System for fast recovery from losses for reliable data communication protocols

• US 20040008693A1
• Filed: 03/25/2003
• Published: 01/15/2004
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Akamai Technologies, Inc.
• Original Assignee: Akamai Technologies, Inc.
• Inventors: Tumarkin, Alexei, Kharitonov, Michael, Grove, Adam J.
• Granted Patent: US 7,607,062 B2
• Time in Patent Office: Days
• US Class Current: 370/395.52
• 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
• CPC Class Codes: H04L 47/43 Assembling or disassembling of packets, e.g. segmentation and reassembly [SAR]
• 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

Abstract

Fast recovery from losses is an important problem for reliable data communication protocols. The Internet standard TCP protocol (Transmission Control Protocol) implements two algorithms for that: an original one based on a special timer, and a later addition to TCP that is triggered when there are three packets received by the client after the missing one. Web communications are most frequently carrying rather small objects that are generally ineligible for anything other than timeout-based retransmission schemes. The present invention describes a system delivering performance improvements to TCP (and other reliable data communication protocols) that are compliant with present Internet standards. One improvement is to send duplicates of packets without waiting for a timeout to occur. Another is to split particular parts of a data stream into smaller packets. A third is to send packets out-of-order to force the remote host to acknowledge all packets that were successfully received.

Claims

1. In a communication protocol wherein, in response to a message communicated from a first communication terminal to a second communication terminal, a message is transmitted from the second terminal to the first terminal acknowledging receipt of the message communicated from the first to the second terminal, a method for reducing communication delays arising from lost messages comprising the steps of:

sending a first message from one terminal to the other; and

without waiting for receipt of a second message acknowledging receipt of the first message, sending a duplicate of the first message or a message duplicating some part of the data contained in the first message from said one terminal to the other.

2. The method of claim 1 where said duplicate message is sent after a predetermined delay.

3. The method of claim 1 where said duplicate message is sent after a predetermined delay said one terminal has not received said second message acknowledging receipt before this delay expires.

4. The method of claim 1 wherein the communication protocol is the Transmission Control Protocol (TCP) and the first message is SYN, SYN-ACK or ACK of a SYN-ACK.

5. The method of claim 2 wherein the communication protocol is the Transmission Control Protocol and duplicates of each of the SYN, SYN-ACK and ACK of a SYN-ARK messages are sent without first waiting for such messages to be acknowledged.

6. The method of claim 1 wherein the first message is a data packet.

7. The method of claim 1 wherein the first message is the last data packet in a message window.

8. The method of claim 1 wherein the message that is duplicated is one or more of the last data packets being communicated in a message window.

9. The method of claim 1 wherein the message that is duplicated is the last byte of the last data packet being communicated in a message window.

10. The method of claim 1 wherein the message that is duplicated is at least the last two bytes of the last data packet being communicated in a message window.

11. The method of claim 1 wherein each of at least the last two bytes of the last data packet is transmitted out-of-order.

12. The method of claim 1 further comprising the steps of splitting the last packet in a message window into first and second packets and transmitting the first and second packets out-of-order.

13. The method of claim 1 further comprising the steps of splitting any data remaining to be transmitted after transmission of the last full data packet in a packet window into first and second packets and transmitting the first and second packets out-of-order.

14. The method of claim 13 wherein the first packet contains only the last byte of data to be transmitted.

15. In a communication protocol wherein, in response to a message communicated from a first communication terminal to a second communication terminal, a message is transmitted from the second terminal to the first terminal acknowledging receipt of the message communicated from the first to the second terminal, a method for reducing communication delays arising from lost messages comprising the step of:

at the end of a communication session between the first and second terminals sending at least one duplicate of one or more of the last packets to be sent without waiting for a message acknowledging receipt of the last packets.

16. In a communication protocol wherein, in response to a message communicated from a first communication terminal to a second communication terminal, a message is transmitted from the second terminal to the first terminal acknowledging receipt of the message communicated from the first to the second terminal, a method for reducing communication delays arising from lost messages comprising the steps of:

at the end of transmission of a packet window, transmitting at least the last two packets out-of-order.

17. In a communication protocol wherein, in response to a message communicated from a first communication terminal to a second communication terminal, a message is transmitted from the second terminal to the first terminal acknowledging receipt of the message communicated from the first to the second terminal, a method for reducing communication delays arising from lost messages comprising the steps of:

at the end of transmission of a packet window, splitting the last packet into first and second packets and transmitting the first and second packets out-of-order.

18. The method of claim 17 wherein the first packet contains only the last byte of data being transmitted.

19. In a communication protocol wherein, in response to a message communicated from a first communication terminal to a second communication terminal, a message is transmitted from the second terminal to the first terminal acknowledging receipt of the message communicated from the first to the second terminal, a method for reducing communication delays arising from lost messages comprising the steps of:

at the end of the transmission of a packet window, splitting any data remaining to be transmitted after transmission of the last full data packet in a packet window into first and second packets and transmitting the first and second packets out-of-order.

20. In a communication protocol wherein, in response to a message communicated from a first communication terminal to a second communication terminal, a message is transmitted from the second terminal to the first terminal acknowledging receipt of the message communicated from the first to the second terminal, a method for reducing communication delays arising from lost messages comprising the steps of:

at the beginning of a communication session between the first and second terminals sending from one terminal at least one duplicate of a first message without first waiting for a second message acknowledging receipt of the first message; and

at the end of the communication session sending from one terminal at least one duplicate of a third message without first waiting for a fourth message acknowledging receipt of the third message.

21. The method of claim 20 wherein the communication protocol is the Transmission Control Protocol (TCP) and the first message is SYN, SYN-ACK or ACK of a SYN-ACK.

22. The method of claim 20 wherein the communication protocol is the Transmission Control Protocol, the first message is at least one of SYN, SYN-ACK or ACK of a SYN-ACK and each first message is sent without first waiting for such message to be acknowledged.

23. The method of claim 20 wherein the third message is a data packet.

24. The method of claim 20 wherein the third message is the last data packet in a message window.

25. The method of claim 20 wherein the third message that is duplicated is one or more of the last data packets being communicated.

26. The method of claim 20 wherein the third message that is duplicated is the last byte of the last data packet being communicated.

27. The method of claim 20 wherein the third message that is duplicated is at least the last two bytes of the last data packet being communicated.