Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure Quality of Service for Outbound Traffic

Steps for Creating a DSCP Policy Based on TCP/UDP Port Number

Classifiers. This procedure creates a DSCP policy for IP packets carrying the selected UDP or TCP port-number classifier.

1.Identify the TCP or UDP port-number classifier you want to use for assigning a DSCP policy.

2.Determine the DSCP policy for packets carrying the selected TCP or UDP port number.

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-mapto configure the priority to the codepoint you selected in step 2a. (For details, refer to the example later in this section, and to “Differentiated Services Codepoint (DSCP)

Mapping” on page 15-51.)

N o t e

A codepoint must have an 802.1p priority assignment (0 - 7) before you can

 

configure a policy for prioritizing packets by TCP or UDP port numbers. If a

 

codepoint you want to use shows No-overridein the Priority column of the

 

DSCP map (show qos dscp-map), then you must assign a 0 - 7 priority before

 

proceeding.

 

4. Configure the switch to assign the DSCP policy to packets with the

 

 

specified TCP or UDP port number.

 

Syntax: qos dscp-map < codepoint > priority < 0 - 7 >

 

This command is optional if a priority has already

 

been assigned to the < codepoint >. The command creates

 

a DSCP policy by assigning an 802.1p priority to a

 

specific DSCP. When the switch applies this policy to a

 

packet, the priority determines the packet’s queue in

 

the outbound port to which it is sent. If the packet leaves

 

the switch in a tagged VLAN, it carries the 802.1p

 

priority with it to the next downstream device. If the

 

packet is IPv4, the packet’s DSCP will be replaced by the

 

codepoint specified in this command. (Default: For

 

most codepoints, No-override. See figure 15-8on page

 

15-52.)

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