qos_mqc_xe

Applying QoS Features Using the MQC

This module contains the concepts about applying QoS features using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC) and the tasks for configuring the MQC. The MQC allows you to define a traffic class, create a traffic policy (policy map), and attach the traffic policy to an interface. The traffic policy contains the QoS feature that will be applied to the traffic class.

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 Applying QoS Features Using the MQC" 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

•Restrictions for Applying QoS Features Using the MQC

•Information About Applying QoS Features Using the MQC

•How to Apply QoS Features Using the MQC

•Configuration Examples for Applying QoS Features Using the MQC

•Additional References

•Feature Information for Applying QoS Features Using the MQC

Restrictions for Applying QoS Features Using the MQC

The MQC supports a maximum of 256 classes in a single policy map.

Information About Applying QoS Features Using the MQC

The MQC Structure

The MQC structure allows you to define a traffic class, create a traffic policy, and attach the traffic policy to an interface.

Step 1 Define a traffic class by using the class-map command. A traffic class is used to classify traffic.

Step 2 Create a traffic policy by using the policy-map command. (The terms traffic policy and policy map are often synonymous.) A traffic policy (policy map) contains a traffic class and one or more QoS features that will be applied to the traffic class. The QoS features in the traffic policy determine how to treat the classified traffic.

Step 3 Attach the traffic policy (policy map) to the interface by using the service-policy command.

Elements of a Traffic Class

A traffic class contains three major elements: a traffic class name, a series of match commands, and, if more than one match command is used in the traffic class, instructions on how to evaluate these match commands.

The match commands are used for classifying packets. Packets are checked to determine whether they meet the criteria specified in the match commands; if a packet meets the specified criteria, that packet is considered a member of the class. Packets that fail to meet the matching criteria are classified as members of the default traffic class.

Available match Commands

Table 1 lists some of the available match commands that can be used with the MQC. The available match commands vary by Cisco IOS XE release. For more information about the commands and command syntax, see the Cisco IOS Quality of Service Solutions Command Reference.

Multiple match Commands in One Traffic Class

If the traffic class contains more than one match command, you need to specify how to evaluate the match commands. You specify this by using either the match-any or match-all keywords of the class-map command. Note the following points about the match-any and match-all keywords:

•If you specify the match-any keyword, the traffic being evaluated by the traffic class must match one of the specified criteria.

•If you specify the match-all keyword, the traffic being evaluated by the traffic class must match all of the specified criteria.

•If you do not specify either keyword, the traffic being evaluated by the traffic class must match all of the specified criteria (that is, the behavior of the match-all keyword is used).

Elements of a Traffic Policy

A traffic policy contains three elements: a traffic policy name, a traffic class (specified with the class command), and the command used to enable the QoS feature.

The traffic policy (policy map) applies the enabled QoS feature to the traffic class once you attach the policy map to the interface (by using the service-policy command).

Note A packet can match only one traffic class within a traffic policy. If a packet matches more than one traffic class in the traffic policy, the first traffic class defined in the policy will be used.

Commands Used to Enable QoS Features

The commands used to enable QoS features vary by Cisco IOS XE release. Table 2 lists some of the available commands and the QoS features that they enable. For complete command syntax, see the command reference for the release that you are using.

For more information about a specific QoS feature that you want to enable, see the appropriate module of the Cisco IOS Quality of Service Solutions Configuration Guide.

Nested Traffic Classes

The MQC does not necessarily require that you associate only one traffic class to one traffic policy. When packets meet more than one match criterion, multiple traffic classes can be associated with a single traffic policy.

Similarly, the MQC allows multiple traffic classes (nested traffic classes, which are also called nested class maps or MQC Hierarchical class maps) to be configured as a single traffic class. This nesting can be achieved with the use of the match class-map command. The only method of combining match-any and match-all characteristics within a single traffic class is with the match class-map command.

For an example of a nested traffic class configuration, see the "Example: Traffic Class as a Match Criterion (Nested Traffic Classes)" section.

match-all and match-any Keywords of the class-map Command

One of the commands used when you create a traffic class is the class-map command. The command syntax for the class-map command includes two keywords: match-all and match-any. The match-all and match-any keywords need to be specified only if more than one match criterion is configured in the traffic class. Note the following points about these keywords:

•The match-all keyword is used when all of the match criteria in the traffic class must be met in order for a packet to be placed in the specified traffic class.

•The match-any keyword is used when only one of the match criterion in the traffic class must be met in order for a packet to be placed in the specified traffic class.

