Configuring Modular QoS Service Packet Classification and Marking on Cisco ASR 9000 Series Routers
Information About Configuring Modular QoS Packet Classification and Marking on Cisco ASR 9000 Series Routers
QC-11
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
OL-23108-02
Information About Configuring Modular QoS Packet
Classification and Marking on Cisco
ASR 9000 Series Routers
To implement QoS packet classification features in this document, you must understand the following
concepts:
• Packet Classification Overview, page 11
• Traffic Class Elements, page 11
• Traffic Policy Elements, page 12
• Default Traffic Class, page 12
• Bundle Traffic Policies, page 13
• Shared Policy Instance, page 13
• Port Shape Policies, page 14
• Class-based Unconditional Packet Marking Feature and Benefits, page 14
• IP Precedence Compared to IP DSCP Marking, page 17
• Specification of the CoS for a Packet with IP Precedence, page 15
• Classification Based on DEI, page 17
• In-Place Policy Modification, page 17
Packet Classification Overview
Packet classification involves categorizing a packet within a specific group (or class) and assigning it a
traffic descriptor to make it accessible for QoS handling on the network. The traffic descriptor contains
information about the forwarding treatment (quality of service) that the packet should receive. Using
packet classification, you can partition network traffic into multiple priority levels or classes of service.
The source agrees to adhere to the contracted terms and the network promises a quality of service. Traffic
policers and traffic shapers use the traffic descriptor of a packet to ensure adherence to the contract.
Traffic policers and traffic shapers rely on packet classification features, such as IP precedence, to select
packets (or traffic flows) traversing a router or interface for different types of QoS service. For example,
by using the three precedence bits in the type of service (ToS) field of the IP packet header, you can
categorize packets into a limited set of up to eight traffic classes. After you classify packets, you can use
other QoS features to assign the appropriate traffic handling policies including congestion management,
bandwidth allocation, and delay bounds for each traffic class.
Note IPv6-based classification is supported only on Layer 3 interfaces.
Traffic Class Elements
The purpose of a traffic class is to classify traffic on your router. Use the class-map command to define
a traffic class.
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