Intel Gigabit Ethernet Controllers Benutzerhandbuch

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•

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

— Sequence Number should be set as appropriate for first packet of send (if not already)

— PSH, and FIN flags should be set as appropriate for last packet of send

— TCP Checksum should be set to the partial pseudo-header checksum as follows:

•

UDP Header

— Checksum should be set as in TCP header, above

The Ethernet controller’s DMA function fetches the ethernet, IP, and TCP/UDP prototype header 
information from the initial descriptor(s) and save them on-chip for individual packet header gen-
eration. The following sections describe the updating process performed by the hardware for each 
frame sent using the TCP Segmentation capability.

TCP Segmentation enables a packet to be segmented to describe more than one data descriptor.   A 

large packet contained in a single virtual-address buffer is better described as a series of data 

descriptors, each referencing a single physical address page.

The only requirement for this use is if multiple data descriptors for TCP segmentation follows this 
guideline:

•

If multiple data descriptors are used to describe the IP/TCP/UDP header section, each 
descriptor must describe one or more complete headers; descriptors referencing only parts of 

headers are not supported.

IP Source Address

IP Destination Address

Zero

Zero

Next Header

Zero

a

a. 82544GC/EI only

Layer 4 

Protocol

a

Zero

a