Queueing And Scheduling Overview - Cisco Catalyst 3750 Software Configuration Manual

Metro switch

Hide thumbs Also See for Catalyst 3750:

Table of Contents

Understanding QoS

The CoS-to-DSCP, DSCP-to-CoS, and the IP-precedence-to-DSCP maps have default values that might

or might not be appropriate for your network.

The default DSCP-to-DSCP-mutation map and the default policed-DSCP map are null maps; they map

an inbound DSCP value to the same DSCP value. The DSCP-to-DSCP-mutation map is the only map

you apply to a specific port. All other maps apply to the entire switch.

For configuration information, see the

For information about the DSCP and CoS input queue threshold maps, see the

Scheduling of Ingress Queues" section on page

queue threshold maps, see the

Queueing and Scheduling Overview

The switch has queues at specific points to help prevent congestion, as shown in

Figure 26-5 Ingress and Egress Queue Location

Catalyst 3750 Metro Switch Software Configuration Guide

Before the traffic reaches the scheduling stage, QoS stores the packet in an ingress and an egress

queue according to the QoS label. The QoS label is based on the DSCP or the CoS value in the

inbound packet. The QoS label selects an ingress queue and an egress queue from the queue-set

through the DSCP input and output queue threshold maps or through the CoS input and output queue

threshold maps. You configure these maps by using the mls qos srr-queue {input | output}

dscp-map and the mls qos srr-queue {input | output} cos-map global configuration commands.

"Queueing and Scheduling of Egress Queue-Sets" section on page

"Configuring DSCP Maps" section on page

26-15. For information about the DSCP and CoS output

Configuring QoS

"Queueing and

Traffic sent to

a standard port

Traffic sent to