LAN9311 Datasheet, PDF (67/461 Pages) SMSC Corporation – Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface

6.4.3
Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
Transmit Priority Queue Selection
The transmit priority queue may be selected from five options. As shown in Figure 6.4, the priority may
be based on:
 the static value for the destination address in the ALR table
 the precedence bits in the IPv4 TOS octet
 the DIFFSERV mapping table indexed by the IPv4 TOS octet or the IPv6 Traffic Class octet
 the VLAN tag priority field using the per port Priority Regeneration table
 the port default
The last four options listed are sent through the Traffic Class table which maps the selected priority to
one of the four output queues. The static value from the ALR table directly specifies the queue.
IPv4(TOS)
IPv6(TC)
Packet is from Host
Packet is Tagged
Packet is IPv 4
Packet is IP
VL Higher Priority
Use Precedence
Use IP
VLAN Enable
6b _programmable
3b
DIFFSERV table
3b
IPv4 Precedence
3b
2b ^programmable
Source Port
port default
table
3b
3b
VLAN Priority
ALR Priority
programmable
Priority
Regeneration
table
per port
2b
ALR Static Bit
DA Highest Priority
priority
calculation
programmable
Traffic Class
table
static DA
override
2b
priority queue
Figure 6.4 Switch Engine Transmit Queue Selection
SMSC LAN9311/LAN9311i
67
DATASHEET
Revision 2.0 (02-14-13)