APPARATUS FOR BLIND CHECKSUM AND CORRECTION FOR NETWORK TRANSMISSIONS

• US 20090083611A1
• Filed: 08/29/2008
• Published: 03/26/2009
• Est. Priority Date: 04/01/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: BASSO, Claude, Damon, Philippe, Vaidhyanathan, Natarajan, Calvignac, Jean Louis, Verplanken, Fabrice Jean, Verrilli, Colin Beaton, Fuhs, Ronald Edward, Chang, Chih-Jen, Willenborg, Scott Michael
• Granted Patent: US 8,225,188 B2
• Time in Patent Office: Days
• US Class Current: 714/807
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/161 Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields

Abstract

Apparatus for providing a checksum in a network transmission. In one aspect of the invention, a checksum for a packet to be transmitted on a network is determined by retrieving packet information from a storage device, the packet information to be included in the packet to be transmitted. A blind checksum value is determined based on the retrieved packet information, and the blind checksum value is adjusted to a protocol checksum based on descriptor information describing the structure of the packet. The protocol checksum is inserted in the packet before the packet is transmitted.

Claims

1. An apparatus for determining a checksum for a packet to be transmitted on a network, the apparatus comprising:

a memory access unit that retrieves packet information from a storage device, the packet information to be included in the packet to be transmitted;

an accumulator that determines a blind checksum value based on the retrieved packet information, the blind checksum value being a sum based on successive values in the retrieved packet information, the successive values ranging from a start of the packet to an end of a body of the packet; and

a transmission unit that receives the packet information and the blind checksum value and adjusts the blind checksum value to a protocol checksum based on descriptor information describing the structure of the packet, wherein the transmission unit inserts the protocol checksum in the packet and outputs the packet for transmission on the network.

2. The apparatus of claim 1 wherein the accumulator determines the blind checksum value by summing all the successive values in the retrieved packet information as it is loaded.

3. The apparatus of claim 1 further comprising a transmission processor, wherein the transmission processor retrieves the descriptor information from the storage device and provides the descriptor information to the transmission unit.

4. The apparatus of claim 3 wherein the transmission processor receives the blind checksum value from the accumulator and provides the blind checksum value to the transmission unit.

5. The apparatus of claim 1 further comprising a data buffer coupled to the memory access unit, wherein the data buffer receives the packet information from the memory access unit, and wherein the packet information is sent from the data buffer to the transmission unit.

6. The apparatus of claim 1 wherein the retrieved packet information includes a header and a body of the packet.

7. The apparatus of claim 1 wherein the retrieved packet information includes a body of the packet and no header of the packet, and wherein the memory access unit retrieves the header of the packet with the descriptor information.

8. The apparatus of claim 7 further comprising a merge unit that merges the header with the body of the packet after the accumulator determines the blind checksum for the body and wherein the transmission unit receives the merged packet information from the merge unit.

9. The apparatus of claim 1 wherein the transmission unit adjusts the blind checksum value includes adding or subtracting at least one halfword value of the packet information to or from the blind checksum value.

10. The apparatus of claim 9 wherein the packet to be transmitted is a TCP/IP packet, and wherein the transmission unit adjusts the blind checksum value by adding a halfword value to the blind checksum value if the halfword value is an IP header field required to determine a TCP checksum value and the halfword value was not included in the blind checksum.

11. The apparatus of claim 9 wherein the packet to be transmitted is a TCP/IP packet, and wherein the transmission unit adjusts the blind checksum value by subtracting a halfword value from the blind checksum value if the halfword value is an IP header field not required to determine a TCP checksum value and the halfword value was included in the blind checksum.

12. The apparatus of claim 3 wherein the transmission processor also retrieves the packet information with the descriptor information from the storage device and provides the packet information to the transmission unit, wherein the transmission unit creates the protocol checksum based on the descriptor information.

13. The apparatus of claim 3 wherein the transmission processor retrieves the packet information with the descriptor information from storage device, and wherein the blind checksum value is determined when a portion of the packet information is stored separately from the descriptor in memory, and

wherein the transmission unit determines the protocol checksum based on descriptor information describing the structure of the packet, if the packet information is stored with and retrieved with the descriptor information.

14. The apparatus of claim 1 further comprising a unit that determines the descriptor information by parsing the packet information.

15. The apparatus of claim 1 wherein the packet is provided according to the TCP/IP protocol.

16. The apparatus of claim 9 wherein the adjusting of the blind checksum value includes subtracting out bytes of an IP header portion of the packet information and leaving in bytes of the IP header portion that are needed for a pseudo header to create a TCP checksum.

17. The apparatus of claim 16 wherein the transmission unit adjusting the blind checksum value includes subtracting out one byte of a halfword and keeping the other byte of the halfword for fields in the IP header portion in which only one byte of the field is needed in the pseudo header.

18. The apparatus of claim 9 wherein the transmission unit adjusting the blind checksum value includes subtracting out one byte of a halfword and keeping the other byte of the halfword if the halfword is positioned on a boundary between a portion of the packet information already included in the blind checksum value and a portion not included in the blind checksum value.

19. The apparatus of claim 1 wherein the transmission unit determines and places the protocol checksum in a protocol checksum field of the packet without creating a pseudo header having specified fields from the packet information.