-
Cisco IOS XE Quality of Service Solutions Configuration Guide, Release 2
-
Quality of Service Overview
- Part 1: Classification
- Part 2: Congestion Management
- Part 3: Congestion Avoidance
- Part 4: Policing and Shaping
- Part 5: Link Efficiency Mechanisms
- Part 6: Quality of Service Solutions
- Part 7: Modular Quality of Service Command-Line Interface
-
Table Of Contents
Restrictions for Traffic Policing
How to Configure Traffic Policing
Monitoring and Maintaining Traffic Policing
Configuration Examples for Traffic Policing
Configuring a Service Policy That Includes Traffic Policing: Example
Feature Information for Traffic Policing
Traffic Policing
This feature module describes the Traffic Policing feature. The Traffic Policing feature performs the following functions:
•
Limits the input or output transmission rate of a class of traffic based on user-defined criteria.
•
Traffic policing allows you to control the maximum rate of traffic that is transmitted or received on an interface. The Traffic Policing feature is applied when a service-policy containing the feature is attached to an interface. A service-policy (traffic policy) is configured using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC). For information about the MQC, see the "Applying QoS Features Using the MQC" module.
For complete conceptual information, see the "Policing and Shaping Overview" module.
For a complete description of the traffic policing commands mentioned in this module, refer to the Cisco IOS Quality of Service Solutions Command Reference.
Finding Feature Information
For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Traffic Policing" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE Software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
This document includes the following sections:
•
•
•
Restrictions for Traffic Policing
•
•
Benefits of Traffic Policing
Bandwidth Management Through Rate Limiting
Traffic policing allows you to control the maximum rate of traffic transmitted or received on an interface. Traffic policing is often configured on interfaces at the edge of a network to limit traffic into or out of the network. In most Traffic Policing configurations, traffic that falls within the rate parameters is transmitted, whereas traffic that exceeds the parameters is dropped or transmitted with a different priority.
Packet Marking
Packet marking allows you to partition your network into multiple priority levels or classes of service (CoS). A packet is marked and these markings can be used to identify and classify traffic for downstream devices. In some cases, such as ATM Cell Loss Priority (CLP) marking or Frame Relay Discard Eligibility (DE) marking, the marking is used to decide whether the packet can be dropped in congested environments.
•
•
Traffic can be marked without using the Traffic Policing feature. If you want to mark traffic but do not want to use Traffic Policing, see the "Marking Network Traffic" module.
Packet Prioritization for Frame Relay Frames
The Traffic Policing feature allows users to mark the Frame Relay DE bit of the Frame Relay frame. The Frame Relay DE bit is one bit and, therefore, can be set to either 0 or 1. In congested environments, frames with the DE bit set to 1 are discarded before frames with the DE bit set to 0.
Packet Prioritization for ATM Cells
The Traffic Policing feature allows users to mark the ATM CLP bit in ATM cells. The ATM CLP bit is used to prioritize packets in ATM networks. The ATM CLP bit is one bit and, therefore, can be set to either 0 or 1. In congested environments, cells with the ATM CLP bit set to 1 are discarded before cells with the ATM CLP bit set to 0.
How to Configure Traffic Policing
See the following sections for configuration tasks for the Traffic Policing feature.
•
Configuring Traffic Policing
To successfully configure the Traffic Policing feature, a traffic class and a traffic policy must be created, and the traffic policy must be attached to a specified interface. These tasks are performed using the MQC. For information about the MQC, see the "Applying QoS Features Using the MQC" module.
The Traffic Policing feature is configured in the traffic policy. To configure the Traffic Policing feature, use the following command in policy map configuration mode:
Router(config-pmap-c)# police bps burst-normal burst-max conform-action action exceed-action action violate-action action
Specifies a maximum bandwidth usage by a traffic class.
For more information about the police command, see the Cisco IOS Quality of Service Solutions Command Reference.
The Traffic Policing feature works with a token bucket mechanism. There are currently two types of token bucket algorithms: a single token bucket algorithm and a two token bucket algorithm. A single token bucket system is used when the violate-action option is not specified, and a two token bucket system is used when the violate-action option is specified.
For more information about token bucket mechanisms, see the "Policing and Shaping Overview" module.
Monitoring and Maintaining Traffic Policing
To monitor and maintain the Traffic Policing feature, use the following commands in EXEC mode, as needed:
For more information about the show policy-map and show policy-map interface commands and how to interpret the information displayed, see the Cisco IOS Quality of Service Solutions Command Reference.
Configuration Examples for Traffic Policing
This section provides the following configuration example:
•
Configuring a Service Policy That Includes Traffic Policing: Example
The following configuration shows how to define a traffic class (with the class-map command) and associate that traffic class with a traffic policy (with the policy-map command). Traffic policing is applied in the traffic policy. The service-policy command is then used to attach the traffic policy to the interface.
For additional information on configuring traffic classes and traffic policies, see the "Applying QoS Features Using the MQC" module.
In this particular example, traffic policing is configured with the Committed Information Rate (CIR) at 8000 bits per second, the normal burst size at 2000 bytes, and the excess burst size at 4000 bytes. Packets coming into FastEthernet interface 1/1/1 are evaluated by the token bucket algorithm to analyze whether packets conform exceed, or violate the specified parameters. Packets that conform are transmitted, packets that exceed are assigned a QoS group value of 4 and are transmitted, and packets that violate are dropped.
For more information about token bucket mechanisms, see the "Policing and Shaping Overview" module.
Router(config)# class-map acgroup2Router(config-cmap)# match access-group 2Router(config-cmap)# exitRouter(config)# policy-map policeRouter(config-pmap)# class acgroup2Router(config-pmap-c)# police 8000 2000 4000 conform-action transmit exceed-action set-qos-transmit 4 violate-action dropRouter(config-pmap-c)# exitRouter(config-pmap)# exitRouter(config)# interface fastethernet1/1/1Router(config-if)# service-policy input policeRouter(config-if)# endAdditional References
The following sections provide references related to the Traffic Policing feature.
Related Documents
QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples
Conceptual information about policing and shaping
MQC
Marking network traffic
"Marking Network Traffic" module
Standards
MIBs
RFCs
Technical Assistance
Feature Information for Traffic Policing
Table 1 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE Software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1 lists only the Cisco IOS XE Software release that introduced support for a given feature in a given Cisco IOS XE Software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE Software release train also support that feature.
Glossary
average rate—Maximum long-term average rate of conforming traffic.
conform action—Action to take on packets with a burst size below the rate allowed by the rate limit.
DSCP—differentiated services code point
exceed action—Action to take on packets that exceed the rate limit.
excess burst size—Bytes allowed in a burst before all packets will exceed the rate limit.
normal burst size—Bytes allowed in a burst before some packets will exceed the rate limit. Larger bursts are more likely to exceed the rate limit.
policing policy—Rate limit, conform actions, and exceed actions that apply to traffic that matches certain criteria.
QoS group—Internal QoS group ID for a packet used to determine weighted fair queuing characteristics for that packet.
CCDE, CCENT, Cisco Eos, Cisco HealthPresence, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco StadiumVision, Cisco TelePresence, Cisco WebEx, DCE, and Welcome to the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn and Cisco Store are service marks; and Access Registrar, Aironet, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, EtherFast, EtherSwitch, Event Center, Fast Step, Follow Me Browsing, FormShare, GigaDrive, HomeLink, Internet Quotient, IOS, iPhone, iQuick Study, IronPort, the IronPort logo, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking Academy, Network Registrar, PCNow, PIX, PowerPanels, ProConnect, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx, and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0812R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
© 2007-2009 Cisco Systems, Inc. All rights reserved.