, an entry in the ordered list corresponding to the sequence number included in the first acknowledgement packet.

4. The method of claim 1, further comprising:

transmitting, by the flow control module, one or more additional data packets from the sender to the remote system prior to retransmitting the first data packet; and

presuming lost, by the flow control module, the one or more additional data packets sent prior to retransmitting the first data packet, responsive to;

(i) determining that the received acknowledgement packet acknowledges receipt by the remote system of the retransmission of the first data packet, and (ii) receipt of the one or more additional data packets not being acknowledged by the remote system.

5. The method of claim 1, wherein the ordered list further comprises a timestamp corresponding to each entry.

6. The method of claim 1, wherein the second acknowledgement packet does not include an explicit identifier indicating the number of times a data packet was retransmitted.

7. The method of claim 1, further comprising:

re-retransmitting, by the flow control module, the first data packet from the sender to the remote system, the re-retransmitted first data packet including the first sequence number.

8. The method of claim 7, further comprising adding, by the flow control module, an entry to the ordered list responsive to re-retransmitting the first data packet, the entry comprising the first sequence number.

9. The method of claim 8, further comprising;

determining, by the flow control module, that the received second acknowledgement packet acknowledges receipt by the remote system of one of;

(i) the transmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the transmission of the first data packet, (ii) the retransmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the retransmission of the first data packet, or (iii) the re-retransmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the re-retransmission of the first data packet.

10. The method of claim 9, further comprising:

transmitting, by the flow control module, one or more additional data packets from the sender to the remote system prior to re-retransmitting the first data packet; and

presuming lost, by the flow control module, the one or more additional data packets sent prior to re-retransmitting the first data packet, responsive to;

(i) determining that the received acknowledgement packet acknowledges receipt by the remote system of the retransmission of the first data packet, and (ii) receipt of the one or more additional data packets not being acknowledged by the remote system.

11. A system for communicating with a remote system using Internet Protocol (IP) via a computer network, the system comprising:

a device deployed between a sender and a remote system, the device comprising a flow control module, the flow control module configured to;

transmit a first data packet from a sender to a remote system, the transmitted first data packet including a first transport layer sequence number;

transmit a second data packet from the sender to the remote system, the second data packet including a second transport layer sequence number;

transmit a third data packet from the sender to the remote system, the third data packet including a third transport layer sequence number;

retransmit, the first data packet from the sender to the remote system, the retransmitted first data packet including the first sequence number;

maintain an ordered list of sequence numbers in order of transmission, the list comprising an entry for each of the transmission of the first, second, and third data packets and the retransmission of the first data packet;

receive from the remote system, a first acknowledgement packet, the first acknowledgement packet including one of;

(i) the second sequence number to indicate receipt by the remote system of the second data packet, or (ii) the third sequence number to indicate receipt by the remote system of the third data packet;

receive from the remote system, a second acknowledgement packet, the second acknowledgement packet including the first sequence number; and

determine whether the received second acknowledgement packet acknowledges receipt by the remote system of one of;

(i) the transmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the transmission of the first data packet, or (ii) the retransmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the retransmission of the first data packet.

12. The system of claim 11, wherein the flow control module is further configured to add an entry to the ordered list responsive to transmission or retransmission of a data packet, the entry comprising the transport layer sequence number of the transmission or retransmission of the data packet.

13. The system of claim 11, wherein the flow control module is further configured to identify as a last known received entry, by the flow control module and responsive to receipt of the first acknowledgement packet, an entry in the ordered list corresponding to the sequence number included in the first acknowledgement packet.

14. The system of claim 11, wherein the flow control module is further configured to:

Transmit one or more additional data packets from the sender to the remote system prior to retransmitting the first data packet; and

presume lost the one or more additional data packets sent prior to retransmitting the first data packet, responsive to;

(i) determining that the received acknowledgement packet acknowledges receipt by the remote system of the retransmission of the first data packet, and (ii) receipt of the one or more additional data packets not being acknowledged by the remote system.

15. The system of claim 11, wherein the ordered list further comprises a timestamp corresponding to each entry.

16. The system of claim 11, wherein the second acknowledgement packet does not include an explicit identifier indicating the number of times a data packet was retransmitted.

17. The system of claim 11, wherein the flow control module is further configured to re-retransmit the first data packet from the sender to the remote system, the re-retransmitted first data packet including the first sequence number.

18. The system of claim 17, wherein the flow control module is further configured to add an entry to the ordered list responsive to re-retransmitting the first data packet, the entry comprising the first sequence number.

19. The system of claim 18, wherein the flow control module is further configured to:

determine that the received second acknowledgement packet acknowledges receipt by the remote system of one of;

(i) the transmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the transmission of the first data packet, (ii) the retransmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the retransmission of the first data packet, or (iii) the re-retransmission of the first data packet, responsive to the entry for the sequence number included in the first acknowledgement packet being closer in the ordered list to the entry for the re-retransmission of the first data packet.

20. The system of claim 19, wherein the flow control module is further configured to:

transmit one or more additional data packets from the sender to the remote system prior to re-retransmitting the first data packet; and

presume lost the one or more additional data packets sent prior to re-retransmitting the first data packet, responsive to;

(i) determining that the received acknowledgement packet acknowledges receipt by the remote system of the retransmission of the first data packet, and (ii) receipt of the one or more additional data packets not being acknowledged by the remote system.