Connectionless protocol

• US 7,013,346 B1
• Filed: 10/06/2000
• Issued: 03/14/2006
• Est. Priority Date: 10/06/2000
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Tucker, Rusty
• Primary Examiner(s): Etienne, Ario
• Assistant Examiner(s): Osman, Ramy M
• Application Number:
  US09/680,990
• Time in Patent Office: 1,985 Days
• Field of Search: 709/230, 709231-235, 709/236, 709/238, 709/250, 709/237, 709/247, 709/249, 345/629, 345/631, 345/635, 370/400, 370/401
• US Class Current: 709/236
• CPC Class Codes: H04L 1/1614 using bitmaps
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1874 Buffer management
• CPC Class Codes: H04L 1/188 Time-out mechanisms

Abstract

Packets transmitted from a server into a computer network are assigned a sequence number, a retransmit time and a time to live. Each packet is retransmitted upon the expiration of the retransmit time if no acknowledgment has been received from a client to which the packet was sent. The packet is removed from a retransmit buffer if the time to live timer expires prior to any acknowledgment being received. Multiple acknowledgments may be combined into a coalesced acknowledgment.

Claims

1. A method for real time transmission of frame-based content between a network server and a network client comprising the steps of:

designating individual packets of said content as either a frame packet that contains information for reconstructing an entire frame of said content or a differential packet that contains changes to a frame;

assigning to each of said packets a sequence number and a timer for retransmission retention, wherein the duration of the timers for frame packets is longer than for differential packets;

transmitting each of said packets to said network client;

detecting an acknowledgment for one or more packets received at said network client;

retransmitting any of said packets for which no acknowledgment is detected if their respective timers have not expired; and

terminating the retention of each packet whose timer has expired, wherein differential packets are removed more frequently than frame packets in order to ensure that critical information is not lost when an acknowledgment is not detected.

2. A method as set forth in claim 1 further comprising terminating the retention of any of said packets upon detecting said acknowledgment for said any of said packets prior to expiration of said timer.

3. A method as set forth in claim 1 further comprising placing said acknowledgment for differing ones of said packets into a coalesced acknowledgment.

4. A method as set forth in claim 1 further comprising:

maintaining the bandwidth of successively transmitted packets to the lesser of a congestion window initially determined to be maximum segment size and a client window size no greater than the size of a UDP socket input buffer at said client.

5. A method as set forth in claim 4 wherein said congestion window is increased by the size of each packet for which an acknowledgment is received.

6. A method as set forth in claim 5 wherein said congestion window is increased until said congestion window exceeds a predetermined threshold, and increases thereafter by said maximum segment size for each acknowledgment received.

7. A method as set forth in claim 6 wherein said threshold is determined by a window size that is last known to be error free in receipt of said successively transmitted packets.

8. A method as set forth in claim 6 wherein said threshold is, upon retransmitting of any of said packets, set to the greater of ½

of the current congestion window size or maximum segment size.

9. A method as set forth in claim 8 wherein said congestion window is reset to said maximum segment size.

10. A network for real time transmission of frame-based content between a network server and a network client comprising the steps of:

means for designating individual packets of said content as either a frame packet that contains information for reconstructing an entire frame of said content or a differential packet that contains changes to a frame;

means for assigning to each of said packets a sequence number and a timer for retransmission retention, wherein the duration of the timers for frame packets is longer than for differential packets;

means for transmitting each of said packets to said network client;

means for detecting an acknowledgment for one or more packets received at said network client;

means for retransmitting any of said packets for which no acknowledgment is detected if their respective timers have not expired; and

means for terminating the retention of each packet whose timer has expired, wherein differential packets are removed more frequently than frame packets in order to ensure that critical information is not lost when an acknowledgment is not detected.

11. A network as set forth in claim 10 further comprising means for terminating the retention of any of said packets upon detecting said acknowledgment for said any of said packets prior to expiration of said timer.

12. A network as set forth in claim 10 further comprising means for placing said acknowledgment for differing ones of said packets into a coalesced acknowledgment.

13. A network as set forth in claim 10 further comprising:

means for maintaining the bandwidth of successively transmitted packets to the lesser of a congestion window initially determined to be maximum segment size and a client window size no greater than the size of a UDP socket input buffer at said client.

14. A network as set forth in claim 13 wherein said congestion window is increased by the size of each packet for which an acknowledgment is received.

