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 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.

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.

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 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. Network Traffic Classification match Commands and Match Criteria lists the available match commands and the corresponding match criterion.

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 DSCP value of 3 is grouped into another class. The match criterion is 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.

Note

In the following task, the matchfr-dlcicommand is shown in Step 4. The matchfr-dlcicommand matches traffic on the basis of the Frame Relay DLCI number. The matchfr-dlcicommand is just an example of one of the match commands that can be used. For a list of other match commands, see Creating a Class Map for Classifying Network Traffic.

1.    enable

2.    configure terminal

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

4.    match fr-dlci dlci-number

5.    end

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), but it is not supported on logical interfaces such as Virtual Access Interface (VAI), Subinterface, and Frame-Relay on Virtual Circuits (FR-VC).

1.    enable

2.    configure terminal

3.    policy-map policy-map-name

4.    class {class-name | class-default}

5.    bandwidth {bandwidth-kbps| remainingpercentpercentage| percentpercentage}

6.    end

7.    show policy-map

8.   

9.    show policy-map policy-map class class-name

10.    Router# show policy-map

11.   

12.    Router# show policy-map policy1 class class1

13.    exit

• What to Do Next
  

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

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

Note	This task is required only if you are using IPsec Virtual Private Networks (VPNs). Otherwise, this task is not necessary. For information about IPsec VPNs, see the "Configuring Security for VPNs with IPsec" module.

Note	This task uses the qospre-classify command to enable QoS preclassification for the packet. QoS preclassification is not supported for all fragmented packets. If a packet is fragmented, each fragment might receive different preclassifications. >

1.    enable

2.    configure terminal

3.    crypto map map-name seq-num

4.    exit

5.    interface type number [name-tag]

6.    qos pre-classify

7.    end