•If neither the match-all keyword nor match-any keyword is specified, the traffic class will behave in a manner consistent with match-all keyword.

input and output Keywords of the service-policy Command

As a general rule, the QoS features configured in the traffic policy can be applied to packets entering the interface or to packets leaving the interface. Therefore, when you use the service-policy command, you need to specify the direction of the traffic policy by using the input or output keyword.

For instance, the service-policy output policy1 command would apply the QoS features in the traffic policy to the interface in the output direction. All packets leaving the interface (output) are evaluated according to the criteria specified in the traffic policy named policy1.

Note For Cisco IOX XE Software Release 2.1 and later, queueing mechanisms are not supported in the input direction. Non-queueing mechanisms (such as traffic policing and traffic marking) are supported in the input direction.

Benefits of Applying QoS Features Using the MQC

The MQC structure allows you to create the traffic policy (policy map) once and then apply it to as many traffic classes as needed. You can also attach the traffic policies to as many interfaces as needed.

How to Apply QoS Features Using the MQC

To create a traffic class, use the class-map command to specify the traffic class name. Then use one or more match commands to specify the appropriate match criteria. Packets matching the criteria that you specify are placed in the traffic class.

The traffic policy (policy map) applies the enabled QoS feature to the traffic class once you attach the policy map to the interface (by using the service-policy command). For more information about the service-policy command, see the "input and output Keywords of the service-policy Command" section.

Depending on the platform and Cisco IOS XE release that you are using, a traffic policy can be attached to an ATM permanent virtual circuit (PVC) subinterface, to a Frame Relay data-link connection identifier (DLCI), or to another type of interface.

Creating a Traffic Class Using the MQC

Note The match cos command is shown in Step 4. The match cos command is simply an example of one of the match commands that you can use. For information about the other available match commands, see Table 1.

SUMMARY STEPS

1. enable

2. configure terminal

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

4. match cos cos-number

5. Enter additional match commands, if applicable; otherwise, continue with Step 6.

6. end

DETAILED STEPS

Creating a Traffic Policy Using the MQC

Note The bandwidth command is shown in Step 5. The bandwidth command is simply an example of one of the commands that you can use in a policy map. For information about other available commands, see Table 2.

SUMMARY STEPS

1. enable

2. configure terminal

3. policy-map policy-map-name

4. class {class-name | class-default}

5. bandwidth {bandwidth-kbps | percent percent}

6. Enter the commands for any additional QoS feature that you want to enable, if applicable; otherwise, continue with Step 7.

7. end

DETAILED STEPS

Attaching a Traffic Policy to an Interface Using the MQC

Restrictions

A traffic policy containing a queueing mechanism or feature cannot be attached to a physical interface or subinterface.

Note Cisco IOS XE Release 2.3.0 and later releases do not support the attachment of policies for ATM interfaces that have unspecified bit rate (UBR) configured as the default mode on their VC or virtual path (VP). An attempt to use this configuration results in an error message: CBWFQ: Not supported on ATM interfaces with UBR configuration.

You can also specify UBR with a rate in the UBR configuration, if you do not want to use the default UBR value.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface interface-type interface-number

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

5. end

DETAILED STEPS

Verifying the Traffic Class and Traffic Policy Information

SUMMARY STEPS

1. enable

2. show class-map

3. show policy-map policy-map-name class class-name

4. show policy-map

5. show policy-map interface interface-type interface-number

6. exit

DETAILED STEPS

Configuration Examples for Applying QoS Features Using the MQC

Example: Creating a Traffic Class

In the following example, two traffic classes are created and their match criteria are defined. For the first traffic class called class1, access control list (ACL) 101 is used as the match criterion. For the second traffic class called class2, ACL 102 is used as the match criterion. Packets are checked against the contents of these ACLs to determine if they belong to the class.

Router(config)# class-map class1

Router(config-cmap)# match access-group 101

Router(config-cmap)# exit

Router(config)# class-map class2

Router(config-cmap)# match access-group 102

Router(config-cmap)# end

Example: Creating a Traffic Policy

In the following example, a traffic policy called policy1 is defined. The traffic policy contains the QoS features to be applied to two classes—class1 and class2. The match criteria for these classes were previously defined (as described in the "Example: Creating a Traffic Class").

For class1, the policy includes a bandwidth allocation request and a maximum packet count limit for the queue reserved for the class. For class2, the policy specifies only a bandwidth allocation request.

