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Cisco IOS XE Quality of Service Solutions Configuration Guide, Release 2
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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
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Table Of Contents
Packet Classification Based on Layer 3 Packet Length
Prerequisites for Packet Classification Based on Layer 3 Packet Length
Restrictions for Packet Classification Based on Layer 3 Packet Length
Information About Packet Classification Based on Layer 3 Packet Length
MQC and Packet Classification Based on Layer 3 Packet Length
How to Configure Packet Classification Based on Layer 3 Packet Length
Configuring the Class Map to Match on Layer 3 Packet Length
Attaching the Policy Map to an Interface
Verifying the Layer 3 Packet Length Classification Configuration
Configuration Examples for Packet Classification Based on Layer 3 Packet Length
Configuring the Layer 3 Packet Length as a Match Criterion: Example
Verifying the Layer 3 Packet Length Setting: Example
Feature Information for Packet Classification Based on Layer 3 Packet Length
Packet Classification Based on Layer 3 Packet Length
First Published: November 25, 2002Last Updated: March 2, 2009This feature provides the added capability of matching and classifying traffic on the basis of the Layer 3 packet length in the IP header. The Layer 3 packet length is the IP datagram length plus the IP header length. This new match criterion supplements the other match criteria, such as the IP precedence, the differentiated services code point (DSCP) value, and the class of service (CoS).
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 Packet Classification Based on Layer 3 Packet Length" 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
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Prerequisites for Packet Classification Based on Layer 3 Packet Length
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Prerequisites for Packet Classification Based on Layer 3 Packet Length
When configuring this feature, you must first create a policy map (sometimes referred to as a service policy or a traffic policy) using the Modular QoS Command-Line Interface (CLI) (MQC). Therefore, you should be familiar with the procedure for creating a policy map using the MQC.
For more information about creating a policy map (traffic policy) using the MQC, see the "Applying QoS Features Using the MQC" module.
Restrictions for Packet Classification Based on Layer 3 Packet Length
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Information About Packet Classification Based on Layer 3 Packet Length
To configure the Packet Classification Based on Layer 3 Packet Length feature, you should understand the following concept:
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MQC and Packet Classification Based on Layer 3 Packet Length
Use the MQC to enable packet classification based on Layer 3 packet length. The MQC is a CLI that allows you to create traffic policies, enable a QoS feature (such as packet classification), and attach these policies to interfaces.
In the MQC, the class-map command is used to define a traffic class (which is then associated with a traffic policy). The purpose of a traffic class is to classify traffic.
The MQC consists of the following three processes:
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A traffic class contains three major elements: a name, a series of match commands, and, if more than one match command exists in the traffic class, an instruction on how to evaluate these match commands. The traffic class is named in the class-map command line; for example, if you enter the class-map cisco command while configuring the traffic class in the CLI, the traffic class would be named "cisco".
The match commands are used to specify various criteria for classifying packets. Packets are checked to determine whether they match the criteria specified in the match commands. If a packet matches the specified criteria, that packet is considered a member of the class and is forwarded according to the QoS specifications set in the traffic policy. Packets that fail to meet any of the matching criteria are classified as members of the default traffic class.
How to Configure Packet Classification Based on Layer 3 Packet Length
This section contains the following procedures. Each procedure is identified as either required or optional.
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Configuring the Class Map to Match on Layer 3 Packet Length
Class maps can be used to classify packets into groups that can then receive specific QoS features. For example, class maps can be configured to match packets on the basis of one or more user-specified criteria (for example, the DSCP value or access list number). In this procedure, the class map is configured to match on the Layer 3 packet length.
To configure the class map to match on the Layer 3 packet length, complete the following steps.
SUMMARY STEPS
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DETAILED STEPS
Attaching the Policy Map to an Interface
After a policy map is created, the next step is to attach the policy map to an interface. Policy maps can be attached to either the input direction or the output direction of the interface.
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To attach the policy map, complete the following steps.
Prerequisite
Before attaching the policy map to an interface, the policy map must be created using the MQC. To create a policy map using the MQC, see the "Applying QoS Features Using the MQC" module.
SUMMARY STEPS
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DETAILED STEPS
Step 1
enable
Example:Router> enable
Enables privileged EXEC mode.
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Step 2
configure terminal
Example:Router# configure terminal
Enters global configuration mode.
