Advanced Traffic Management Guide K/KA/KB.15.15

The 802.1p priority determines the packet's queue in the outbound port on the
switch. If the packet leaves the switch on a tagged VLAN port, it carries the 802.1p
priority with it to the next downstream device.
Default: Disabled — No 802.1p priority is assigned.
The no form of the command deletes the specified UDP or TCP port number or
range of port numbers as a QoS classifier.
NOTE: If you have specified a range of port numbers, you must specify the entire
range in the no command; you cannot remove part of a range.
Viewing a list of all TCP and UDP QoS classifiers
Syntax:
show qos tcp-udp-port-priority
Displays a listing of all TCP and UDP QoS classifiers currently in the running-config
file.
Assigning a DSCP policy for a global TCP/UDP classifier
This global QoS packet-marking option assigns a previously configured or default DSCP policy
(codepoint and 802.1p priority) to TCP or UDP packets having the specified port number or range
of port numbers. When assigning a DSCP policy, the switch performs the following actions:
1. Selects an incoming IP packet if the TCP or UDP port number it carries matches the port number
specified in the TCP or UDP classifier.
2. Overwrites (re-marks) the packet's DSCP with the new DSCP configured for matching packets.
3. Assigns the 802.1p priority associated with the new DSCP.
4. Forwards the packet through the appropriate outbound port queue.
Creating a DSCP policy based on TCP/UDP port number classifiers
The following procedure creates a DSCP policy for IP packets carrying the selected TCP or UDP
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 or range
of port numbers.
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. If necessary, use the qos dscp-map codepoint priority 0 - 7 command to configure
the DSCP policy (codepoint and associated 802.1p priority) that you want to use to mark
matching packets.
NOTE: Prerequisite: A DSCP codepoint must have a preconfigured 802.1p priority (0 - 7)
before you can use the codepoint to mark matching packets. If a codepoint you want to use
shows No-override in the Priority column of the DSCP Policy table (show qos dscp-map
command), you must first configure a priority for the codepoint before proceeding (qos
dscp-map priority command).
Syntax:
qos dscp-map codepoint priority 0 - 7
192 Quality of Service: Managing bandwidth effectively