SYSTEMS AND METHODS FOR PROVIDING QUALITY OF SERVICE PRECEDENCE IN TCP CONGESTION CONTROL

• US 20080225721A1
• Filed: 03/12/2007
• Published: 09/18/2008
• Est. Priority Date: 03/12/2007
• Status: Active Grant

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Inventors: Plamondon, Robert
• Granted Patent: US 7,760,642 B2
• Time in Patent Office: Days
• US Class Current: 370/235
• 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 47/27 Evaluation or update of window size, e.g. using information derived from acknowledged [ACK] packets

Abstract

Systems and methods for dynamically controlling bandwidth of connections are described. In some embodiments, a proxy for one or more connections may allocate, distribute, or generate indications of network congestion via one or more connections in order to induce the senders of the connections to reduce their rates of transmission. The proxy may allocate, distribute, or generate these indications in such a way as to provide quality of service to one or more connections, or to ensure that a number of connections transmit within an accepted bandwidth limit. In other embodiments, a sender of a transport layer connection may have a method for determining a response to congestion indications which accounts for a priority of the connection. In these embodiments, a sender may reduce or increase parameters related to transmission rate at different rates according to a priority of the connection.

Claims

1. A method for dynamically controlling connection bandwidth by a sender of one or more transport layer connections according to a priority assigned to one or more of the transport layer connections, the method comprising:

(a) transmitting, by a sender, data via a first transport layer connection, wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver;

(b) receiving, by the sender via the first transport layer connection, an indication of a packet loss via the first transport layer connection;

(c) identifying a reduction factor, the reduction factor corresponding to a priority assigned by the sender to the first transport layer connection;

(d) determining a second congestion window size, the second congestion window size comprising the first congestion window size reduced by the reduction factor; and

(e) transmitting, by the sender via the first transport-layer connection, data according to the second congestion window size.

2. The method of claim 1, wherein step (a) comprises transmitting data via a first TCP connection, wherein the first TCP connection has a congestion window corresponding to the maximum amount of unacknowledged data to be transmitted.

3. The method of claim 1, wherein step (d) comprises determining a second congestion window size, the second congestion window size comprising the first congestion window size divided by the reduction factor.

4. The method of claim 3, wherein the determined reduction factor is greater than 2.

5. The method of claim 3, wherein the predetermined reduction factor is less than 2.

6. The method of claim 1, wherein the sender assigns higher priority connections lower reduction factors relative to lower priority connections.

7. The method of claim 1, wherein step (a) comprises:

(a-a) transmitting data via a first transport layer connection having a first assigned priority; and

(a-b) transmitting data via a second transport layer connection having a second assigned priority.

8. The method of claim 7, further comprising identifying a reduction factor for the first transport layer connection that is at least twice an identified reduction factor for the second transport layer connection.

9. The method of claim 7, further comprising identifying a reduction factor for the first transport layer connection that is at least three times an identified reduction factor for the second transport layer connection.

10. The method of claim 1, wherein step (a) comprises:

(a-a) transmitting data via a first transport layer connection having a first assigned priority; and

(a-b) transmitting data via a second transport layer connection having no assigned priority.

11. The method of claim 10, wherein step (c) comprises:

(c-a) identifying a reduction factor of 2 for the second transport layer connection; and

(c-b) identifying a reduction factor not equal to 2 for the first transport layer connection.

12. A system for dynamically controlling connection bandwidth according to a priority assigned to one or more transport layer connections by a network appliance serving as an intermediary for the one or more transport layer connections, the system comprising:

a network appliance which serves as an intermediary for a first transport layer connection between a sender and a receiver, the network appliance comprising;

a packet processing engine which transmits data via the first transport layer connection, wherein the first transport layer connection has a first congestion window size corresponding to the maximum amount of unacknowledged data to be transmitted; and

receives, via the first transport layer connection, an indication of a packet loss; and

a flow control module in communication with the packet processing engine which computes a reduction factor, the reduction factor corresponding to a priority assigned by the appliance to the first transport layer connection;

computes a second congestion window size, the second congestion window size comprising the first congestion window size divided by the reduction factor; and

transmits, via the first transport layer connection, data according to the second congestion window size.

13. The system of claim 12, wherein the packet processing engine transmits data via a first TCP connection, wherein the first TCP connection has a congestion window corresponding to the maximum amount of unacknowledged data to be transmitted.

14. The system of claim 12, wherein the determined reduction factor is greater than 2.

15. The system of claim 12, wherein the predetermined reduction factor is less than 2.

16. The system of claim 12, wherein the network appliance assigns higher priority connections lower reduction factors relative to lower priority connections.

17. The system of claim 12, wherein the packet processing engine transmits data via a first transport layer connection having a first assigned priority;

and transmits data via a second transport layer connection having a second assigned priority.

