LAN9312 datasheet(67/458 Pages) SMSC

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High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface

Datasheet

SMSC LAN9312

Revision 1.2 (04-08-08)

DATASHEET

6.4.3

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.

Figure 6.4 Switch Engine Transmit Queue Selection

priority

calculation

programmable

DIFFSERV table

programmable

port default

table

programmable

Priority

Regeneration

table

per port

static DA

override

programmable

Traffic Class

table

Packet is Tagged

VL Higher Priority

Packet is IPv 4

Packet is IP

Use Precedence

Use IP

ALR Static Bit

IPv4(TOS)

IPv6(TC)

DA Highest Priority

priority queue

Source Port

ALR Priority

VLAN Priority

IPv4 Precedence

VLAN Enable

Packet is from Host

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