Data protocol

• US 20070162609A1
• Filed: 03/03/2004
• Published: 07/12/2007
• Est. Priority Date: 03/03/2003
• Status: Active Grant

• Current Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Original Assignee: Level 5 Networks, Inc. (Advanced Micro Devices, Inc.)
• Inventors: Riddoch, David, Pope, Steve, Roberts, Derek, Clarke, David
• Granted Patent: US 7,934,141 B2
• Time in Patent Office: Days
• US Class Current: 709/230
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35
• CPC Class Codes: H04L 1/0078 Avoidance of errors by organising the transmitted data in a format specifically designed to deal with errors, e.g. location forward error control, e.g. FEC, CRC H04L1/004; adaptive formatting H04L1/0006; mappings H04L27/00

Abstract

A method of transmitting data according to a data transmission protocol wherein the data is transmitted as a plurality of data frames and each data frame includes an error checking field comprising at least two sub-fields, the data of the first sub-field being formed by a first error checking method performed on data of the frame and the data of the second sub-field being formed by a second error checking method performed on the said data of the frame, the first and second methods being such that the data of the first sub-field has different error checking properties from those of the data of the second sub-field.

Claims

7. (canceled)

20. A method of transmitting data according to a data transmission protocol wherein the data is transmitted as a plurality of data frames and each data frame comprises one or more sections, each of which includes traffic data, a destination address for the traffic data of that section and error checking data for the traffic data of that section.

1. A method of transmitting data according to a data transmission protocol wherein the data is transmitted as a plurality of data frames and each data frame includes an error checking field comprising at least two sub-fields, the data of the first sub-field being formed by a first error checking method performed on data of the frame and the data of the second sub-field being formed by a second error checking method performed on the data of the frame, the first and second methods being such that the data of the first sub-field has different error checking properties from those of the data of the second sub-field.

2. A method as claimed in claim 1, wherein the error checking field is a data word in the data frame.

3. A method as claimed in claim 2, wherein the error checking field consists of data bits that are contiguous in the frame.

4. A method as claimed in claim 1, wherein the first sub-field consists of bits that are contiguous in the frame.

5. A method as claimed in claim 1, wherein the each of the first and second sub-fields consists of bits that are respectively contiguous in the frame.

6. A method as claimed in claim 1, wherein the first sub-field and the second sub-field are of equal length.

8. A method as claimed in claim 1, wherein the first and second error checking methods are cyclic redundancy check methods and the generator polynomial for the first error checking method is different from the generator polynomial for the second error checking method.

9. A method as claimed in claim 8, wherein one of the generator polynomials is the X25 polynomial.

10. A method as claimed in claim 8, wherein one of the generator polynomials is the USB CRC-16 polynomial.

11. A method as claimed in claim 1, wherein the first and second error checking methods are such that they result in the data of the first sub-field having different statistical properties from the data of the second sub-field as regards its indication of errors in the data.

12. A method as claimed in claim 1, wherein the protocol is such that each data frame comprises at least one data section, each data section comprising an address and traffic data to be applied to that address by a recipient of the data frame.

13. A method as claimed in claim 1, wherein the protocol is such that each data frame comprises at least one error checking field, the data of the first and second sub-fields of each error checking field subsequent to the first error checking field in a frame being formed respectively by the first and second error checking methods performed on the data on which the first and second error checking methods were performed to form the preceding error checking field in the frame together with data located between the preceding error checking field and the respective error checking field.

14. A method as claimed in claim 1, wherein the data frame comprises a frame header and wherein the frame header is excluded from the data on which the first and second error checking methods are performed to form the error checking fields.

15. A method as claimed in claim 14, wherein the frame header indicates a member of the group consisting of a source address of the data frame, a destination address of the data frame and a hop count for the data frame.

16. A method as claimed in claim 1, wherein the data frame is an Ethernet frame.

17. A method as claimed in claim 1, wherein the protocol is such that the data frame comprises a frame checksum calculated over the frame.

18. A method as claimed in claim 17, wherein the data frame comprises a frame header and wherein the frame header is excluded from the data on which the first and second error checking methods are performed to form the error checking fields, wherein the frame header is included in the data on which the frame checksum is calculated.