18. The system of claim 17, wherein the computed reduction factor of the first transport layer connection is substantially twice a computed reduction factor corresponding to the second transport layer connection.

19. The system of claim 17, wherein the computed reduction factor of the first transport layer connection is substantially three times a computed reduction factor corresponding to the second transport layer connection.

21. The system of claim 12, wherein the packet processing engine transmits data via a first transport layer connection having a first assigned priority;

and transmits data via a second transport layer connection having no assigned priority.

22. The system of claim 21, wherein the reduction factor of the first transport layer connection is not equal to 2, and the reduction factor of the second transport layer connection is equal to 2.

20. The system of claim 0, wherein the packet processing engine transmits, via the first transport-layer connection, an acknowledgement comprising the second congestion window size.

23. A computer-implemented system for dynamically controlling connection bandwidth by a sender of one or more transport layer connections according to a priority assigned to one or more of the transport layer connections, the system comprising:

a network stack which transmits data via a first transport layer connection, wherein the first transport layer connection has a first congestion window size corresponding to the maximum amount of unacknowledged data to be transmitted; and

receives, via the first transport layer connection, an indication of a packet loss; and

a flow controller in communication with the network stack which computes a reduction factor, the reduction factor corresponding to a priority assigned by the flow controller to the first transport layer connection;

computes a second congestion window size, the second congestion window size comprising the first congestion window size divided by the reduction factor; and

transmits, via the first transport layer connection, data according to the second congestion window size.

24. The system of claim 23, wherein the packet processing engine transmits data via a first TCP connection, wherein the first TCP connection has a congestion window corresponding to the maximum amount of unacknowledged data to be transmitted.

25. The system of claim 23, wherein the determined reduction factor is greater than 2.

26. The system of claim 23, wherein the predetermined reduction factor is less than 2.

27. The system of claim 23, wherein the network appliance assigns higher priority connections lower reduction factors relative to lower priority connections.

28. The system of claim 23, wherein the packet processing engine transmits data via a first transport layer connection having a first assigned priority;

and transmits data via a second transport layer connection having a second assigned priority.

29. The system of claim 28, wherein the computed reduction factor of the first transport layer connection is substantially twice a computed reduction factor corresponding to the second transport layer connection.

30. The system of claim 28, wherein the computed reduction factor of the first transport layer connection is substantially three times a computed reduction factor corresponding to the second transport layer connection.

31. The system of claim 23, wherein the packet processing engine transmits, via the first transport-layer connection, an acknowledgement comprising the second congestion window size.

32. The system of claim 23, wherein the packet processing engine transmits data via a first transport layer connection having a first assigned priority;

and transmits data via a second transport layer connection having no assigned priority.

33. The system of claim 32, wherein the reduction factor of the first transport layer connection is not equal to 2, and the reduction factor of the second transport layer connection is equal to 2.

34. A method for dynamically controlling connection bandwidth by a sender of one or more transport layer connections according to a priority assigned to one or more of the transport layer connections, the method comprising:

(a) transmitting, by a sender, data via a first transport layer connection, wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver;

(b) receiving, by the sender via the first transport layer connection, no indications of packet loss events during a time interval;

(c) determining an enlargement factor, the enlargement factor corresponding to a priority assigned by the sender to the first transport layer connection;

(d) computing a second congestion window size, the second congestion window size computed with respect to the first congestion window size and an enlargement factor; and

(e) transmitting, by the sender via the first transport layer connection, data according to the second congestion window size.

35. The method of claim 34, wherein step (a) comprises transmitting, by a sender, data via a first TCP connection, wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver.

36. The method of claim 34, wherein step (b) comprises receiving, by the sender, no indications of packet loss events during a time interval equal to a round trip time corresponding to the first transport layer connection.

37. The method of claim 34 wherein the enlargement factor is less than 1.

38. The method of claim 34, wherein the enlargement factor is greater than 1.

39. The method of claim 34, wherein step (d) comprises computing a second congestion window size, the second congestion window size equal to the previous congestion window size multiplied by the enlargement factor.

40. The method of claim 34, wherein step (d) comprises computing a second congestion window size, the second congestion window size equal to the first congestion window size plus a quantity, wherein the quantity is equal to a maximum packet size of the first transport layer connection multiplied by the enlargement factor.

41. The method of claim 34, wherein step (d) comprises computing a second congestion window size, the congestion window size equal to the first congestion window size multiplied by a minimum round trip time divided by an average round trip time plus a quantity, wherein the quantity is equal to a maximum packet size multiplied by the enlargement factor.

42. The method of claim 34, wherein step (a) comprises:

(a-a) transmitting data via a first transport layer connection having a first priority; and

(a-b) transmitting data via a second transport layer connection having a second priority.

