Enhanced error detection in multilink serdes channels

• US 8,332,721 B2
• Filed: 03/03/2009
• Issued: 12/11/2012
• Est. Priority Date: 01/21/2009
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Lawson, Matthew Todd, Walker, David S.
• Primary Examiner(s): Baderman, Scott
• Assistant Examiner(s): MILES, NEIL D
• Application Number:
  US12/396,651
• Publication Number:
  US 20100185919A1
• Time in Patent Office: 1,379 Days
• Field of Search: 714/807, 714/758
• US Class Current: 714/758
• CPC Class Codes: H03M 13/09 Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 2001/0094 Bus

Abstract

A method for receiving packet data at a communication channel and transmitting the packet data over serial links of the communication channel. The packet data is sliced into n-bit data portions which are concatenated with a header prior to transmitting an n-bit portion across one of the serial links of the communication channel. The header includes a CRC to provide improved error detection.

Claims

1. A method comprising:

receiving an encoded frame via a plurality of serial communication links, wherein

the encoded frame comprises at least one of an error check code or a virtual delimiter;

calculating a first cyclic redundancy check (CRC) for the encoded frame;

detecting whether an error occurred during transmission of the encoded frame, wherein

the detecting comprises comparing the first CRC with a second CRC,

the encoded frame comprises the second CRC, and

the second CRC is separate from the error check code; and

forming a plurality of segments, wherein

a first segment of the plurality of segments comprises a portion of the encoded frame, wherein the portion is less than all of the encoded frame, and

each segment of the plurality of segments comprises respective frame header information and respective frame payload information.

2. The method of claim 1, wherein

the first segment comprises 24 bits of frame payload information and 2 bits of frame header information.

3. The method of claim 1, wherein

the first segment comprises one bit of the second CRC.

4. The method of claim 1, further comprising

extracting frame payload information from the first segment to produce extracted frame payload information;

and

forming a transport layer packet, wherein

the transport layer packet includes the extracted frame payload information, and

the transport layer packet includes a third CRC.

5. The method of claim 1, further comprising:

determining whether frame payload information from the first segment comprises a portion of one or more transport layer packets, wherein the determining is based on the value of a virtual delimiter included in the encoded frame.

6. The method of claim 1, wherein the second CRC is calculated using the same algorithm that was used to calculate the first CRC.

7. The method of claim 1, further comprising descrambling the encoded frame.

8. The method of claim 7, further comprising

initializing a descrambler with an initial value that was used to initialize a scrambler, wherein the scrambler scrambled the encoded frame.

9. An apparatus comprising:

a first circuit configured to

receive an encoded frame via a plurality of serial communication links, wherein

the encoded frame comprises at least one of an error check code or a virtual delimiter;

calculate a first cyclic redundancy check (CRC) for the encoded frame;

detect whether an error occurred during transmission of the encoded frame, wherein

detecting whether an error occurred comprises comparing the first CRC with a second CRC,

the encoded frame comprises the second CRC, and

the second CRC is separate from the error check code; and

form a plurality of segments, wherein

a first segment of the plurality of segments comprises a portion of the encoded frame, wherein the portion is less than all of the encoded frame, and

each segment of the plurality of segments comprises respective frame header information and respective frame payload information.

10. The apparatus of claim 9, wherein

the first segment comprises 24 bits of frame payload information and 2 bits of frame header information.

11. The apparatus of claim 9, wherein

the first segment comprises one bit of the second CRC.

12. The apparatus of claim 9, further comprising

a third circuit configured to

extract frame payload information from the first segment to produce extracted frame payload information;

and

form a transport layer packet, wherein

the transport layer packet includes the extracted frame payload information, and

the transport layer packet includes a third CRC.

13. The apparatus of claim 9, further comprising:

determining whether frame payload information from the first segment comprises a portion of one or more transport layer packets, wherein the determining is based on the value of a virtual delimiter included in the encoded frame.

14. The apparatus of claim 10 wherein the second CRC is calculated using the same algorithm that was used to calculate the first CRC.

15. The apparatus of claim 9, further comprising

a fourth circuit configured to descramble the encoded frame.

16. The apparatus of claim 15, further comprising

a fifth circuit configured to

initialize a descrambler with an initial value that was used to initialize a scrambler, wherein the scrambler scrambled the encoded frame.

17. An apparatus comprising:

a first means for

receiving an encoded frame via a plurality of serial communication links, wherein

the encoded frame comprises at least one of an error check code or a virtual delimiter;

calculating a first cyclic redundancy check (CRC) for the encoded frame;

detecting whether an error occurred during transmission of the encoded frame, wherein

the detecting comprises comparing the first CRC with a second CRC,

the encoded frame comprises the second CRC, and

the second CRC is separate from the error check code; and

forming a plurality of segments, wherein

a first segment of the plurality of segments comprises a portion of the encoded frame, wherein the portion is less than all of the encoded frame, and

each segment of the plurality of segments comprises respective frame header information and respective frame payload information.