Data Sheet

Packet Types—Ethernet Controller I210
873
UDP pseudo header has the same format as the TCP pseudo header. The pseudo header conceptually
prefixed to the UDP header contains the IPv4 source address, the IPv4 destination address, the IPv4
protocol field, and the UDP length (same as the TCP Length discussed above). This checksum procedure
is the same as is used in TCP.
Unlike the TCP checksum, the UDP checksum is optional (for IPv4). Software must set the TXSM bit in
the TCP/IP Context Transmit Descriptor to indicate that a UDP checksum should be inserted. Hardware
will not overwrite the UDP checksum unless the TXSM bit is set.
Table A-11. UDP Header (Little Endian Order)
Byte3 Byte2 Byte1 Byte0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
Destination Port Source Port
Checksum Length