82598EB Datasheet, PDF (268/596 Pages) Intel Corporation – Intel® 82598EB 10 Gigabit Ethernet Controller Datasheet

Intel^® 82598EB 10 GbE Controller - Transmit Functionality
IPv4 Header
• IP Identification: incremented from last value (wrap around)
• IP Total Length = MSS + L4LEN + IPLEN
• IP Checksum
IPv6 Header
• Payload Length = MSS + L4LEN + IPLEN – 0x28 (IP base header length)
TCP Header
• Sequence Number update: Add previous TCP payload size to the previous sequence number
value. This is equivalent to adding the MSS to the previous sequence number.
• If FIN flag = 1b, it is cleared in these frames.
• If PSH flag =1b, it is cleared in these frames.
• TCP Checksum
UDP Header
• UDP Length: MSS + L4LEN
• UDP Checksum
3.5.3.4.7.3 TCP/IP/UDP Header for the Last Frame
The hardware makes the following changes to the headers for the last frame of a TCP segmentation
context:
Last frame payload bytes = PAYLEN – (N * MSS)
MAC Header (for SNAP packets)
• Type/LEN field = Last frame payload bytes + MACLEN + IPLEN + L4LEN – 14
IPv4 Header
• IP total length = last frame payload bytes + L4LEN + IPLEN
• IP identification: incremented from last value (wrap around configurable based on 15-bit width or
16-bit width)
• IP Checksum
IPv6 Header
• Payload length = last frame payload bytes + L4LEN + IPLEN – 0x28 (IP base header length)
TCP Header
• Sequence number update: Add previous TCP payload size to the previous sequence number
value. This is equivalent to adding the MSS to the previous sequence number.
• If FIN flag = 1b, set it in this last frame
• If PSH flag =1b, set it in this last frame
• TCP Checksum
UDP Header
• UDP length: last frame payload bytes + L4LEN
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