EP80579 Datasheet, PDF (1365/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
Figure 37-15.IPv6 Extension Header Structure
NEXT HEADER
HDR EXT LEN
NEXT HEADER is a value that identifies the header type. The supported IPv6 next
headers values are:
• Hop-by-Hop = 00h
• Destination Options = 3Ch
• Routing = 2Bh
HDR EXT LEN is the 8 byte count of the header length, not including the first 8 bytes.
For example, a value of 3 means that the total header size including the NEXT HEADER
and HDR EXT LEN fields is 32 bytes (8 + 3*8).
37.5.5.8.5 UDP/TCP Filter
This filter checks for a valid UDP or TCP header. The prototype next header values are
11h and 06h, respectively. The RXCSUM.TUOFL bit must be set for this filter to pass.
37.5.6
Packet Transmission
Output packets are made up of pointer-length pairs constituting a descriptor chain (so
called descriptor based transmission). Software forms transmit packets by assembling
the list of pointer-length pairs, storing this information in the transmit descriptor, and
then updating the GbE hardware transmit tail pointer to the descriptor. The transmit
descriptor and buffers are stored in host memory. Hardware typically transmits the
packet only after it has completely fetched all packet data from host memory and
deposited it into the TX portion of the packet buffer. This permits TCP or UDP checksum
computation, and avoids problems with internal bus under-runs.
Another transmit feature of the GbE is TCP Segmentation. The hardware has the
capability to perform packet segmentation on large data buffers off-loaded from the
NOS. This feature is discussed in detail in “TCP Segmentation” on page 1380.
37.5.6.1
Transmit Data Storage
Data are stored in buffers pointed to by the descriptors. Alignment of data is on an
arbitrary byte boundary with the maximum size per descriptor limited only to the
maximum allowed packet size (16288 bytes¹). A packet typically consists of two (or
more) descriptors, one (or more) for the header and one for the actual data. Some
software implementations copy the header(s) and packet data into one buffer and use
only one descriptor per transmitted packet.
37.5.6.2
Transmit Descriptor Formats
The EP80579’s GbE has an expanded transmit descriptor format in that additional
descriptor types have been introduced. The intent of the descriptor type field is to
provide an extensible interface to the GbE descriptor mechanisms while maintaining a
great deal of compatibility with the existing descriptor format that the 82542 used.
1. This value is based on the default packet buffer allocation of 16KB Transmit; 48KB Receive. The maximum allowable transmit
packet size is the transmit allocation minus 96 bytes with an upper limit of 24KB due to receive synchronization limitations.
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
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