Classifying Network Traffic

Classifying network traffic allows you to organize traffic (that is, packets) into traffic classes or categories on the basis of whether the traffic matches specific criteria. Classifying 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 classifying network traffic.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About Classifying Network Traffic

Purpose of Classifying Network Traffic

Classifying network traffic allows you to see what kinds of traffic you have, organize traffic (that is, packets) into traffic classes or categories on the basis of whether the traffic matches specific criteria, and treat some types of traffic differently than others. Classifying network traffic is the foundation for enabling other QoS features such as traffic shaping and traffic policing on your network.

The goal of network traffic classification is to group traffic based on user-defined criteria so that the resulting groups of network traffic can then be subjected to specific QoS treatments. The QoS treatments might include faster forwarding by intermediate routers and switches or reduced probability of the traffic being dropped due to lack of buffering resources.

Identifying and categorizing network traffic into traffic classes (that is, classifying packets) enables distinct handling for different types of traffic, effectively separating network traffic into different categories. This classification can be associated with a variety of match criteria such as the IP Precedence value, differentiated services code point (DSCP) value, class of service (CoS) value, source and destination MAC addresses, input interface, or protocol type. You classify network traffic by using class maps and policy maps with the Modular Quality of Service Command-Line Interface (MQC). For example, you can configure class maps and policy maps to classify network traffic on the basis of the QoS group, Frame Relay DLCI number, Layer 3 packet length, or other criteria that you specify.

Restrictions for Classifying Network Traffic

  • When access lists are used for classification in QoS policies, the following limitations are applicable:

    • The use of wildcards (For example, the any keyword, masks using zeros like 172.0.0.0, subnet masks) in source or destination addresses of permit or deny statements causes a greater consumption of memory on the device. This behavior is particularly important on devices that use software based classification (like Cisco ISR 4000 series devices or CSR1000v) and lower-end platforms with smaller memory capacities and ternary content-addressable memor (TCAMs).

    • The use of deny statements causes greater consumption of TCAM resources on systems that use HW-based classification (ASR1k).

Benefits of Classifying Network Traffic

Classifying network traffic allows you to see what kinds of traffic you have, organize the various kinds of network traffic into traffic classes, and treat some types of traffic differently than others. Identifying and organizing network traffic is the foundation for applying the appropriate QoS feature to that traffic, enabling you to allocate network resources to deliver optimal performance for different types of traffic. For example, high-priority network traffic or traffic matching specific criteria can be singled out for special handling, and thus, help to achieve peak application performance.

MQC and Network Traffic Classification

To configure network traffic classification, you use the Modular Quality of Service Command-Line Interface (MQC).

The MQC is a CLI structure that allows you to complete the following tasks:

  • Specify the matching criteria used to define a traffic class.

  • Create a traffic policy (policy map). The traffic policy defines the QoS policy actions to be taken for each traffic class.

  • Apply the policy actions specified in the policy map to an interface, subinterface, or ATM permanent virtual circuit (PVC) by using the service-policy command.

Network Traffic Classification match Commands and Match Criteria

Network traffic classification allows you to group or categorize traffic on the basis of whether the traffic meets one or more specific criteria. For example, network traffic with a specific IP precedence can be placed into one traffic class, while traffic with a specific DSCP value can be placed into another traffic class. The network traffic within that traffic class can be given the appropriate QoS treatment, which you can configure in a policy map later.

You specify the criteria used to classify traffic with a match command. The table below lists the available match commands and the corresponding match criterion.

Table 1. match Commands and Corresponding Match Criterion

match Commands1

Match Criterion

match access group

Access control list (ACL) number

match any

Any match criteria

match atm clp

ATM cell loss priority (CLP)

match class-map

Traffic class name

match cos

Layer 2 class of service (CoS) value

match destination-address mac

MAC address

match discard-class

Discard class value

match dscp

DSCP value

match field

Fields defined in the protocol header description files (PHDFs)

match fr-de

Frame Relay discard eligibility (DE) bit setting

match fr-dlci

Frame Relay data-link connection identifier (DLCI) number

match input-interface

Input interface name

match ip rtp

Real-Time Transport Protocol (RTP) port

match mpls experimental

Multiprotocol Label Switching (MPLS) experimental (EXP) value

match mpls experimental topmost

MPLS EXP value in the topmost label

match not

Single match criterion value to use as an unsuccessful match criterion

match packet length (class-map)

