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CHAPTER
23-1
Cisco ASA Series Firewall ASDM Configuration Guide
23
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.
Note For the ASASM, we suggest performing QoS on the switch instead of the ASASM. Switches have more
capability in this area.
This chapter describes how to apply QoS policies and includes the following sections:
• Information About QoS, page 23-1
• Licensing Requirements for QoS, page 23-5
• Guidelines and Limitations, page 23-5
• Configuring QoS, page 23-6
• Monitoring QoS, page 23-11
• Feature History for QoS, page 23-14
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 23-2
• What is a Token Bucket?, page 23-2
• Information About Policing, page 23-3
• Information About Priority Queuing, page 23-3
• Information About Traffic Shaping, page 23-4
• DSCP and DiffServ Preservation, page 23-5