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Quality of Service (QoS): Managing Bandwidth More Effectively
Using QoS Classifiers To Configure Quality of Service for Outbound Traffic
If you then decided to remove VLAN_20 from QoS prioritization:
In this instance, No- override
indicates that VLAN 20 is not
prioritized by QoS.
Figure 15-22. Returning a QoS-Prioritized VLAN to “No-override” Status
Assigning a DSCP Policy Based on VLAN-ID (VID)
This option assigns a previously configured DSCP policy (codepoint and
802.1p priority) to outbound IP packets having the specified VLAN-ID (VID).
That is, the switch:
1. Selects an incoming IP packet on the basis of the VLAN-ID it carries.
2. Overwrites the packet’s DSCP with the DSCP configured in the switch for
such packets.
3. Assigns the 802.1p priority configured in the switch for the new DSCP.
(Refer to “Differentiated Services Codepoint (DSCP) Mapping” on page
15-51.)
4. Forwards the packet through the appropriate outbound port queue.
For more on DSCP, refer to “Terminology” on page 15-5.
Steps for Creating a Policy Based on VLAN-ID Classifier.
1. Determine the VLAN-ID classifier to which you want to assign a DSCP
policy.
2. Determine the DSCP policy for packets carrying the selected VLAN-ID:
a. Determine the DSCP you want to assign to the selected packets. (This
codepoint will be used to overwrite the DSCP carried in packets
received from upstream devices.)
b. Determine the 802.1p priority you want to assign to the DSCP.
3. Configure the DSCP policy by using qos dscp-map to configure the priority
for each codepoint. (For details, see the example later in this section, and
to
“Differentiated Services Codepoint (DSCP) Mapping” on page 15-51.)
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