43. The method of claim 42, wherein the enlargement factor corresponding to the connection priority of the first transport layer connection is at least twice an enlargement factor of the second transport layer connection.

44. The method of claim 42, wherein the enlargement factor corresponding to the priority of the first transport layer connection is at least three times an enlargement factor of the second transport layer connection.

45. A computer-implemented system for dynamically controlling connection bandwidth by a sender of one or more transport layer connections according to a priority assigned to one or more of the transport layer connections, the system comprising:

a network appliance which serves as an intermediary for a first transport layer connection between a sender and a receiver, the network appliance comprising;

a packet processing engine which transmits data via a first transport layer connection, wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver; and

receives, via the first transport layer connection, no indications of packet loss events during a time interval;

a flow controller which determines an enlargement factor, the enlargement factor corresponding to a priority assigned by the network appliance to the first transport layer connection;

computes a second congestion window size, the second congestion window size computed with respect to the first congestion window size and an enlargement factor; and

transmits, via the first transport layer connection, data according to the second congestion window size.

46. The system of claim 45, wherein the packet processing engine transmits, via a first TCP connection, data wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver.

47. The system of claim 45, wherein the packet processing engine receives no indications of packet loss events during a time interval equal to a round trip time corresponding to the first transport layer connection.

48. The system of claim 45, wherein the enlargement factor is less than 1.

49. The system of claim 45, wherein the enlargement factor is greater than 1.

50. The system of claim 45, wherein the flow controller computes a second congestion window size, the second congestion window size equal to the previous congestion window size multiplied by the enlargement factor.

51. The system of claim 45 wherein the flow controller computes a second congestion window size, the second congestion window size equal to the first congestion window size plus a quantity, wherein the quantity is equal to a maximum packet size of the first transport layer connection multiplied by the enlargement factor.

52. The system of claim 45, wherein the flow controller computes a second congestion window size, the congestion window size equal to the first congestion window size multiplied by a minimum round trip time divided by an average round trip time plus a quantity, wherein the quantity is equal to a maximum packet size multiplied by the enlargement factor.

53. The system of claim 45, wherein the packet processing engine transmits data via a first transport layer connection having a first priority and transmits data via a second transport layer connection having a second priority.

54. The system of claim 53, wherein the enlargement factor corresponding to the connection priority of the first transport layer connection is at least twice an enlargement factor of the second transport layer connection.

55. The system of claim 53, wherein the enlargement factor corresponding to the priority of the first transport layer connection is at least three times an enlargement factor of the second transport layer connection.

56. A computer-implemented system for dynamically controlling connection bandwidth by a sender of one or more transport layer connections according to a priority assigned to one or more of the transport layer connections, the system comprising:

a network stack which transmits data via a first transport layer connection, wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver; and

receives, via the first transport layer connection, no indications of packet loss events during a time interval;

a flow controller which determines an enlargement factor, the enlargement factor corresponding to a priority assigned by the network appliance to the first transport layer connection;

computes a second congestion window size, the second congestion window size computed with respect to the first congestion window size and an enlargement factor; and

transmits, via the first transport layer connection, data according to the second congestion window size.

57. The system of claim 56, wherein the network stack transmits, via a first TCP connection, data wherein the first transport layer connection has a first congestion window size identifying an amount data to be transmitted by the sender in the absence of an acknowledgement from a receiver.

58. The system of claim 56, wherein the network stack receives no indications of packet loss events during a time interval equal to a round trip time corresponding to the first transport layer connection.

59. The system of claim 56, wherein the enlargement factor is less than 1.

60. The system of claim 56, wherein the enlargement factor is greater than 1.

61. The system of claim 56, wherein the flow controller computes a second congestion window size, the second congestion window size equal to the previous congestion window size multiplied by the enlargement factor.

62. The system of claim 56, wherein the flow controller computes a second congestion window size, the second congestion window size equal to the first congestion window size plus a quantity, wherein the quantity is equal to a maximum packet size of the first transport layer connection multiplied by the enlargement factor.

63. The system of claim 56, wherein the flow controller computes a second congestion window size, the congestion window size equal to the first congestion window size multiplied by a minimum round trip time divided by an average round trip time plus a quantity, wherein the quantity is equal to a maximum packet size multiplied by the enlargement factor.

64. The system of claim 56, wherein the network stack transmits data via a first transport layer connection having a first priority and transmits data via a second transport layer connection having a second priority.

65. The system of claim 64, wherein the enlargement factor corresponding to the connection priority of the first transport layer connection is at least twice an enlargement factor of the second transport layer connection.

66. The system of claim 64, wherein the enlargement factor corresponding to the priority of the first transport layer connection is at least three times an enlargement factor of the second transport layer connection.