82583V Datasheet, PDF (156/374 Pages) Intel Corporation – Intel® 82583V GbE Controller

82583V GbE Controller—Inline Functions
7.3.4
7.3.5
TCP Segmentation Source Data
Once the TCP segmentation context has been set, the next descriptor (data descriptor)
provides the initial data to transfer. This first data descriptor must point to data
containing an Ethernet header of the type indicated. The 82583V fetches the prototype
(partial pseudo-header) header from the host data buffer into an internal buffer and
this header is prepended to every packet for this TSO operation. The prototype (partial
pseudo-header) header is modified accordingly for each MSS sized segment. The
following sections describe the supported packet types and the various updates that
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 (partial pseudo-
header) header.
The following summarizes the fields considered by the driver for modification in
constructing the prototype (partial pseudo-header) header.
MAC Header (for SNAP)
• MAC Header LEN field should be set to 0b.
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
software device 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.
UDP Header
• UDP checksum should be set to the partial pseudo-header checksum.
The 82583V's DMA function fetches the IP, and TCP/UDP prototype (partial pseudo-
header) header information from the initial descriptor and save them on-chip for
individual packet header generation.
Hardware Performed Updating for Each Frame
The following sections describe the updating process performed by the hardware for
each frame sent using the TCP segmentation capability.
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