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CHAPTER
54-1
Cisco ASA 5500 Series Configuration Guide using the CLI
54
Configuring QoS
Have you ever participated in a long-distance phone call that involved a satellite connection? The
conversation might be interrupted with brief, but perceptible, gaps at odd intervals. Those gaps are the
time, called the latency, between the arrival of packets being transmitted over the network. Some network
traffic, such as voice and video, cannot tolerate long latency times. Quality of service (QoS) is a feature
that lets you give priority to critical traffic, prevent bandwidth hogging, and manage network bottlenecks
to prevent packet drops.
This chapter describes how to apply QoS policies and includes the following sections:
• Information About QoS, page 54-1
• Licensing Requirements for QoS, page 54-5
• Guidelines and Limitations, page 54-5
• Configuring QoS, page 54-6
• Monitoring QoS, page 54-15
• Feature History for QoS, page 54-18
Information About QoS
You should consider that in an ever-changing network environment, QoS is not a one-time deployment,
but an ongoing, essential part of network design.
This section describes the QoS features supported by the ASA and includes the following topics:
• Supported QoS Features, page 54-2
• What is a Token Bucket?, page 54-2
• Information About Policing, page 54-3
• Information About Priority Queuing, page 54-3
• Information About Traffic Shaping, page 54-4
• How QoS Features Interact, page 54-4
• DSCP and DiffServ Preservation, page 54-5