WG82574IT S LBAC Intel, WG82574IT S LBAC Datasheet - Page 178

• Manufacturer Part Number: WG82574IT S LBAC
• Description: CONTROLLER, ENET, INTEL 82574IT, 64PQFN
• Manufacturer: Intel

Specifications of WG82574IT S LBAC

• Ethernet Type: IEEE 802.3, IEEE 802.3u, IEEE 802.3ab
• Supply Voltage Range: 3V To 3.6V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: QFN
• No. Of Pins: 64
• Package / Case: QFN
• Interface Type: I2C, JTAG, PCI, SPI
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7.3.6.2
7.3.6.2.1
7.3.6.2.2
Note:
178
IP/TCP/UDP Header Updating
IP/TCP/UDP header is updated for each outgoing frame based on the IP/TCP header
prototype (partial pseudo-header) which the hardware gets from the first descriptor(s)
and stores on chip. The IP/TCP/UDP headers are fetched from host memory into an on-
chip 240 byte header buffer once for each TCP segmentation context (for performance
reasons, this header is not fetched for each additional packet that will be derived from
the TCP segmentation process). The checksum fields and other header information are
updated on a frame-by-frame basis. The updating process is performed concurrently
with the packet data fetch.
TCP/IP/UDP Header for the First Frame
The hardware makes the following changes to the headers of the first packet that is
derived from each TCP segmentation context.
MAC Header (for SNAP)
IPv4 Header
IPv6 Header
TCP Header
UDP Header
TCP/IP/UDP Header for the Subsequent Frames
The hardware makes the following changes to the headers of the subsequent packets
that is derived from each TCP segmentation context.
Number of bytes left for transmission = PAYLEN - (N * MSS). Where N is the number of
frames that have been transmitted.
MAC Header (for SNAP Packets)
• Type/Len field = MSS + HDRLEN - 14
• IP Total Length = MSS + HDRLEN - IPCSS
• IP Checksum
• Payload Length = MSS + HDRLEN - IPCSS - Ipv6Size (while Ipv6Size = 40Bytes)
• Sequence Number: The value is the Sequence Number of the first TCP byte in this
• If FIN flag = 1b, it is cleared in the first frame.
• If PSH flag =1b, it is cleared in the first frame.
• TCP Checksum
• UDP length: MSS + HDRLEN - TUCSS
• UDP Checksum
• Type/Len field = MSS + HDRLEN - 14
frame.
82574 GbE Controller—Inline Functions