Cisco WS-C2960-24TC-S Software Guide - Page 562

Configuring Standard QoS Chapter 28 Configuring QoS 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 Configuring Egress Queue Characteristics Depending on the complexity of your network and your QoS solution, you might need to perform all of the tasks in the next sections. You will need to make decisions about these characteristics: • Which packets are mapped by DSCP or CoS value to each queue and threshold ID? • What drop percentage thresholds apply to the queue-set (four egress queues per port), and how much reserved and maximum memory is needed for the traffic type? • How much of the fixed buffer space is allocated to the queue-set? • Does the bandwidth of the port need to be rate limited? • How often should the egress queues be serviced and which technique (shaped, shared, or both) should be used? These sections contain this configuration information: • Configuration Guidelines, page 28-62 • Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set, page 28-62 (optional) • Mapping DSCP or CoS Values to an Egress Queue and to a Threshold ID, page 28-65 (optional) • Configuring SRR Shaped Weights on Egress Queues, page 28-66 (optional) • Configuring SRR Shared Weights on Egress Queues, page 28-67 (optional) • Configuring the Egress Expedite Queue, page 28-68 (optional) • Limiting the Bandwidth on an Egress Interface, page 28-68 (optional) Configuration Guidelines Follow these guidelines when the expedite queue is enabled or the egress queues are serviced based on their SRR weights: • If the egress expedite queue is enabled, it overrides the SRR shaped and shared weights for queue 1. • If the egress expedite queue is disabled and the SRR shaped and shared weights are configured, the shaped mode overrides the shared mode for queue 1, and SRR services this queue in shaped mode. • If the egress expedite queue is disabled and the SRR shaped weights are not configured, SRR services this queue in shared mode. Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set You can guarantee the availability of buffers, set WTD thresholds, and configure the maximum memory allocation for a queue-set by using the mls qos queue-set output qset-id threshold queue-id drop-threshold1 drop-threshold2 reserved-threshold maximum-threshold global configuration command. 28-62 Catalyst 2960 Switch Software Configuration Guide OL-8603-04