Chapter 24 Applying Qos Policies; Overview - Cisco PIX 500 Series Configuration Manual

Applying QoS Policies
This chapter describes how to apply QoS policies, and includes the following sections:
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Overview

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 streaming video, cannot tolerate long latency times. Quality of Service
(QoS) is a network feature that lets you give priority to these types of traffic.
As the Internet community of users upgrades their access points from modems to high-speed broadband
connections like DSL and cable, the likelihood increases that at any given time, a single user might be
able to absorb most, if not all, of the available bandwidth, thus starving the other users. To prevent any
one user or site-to-site connection from consuming more than its fair share of bandwidth, QoS provides
a policing feature that regulates the maximum bandwidth that any user can use.
QoS refers to the capability of a network to provide better service to selected network traffic over various
technologies for the best overall services with limited bandwidth of the underlying technologies.
The primary goal of QoS in the security appliance is to provide rate limiting on selected network traffic
for both individual flow and VPN tunnel flow to ensure that all traffic gets its fair share of limited
bandwidth. A flow can be defined in a number of ways. In the security appliance, QoS can apply to a
combination of source and destination IP addresses, source and destination port number, and the TOS
byte of the IP header.
OL-12172-03
Overview, page 24-1
QoS Concepts, page 24-2
Implementing QoS, page 24-2
Identifying Traffic for QoS, page 24-4
Defining a QoS Policy Map, page 24-5
Applying Rate Limiting, page 24-6
Activating the Service Policy, page 24-7
Applying Low Latency Queueing, page 24-8
Configuring QoS, page 24-9
Viewing QoS Configuration, page 24-12
Viewing QoS Statistics, page 24-14
C H A P T E R
Cisco Security Appliance Command Line Configuration Guide
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