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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration 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, regar dless of the p acket
contents or size. It sends the packets without any assurance of r elia bilit y, delay bounds, or t hrough put .
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/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_r/index.htm
For complete syntax and usage information for the platform-specif ic comm ands used in this chapte r , see
the command reference for this release.
This chapter consists of these sections:
•Understanding QoS, page 30-1
•Configuring QoS, page 30-26
•Displaying QoS Information, page 30-55
•Configuration Examples for Policy Maps, page 30-56

Understanding QoS

Typically, networks operate on a best-ef fort de liv ery basis, which mean s that all t raff ic h as 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 p rovide pr ef er en tial tre at me nt.
Implementing QoS in your network makes network performance more predictable and bandwidth
utilization more effective.
Figure 30-1 shows the MQC model.