System and method for in-line consistency checking of packetized data

• US 7,607,070 B2
• Filed: 09/13/2004
• Issued: 10/20/2009
• Est. Priority Date: 09/13/2004
• Status: Active Grant

• Current Assignee: National Instruments Corporation (Emerson Electric Company)
• Original Assignee: National Instruments Corporation (Emerson Electric Company)
• Inventors: Kovner, Scott B., Clark, Chris A.
• Primary Examiner(s): Torres; Joseph D
• Application Number:
  US10/939,858
• Publication Number:
  US 20060059400A1
• Time in Patent Office: 1,863 Days
• Field of Search: 714/776, 714/774, 714/779
• US Class Current: 714/776
• CPC Class Codes: H04L 1/1838 for semi-reliable protocols, e.g. for less sensitive applications such as streaming video buffer level management for video bitstream receiver H04N21/44004

Abstract

A system and method for efficiently detecting and correcting transmission errors in packet-based communications by using cumulative error detection codes. The system may comprise a transmitting unit, which transmits one or more data packets. Each of the transmitted packets may comprise a plurality of transmission subunits. The transmitting unit preferably generates a cumulative error detection code (e.g., cumulative CRC code) for each of the transmission subunits of a packet. The system may further comprise a receiving unit to receive each of the transmission subunits of the packet. The receiving unit preferably generates a new cumulative error detection code for each of the received transmission subunits. The new cumulative error detection code is compared to the received cumulative error detection code to determine if any errors occurred in the transmission of the transmission subunit.

Claims

1. An apparatus for transmitting packets, which is operable to implement a protocol for detecting and correcting transmission errors in packet-based communications, the apparatus comprising:

a device configured to transmit one or more packets, wherein each packet comprises a header and a footer and is configured for transmission as a single entity, wherein each packet comprises a plurality of transmission subunits, and wherein each of the plurality of transmission subunits does not have a header and a footer; and

a code generation unit coupled to the device and configured to generate a cumulative error detection code for each of the plurality of transmission subunits of a packet wherein the first error detection code is seeded with a value;

wherein the cumulative error detection code for each transmission subunit of the packet is generated based on data comprised in the each transmission subunit and a previous cumulative error detection code corresponding to one or more previously transmitted transmission subunits of the packet.

2. The apparatus of claim 1, wherein the code generation unit is further configured to generate the cumulative error detection code for each of the plurality of transmission subunits of the packet with the exception of a first transmission subunit, wherein the cumulative error detection code is based on the data comprised in the transmission subunit and the previous cumulative error detection code corresponding to the one or more previously transmitted transmission subunit of the packet.

3. The apparatus of claim 1, wherein the code generation unit is configured to store the previous cumulative error detection code.

4. The apparatus of claim 1, wherein the code generation unit is configured to set the previous cumulative error detection code to zero before generating the cumulative error detection code for a first transmission subunit of the packet, wherein the cumulative error detection code for the first transmission subunit of the packet is generated based on the data comprised in the first transmission subunit and the value zero.

5. The apparatus of claim 4, wherein the code generation unit is configured to generate the cumulative error detection code for a second transmission subunit of the packet based on the data comprised in the second transmission subunit and the cumulative error detection code associated with the first transmission subunit of the packet.

6. The apparatus of claim 5, wherein the code generation unit is configured to generate the cumulative error detection code for a third transmission subunit of the packet based on the data comprised in the third transmission subunit and the cumulative error detection code associated with the second transmission subunit.

7. The apparatus of claim 1, wherein the device is further configured to transmit a header within each packet, wherein the header is comprised in one or more transmission subunits of each packet.

8. The apparatus of claim 7, wherein the header comprises a global transmission count (GTC), wherein the GTC is a total size of data transmitted by the device since a previous initialization, up to and including the one or more previously transmitted transmission subunits of a one or more previously transmitted packet.

9. The apparatus of claim 8, wherein the GTC is incremented by a value corresponding to a size of a transmitted subunit.

10. The apparatus of claim 8, wherein the device is configured to transmit a GTC packet during idle periods, wherein the GTC packet is a null packet including only the GTC.

11. The apparatus of claim 1, configured to transmit packets over a system interconnect to a second apparatus.

12. The apparatus of claim 1, wherein the cumulative error detection code is a cumulative cyclic redundant checking (CRC) code.

