Contents - Cisco Catalyst 4500 series Administration Manual

Chapter 42 Configuring Quality of Service

Contents

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Information About Marking Network Traffic
To mark network traffic, you should understand the following concepts:
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Purpose of Marking Network Traffic
Traffic marking is used to identify certain traffic types for unique handling, effectively partitioning
network traffic into different categories.
After the network traffic is organized into classes by traffic classification, traffic marking allows you to
mark (that is, set or change) a value (attribute) for the traffic belonging to a specific class. For instance,
you may want to change the class of service (CoS) value from 2 to 1 in one class, or you may want to
change the differentiated services code point (DSCP) value from 3 to 2 in another class. In this module,
these values are referred to as attributes or marking fields.
Attributes that can be set and modified include the following:
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Benefits of Marking Network Traffic
Traffic marking allows you to fine-tune the attributes for traffic on your network. This increased
granularity helps isolate traffic that requires special handling, and thus, helps to achieve optimal
application performance.
Traffic marking allows you to determine how traffic will be treated, based on how the attributes for the
network traffic are set. It allows you to segment network traffic into multiple priority levels or classes of
service based on those attributes, as follows:
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Configuring QoS on a Standalone Supervisor Engine 6-E/6L-E or Supervisor Engine 7-E/7L-E/8-E
"Information About Marking Network Traffic" section on page 42-53
"Marking Action Drivers" section on page 42-55
"Traffic Marking Procedure Flowchart" section on page 42-55
"Restrictions for Marking Network Traffic" section on page 42-56
"Multi-attribute Marking Support" section on page 42-56
"Hardware Capabilities for Marking" section on page 42-57
"Configuring the Policy Map Marking Action" section on page 42-57
"Marking Statistics" section on page 42-59
"Purpose of Marking Network Traffic" section on page 42-53
"Benefits of Marking Network Traffic" section on page 42-53
"Two Methods for Marking Traffic Attributes" section on page 42-54
CoS value of a tagged Ethernet frame
DSCP/Precedence value in the Type of Service (ToS) byte of IPv4.
QoS group identifier (ID)
DSCP /Precedence value in the traffic class byte of IPv6
Traffic marking is often used to set the IP precedence or IP DSCP values for traffic entering a
network. Networking devices within your network can then use the newly marked IP precedence
values to determine how traffic should be treated. For example, voice traffic can be marked with a
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
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