Chapter 27 Configuring Qos; Understanding Qos - Cisco 3020 - Catalyst Blade Switch Configuration Manual

Configuring QoS
This chapter describes how to configure quality of service (QoS) by using automatic QoS (auto-QoS)
commands or by using standard QoS commands on the switch. With QoS, you can provide preferential
treatment to certain types of traffic at the expense of others. Without QoS, the switch offers best-effort
service to each packet, regardless of the packet contents or size. It sends the packets without any
assurance of reliability, delay bounds, or throughput.
You can configure QoS on physical ports and on switch virtual interfaces (SVIs). Other than to apply
policy maps, you configure the QoS settings, such as classification, queueing, and scheduling, the same
way on physical ports and SVIs. When configuring QoS on a physical port, you apply a nonhierarchical
policy map. When configuring QoS on an SVI, you apply a nonhierarchical or a hierarchical policy map.
For complete syntax and usage information for the commands used in this chapter, see the command
Note
reference this release.
This chapter consists of these sections:
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•
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The switch supports some of the modular QoS CLI (MQC) commands. For more information about the
MQC commands, see the "Modular Quality of Service Command-Line Interface Overview" at this site:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/fqcprt8/
qcfmdcli.htm#89799

Understanding QoS

Typically, networks operate on a best-effort delivery basis, which means that all traffic has equal priority
and an equal chance of being delivered in a timely manner. When congestion occurs, all traffic has an
equal chance of being dropped.
When you configure the QoS feature, you can select specific network traffic, prioritize it according to
its relative importance, and use congestion-management and congestion-avoidance techniques to
provide preferential treatment. Implementing QoS in your network makes network performance more
predictable and bandwidth utilization more effective.
OL-8915-01
Understanding QoS, page 27-1
Configuring Auto-QoS, page 27-20
Displaying Auto-QoS Information, page 27-29
Configuring Standard QoS, page 27-29
Displaying Standard QoS Information, page 27-77
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