Cisco Systems 4500 Marking Network Traffic

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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 37 Configuring Quality of Service Configuring QoS on Supervisor Engine 6-E, Supervisor Engine 6L-E, Catalyst 4900M, and Catalyst 4948E
Marking Network Traffic
Marking network traffic allows you to set or modify the attributes of traffic (that is, packets) belonging
to a specific class or category. When used in conjunction with network traffic classification, marking
network traffic is the foundation for enabling many quality of service (QoS) features on your network
This module contains conceptual information and the configuration tasks for marking network traffic.
This section describes the following topics:
• Information about Marking Network Traffic, page 37-69
• Marking Action Drivers, page 37-71
• Traffic Marking Procedure Flowchart, page 37-72
• Restrictions for Marking Network Traffic, page 37-72
• Multi-attribute Marking Support, page 37-73
• Hardware Capabilities for Marking, page 37-73
• Configuring the Policy-Map Marking Action, page 37-73
• Marking Statistics, page 37-75
Information about Marking Network Traffic
To mark network traffic, you should understand the following concepts:
• Purpose of Marking Network Traffic, page 37-69
• Benefits of Marking Network Traffic, page 37-69
• Methods for Marking Traffic Attributes, page 37-70
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:
• 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
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, which helps to achieve optimal application
performance.