EP80579 Datasheet, PDF (1381/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
37.5.7.1
Assumptions
The GbE TCP Segmentation implementation assumes the RS bit operation is not
changed. Interrupts are set after data in buffers pointed to by individual descriptors is
transferred from host memory to GbE hardware.
37.5.7.2
Transmission Process
The transmission process for regular (non-TCP Segmentation packets) involves the
following:
• The protocol stack receives a block of data that is to be transmitted from an
application.
• The protocol stack calculates the number of packets required to transmit this block
based on the MTU size of the media and required packet headers.
• For each packet of the data block:
— The stack prepares Ethernet, IP and TCP/UDP headers.
— The stack interfaces with the device driver and commands the driver to send
the individual packet.
— The driver gets the frame and interfaces with the hardware.
— The hardware reads the packet from host memory (via DMA transfers).
— The driver returns ownership of the packet to the NOS when the hardware has
completed the DMA transfer of the frame (indicated by an interrupt).
The transmission process for the GbE TCP segmentation off load implementation
involves the following:
• The protocol stack receives a block of data that is to be transmitted from an
application.
• The stack interfaces to the device driver and passes the block down with the
appropriate header information.
• The device driver sets up the interface to the hardware (via descriptors) for the TCP
Segmentation context.
• The hardware transfers the packet data from host memory and performs the
Ethernet packet segmentation and transmission based on offset and payload length
parameters in the TCP/IP context descriptor including:
— Packet encapsulation
— Header generation and field updates including IP and TCP/UDP checksum
generation
• The driver returns ownership of the block of data to the NOS when the hardware
has completed the DMA transfer of the entire data block (indicated by an interrupt).
37.5.7.2.1 TCP Segmentation Data Fetch Control
To perform TCP Segmentation in the GbE, the DMA must ensure that the entire payload
of the segmented packet will fit into the available space in the GbE Packet Buffer. The
segmentation process should be performed without interruption. The DMA will do
various comparisons between the payload and the Packet Buffer to ensure no
interruptions occur as well as general efficiencies in the operation of the TCP
Segmentation feature. The “TSPMT – TCP Segmentation Pad and Minimum Threshold
Register” on page 1503 is used to allow software to program the minimum threshold
required for a TCP Segmentation payload. Consideration should be made for the MTU
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
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