Step 3
interface type number
Example:Router(config)# interface serial4/0/0
Configures an interface (or subinterface) type and enters interface configuration mode
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Step 4
pvc [name] vpi/vci [ilmi | qsaal | smds]
Example:Router(config-if)# pvc cisco 0/16 ilmi
(Optional) Creates or assigns a name to an ATM PVC, specifies the encapsulation type on an ATM PVC, and enters ATM VC configuration mode.
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Step 5
service-policy {input | output} policy-map-name
Example:Router(config-if)# service-policy input policy1
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Example:Router(config-if-atm-vc)# service-policy input policy1
Specifies the name of the policy map to be attached to either the input or output direction of the interface.
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Step 6
end
Example:Router(config-if)# end
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Example:Router(config-if-atm-vc)# end
(Optional) Exits interface configuration mode and returns to privileged EXEC mode.
Verifying the Layer 3 Packet Length Classification Configuration
This task allows you to verify that you created the configuration that you intended and that the feature is functioning correctly.
To verify the configuration, use one or more of the show commands listed in the following steps.
SUMMARY STEPS
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DETAILED STEPS
Troubleshooting Tips
The commands in the "Verifying the Layer 3 Packet Length Classification Configuration" section allow you to verify that you achieved the intended configuration and that the feature is functioning correctly. If, after using the show commands listed above, you find that the configuration is not correct or that the feature is not functioning as expected, perform these operations:
If the configuration is not the one that you intended, perform the following operations:
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If the packets are not being matched correctly (for example, the packet counters are not incrementing correctly), performs the following operations:
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Configuration Examples for Packet Classification Based on Layer 3 Packet Length
This section provides the following configuration examples:
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Configuring the Layer 3 Packet Length as a Match Criterion: Example
In the following example, a class map called "class 1" has been created, and the Layer 3 packet length has been specified as a match criterion. In this example, packets with a minimum Layer 3 packet length of 100 bytes and a maximum Layer 3 packet length of 300 bytes are viewed as meeting the match criterion. Packets matching this criterion are placed in class1.
Router(config)# class map class1Router(config-cmap)# match packet length min 100 max 300Verifying the Layer 3 Packet Length Setting: Example
Use either the show class-map command or the show policy-map interface command to verify the setting of the Layer 3 packet length value used as a match criterion for the class map and the policy map. The following section begins with sample output of the show class-map command and concludes with sample output of the show policy-map interface command.
The sample output of the show class-map command shows the defined class map and the specified match criterion. In the following example, a class map called "class1" is defined. The Layer 3 packet length has been specified as a match criterion for the class. Packets with a Layer 3 length of between 100 bytes and 300 bytes belong to class1.
Router# show class-mapclass-map match-all class1match packet length min 100 max 300The sample output of the show policy-map interface command displays the statistics for FastEthernet interface 4/1/1, to which a service policy called "mypolicy" is attached. The configuration for the policy map called "mypolicy" is given below.
Router(config)# policy-map mypolicyRouter(config-pmap)# class class1Router(config-pmap-c)# set qos-group 20Router(config-pmap-c)# exitRouter(config-pmap)# exitRouter(config)# interface fastethernet4/1/1Router(config-if)# service-policy input mypolicyThe following are the statistics for the policy map called "mypolicy" attached to FastEthernet interface 4/1/1. These statistics confirm that matching on the Layer 3 packet length has been configured as a match criterion.
Router# show policy-map interface FastEthernet4/1/1FastEthernet4/1/1Service-policy input: mypolicyClass-map: class1 (match-all)500 packets, 125000 bytes5 minute offered rate 4000 bps, drop rate 0 bpsMatch: packet length min 100 max 300QoS Setqos-group 20Packets marked 500Additional References
The following sections provide additional references related to the Packet Classification Based on Layer 3 Packet Length feature.
Related Documents
QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples
MQC and information about attaching policy maps to interfaces
Additional match criteria that can be used for packet classification
Marking network traffic
"Marking Network Traffic" module
Standards
No new or modified standards are supported, and support for existing standards has not been modified.
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MIBs
RFCs
No new or modified RFCs are supported, and support for existing RFCs has not been modified.
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Technical Assistance
Feature Information for Packet Classification Based on Layer 3 Packet Length
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.
Note
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