13. The apparatus of claim 1, wherein the cumulative error detection code is a cumulative checksum.

14. The apparatus of claim 1, wherein the device is also configured to receive data.

15. The apparatus of claim 1, wherein the device is configured as a transceiver.

16. An apparatus for receiving packets, which is operable to implement a protocol for detecting and correcting transmission errors in packet-based communications, the apparatus comprising:

a device configured to receive one or more packets, wherein each packet comprises a plurality of transmission subunits, wherein each packet comprises a header and a footer, wherein each of the received transmission subunits of a packet comprises data comprised in the received transmission subunit and a received cumulative error detection code, and wherein each of the received transmission subunits do not comprise a header and a footer;

a code generation unit coupled to the device and configured to generate a new cumulative error detection code for each of the received transmission subunits of the packet, wherein the new cumulative error detection code for each received transmission subunit of the packet is generated based on the received data comprised in the each received transmission subunit and a new cumulative error detection code corresponding to one or more previously received transmission subunits of the packet wherein the first error detection code is seeded with a value; and

an error detection unit coupled to the code generation unit and configured to compare the new cumulative error detection code to the received cumulative error detection code to determine if a transmission error occurred.

17. The apparatus of claim 16, wherein the apparatus is operable to consume the received data comprised in the received transmission subunit if the new cumulative error detection code matches the received cumulative error detection code.

18. The apparatus of claim 16, wherein the apparatus is operable to discard the received data comprised in the received transmission subunit if the new cumulative error detection code does not match the received cumulative error detection code.

19. The apparatus of claim 16, wherein the code generation unit is further configured to generate the new cumulative error detection code for each of the received transmission subunits of the packet with the exception of a first received transmission subunit, wherein the new cumulative error detection code is based on the received data comprised in the received transmission subunit and a previously generated new cumulative error detection code corresponding to the one or more previously received transmission subunits of the packet.

20. The apparatus of claim 16, wherein the code generation unit is configured to generate the new cumulative error detection code for each of the received transmission subunits of the packet based on the received data comprised in the received transmission subunit and a stored cumulative error detection code.

21. The apparatus of claim 16, wherein the device is further configured to receive a header within each of the received packets, wherein the header is comprised in one or more of the received transmission subunits of each received packet.

22. The apparatus of claim 21, wherein the device is configured to detect a global transmission count (GTC) in the received header, wherein the GTC is a total size of data transmitted since a previous initialization, up to and including the one or more previously transmitted transmission subunits of a one or more previously transmitted packet.

23. The apparatus of claim 22, wherein a global reception count (GRC) is compared with the received GTC, wherein the GRC is a total size of data received by the device since a previous initialization, up to and including the one or more previously received transmission subunits of a one or more previously received packet.

24. The apparatus of claim 23, wherein the device is operable to request a retransmission of a previously received packet if the GRC is less than the received GTC.

25. The apparatus of claim 23, wherein the device is operable to receive additional transmission subunits corresponding to a current packet associated with the received header if the GRC is equal to the received GTC.

26. The apparatus of claim 16, wherein the received cumulative error detection code and the new cumulative error detection code are cumulative cyclic redundant checking (CRC) codes.

27. The apparatus of claim 16, wherein the received cumulative error detection code and the new cumulative error detection code are cumulative checksums.

28. The apparatus of claim 16, wherein the device is also configured to transmit data.

29. The apparatus of claim 16, wherein the device is configured as a transceiver.

30. A system for implementing a protocol for detecting and correcting transmission errors in packet-based communications, the system comprising:

a host computer comprising a first module for transmitting packets, where the first module is operable to implement the protocol for detecting and correcting transmission errors in packet-based communications, and wherein the first module comprises;

a first device configured to transmit one or more packets, wherein each packet comprises a header and a footer and is configured for transmission as a single entity, wherein each packet comprises a plurality of transmission subunits, and wherein each of the plurality of transmission subunits does not have a header and a footer, and

a first code generation unit coupled to the first device and configured to generate a cumulative error detection code for each of the plurality of transmission subunits of a packet,

wherein the cumulative error detection code for each transmission subunit of the packet is generated based on data comprised in the each transmission subunit and a cumulative error detection code corresponding to one or more previously transmitted transmission subunits of the packet wherein the first error detection code is seeded with a value;

a system interconnect coupled to the first module of the host computer; and

a remote chassis coupled to the system interconnect and comprising a second module for receiving packets, wherein the second module is operable to implement the protocol for detecting and correcting transmission errors in packet-based communications, and wherein the second module comprises;

a second device configured to receive each of the plurality of transmitted transmission subunits of the one or more packets, wherein each of the received transmission subunits of the packet comprises the data comprised in the received transmission subunit and the received cumulative error detection code, and

a second code generation unit coupled to the second device and configured to generate a new cumulative error detection code for each of the received transmission subunits of the packet, wherein the new cumulative error detection code for each received transmission subunit of the packet is generated based on the received data comprised in the each received transmission subunit and a new cumulative error detection code corresponding to one or more previously received transmission subunits of the packet, and

an error detection unit coupled to the second code generation unit and configured to compare the new cumulative error detection code to the received cumulative error detection code to determine if a transmission error occurred.

31. The system of claim 30, wherein the second module is operable to consume the received data comprised in the received transmission subunit if the new cumulative error detection code matches the received cumulative error detection code.