19. A method as claimed in claim 1, comprising:

at a data transmitter forming a data frame according to the data transmission protocol;

transmitting the data frame over a data network from the data transmitter to a data receiver; and

at the data receiver verifying the received data on the basis of the data of each error checking field.

21. A method as claimed in claim 20, wherein the error checking data of a data section is calculated over all the traffic data of that section.

22. A method as claimed in claim 21, wherein the error checking data of a data section is calculated over all the traffic data of that section and that of any preceding data section of the frame.

23. A method as claimed in claim 20, wherein the data protocol is such that each data section may include two or more blocks of error checking data, each block of error checking data being calculated over the traffic data of that section that precedes the respective block of error checking data.

24. A method as claimed in claim 20, wherein the error checking data includes data calculated according to a cyclic redundancy check algorithm.

25. A method as claimed in claim 20, wherein the data frame comprises a frame header and wherein the frame header is excluded from the data on which error checking data is calculated.

26. A method as claimed in claim 25, wherein the frame header indicates at least one member of the group consisting of a source address of the data frame, a destination address of the data frame and a hop count for the data frame.

27. A method as claimed in claim 20, wherein the data frame is an Ethernet frame.

28. A method as claimed in claim 20, wherein the protocol is such that the data frame comprises a frame checksum calculated over the frame.

29. A method as claimed in claim 28 wherein the data frame comprises a frame header and wherein the frame header is excluded from the data on which error checking data is calculated,

wherein the frame header is included in the data on which the frame checksum is calculated.

30. A method as claimed in claim 29, where a data section includes two or more blocks of error checking data, each block of error checking data being calculated over the traffic data of that section that precedes the respective block of error checking data, comprising:

if a block of error checking data is successfully verified applying the traffic data preceding that block to the destination address of that section, and

if a block of error checking data is not successfully verified requesting retransmission of at least some of the data of the section from the transmitter.

31. A method as claimed in claim 30, wherein the at least some of the data comprises all the traffic data between the block of error checking data that is not successfully verified and the preceding block of error checking data or the beginning of the data section if there was no preceding block of error checking data.

40. A data transceiver arranged to perform a method according to claim 1.

29-1. A method as claimed in claim 20, comprising:

at a data transmitter forming a data frame according to the data transmission protocol;

transmitting the data frame over a data network from the data transmitter to a data receiver; and

at the data receiver verifying the received data on the basis of the data of each error checking field.

32. A method of receiving traffic data over a data link and writing the traffic data to a memory accessible to an application, the method comprising:

maintaining first and second pointers to locations in the memory;

analyzing data received over the data link to determine whether it represents traffic data or error checking data, and;

if the received data represents traffic data writing the received data to the memory at the location indicated by the first pointer, and updating the first pointer to point to the next location in the memory; and

if the received data represents error check data verifying the error check data, and if the error check data is successfully verified updating the second pointer to point to the same location as the first pointer.

33. A method as claimed in claim 32, comprising:

at a transmitter forming data sections according to a protocol such that each data section comprises traffic data and one or more blocks of error checking data for the traffic data, and such that when a data section comprises two or more blocks of error checking data each block of error checking data is calculated over the traffic data preceding it in the data section; and

transmitting the data sections over the data link to form the said data received over the data link.

34. A method as claimed in claim 33, comprising:

if the error check data is not successfully verified and is the first error check data of a data section requesting retransmission of at least the traffic data preceding that error check data in the data section; and

if the error check data is not successfully verified and is not the first error check data of a data section requesting retransmission of at least the traffic data preceding that error check data and subsequent to the preceding error check data in the data section.

35. A method as claimed in claim 33, comprising:

if the error check data is not successfully verified reporting that to the transmitter of the data.

36. A method as claimed in claim 33, comprising:

if the error check data is not successfully verified reporting that to the transmitter of the data and initiating renegotiation of parameters for data transmission over the link.

37. A method as claimed in claim 32, wherein the traffic data is carried over the link in the form of data frames.

38. A method as claimed in claim 37, wherein at least one network device on the route between the transmitter and the receiver of the data performs cut-through forwarding of the data frames.

39. A method as claimed in claim 38, wherein the traffic data is associated with an address transmitted over the data link and indicating the initial location of the first pointer.

41. A data transceiver arranged to perform a method according to claim 32.