Low Latency Queueing with Priority Percentage Support

First Published: February 28, 2006
Last Updated: March 23, 2011

This feature allows you to configure bandwidth as a percentage within low latency queueing (LLQ). Specifically, you can designate a percentage of the bandwidth to be allocated to an entity (such as a physical interface, a shaped ATM permanent virtual circuit [PVC], or a shaped Frame Relay PVC to which a policy map is attached). Traffic associated with the policy map will then be given priority treatment.

This feature also allows you to specify the percentage of bandwidth to be allocated to nonpriority traffic classes. It modifies two existing commands—bandwidth and priority—and provides additional functionality to the way that bandwidth can be allocated using these two commands.

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 LLQ with Priority Percentage Support" 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 LLQ with Priority Percentage Support

•TInformation About LLQ with Priority Percentage Support

•How to Configure LLQ with Priority Percentage Support

•Configuration Examples for LLQ with Priority Percentage Support

•Additional References

•Feature Information for LLQ with Priority Percentage Support

Restrictions for LLQ with Priority Percentage Support

Dropping Excess Traffic

If the incoming high priority traffic exceeds the bandwidth percentage calculated by the priority percent command, and there is congestion in the network, the excess traffic is dropped. This is identical to the behavior demonstrated when the priority command uses bandwidth in kbps. In both cases, if the high priority traffic exceeds the bandwidth, and there is congestion in the network, excess traffic is dropped.

Exceeding the Configured Bandwidth Percentage Calculated by the bandwidth percent and priority percent Commands

By default, when the bandwidth percent and priority percent commands are used to allocate bandwidth, the sum of the bandwidth percentage allocated to the high priority traffic and the bandwidth percentage allocated to the nonpriority traffic cannot exceed 99 percent of the total bandwidth available on the interface.

The remaining 1 percent of the total bandwidth available on the interface is kept in reserve for the unclassified traffic and routing traffic, if any, and is proportionally divided among the defined traffic classes.

TInformation About LLQ with Priority Percentage Support

To configure the Low Latency Queueing with Priority Percentage Support feature, you should understand the following concepts:

•Benefits of LLQ with Priority Percentage Support

•Changes to the bandwidth Command for LLQ with Priority Percentage Support

•Changes to the priority Command for LLQ with Priority Percentage Support

•Bandwidth Calculations in LLQ with Priority Percentage Support

Benefits of LLQ with Priority Percentage Support

This feature allows the Cisco IOS XE Software to accommodate networks with a large number of interfaces, all with differing bandwidths. This feature is useful when all of those interfaces with differing bandwidths need to be associated with a policy map that allocates proportional bandwidths to multiple classes.

Additionally, configuring bandwidth in percentages is most useful when the underlying link bandwidth is unknown or the relative class bandwidth distributions are known. For interfaces that have adaptive shaping rates (such as available bit rate [ABR] virtual circuits), CBWFQ can be configured by configuring class bandwidths in percentages.

Changes to the bandwidth Command for LLQ with Priority Percentage Support

This feature adds a new keyword to the bandwidth command—remaining percent. The feature also changes the functionality of the existing percent keyword. These changes result in the following commands for bandwidth: bandwidth percent and bandwidth remaining percent.

The bandwidth percent command configures bandwidth as an absolute percentage of the total bandwidth on the interface.

The bandwidth remaining percent command allows you to allocate bandwidth as a relative percentage of the total bandwidth available on the interface. This command allows you to specify the relative percentage of the bandwidth to be allocated to the classes of traffic. For instance, you can specify that 30 percent of the available bandwidth be allocated to class1, and 60 percent of the bandwidth be allocated to class2. Essentially, you are specifying the ratio of the bandwidth to be allocated to the traffic class. In this case, the ratio is 1 to 2 (30 percent allocated to class1 and 60 percent allocated to class2). The sum of the numbers used to indicate this ratio cannot exceed 100 percent. This way, you need not know the total amount of bandwidth available, just the relative percentage you want to allocate for each traffic class.

Each traffic class gets a minimum bandwidth as a relative percentage of the remaining bandwidth. The remaining bandwidth is the bandwidth available after the priority queue, if present, is given its required bandwidth, and after any Resource Reservation Protocol (RSVP) flows are given their requested bandwidth.

Because this is a relative bandwidth allocation, the packets for the traffic classes are given a proportionate weight only, and no admission control is performed to determine whether any bandwidth (in kbps) is actually available. The only error checking that is performed is to ensure that the total bandwidth percentages for the classes do not exceed 100 percent.

For more information about how this feature defines and calculates bandwidth, see the "Bandwidth Calculations in LLQ with Priority Percentage Support" section of this document. For the bandwidth command syntax description and usage guidelines, see the Cisco IOS Quality of Service Solutions Command Reference.