Router(config)# policy-map policy1

Router(config-pmap)# class class1

Router(config-pmap-c)# bandwidth 3000

Router(config-pmap-c)# queue-limit 30

Router(config-pmap-c)# exit

Router(config-pmap)# class class2

Router(config-pmap-c)# bandwidth 2000

Router(config-pmap-c)# end

Example: Attaching a Traffic Policy to an Interface

The following example shows how to attach an existing traffic policy to an interface. After you define a traffic policy with the policy-map command, you can attach it to one or more interfaces by using the service-policy command in interface configuration mode. Although you can assign the same traffic policy to multiple interfaces, each interface can have only one traffic policy attached in the input direction and only one traffic policy attached in the output direction.

Router(config)# interface fastethernet1/1/1

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

Router(config-if)# exit

Router(config)# interface fastethernet1/0/0

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

Router(config-if)# end

Example: match not Command

The match not command is used to specify a specific QoS policy value that is not used as a match criterion. When using the match not command, all other values of that QoS policy become successful match criteria.

For instance, if the match not qos-group 4 command is issued in class-map configuration mode, the specified class will accept all QoS group values except 4 as successful match criteria.

In the following traffic class, all protocols except IP are considered successful match criteria:

Router(config)# class-map noip

Router(config-cmap)# match not protocol ip

Router(config-cmap)# end

Example: Default Traffic Class Configuration

Unclassified traffic (traffic that does not meet the match criteria specified in the traffic classes) is treated as belonging to the default traffic class.

If you do not configure a default class, packets are still treated as members of the default class. However, by default, the default class has no QoS features enabled. Therefore, packets belonging to a default class have no QoS functionality. These packets are placed into a first-in, first-out (FIFO) queue managed by tail drop. Tail drop is a means of avoiding congestion that treats all traffic equally and does not differentiate between classes of service. Queues fill during periods of congestion. When the output queue is full and tail drop is in effect, packets are dropped until the congestion is eliminated and the queue is no longer full.

The following example configures a traffic policy for the default class of the traffic policy called policy1. The default class (which is always called class-default) has these characteristics: 10 queues for traffic that does not meet the match criteria of other classes whose policy is defined by the traffic policy policy1, and a maximum of 20 packets per queue before tail drop is enacted to handle additional queued packets.

Router(config)# policy-map policy1

Router(config-pmap)# class class-default

Router(config-pmap-c)# fair-queue

Router(config-pmap-c)# queue-limit 20

Example: class-map match-any and class-map match-all Commands

This example illustrates the difference between the class-map match-any command and the class-map match-all command. The match-any and match-all keywords determine how packets are evaluated when multiple match criteria exist. Packets must either meet all of the match criteria (match-all) or meet one of the match criterion (match-any) to be considered a member of the traffic class.

The following example shows a traffic class configured with the class-map match-all command:

Router(config)# class-map match-all cisco1

Router(config-cmap)# match protocol ip

Router(config-cmap)# match qos-group 4

Router(config-cmap)# match access-group 101

If a packet arrives on a router with the traffic class called cisco1 configured on the interface, the packet is evaluated to determine if it matches the IP protocol, QoS group 4, and access group 101. If all three of these match criteria are met, the packet is classified as a member of the traffic class cisco1.

The following example shows a traffic class that is configured with the class-map match-any command:

Router(config)# class-map match-any cisco2

Router(config-cmap)# match protocol ip

Router(config-cmap)# match qos-group 4

Router(config-cmap)# match access-group 101

In the traffic class called cisco2, the match criteria are evaluated consecutively until a successful match criterion is located. The packet is first evaluated to the determine whether the IP protocol can be used as a match criterion. If the IP protocol can be used as a match criterion, the packet is matched to traffic class cisco2. If the IP protocol is not a successful match criterion, then QoS group 4 is evaluated as a match criterion. Each criterion is evaluated to see if the packet matches that criterion. Once a successful match occurs, the packet is classified as a member of traffic class cisco2. If the packet matches none of the specified criteria, the packet is classified as a member of the default traffic class (class default-class).

Note that the class-map match-all command requires that all of the match criteria be met in order for the packet to be considered a member of the specified traffic class (a logical AND operator). In the first example, protocol IP AND QoS group 4 AND access group 101 must be successful match criteria. However, only one match criterion must be met in order for the packet in the class-map match-any command to be classified as a member of the traffic class (a logical OR operator). In the second example, protocol IP OR QoS group 4 OR access group 101 must be successful match criterion.

Example: Traffic Class as a Match Criterion (Nested Traffic Classes)

There are two reasons to use the match class-map command. One reason is maintenance; if a large traffic class currently exists, using the traffic class match criterion is simply easier than retyping the same traffic class configuration. The more common reason for the match class-map command is to allow users to use match-any and match-all statements in the same traffic class. If you want to combine match-all and match-any characteristics in a traffic policy, create a traffic class using one match criterion evaluation instruction (either match-any or match-all) and then use this traffic class as a match criterion in a traffic class that uses a different match criterion type.