32. The system of claim 30, wherein the second module is operable to discard the received data comprised in the received transmission subunit if the new cumulative error detection code does not match the received cumulative error detection code.

33. The system of claim 30, wherein the first code generation unit is configured to generate the cumulative error detection code for each of the plurality of transmission subunits of the packet based on the data comprised in the transmission subunit and a first stored cumulative error detection code.

34. The system of claim 30, wherein the second code generation unit is configured to generate the new cumulative error detection code for each of the received transmission subunits of the packet based on the received data comprised in the received transmission subunit and a second stored cumulative error detection code.

35. A method for transmitting packets, which implements a protocol for detecting and correcting transmission errors in packet-based communications, the method comprising:

generating a cumulative error detection code for each of a plurality of transmission subunits of a packet, wherein each of the plurality of transmission subunits does not have a header and footer; and

transmitting each of the plurality of transmission subunits of the packet;

wherein the cumulative error detection code for each transmission subunit of the packet is generated based on data comprised in the each transmission subunit and a cumulative error detection code corresponding to one or more previously transmitted transmission subunits of the packet wherein the first error detection code is seeded with a value.

36. The method of claim 35, wherein the cumulative error detection code for each of the plurality of transmission subunits of the packet, with the exception of a first transmission subunit, is generated based on the data comprised in the transmission subunit and a previously generated cumulative error detection code corresponding to the one or more previously transmitted transmission subunits of the packet.

37. The method of claim 35, wherein the cumulative error detection code for each of the plurality of transmission subunits of the packet is generated based on the data comprised in the transmission subunit and a stored cumulative error detection code.

38. The method of claim 35, wherein the cumulative error detection code is set to zero before generating the cumulative error detection code for a first transmission subunit of the packet, wherein the cumulative error detection code for the first transmission subunit of the packet is generated based on the data comprised in the first transmission subunit and the value zero.

39. The method of claim 38, wherein the cumulative error detection code for a second transmission subunit of the packet is generated based on the data comprised in the second transmission subunit and the cumulative error detection code associated with the first transmission subunit of the packet.

40. A method for receiving packets that implements a protocol for detecting and correcting transmission errors in packet-based communications, the method comprising:

receiving one or more packets, wherein each packet comprises a header and a footer, wherein each packet comprises a plurality of transmission subunits, wherein each of the plurality of transmission subunits does not have a header and a footer, and wherein a particular received transmission subunit of the plurality of transmission subunits of a packet comprises data comprised in the particular received transmission subunit and a received cumulative error detection code;

generating a new cumulative error detection code for each of the received transmission subunits of the packet, wherein the new cumulative error detection code for each received transmission subunit of the packet is generated based on the received data comprised in the each received transmission subunit and a new cumulative error detection code corresponding to one or more previously received transmission subunits of the packet wherein the first error detection code is seeded with a value; and

comparing the new cumulative error detection code with the received cumulative error detection code to determine if a transmission error occurred.

41. The method of claim 40, wherein the received data associated with the received transmission subunit is consumed if the new cumulative error detection code matches the received cumulative error detection code.

42. The method of claim 40, wherein the received data associated with the received transmission subunit is discarded if the new cumulative error detection code does not match the received cumulative error detection code.

43. The method of claim 40, wherein the new cumulative error detection code for each of the received transmission subunits of the packet, with the exception of a first received transmission subunit, is generated based on the received data comprised in the received transmission subunit and a previously generated new cumulative error detection code corresponding to the one or more previously received transmission subunits of the packet.

44. The method of claim 40, wherein the new cumulative error detection code for each of the received transmission subunits of the packet is generated based on the received data comprised in the received transmission subunit and a stored cumulative error detection code.

45. A computer readable memory medium comprising program instructions, wherein the program instructions are executable by a processor to:

generate a cumulative error detection code for each of a plurality of transmission subunits of a packet, wherein each of the plurality of transmission subunits does not comprise a header and a footer; and

transmit each of the plurality of transmission subunits of the packet;

wherein the cumulative error detection code for each transmission subunit of the packet is generated based on data comprised in the each transmission subunit and a cumulative error detection code corresponding to one or more previously transmitted transmission subunits of the packet wherein the first error detection code is seeded with a value.

46. A computer readable memory medium comprising program instructions, wherein the program instructions are executable by a processor to:

generate a new cumulative error detection code for each received transmission subunits of a packet, wherein each of the transmission subunits do not comprise a header and a footer, wherein the new cumulative error detection code for each received transmission subunit of the packet is generated based on received data comprised in the each received transmission subunit and a new cumulative error detection code corresponding to one or more previously received transmission subunits of the packet wherein the first error detection code is seeded with a value; and

compare the new cumulative error detection code with a received cumulative error detection code to determine if a transmission error occurred.