Layer 3 packet length in the IP header

match port-type

Port type

match precedence

IP precedence values

match protocol

Protocol type

match protocol (NBAR)

Protocol type known to network-based application recognition (NBAR)

match protocol citrix

Citrix protocol

match protocol fasttrack

FastTrack peer-to-peer traffic

match protocol gnutella

Gnutella peer-to-peer traffic

match protocol http

Hypertext Transfer Protocol

match protocol rtp

RTP traffic

match qos-group

QoS group value

match source-address mac

Source Media Access Control (MAC) address

match start

Datagram header (Layer 2) or the network header (Layer 3)

match tag (class-map)

Tag type of class map

match vlan (QoS)

Layer 2 virtual local-area network (VLAN) identification number

1 Cisco match commands can vary by release and platform. For more information, see the command documentation for the Cisco release and platform that you are using.

Traffic Classification Compared with Traffic Marking

Traffic classification and traffic marking are closely related and can be used together. Traffic marking can be viewed as an additional action, specified in a policy map, to be taken on a traffic class.

Traffic classification allows you to organize into traffic classes on the basis of whether the traffic matches specific criteria. For example, all traffic with a CoS value of 2 is grouped into one class, and traffic with a DSCP value of 3 is grouped into another class. The match criteria are user-defined.

After the traffic is organized into traffic classes, traffic marking allows you to mark (that is, set or change) an attribute for the traffic belonging to that specific class. For instance, you may want to change the CoS value from 2 to 1, or you may want to change the DSCP value from 3 to 2.

The match criteria used by traffic classification are specified by configuring a match command in a class map. The marking action taken by traffic marking is specified by configuring a set command in a policy map. These class maps and policy maps are configured using the MQC.

The table below compares the features of traffic classification and traffic marking.

Table 2. Traffic Classification Compared with Traffic Marking

Feature

Traffic Classification

Traffic Marking

Goal

Groups network traffic into specific traffic classes on the basis of whether the traffic matches the user-defined criterion.

After the network traffic is grouped into traffic classes, modifies the attributes for the traffic in a particular traffic class.

Configuration Mechanism

Uses class maps and policy maps in the MQC.

Uses class maps and policy maps in the MQC.

CLI

In a class map, uses match commands (for example, match cos ) to define the traffic matching criteria.

Uses the traffic classes and matching criteria specified by traffic classification.

In addition, uses set commands (for example, set cos ) in a policy map to modify the attributes for the network traffic.

How to Classify Network Traffic

Creating a Class Map for Classifying Network Traffic


Note

In the following task, the match fr-dlci command is shown in Step 4. The match fr-dlci command matches traffic on the basis of the Frame Relay DLCI number. The match fr-dlci command is just an example of one of the match commands that can be used. For a list of other match commands, see the Network Traffic Classification match Commands and Match Criteria section.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. class-map class-map-name [match-all | match-any ]
  4. match fr-dlci dlci-number
  5. end

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

class-map class-map-name [match-all | match-any ]

Example:


Router(config)# class-map class1

Creates a class map to be used for matching traffic to a specified class, and enters class-map configuration mode.

  • Enter the class map name.

Step 4

match fr-dlci dlci-number

Example:


Router(config-cmap)# match fr-dlci 500

(Optional) Specifies the match criteria in a class map.

Note 

The match fr-dlci command classifies traffic on the basis of the Frame Relay DLCI number. The match fr-dlci command is just an example of one of the match commands that can be used. For a list of other match commands, see the Network Traffic Classification match Commands and Match Criteria section.

Step 5

end

Example:


Router(config-cmap)# end

(Optional) Returns to privileged EXEC mode.

Creating a Policy Map for Applying a QoS Feature to Network Traffic


Note
In the following task, the bandwidth command is shown at Step 5. The bandwidth command configures the QoS feature class-based weighted fair queuing (CBWFQ). CBWFQ is just an example of a QoS feature that can be configured. Use the appropriate command for the QoS feature that you want to use.

Note
Configuring bandwidth on policies that have the class-default class is supported on physical interfaces such as Gigabit Ethernet (GigE), Serial, Mobile Location Protocol (MLP), and Multilink Frame-Relay (MFR).

