Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure QoS for Outbound Traffic

N o t e o n

C o m b i n i n g

P o l i c y Ty p e s

Assigning a DSCP Policy Based on TCP or UDP Port Number

This option assigns a previously configured DSCP policy (codepoint and 802.1p priority) to (IPv4) TCP or UDP packets having the specified port number. That is, the switch:

1.Selects an incoming IP packet if the TCP or UDP port number (or range) it carries matches the port number specified in the TCP or UDP classifier (as shown in figure 6-6,above).

2.Overwrites (re-marks) the packet’s DSCP with the new user-configured DSCP for this type of packet.

3.Assigns the 802.1p priority for that new DSCP codepoint, as configured automatically or by the user in the QoS DSCP-Map table. (Refer to “Differentiated Services Codepoint (DSCP) Mapping” on page 6-58.)

4.Forwards the packet through the appropriate outbound port queue.

On switches covered in this guide, “mixing” ToS DSCP policies and 802.1p priorities is not recommended. Refer to the Note on page 6-10.

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

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

Classifiers. This procedure creates a DSCP policy for IPv4 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 (re-mark) 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 6-58.)

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