82598EB Datasheet, PDF (234/596 Pages) Intel Corporation – Intel® 82598EB 10 Gigabit Ethernet Controller Datasheet

Intel^® 82598EB 10 GbE Controller - Receive Functionality
Table 3-58. Mode Behavior for 82598
DESCTYPE
Condition
SPH HBO
PKT_LEN
HDR_LEN
Copy
Split
1. Header can't be
decoded
0b
0b
Min (packet length,
N/A
buffer size)
Header + Payload 
Packet buffer
2. Header <=
BSIZEHEADER
3. Header >
BSIZEHEADER
1b
0b
Min (payload length, Header size
buffer size)³
Header  Header buffer
Payload  Packet
buffer
1b
1b
Min (packet length,
Header size⁶
Header + Payload 
buffer size)
Packet buffer
Split –
always use
header
buffer
1. Packet length <=
BSIZEHEADER
0b
0b
0b
Packet length
Header + Payload 
Header buffer
Replicate
2. Header can’t be
Decoded (Packet
length >
BSIZEHEADER)
3. Header <=
BSIZEHEADER
4. Header >
BSIZEHEADER
1. Header + Payload
<= BSIZEHEADER
0b
0b
Min (packet length –
BSIZEHEADE
Header + Payload 
BSIZEHEADER, data R
Header + Packet buffers⁴
buffer size)
1b
0b
1b
1b
0b/
0b
1b
Min (payload length,
data Buffer size)
Min (packet length –
BSIZEHEADER, data
buffer size)
Packet length
Header Size
Header Size⁶
Header size,
N/A⁵
Header  Header buffer
Payload  Packet
buffer
Header + Payload 
Header + Packet buffer
Header + Payload 
Header buffer
2. Header + Payload
> BSIZEHEADER
0b/
0b/
Min (packet length,
1b
1b²
buffer size)
Header size,
N/A⁵
(Header +
Payload)(partial¹) 
Header buffer
Header + Payload 
Packet buffer
Notes:
1. Partial means up to BSIZEHEADER
2. HBO is 1b if the Header size is bigger than BSIZEHEADER and zero otherwise.
3. In a header only packet (such as TCP ACK packet), the PKT_LEN is zero.
4. If the packet spans more than one descriptor, only the header buffer of the first descriptor is used.
5. If SPH = 0b, then the header size is not relevant. In any case, the HDR_LEN doesn't reflect the actual data size stored in the
Header buffer.
6. The HDR_LEN doesn't reflect the actual data size stored in the header buffer. It reflects the header size determined by the
parser.
Note: If SRRCTL#.NSE is set, All buffers' addresses in a packet descriptor must be word aligned.
Packet header cannot span across buffers, therefore, the size of the header buffer must be larger than
any expected header size. Otherwise only the part of the header fitting the header buffer is replicated.
If header split mode (SRRCTL.DESCTYPE = 010b), a packet with a header larger than the header buffer
is not split.
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