Detecting change in a transport protocol window size without data transmission

• US 20060268710A1
• Filed: 05/19/2005
• Published: 11/30/2006
• Est. Priority Date: 05/19/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ramaiah, Anantha, Appanna, Chandrashekhar, Khare, Amol
• Granted Patent: US 7,613,118 B2
• Time in Patent Office: Days
• US Class Current: 370/235
• 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 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A method detects a change in TCP receive window size while preventing fragmentation of data. A TCP stack receives a segment that advertises a receive window size of zero. If data needs to be sent, and only if so, a timer is started. When the timer expires, a TCP segment that contains a first sequence number value equal to second sequence number representing sent but unacknowledged data minus one, and a segment length value of zero, is sent. Without sending a fragment of data, this triggers a peer TCP process to send an updated window size. A TCP ACK segment is received and contains an updated receive window size. If the updated receive window size is greater than a specified value, then the data is sent. Otherwise, a counter is incremented, and the steps are re-performed if the counter is less than a specified value.

Claims

1. A method of detecting a change in a transport protocol window size performed by a transmission control protocol (TCP) process in a network element, comprising the computer-implemented steps of:

receiving, from a TCP application, a first TCP segment that advertises a first receive window size of zero;

determining whether data needs to be sent to the TCP application, and only if so;

starting a timer;

when the timer expires, creating and sending a second TCP segment that contains a first sequence number value equal to second sequence number of sent but unacknowledged data minus one, and a segment length value of zero;

receiving a TCP ACK segment that acknowledges the second TCP segment and that contains a second receive window size;

determining whether the second window size is greater than a specified value;

sending the data to the TCP application only when the second receive window size is greater than the specified value;

incrementing a counter when the data is not sent to the TCP application; and

re-performing the steps of creating and sending only when the counter is less than a specified value.

2. A method as recited in claim 1, wherein a BGP application runs on top of the TCP application, and wherein the specified value is selected to prevent excessive fragmentation of the data.

3. A method as recited in claim 1, wherein a TCP stack of a router performs the steps.

4. A method, comprising the computer-implemented steps of:

receiving a first data segment that comprises a first receive window size of zero;

creating and sending a second segment that contains a first sequence number value equal to a second sequence number of sent but unacknowledged data minus one, and a segment length value of zero;

receiving a third segment that comprises a second receive window size;

sending data only when the second receive window size is greater than a specified value.

5. A method as recited in claim 4, wherein the specified value is selected to prevent excessive fragmentation of the data.

6. A method as recited in claim 4, wherein a timer is set after the determining step, and wherein the steps of creating and sending are performed only when the timer expires.

7. A method as recited in claim 4, wherein a counter is incremented when the data is not sent, and wherein the steps of creating and sending are re-performed only when the counter is less than a specified value.

8. A method as recited in claim 4, wherein a TCP stack of a router performs the steps.

9. A method as recited in claim 4, wherein the first data segment, second segment, and third segment are TCP segments.

10. A method as recited in claim 4, wherein the creating and sending steps are performed only when data needs to be sent.

11. A computer-readable medium carrying one or more sequences of instructions for detecting a change in a data transmission window size, which instructions, when executed by one or more processors that host a transmission control protocol (TCP) process in a network element, cause the one or more processors to perform the steps of:

receiving a first data segment that comprises a first receive window size of zero;

creating and sending a second segment that contains a first sequence number value equal to a second sequence number of sent but unacknowledged data minus one, and a segment length value of zero;

receiving a third segment that comprises a second receive window size;

sending data only when the second receive window size is greater than a specified value.

12. A computer-readable medium as recited in claim 11, wherein a BGP application runs on top of the TCP application, and wherein the specified value is selected to prevent excessive fragmentation of the data.

13. A computer-readable medium as recited in claim 11, wherein a timer is set after the determining step, and wherein the steps of creating and sending are performed only when the timer expires.

14. A computer-readable medium as recited in claim 11, wherein a counter is incremented when the data is not sent, and wherein the steps of creating and sending are re-performed only when the counter is less than a specified value.

15. A computer-readable medium as recited in claim 11, wherein a TCP stack of a router performs the steps.

16. A computer-readable medium as recited in claim 11, wherein the first data segment, second segment, and third segment are TCP segments.

17. A computer-readable medium as recited in claim 11, wherein the creating and sending steps are performed only when data needs to be sent.

18. A network element, comprising:

means for receiving a first data segment that comprises a first receive window size of zero;

means for creating and sending a second segment that contains a first sequence number value equal to a second sequence number of sent but unacknowledged data minus one, and a segment length value of zero;

means for receiving a third segment that comprises a second receive window size;

means for sending data only when the second receive window size is greater than a specified value.

19. A network element as recited in claim 18, wherein a BGP application runs on top of the TCP application, and wherein the specified value is selected to prevent excessive fragmentation of the data.

20. A network element as recited in claim 18, wherein a timer is set after the determining step, and wherein the steps of creating and sending are performed only when the timer expires.

21. A network element as recited in claim 18, wherein a counter is incremented when the data is not sent, and wherein the steps of creating and sending are re-performed only when the counter is less than a specified value.

22. A network element as recited in claim 18, wherein a TCP stack of a router performs the steps.

23. A network element as recited in claim 18, wherein the first data segment, second segment, and third segment are TCP segments.

24. A network element as recited in claim 18, wherein the creating and sending steps are performed only when data needs to be sent.

25. A network element, comprising:

one or more processors;

a network interface coupled to a network for communicating one or more packet flows to the network;

a computer-readable medium accessible to the one or more processors and carrying one or more sequences of instructions for preventing network reset attacks, which instructions, when executed by one or more processors that host a transmission control protocol (TCP) process in a network element, cause the one or more processors to perform the steps of;

receiving a first data segment that comprises a first receive window size of zero;

creating and sending a second segment that contains a first sequence number value equal to a second sequence number of sent but unacknowledged data minus one, and a segment length value of zero;

receiving a third segment that comprises a second receive window size;

sending data only when the second receive window size is greater than a specified value.

26. A apparatus as recited in claim 25, wherein a BGP application runs on top of the TCP application, and wherein the specified value is selected to prevent excessive fragmentation of the data.

27. A apparatus as recited in claim 25, wherein a timer is set after the determining step, and wherein the steps of creating and sending are performed only when the timer expires.

28. A apparatus as recited in claim 25, wherein a counter is incremented when the data is not sent, and wherein the steps of creating and sending are re-performed only when the counter is less than a specified value.

29. A apparatus as recited in claim 25, wherein a TCP stack of a router performs the steps.

30. A apparatus as recited in claim 25, wherein the first data segment, second segment, and third segment are TCP segments.

31. A apparatus as recited in claim 25, wherein the creating and sending steps are performed only when data needs to be sent.