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 port A1 from QoS prioritization:

In this instance, No-overrideindicates that port A1 is not prioritized by QoS.

Figure 5-12. Returning a QoS-Prioritized VLAN to “No-override” Status

Assigning a DSCP Policy Based on the Source-Port

This option assigns a previously configured DSCP policy (codepoint and 802.1p priority) to outbound IP packets (received from the specified source- ports). That is, the switch:

 

1.

Selects an incoming IP packet on the basis of its source-port on the switch.

 

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

 

 

5-33.)

 

4.

Forwards the packet through the appropriate outbound port queue.

 

For more on DSCP, refer to “Terminology” on page 5-6.

 

Steps for Creating a Policy Based on Source-Port Classifiers.

 

 

N o t e

You can select one DSCP per source-port. Also, configuring a new DSCP for

 

a source-port automatically overwrites (replaces) any previous DSCP or

 

802.1p priority configuration for that port.)

 

1.

Identify the source-port classifier to which you want to assign a DSCP

 

 

 

policy.

 

2.

Determine the DSCP policy for packets having the selected source-port:

 

 

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 through the source-port from upstream devices.)

 

 

b.

Determine the 802.1p priority you want to assign to the DSCP.

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