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Receive and Transmit Description
Software Developer’s Manual 63
TCP Length = Payload + HDRLEN - TUCSS
“Payload” is normally MSS except for the last packet where it represents the remainder of the
payload.
Figure 3-13. TCP Pseudo Header Content (Traditional Representation)
Figure 3-14. TCP PseudoHeader Content for IPv6
Note: The IP Destination address is the final destination of the packet. Therefore, if a routing header is
used, the last address in the route list is used in this calculation. The upper-layer packet length is
the length of the TCP header and the TCP payload.
The UDP header is always 8 bytes in size with no options.
Figure 3-15. UDP Header (Traditional Representation)
Figure 3-16. UDP Header (Little-Endian Order)
031
IP Source Address
IP Destination Address
Zero
Layer 4 Protocol
ID
TCP Length
IP Source Address
IP Destination Address
Upper Layer Packet Length
Zero Next Header
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Source Port Destination Port
Length Checksum
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