EP80579 Datasheet, PDF (1383/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
Note:
IP tunneled packets are not supported for Large Send operation.
37.5.7.5 TCP Segmentation Indication
Software indicates a TCP Segmentation transmission context to the hardware by
setting up a TCP/IP Context Transmit Descriptor (refer to “TCP/IP Context Transmit
Descriptor Format” on page 1369). The purpose of this descriptor is to provide
information to the hardware to be used during the TCP segmentation off load process.
The layout of this descriptor is reproduced in Figure 37-32.
Figure 37-32.TCP/IP Context Transmit Descriptor & Command Layout
63
48 47 40 39
32 31
16 15
87
0
0
TUCSE
TUCSO
TUCSS
IPCSE
IPCSO
IPCSS
8
MSS
HDRLEN Rsvd
STA
TUCMD
DTYP
PAYLEN
63
48 47 40 39 36 35 32 31 24 23 20 19
0
7
6
5
4
3
2
1
0
IDE
Rsvd
DEXT
Rsvd
RS
TSE
IP
TCP
Setting the TSE bit in the Command field to ‘1’ indicates that this descriptor refers to
the TCP Segmentation context (as opposed to the normal checksum off loading
context). This will cause the checksum off loading, packet length, header length, and
maximum segment size parameters to be loaded from the descriptor into the device.
The TCP Segmentation prototype header is taken from the packet data itself. Software
must identity the type of packet that is being sent (IP/TCP, IP/UDP, other), calculate
appropriate checksum off loading values for the desired checksums, and calculate the
length of the header which is prepended. The header may be up to 240 bytes in length.
37.5.7.6 TCP Segmentation Data Descriptors
37.5.7.6.1 TCP Segmentation Source Data
Once the TCP Segmentation context has been set, the next descriptor provides the
initial data to transfer. This first descriptor(s) must point to a packet of the type
indicated. Furthermore, the data it points to may need to be modified by software as it
will serve as the prototype header for all packets within the TCP Segmentation context.
The following sections describe the supported packet types and the various updates
which are performed by hardware. This should be used as a guide to determine what
must be modified in the original packet header to make it a suitable prototype header.
The following summarizes the fields considered by the driver for modification in
constructing the prototype header.
• IPv4 Header
— Length should be set to zero
— Identification Field should be set as appropriate for first packet of send (if not
already)
— Header Checksum should be zeroed out unless some adjustment is needed by
the driver
• IPv6 Header
— Length should be set to zero
• TCP Header
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
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