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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Configuring QoS
This chapter describes how to configure quality of service (QoS) by using the modular QoS
command-line interface (CLI), or MQC, commands on the Cisco ME 3400 Ethernet Access switch. With
QoS, you can provide preferential treatment to certain types of traffic at the expense of others. When
QoS is not configured, 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.
MQC provides a comprehensive hierarchical configuration framework for prioritizing or limiting
specific streams of traffic.
For more information about Cisco IOS MQC commands, see the “Cisco IOS Quality of Service
Solutions Command Reference” at this site:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_command_reference_book09186a
0080087f48.html
For complete syntax and usage information for the platform-specific commands used in this chapter, see
the command reference for this release.
This chapter consists of these sections:
• Understanding QoS, page 33-1
• Configuring QoS, page 33-29
• Displaying QoS Information, page 33-64
• Configuration Examples for Policy Maps, page 33-64

Understanding QoS

Typically, networks operate on a best-effort deliver y basis, which means that all traff ic 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 traffic-management techniques to provide preferential treatment.
Implementing QoS in your network makes network performance more predictable and bandwidth
utilization more effective.
Figure 33-1 shows the MQC model.