Dell FCX624-I Laptop User Manual


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600 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
Configuring the QoS mappings
17
PowerConnect stackable devices
PowerConnect B-Series FCX devices support DSCP-based QoS on a per-port basis. DSCP-based
QoS is not automatically honored for switched traffic. The default is 802.1p to CoS mapping. To
honor DSCP-based QoS, enter the following command at the interface level of the CLI.
PowerConnect(config-if-e1000-11)#trust dscp
Syntax: trust dscp
When trust dscp is enabled, the interface honors the Layer 3 DSCP value. By default, the interface
honors the Layer 2 CoS value.
NOTE
This feature is not supported together with 802.1p priority override.
Configuring the QoS mappings
You can optionally change the following QoS mappings:
DSCP to internal forwarding priority
VLAN priority (802.1p) to hardware forwarding queue
The mappings are globally configurable and apply to all interfaces.
Default DSCP to internal forwarding priority mappings
The DSCP values are described in RFCs 2474 and 2475. Table 99 lists the default mappings of
DSCP values to internal forwarding priority values.
Notice that DSCP values range from 0 through 63, whereas the internal forwarding priority values
range from 0 through 7. Any DSCP value within a given range is mapped to the same internal
forwarding priority value. For example, any DSCP value from 8 through 15 maps to priority 1.
After performing this mapping, the device maps the internal forwarding priority value to one of the
hardware forwarding queues.
Table 100 lists the default mappings of internal forwarding priority values to the hardware
forwarding queues.
TABLE 99 Default DSCP to internal forwarding priority mappings
Internal forwarding priority DSCP value
0 (lowest priority queue) 0 – 7
18 15
2 16 – 23
3 24 – 31
4 32 – 39
5 40 – 47
6 48 – 55
7 (highest priority queue) 56 – 63