Receive and Transmit Description

3.3.6TCP/IP Context Descriptor Layout

The following section describes the layout of the TCP/IP context transmit descriptor.

To select this descriptor format, bit 29 (TDESC.DEXT) must be set to 1b and TDESC.DTYP must be set to 0000b. In this case, the descriptor format is defined as shown in Table 3-13.

Note that the TCP/IP context descriptor does not transfer any packet data. It merely prepares the checksum hardware for the TCP/IP Data descriptors that follow.

Table 3-13. Transmit Descriptor (TDESC) Layout – (Type = 0000b)

63

 

48 47

40 39

 

 

32 31

 

 

16 15

8 7

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

TUCSE

 

TUCSO

 

TUCSS

 

 

IPCSE

 

 

IPCSO

 

IPCSS

 

 

 

 

 

 

 

 

 

 

 

 

8

 

MSS

 

HDRLEN

RSV

STA

TUCMD

DTYP

 

 

PAYLEN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

63

 

48 47

40 39

36 35

32 31

24

23

20 19

 

 

 

0

Note: The first quadword of this descriptor type contains parameters used to calculate the two checksums which may be offloaded.

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Software Developer’s Manual

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Intel Intel Gigabit Ethernet Controllers 6 TCP/IP Context Descriptor Layout, Transmit Descriptor Tdesc Layout Type = 0000b