Chapter 28 Configuring Qos; Understanding Qos - Cisco WS-C3560-48PS-S Software 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 Catalyst 3560 switch. With QoS, you can provide
preferential treatment to certain 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.
Note For complete syntax and usage information for the commands used in this chapter, refer to the command
reference this release.
This chapter consists of these sections:
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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.
The QoS implementation is based on the Differentiated Services (Diff-Serv) architecture, an emerging
standard from the Internet Engineering Task Force (IETF). This architecture specifies that each packet
is classified upon entry into the network.
78-16156-01
Understanding QoS, page 28-1
Configuring Auto-QoS, page 28-18
Displaying Auto-QoS Information, page 28-26
Configuring Standard QoS, page 28-26
Displaying Standard QoS Information, page 28-64
C H A P T E R
Catalyst 3560 Switch Software Configuration Guide
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