15. A network as set forth in claim 14 wherein said congestion window is increased until said congestion window exceeds a predetermined threshold, and increases thereafter by said maximum segment size for each acknowledgment received.

16. A network as set forth in claim 15 wherein said threshold is determined by a window size that is last known to be error free in receipt of said successively transmitted packets.

17. A network as set forth in claim 15 wherein said threshold is, upon retransmitting of any of said packets, set to the greater of ½

of the current congestion window size or maximum segment size.

18. A network as set forth in claim 17 wherein said congestion window is reset to said maximum segment size.

19. A computer readable medium containing a program which implements a procedure for real time transmission of frame-based content between a network server and a network client comprising:

designating individual packets of said content as either a frame packet that contains information for reconstructing an entire frame of said content or a differential packet that contains changes to a frame;

assigning to each of said packets a sequence number and a timer for retransmission retention, wherein the duration of the timers for frame packets is longer than for differential packets;

transmitting each of said packets to said network client;

detecting an acknowledgment for one or more packets received at said network client;

retransmitting any of said packets for which no acknowledgment is detected if their respective timers have not expired; and

terminating the retention of each packet whose timer has expired, wherein differential packets are removed more frequently than frame packets in order to ensure that critical information is not lost when an acknowledgment is not detected.

20. A computer readable medium as set forth in claim 19 further comprising terminating the retention of any of said packets upon detecting said acknowledgment for said any one of said packets prior to expiration of said timer.

21. A computer readable medium as set forth in claim 19 further comprising placing said acknowledgment for differing ones of said packets into a coalesced acknowledgment.

22. A computer readable medium as set forth in claim 19 further comprising:

maintaining the bandwidth of successively transmitted packets to the lesser of a congestion window initially determined to be maximum segment size and a client window size no greater than the size of a UDP socket input buffer at said client.

23. A computer readable medium as set forth in claim 22 wherein said congestion window is increased by the size of each packet for which an acknowledgment is received.

24. A computer readable medium as set forth in claim 23 wherein said congestion window is increased until said congestion window exceeds a predetermined threshold, and increases thereafter by said maximum segment size for each acknowledgment received.

25. A computer readable medium as set forth in claim 24 wherein said threshold is determined by a window size that is last known to be error free in receipt of said successively transmitted packets.

26. A computer readable medium as set forth in claim 24 wherein said threshold is, upon retransmitting of any of said packets, set to the greater of ½

of the current congestion window size or maximum segment size.

27. A computer readable medium as set forth in claim 26 wherein said congestion window is reset to said maximum segment size.

28. A computer network comprising:

a server operative to send successive packets of frame-based content into said network;

a network client which receives said packets from said network;

a retransmit module responsive to said packets sent by said server to assign to each of said packets a sequence number and a timer for retention by said module and to designate said packet as one of a frame packet and a differential packet based upon whether said packet contains information for reconstructing an entire frame of said content, said network client transmitting to said retransmit module an acknowledgment for one or more packets received at said network client, said retransmit module retransmitting selected packets in the absence of an acknowledgment for said selected packets, and

said retransmit module further removing any of said packets upon expiration of said timer assigned thereto wherein said differential packets are removed after a shorter time period than frame packets in order to ensure that critical information is not lost when an acknowledgment is not received.

29. A network as set forth in claim 28 wherein said retransmit module removes packets upon receipt of an acknowledgment for said packets prior to expiration of said timer.

30. A network as set forth in claim 28 wherein said client is further adapted to place said acknowledgment for differing ones of said packets into a coalesced acknowledgment.

31. A network as set forth in claim 28 wherein said server further maintains a bandwidth of successively transmitted packets to the lesser of a congestion window initially determined to be maximum segment size and a client window size no greater than the size of a UDP socket input buffer at said client.

32. A network as set forth in claim 31 wherein said congestion window is increased by the size of each packet for which an acknowledgment is received.

33. A network as set forth in claim 32 wherein said congestion window is increased until said congestion window exceeds a predetermined threshold, and increases thereafter by said maximum segment size for each acknowledgment received.

34. A network as set forth in claim 33 wherein said threshold is determined by a window size that is last known to be error free in receipt of said successively transmitted packets.

35. A network as set forth in claim 33 wherein said threshold is, upon retransmitting of any of said packets, set to the greater of ½

of the current congestion window size or maximum segment size.

36. A network as set forth in claim 35 wherein said congestion window is reset to said maximum segment size.