KB.15.15

Figure 36 Enabling ToS IP-precedence prioritization

To change from IP-precedence to IP-Diffserv mode, follow the procedure in “Assigning a priority

for a global IP-device classifier” (page 197), which automatically disables IP-Precedence. To disable

IP-Precedence without enabling the IP-Diffserv option, enter the no qos type-of-service

command.

Using a global IP-Diffserv classifier to mark matching packets with an

802.1p priority

1. Identify a DSCP used to set a policy in packets received from an upstream or edge switch.

2. Determine the 802.1p priority (0 - 7) you want to apply to packets carrying the identified

DSCP. (You can either maintain the priority assigned in the upstream or edge switch, or assign

a new priority.)

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.

4. Enable IP-Diffserv mode by entering the qos type-of-service diff-services

command.

Syntax:

qos type-of-service diff-services codepoint

Causes the switch to read the codepoint (DSCP) of an incoming IP packet and, when a match

occurs, assign the associated 802.1p priority in the DSCP Policy table.

Options

no qos type-of-service Disables all ToS classifier operation.

no qos dscp-map codepoint Disables direct 802.1p priority assignment to packets

carrying the codepoint , by reconfiguring the codepoint

priority assignment in the DSCP table to No-override.

Note that if this codepoint is in use as a DSCP policy for

another Diffserv codepoint, you must disable or redirect the

other Diffserv codepoint's DSCP policy before you can

disable or change the codepoint. For example, in

Figure 37 (page 205) you cannot change the priority for the

000000 codepoint until you redirect the DSCP policy for

000001 from using 000000 as a policy.

show qos type-of-service Displays the current Type-of-Service configuration. In

IP-Diffserv mode it also shows the current direct 802.1p

assignments and the current DSCP assignments covered

later in this section.

204 Quality of Service: Managing bandwidth effectively