Cisco 3560G 48TS Software Configuration Guide - Page 578

Configuring Standard QoS Chapter 28 Configuring QoS Configuring the Ingress Priority Queue You should use the priority queue only for traffic that needs to be expedited (for example, voice traffic, which needs minimum delay and jitter). The priority queue is guaranteed part of the bandwidth to reduce the delay and jitter under heavy network traffic on an oversubscribed ring (when there is more traffic than the backplane can carry, and the queues are full and dropping frames). SRR services the priority queue for its configured weight as specified by the bandwidth keyword in the mls qos srr-queue input priority-queue queue-id bandwidth weight global configuration command. Then, SRR shares the remaining bandwidth with both ingress queues and services them as specified by the weights configured with the mls qos srr-queue input bandwidth weight1 weight2 global configuration command. Beginning in privileged EXEC mode, follow these steps to configure the priority queue. This procedure is optional. Step 1 Step 2 Command configure terminal mls qos srr-queue input priority-queue queue-id bandwidth weight Step 3 Step 4 Step 5 end show mls qos interface queueing or show mls qos input-queue copy running-config startup-config Purpose Enter global configuration mode. Assign a queue as the priority queue and guarantee bandwidth on the internal ring if the ring is congested. By default, the priority queue is queue 2, and 10 percent of the bandwidth is allocated to it. • For queue-id, the range is 1 to 2. • For bandwidth weight, assign the bandwidth percentage of the internal ring. The range is 0 to 40. The amount of bandwidth that can be guaranteed is restricted because a large value affects the entire ring and can degrade performance. Return to privileged EXEC mode. Verify your entries. (Optional) Save your entries in the configuration file. To return to the default setting, use the no mls qos srr-queue input priority-queue queue-id global configuration command. To disable priority queueing, set the bandwidth weight to 0, for example, mls qos srr-queue input priority-queue queue-id bandwidth 0. This example shows how to assign the ingress bandwidths to the queues. Queue 1 is the priority queue with 10 percent of the bandwidth allocated to it. The bandwidth ratios allocated to queues 1 and 2 is 4/(4+4). SRR services queue 1 (the priority queue) first for its configured 10 percent bandwidth. Then SRR equally shares the remaining 90 percent of the bandwidth between queues 1 and 2 by allocating 45 percent to each queue: Switch(config)# mls qos srr-queue input priority-queue 1 bandwidth 10 Switch(config)# mls qos srr-queue input bandwidth 4 4 28-56 Catalyst 3560 Switch Software Configuration Guide 78-16156-01