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Software Developer’s Manual 61
Figure 3-9. IPv4 Header (Little-Endian Order)
Flags Field Definition:
The Flags field is defined below. Note that hardware does not evaluate or change these bits.
• MF More Fragments
• NF No Fragments
• Reserved
Note: The IPv6 header is first shown in the traditional (RFC 2460), big-endian representation. The actual
data is fetched from memory in little-endian format.
Figure 3-10. IPv6 TCP Header (Traditional Representation)
A TCP or UDP frame uses a 16 bit wide one’s complement checksum. The checksum word is
computed on the outgoing TCP or UDP header and payload, and on the Pseudo Header. Details on
checksum computations are provided in Section 3.5. TCP requires the use of checksum, where it is
optional for UDP.
Byte 3 Byte 2 Byte 1 Byte 0
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
LSB Total length MSB TYPE of service Version
IP Hdr
Length
Fragment Offset Low
R
E
S
N
F
M
F
Fragment
Offset High
LSB Identification MSB
Header Checksum Layer 4 Protocol ID Time to Live
Source Address
Destination Address
Options
0 1 2 3 4 5 6 7 8 9
1
0 1 2 3 4 5 6 7 8 9
2
0 1 2 3 4 5 6 7 8 9
3
0 1
Version Traffic Class Flow Label
Payload Length Next Header Hop Limit
Source Address
Destination Address