EP80579 Datasheet, PDF (1380/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
Figure 37-30.Transmit Descriptor and TUCMD Field (TDESC) Layouts - (Type = 0000)
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
37.5.7
Note:
7
6
5
4
3
2
1
0
IDE
Rsvd
DEXT
Rsvd
RS
TSE
IP
TCP
IDE: Interrupt Delay Enable
Rsvd: Reserved
DEXT: Descriptor Extension (Must be 1)
Rsvd: Reserved
RS: Report Status
TSE: TCP Segmentation Enable
IP: IPv4 Header Update Enable
TCP: Packet Type (TCP=1,UDP=0)
TCP Segmentation
Hardware TCP Segmentation is one of the off-loading options of the Windows 2000*
TCP/IP stack. This is often referred to as “Large send” off loading. This feature allows
the TCP/IP stack to pass to the network device driver a message to be transmitted that
is bigger than the Maximum Transmission Unit (MTU) of the medium. It is then the
responsibility of the device driver and hardware to carve the TCP message into MTU
size frames that have appropriate layer 2 (Ethernet), 3 (IP), and 4 (TCP) headers.
These headers must include sequence number, checksum fields, options and flag values
as required. Note that some of these values (such as the checksum values) will be
unique for each packet of the TCP message, and other fields such as the source IP
address will be constant for all packets associated with the TCP message.
The off loading of these mechanisms to the device driver and the EP80579’s GbE will
save significant CPU cycles. The device driver and the EP80579’s GbE will share the
additional tasks in order to support this feature.
Prior to Windows 2000*, the Microsoft* TCP/IP stack (TCPIP.SYS) had always
transferred (to the miniport device driver and eventually to the MAC) a frame with
bytes up to the size of MTU for the media (up to 1514 bytes for 802.3 Ethernet
packets).
Although the GbE TCP segmentation off load implementation was specifically designed
to take advantage of the new “TCP Segmentation offload” feature from Microsoft, the
hardware implementation was made generic enough so that it could also be used to
“segment” traffic from other protocols. For instance this feature could be used any time
it is desirable for HW to segment a large block of data for transmission into multiple
packets that contain the same generic header.
Intel^® EP80579 Integrated Processor Product Line Datasheet
1380
August 2009
Order Number: 320066-003US