Apparatus and method for performing cyclic redundancy check (CRC) on partial protocol data units (PDUS)

• US 20060114909A1
• Filed: 10/26/2005
• Published: 06/01/2006
• Est. Priority Date: 10/26/2004
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Silverback Systems, Inc. (Broadcom, Inc.)
• Inventors: Uzrad-Nali, Oran, Plotz, Kevin G., Leichty, Phil L.
• Granted Patent: US 7,577,896 B2
• Time in Patent Office: Days
• US Class Current: 370/394
• CPC Class Codes: H04L 49/90 Buffering arrangements

Abstract

The present invention discloses an apparatus and method for performing cyclic redundancy check (CRC) on partial protocol data units (PDUs). The disclosed apparatus is designed to off-load the CRC calculation for transmit or receive from a host computer. According to the disclosed method, when generating CRC for partial PDUs, for each such PDUs a decision is made to determine whether a CRC action is required, i.e., if CRC should be calculated, checked or placed in the outgoing byte stream. When partial CRC calculation is performed the intermediate value is saved into memory and later is used for calculating the CRC for a consecutive partial PDU. In accordance with a preferred embodiment of the invention, the need to re-calculate the CRC in a case of a re-transmit request is eliminated.

Claims

1. An apparatus for performing CRC operations on protocol data units (PDUs), the apparatus comprising:

a queue manager and scheduler capable of managing a plurality of queues, wherein each of queues comprise a plurality of memory object descriptors (MODs);

a CRC controller capable of performing said CRC operations;

a plurality of processing nodes capable of controlling said CRC operations;

a transmit handler capable of calculating said CRC values of segments flow to a network;

a first memory for maintaining at least said partial PDUs; and

,

a second memory for maintaining at least said plurality of MODs and partial CRC values;

whereby said apparatus is designed to off-load the CRC calculation for PDUs transmitted or received from a host computer.

2. The apparatus of claim 1, further comprising:

a direct memory access coupled to said CRC controller, said first memory and a host memory.

3. The apparatus of claim 1, wherein said CRC controller further includes a database of partial CRC values.

4. The apparatus of claim 1, wherein said CRC operations comprises at least one of:

generating a CRC value, checking a CRC value, inserting a CRC value in a CRC trailer, re-transmitting a CRC value.

5. The apparatus of claim 1, wherein each of said MOD points to a data block.

6. The apparatus of claim 5, wherein each of said MOD is marked with a different color to indicate whether said data block pointed by said MOD requires a CRC generation.

7. The apparatus of claim 1, wherein said PDUs are of the fifth layer of the standard communication model.

8. The apparatus of claim 1, wherein said apparatus is further configured to generate a CRC for a partial PDU.

9. The apparatus of claim 8, wherein the generation of CRC for a partial PDU comprises the steps of:

identifying the color of the MOD respective of said partial PDU;

waiting for MOD color change if MOD color is red and then proceeding with the following steps;

calculating the CRC if the MOD color is not blue;

otherwise, performing the following steps;

inserting CRC result in trailer;

resetting the CRC channel;

writing CRC result to memory.

10. The apparatus of claim 1, wherein said apparatus is further configured to check a CRC for a partial PDU.

11. The apparatus of claim 10, wherein the check of CRC of a partial PDU comprises the steps of:

sending a check command per segment; and

,

reporting the CRC check results.

12. The apparatus of claim 1, wherein said apparatus performed the CRC generation upon detection of a partial iSCSI PDU.

13. A computer network configured with the apparatus for performing CRC operations on protocol data units (PDUs) of claim 1.

14. A method for generating a CRC for a partial PDU comprising the steps of:

identifying the color of the MOD respective of said partial PDU;

waiting for MOD color change if MOD color is red and then proceeding with the following steps;

calculating the CRC if the MOD color is not blue;

otherwise,

performing the following steps;

inserting CRC result in trailer;

resetting the CRC channel;

writing CRC result to memory.

15. The method of claim 14, wherein said partial PDU is a partial iSCSI PDU.

16. The method of claim 14, wherein said method is operative to off-load the CRC calculation for PDUs transmitted or received from a host computer.

17. A computer network configured to operate the method for generating a CRC for a partial PDU of claim 14.