Intel Intel Gigabit Ethernet Controllers, PCI IP and TCP/UDP Headers, Version IP Hdr, Options

Receive and Transmit Description

Note: It is recommended that the entire header section, as described by the TCP Context Descriptor HDRLEN field, be coalesced into a single buffer and described using a single data descriptor.

3.5.7IP and TCP/UDP Headers

This section outlines the format and content for the IP, TCP and UDP headers. The Ethernet controller requires baseline information from the software device driver in order to construct the appropriate header information during the segmentation process.

Header fields that are modified by the Ethernet controller are highlighted in the figures that follow.

The IPv4 header is first shown in the traditional (RFC 791) representation, and because byte and bit ordering is confusing in that representation, the IP header is also shown in little-endian format. The actual data is fetched from memory in little-endian format.

										1									2								3
0	1	2	3	4	5	6	7	8	9	0	1 2	3	4	5	6	7	8	9	0	1	2	3 4	5	6 7	8	9	0	1
	Version					IP Hdr				TYPE of service												Total length
						Length
							Identification									Flags							Fragment Offset
			Time to Live						Layer 4 Protocol ID												Header Checksum
														Source Address
													Destination Address
															Options

Figure 3-8. IPv4 Header (Traditional Representation)

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