Filter
Top Products
Intel
®
82575EB Gigabit Ethernet Controller — Advanced Transmit Context Descriptor
Intel
®
82575EB Gigabit Ethernet Controller 324632-003
Software Developer’s Manual and EEPROM Guide Revision: 2.1
140 January 2011
Table 39. Special Field (TDESC.SPECIAL) Layout
5.6.7 Advanced Transmit Context Descriptor
Table 40. Transmit Context Descriptor (TDESC) Layout – (Type = 0010b)
Table 41. Transmit Context Descriptor (TDESC) Layout
15 13 12 11 0
PRI CFI VLAN
TDESC.SPECIAL Description
PRI User Priority
3 bits that provide the VLAN user priority field to be inserted in the 802.1Q tag.
CFI Canonical Form Indicator.
VLAN VLAN Identifier
12 bits that provide the VLAN identifier field to be inserted in the 802.1Q tag.
63 48 47 40 39 32 31
1
6
15 9 8 0
0 SN VLAN MACLEN IPLEN
8 MSS L4LEN IDX RSV ADV DTYP TCMD MKRLOC
63 48 47 40 39 36 35 32 31 24 23
2
0
1
9
80
Field Description
IPLEN IP Header Length
If an offload is requested, IPLEN must be greater than or equal to 6 and less than or equal to 511.
MACLEN MAC Header Length
When an offload is requested (one of TSE or IXSM or TXSM is set), MACHDR must be larger than or equal
to 14 and less than or equal to 127.
VLAN Insert 802.1Q VLAN tag in Packet During Transmission
This VLAN tag is inserted and needed only when a packet using this context has its DCMD.VLE bit set.
Reserved Reserved
MKRLOC IP Checksum Offset
For MPA streams, the location of markers in the TCP stream is at (SeqNum mod 512) = MKRLOC. Markers
are inserted when DCMD.
TUCMD TCP/UDP command field
The command field provides options that control the checksum offloading, along with some of the generic
descriptor processing functions.
Bits 10:5 - Reserved
Bit 4 - MKRREQ, when set to 1b, indicates that markers are required for this request.
Bit 3:2 - L4T Packet Type (L4T), 00b = UDP; 01 = TCP; 10b, 11b = Reserved.
Bit 1 - IP Packet Type (IPv4), when set to 1b = IPv4; when set to 0b = IPv6.
Bit 0 - SNAP indication.