High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
Revision 1.4 (08-19-08)
72
SMSC LAN9312
DATASHEET
After each packet is received, the bucket is decremented. If the Committed Burst bucket has sufficient
tokens, it is debited and the packet is colored Green. If the Committed Burst bucket lacks sufficient
tokens for the packet, the Excess Burst bucket is checked. If the Excess Burst bucket has sufficient
tokens, it is debited, the packet is colored Yellow and is subjected to random discard. If the Excess
Burst bucket lacks sufficient tokens for the packet, the packet is colored Red and is discarded.
Note:
All of the token buckets are initialized to the default value of 1536. If lower values are
programmed into the CBS and EBS parameters, the token buckets will need to be normally
depleted below these values before the values have any affect on limiting the maximum value
of the token buckets.
Refer to
Section 14.5.3.25, on page 393
through
Section 14.5.3.29, on page 398
for detailed register
descriptions.
6.4.6.1
Ingress Flow Calculation
Based on the flow monitoring mode, an ingress flow definition can include the ingress priority. This is
calculated similarly to the transmit queue with the exception that the Priority Regeneration and the
Traffic Class table are not used. As shown in
, the priority can be based on:
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 (but not through the per port Priority Regeneration table)
The port default
Table 6.3 Typical Ingress Rate Settings
CIR Setting
Time Per Byte
Bandwidth
0-3
80 nS
100 Mbps
4
100 nS
80 Mbps
5
120 nS
67 Mbps
6
140 nS
57 Mbps
7
160 nS
50 Mbps
9
200 nS
40 Mbps
12
260 nS
31 Mbps
19
400 nS
20 Mbps
39
800 nS
10 Mbps
79
1600 nS
5 Mbps
160
3220 nS
2.5 Mbps
402
8060 nS
1 Mbps
804
16100 nS
500 Kbps
1610
32220 nS
250 Kbps
4028
80580 nS
100 Kbps
8056
161140 nS
50 Kbps