Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 411
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Configuring the QoS mappings
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Application notes
• DSCP-based QoS is not automatically honored for routed and switched traffic. The default is
802.1p to CoS mapping. To honor DSCP-based QoS, you must change the priority mapping to
DSCP to CoS mapping. Refer to “Using ACLs to honor DSCP-based QoS” on page 411.
• When DSCP marking is enabled, the device changes the contents of the inbound packet ToS
field to match the DSCP-based QoS value. This differs from the BigIron, which marks the
outbound packet ToS field.
Using ACLs to honor DSCP-based QoS
This section shows how to configure devices to honor DSCP-based QoS for routed and switched
traffic.
PowerConnect B-Series TI24X Devices
These 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-e10000-11)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
Use the bridged-routed keyword in the ACL to honor DSCP for switched traffic in the Layer 3 image.
Refer to “Enabling ACL support for switched traffic in the router image” on page 384.
Configuring the QoS mappings
You can optionally change the following QoS mappings:
• DSCP –> internal forwarding priority
• Internal forwarding priority –> hardware forwarding queue
The mappings are globally configurable and apply to all interfaces.
Default DSCP –> Internal forwarding priority mappings
The DSCP values are described in RFCs 2474 and 2475. Table 63 list the default mappings of
DSCP values to internal forwarding priority values.
TABLE 63 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