Here is a possible scenario: Suppose A, B, C, and D were all separate match criterion, and you wanted traffic matching for A, orB, or C and D (A or B or [C and D]) to be classified as belonging to the traffic class. Without the nested traffic class, traffic would either have to match all four of the match criterion (A and B and C and D) or match any of the match criterion (A or B or C or D) to be considered part of the traffic class. You would not be able to combine "and" (match-all) and "or" (match-any) statements within the traffic class, and you would therefore be unable to configure the desired configuration.

The solution: Create one traffic class using match-all for C and D (which we will call criterion E), and then create a new match-any traffic class using A, B, and E. The new traffic class would have the correct evaluation sequence (A or B or E, which would also be A or B or [C and D]). The desired traffic class configuration has been achieved.

The only method of mixing match-all and match-any statements in a traffic class is through the use of the traffic class match criterion.

Example: Nested Traffic Class for Maintenance

In the following example, the traffic class called class1 has the same characteristics as the traffic class called class2, with the exception that traffic class class1 has added a destination address as a match criterion. Rather than configuring traffic class class1 line by line, you can enter the match class-map class2 command. This command allows all of the characteristics in the traffic class called class2 to be included in the traffic class called class1, and you can simply add the new destination address match criterion without reconfiguring the entire traffic class.

Router(config)# class-map match-any class2

Router(config-cmap)# match protocol ip

Router(config-cmap)# match qos-group 3

Router(config-cmap)# match access-group 2

Router(config-cmap)# exit

Router(config)# class-map match-all class1

Router(config-cmap)# match class-map class2

Router(config-cmap)# match destination-address mac 00.00.00.00.00.00 

Router(config-cmap)# exit

Example: Nested Traffic Class to Combine match-any and match-all Characteristics in One Traffic Class

The only method of including both match-any and match-all characteristics in a single traffic class is to use the match class-map command. To combine match-any and match-all characteristics into a single class, a traffic class created with the match-any instruction must use a class configured with the match-all instruction as a match criterion (through the match class-map command) or vice versa.

The following example shows how to combine the characteristics of two traffic classes, one with match-any and one with match-all characteristics, into one traffic class with the match class-map command. The result requires a packet to match one of the following three match criteria to be considered a member of traffic class class4: IP protocol and QoS group 4, destination MAC address 00.00.00.00.00.00, or access group 2.

In this example, only the traffic class called class4 is used with the traffic policy called policy1.

Router(config)# class-map match-all class3

Router(config-cmap)# match protocol ip

Router(config-cmap)# match qos-group 4

Router(config-cmap)# exit

Router(config)# class-map match-any class4

Router(config-cmap)# match class-map class3

Router(config-cmap)# match destination-address mac 00.00.00.00.00.00 

Router(config-cmap)# match access-group 2

Router(config-cmap)# exit

Router(config)# policy-map policy1

Router(config-pmap)# class class4

Router(config-pmap-c)# police 8100 1500 2504 conform-action transmit exceed-action 
set-qos-transmit 4

Router(config-pmap-c)# end

Example: Traffic Policy as a QoS Policy (Hierarchical Traffic Policies)

A traffic policy can be included in a QoS policy when the service-policy command is used in policy-map class configuration mode. A traffic policy that contains a traffic policy is called a hierarchical traffic policy.

A hierarchical traffic policy contains a child policy and a parent policy. The child policy is the previously defined traffic policy that is being associated with the new traffic policy through the use of the service-policy command. The new traffic policy using the preexisting traffic policy is the parent policy. In the example in this section, the traffic policy called child is the child policy and traffic policy called parent is the parent policy.

Hierarchical traffic policies can be attached to subinterfaces and ATM PVCs. When hierarchical traffic policies are used, a single traffic policy (with a child and a parent policy) can be used to shape and prioritize PVC traffic. In the following example, the child policy is responsible for prioritizing traffic and the parent policy is responsible for shaping traffic. In this configuration, the parent policy allows packets to be sent from the interface, and the child policy determines the order in which the packets are sent.

Router(config)# policy-map child

Router(config-pmap)# class voice

Router(config-pmap-c)# priority 50

Router(config)# policy-map parent

Router(config-pmap)# class class-default

Router(config-pmap-c)# shape average 10000000

Router(config-pmap-c)# service-policy child

The value used with the shape command is provisioned from the committed information rate (CIR) value from the service provider.

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for Applying QoS Features Using the MQC

Table 3 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 Table 3 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.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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