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. policy-map policy-map-name
  4. class {class-name | class-default }
  5. bandwidth {bandwidth-kbps | remaining percent percentage | percent percentage }
  6. end
  7. show policy-map
  9. show policy-map policy-map class class-name
  10. Router# show policy-map
  12. Router# show policy-map policy1 class class1
  13. exit

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

policy-map policy-map-name

Example:


Router(config)# policy-map policy1

Specifies the name of the policy map to be created and enters policy-map configuration mode.

  • Enter the policy map name.

Step 4

class {class-name | class-default }

Example:


Router(config-pmap)# class class1

Specifies the name of the class and enters policy-map class configuration mode. This class is associated with the class map created earlier.

  • Enter the name of the class or enter the class-default keyword.

Step 5

bandwidth {bandwidth-kbps | remaining percent percentage | percent percentage }

Example:


Router(config-pmap-c)# bandwidth percent 50

(Optional) Specifies or modifies the bandwidth allocated for a class belonging to a policy map.

  • Enter the amount of bandwidth as a number of kbps, a relative percentage of bandwidth, or an absolute amount of bandwidth.

Note 
The bandwidth command configures the QoS feature class-based weighted fair queuing (CBWFQ). CBWFQ is just an example of a QoS feature that can be configured. Use the appropriate command for the QoS feature that you want to use.
Step 6

end

Example:


Router(config-pmap-c)# end

Returns to privileged EXEC mode.

Step 7

show policy-map

(Optional) Displays all configured policy maps.

Step 8

or

Step 9

show policy-map policy-map class class-name

Example:

(Optional) Displays the configuration for the specified class of the specified policy map.

  • Enter the policy map name and the class name.

Step 10

Router# show policy-map

Step 11

Step 12

Router# show policy-map policy1 class class1

Step 13

exit

Example:


Router# exit

(Optional) Exits privileged EXEC mode.

What to Do Next

Create and configure as many policy maps as you need for your network. To create and configure additional policy maps, repeat the steps in the “Creating a Policy Map for Applying a QoS Feature to Network Traffic” section. Then attach the policy maps to the appropriate interface, following the instructions in the “Attaching the Policy Map to an Interface” section.

Attaching the Policy Map to an Interface


Note
Depending on the needs of your network, policy maps can be attached to an interface, a subinterface, or an ATM PVC.

Note
A policy with the command match fr-dlic can only be attached to a Frame Relay main interface with point-to-point connections.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number [name-tag ]
  4. pvc [name ] vpi / vci [ilmi |qsaal |smds | l2transport ]
  5. exit
  6. service-policy {input | output }policy-map-name
  7. end
  8. show policy-map interface type number
  9. exit

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

interface type number [name-tag ]

Example:


Router(config)# interface serial4/0/0

Configures an interface type and enters interface configuration mode.

  • Enter the interface type and number.

Step 4

pvc [name ] vpi / vci [ilmi |qsaal |smds | l2transport ]

Example:


Router(config-if)# pvc cisco 0/16

(Optional) Creates or assigns a name to an ATM PVC, specifies the encapsulation type on an ATM PVC, and enters ATM virtual circuit configuration mode.

  • Enter the PVC name, the ATM network virtual path identifier, and the network virtual channel identifier.

Note 
This step is required only if you are attaching the policy map to an ATM PVC. If you are not attaching the policy map to an ATM PVC, advance to .
Step 5

exit

Example:


Router(config-atm-vc)# exit

(Optional) Returns to interface configuration mode.

Note 

This step is required only if you are attaching the policy map to an ATM PVC and you completed Step 4. If you are not attaching the policy map to an ATM PVC, advance to Step 6.

Step 6

service-policy {input | output }policy-map-name

Example:


Router(config-if)# service-policy input policy1

Attaches a policy map to an input or output interface.

  • Enter the policy map name.

Note 

Policy maps can be configured on ingress or egress routers. They can also be attached in the input or output direction of an interface. The direction (input or output) and the router (ingress or egress) to which the policy map should be attached varies according your network configuration. When using the service-policy command to attach the policy map to an interface, be sure to choose the router and the interface direction that are appropriate for your network configuration.

Step 7

end

Example:


Router(config-if)# end

Returns to privileged EXEC mode.

