EP80579 Datasheet, PDF (1387/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
The TCP Length field is the TCP Header Length including option fields plus the data
length in bytes, which is calculated by hardware on a frame by frame basis. The TCP
Length does not count the 12 bytes of the pseudo header. The TCP length of the packet
is determined by hardware as:
TCP Length = Payload + HDRLEN - TUCSS
“Payload” is normally MSS except for the last packet where it represents the remainder
of the payload.
Figure 37-40.TCP Pseudo Header Content (Traditional Representation)
0
Zero
31
IP Source Address
IP Destination Address
Protocol ID
TCP Length
Figure 37-41.TCP Pseudo-Header Content for IPv6
0
31
IP Source Address
IP Destination Address
Upper Layer Packet Length
Zero
Next Header
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 TCP payload.
The UDP header is always 8 bytes in size with no options.
Figure 37-42.UDP Header (Traditional Representation)
00000000001111111111222222222233
01234567890123456789012345678901
Source Port
Length
Destination Port
Checksum
Figure 37-43.UDP Header (Little-Endian Order)
Byte 3
Byte 2
Byte 1
Byte 0
76543210765432107654321076543210
Destination Port
Checksum
Source Port
Length
UDP pseudo header has the same format as the TCP pseudo header. The IPv4 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). The IPv6 pseudo header for UDP is the same as the IPv6
pseudo header for TCP. The checksum procedure is the same as is used in TCP.
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
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