Step 8

show policy-map interface type number

Example:


Router# 
show policy-map interface serial4/0/0

(Optional) Displays the traffic statistics of all traffic classes that are configured for all service policies either on the specified interface or subinterface or on a specific PVC on the interface.

  • Enter the type and number.

Step 9

exit

Example:


Router# exit

(Optional) Exits privileged EXEC mode.

Configuration Examples for Classifying Network Traffic

Example Creating a Class Map for Classifying Network Traffic

The following is an example of creating a class map to be used for traffic classification. In this example, a traffic class called class1 has been created. Traffic with a Frame Relay DLCI value of 500 will be put in this traffic class. 


Router> enable  

Router# configure  terminal  

Router(config)# class-map  class1  

Router(config-cmap)# match  fr-dlci  500  

Router(config-cmap)# end

Note

This example uses the match fr-dlci command. The match fr-dlci command is just an example of one of the match commands that can be used. For a list of other match commands, see Network Traffic Classification match Commands and Match Criteria.

A policy with match fr-dlic can only be attached to a Frame Relay main interface with point-to-point connections.

Example Creating a Policy Map for Applying a QoS Feature to Network Traffic

The following is an example of creating a policy map to be used for traffic classification. In this example, a policy map called policy1 has been created, and the bandwidth command has been configured for class1. The bandwidth command configures the QoS feature CBWFQ. 


Router> enable
Router# configure terminal
Router(config)# policy-map policy1
Router(config-pmap)# class class1
Router(config-pmap-c)# bandwidth percent 50 
Router(config-pmap-c)# end
Router# 
show policy-map policy1 class class1
Router# exit

Note

This example uses the bandwidth command. The bandwidth command configures the QoS feature class-based weighted fair queuing (CBWFQ). CBWFQ is just an example of a QoS feature that can be configured. Use the appropriate command for the QoS feature that you want to use.

Example Attaching the Policy Map to an Interface

The following is an example of attaching the policy map to an interface. In this example, the policy map called policy1 has been attached in the input direction of serial interface 4/0. 


Router> enable
Router# configure terminal
Router(config)# interface serial4/0/0
Router(config-if)# service-policy input policy1 
Router(config-if)# end
Router# 
show policy-map interface serial4/0/0
Router# exit

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco IOS Quality of Service Solutions Command Reference

MQC

"Applying QoS Features Using the MQC" module

Marking network traffic

"Marking Network Traffic" module

IPsec and VPNs

"Configuring Security for VPNs with IPsec" module

NBAR

"Classifying Network Traffic Using NBAR" module

IPv6 QoS

“IPv6 Quality of Service” module

IPv6 MQC Packet Classification

“IPv6 QoS: MQC Packet Classification” module

Standards

Standard

Title

No new or modified standards are supported, and support for existing standards has not been modified.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported, and support for existing MIBs has not been modified.

To locate and download MIBs for selected platforms, Cisco IOS XE Software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

No new or modified RFCs are supported, and support for existing RFCs has not been modified.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for Classifying Network Traffic

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 3. Feature Information for Classifying Network Traffic

Feature Name

Releases

Feature Information

Packet Classification Using Frame Relay DLCI Number

12.2(13)T

Cisco IOS XE Release 2.1

Cisco IOS XE Release 3.12

The Packet Classification Using the Frame Relay DLCI Number feature allows customers to match and classify traffic based on the Frame Relay data-link connection identifier (DLCI) number associated with a packet. This new match criteria is in addition to the other match criteria, such as the IP Precedence, differentiated services code point (DSCP) value, class of service (CoS), currently available.

The following commands were added or modified:match fr-dlci

QoS: Local Traffic Matching Through MQC

Cisco IOS XE Release 2.1

This feature was introduced on Cisco ASR 1000 Series Routers.

QoS: Match ATM CLP

Cisco IOS XE Release 2.3

The QoS: Match ATM CLP features allows you to classify traffic on the basis of the ATM cell loss priority (CLP) value.

The following command was introduced or modified: match atm-clp .

QoS: MPLS EXP Bit Traffic Classification

Cisco IOS XE Release 2.3

The QoS: MPLS EXP Bit Traffic Classification feature allows you to classify traffic on the basis of the Multiprotocol Label Switching (MPLS) experimental (EXP) value.

The following command was introduced or modified: match mpls experimental .