Changes to the priority Command for LLQ with Priority Percentage Support

This feature also adds the percent keyword to the priority command. The priority percent command indicates that the bandwidth will be allocated as a percentage of the total bandwidth of the interface. You can then specify the percentage (that is, a number from 1 to 100) to be allocated by using the percentage argument with the priority percent command.

Unlike the bandwidth command, the priority command provides a strict priority to the traffic class, which ensures low latency to high priority traffic classes.

Bandwidth Calculations in LLQ with Priority Percentage Support

When the bandwidth and priority commands calculate the total amount of bandwidth available on an entity, the following guidelines are invoked:

•If the entity is a physical interface, the total bandwidth is the bandwidth on the physical interface.

•If the entity is a shaped ATM PVC, the total bandwidth is calculated as follows:

–For a variable bit rate (VBR) VC, the average shaping rate is used in the calculation.

–For an available bit rate (ABR) VC, the minimum shaping rate is used in the calculation.

How to Configure LLQ with Priority Percentage Support

This section contains the following procedures.

•Specifying the Bandwidth Percentage (required)

•Verifying the Bandwidth Percentage (optional)

Specifying the Bandwidth Percentage

SUMMARY STEPS

1. enable

2. configure terminal

3. policy-map policy-map

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

5. priority {bandwidth-kbps | percent percentage} [burst]

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

7. end

 
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

Example:

Router(config)# policy-map policy1

Specifies the name of the policy map to be created or modified. 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 class so that you can configure or modify its policy. Enters policy-map class configuration mode.

•Enter the class name.

Step 5 

priority {bandwidth-kbps | percent percentage} [burst]

Example:

Router(config-pmap-c)# priority percent 10

Gives priority to a class of traffic belonging to the policy map.

•Enter the priority percentage.

Step 6 

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

Example:

Router(config-pmap-c)# bandwidth percent 30

Specifies the bandwidth for a class of traffic belonging to the policy map.

•Enter the bandwidth percentage.

Step 7 

end


Router(config-pmap-c)# end

(Optional) Exits policy-map class configuration mode and returns to privileged EXEC mode.

DETAILED STEPS

Verifying the Bandwidth Percentage

SUMMARY STEPS

1. enable

2. show policy-map policy-map

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

4. show policy-map interface interface type

5. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

show policy-map policy-map

Example:

Router# show policy-map policy1

(Optional) Displays the configuration of all classes for a specified service policy map or the configuration of all classes for all existing policy maps

•Enter the name of the policy map whose complete configuration is to be displayed.

Step 3 

show policy-map policy-map class class-name

Example:

Router# show policy-map policy1 class class1

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

•Enter the policy map name and the class name.

Step 4 

show policy-map interface type number

Example:

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

(Optional) Displays the packet statistics of all 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 interface type and number.

Step 5 

exit

Example:

Router# exit

(Optional) Exits privileged EXEC mode.

Configuration Examples for LLQ with Priority Percentage Support

This section provides the following configuration examples:

•Example: Specifying the Bandwidth Percentage

•Example: Mixing the Units of Bandwidth for Nonpriority Traffic

•Verifying the Bandwidth Percentage

Example: Specifying the Bandwidth Percentage

The following example uses the priority percent command to specify a bandwidth percentage of 10 percent for the class called voice-percent. Then the bandwidth remaining percent command is used to specify a bandwidth percentage of 30 percent for the class called data1 and a bandwidth percentage of 20 percent for the class called data2. 

Router> enable

Router# configure terminal

Router(config)# policy-map policy1

Router(config-pmap)# class voice-percent

Router(config-pmap-c)# priority percent 10

Router(config-pmap-c)# exit

Router(config-pmap)# class data1

Router(config-pmap-c)# bandwidth remaining percent 30

Router(config-pmap-c)# exit

Router(config-pmap)# class data2

Router(config-pmap-c)# bandwidth remaining percent 20

Router(config-pmap-c)# end

As a result of this configuration, 10 percent of the interface bandwidth is guaranteed for the class called voice-percent. The classes called data1 and data2 get 30 percent and 20 percent of the remaining bandwidth, respectively.

Example: Mixing the Units of Bandwidth for Nonpriority Traffic

If a particular unit (that is, kbps or percentages) is used when specifying the bandwidth for a specific class of nonpriority traffic, the same bandwidth unit must be used when specifying the bandwidth for the other nonpriority classes in that policy map. The bandwidth units within the same policy map must be identical. However, the unit for the priority command in the priority class can be different from the bandwidth unit of the nonpriority class. The same configuration can contain multiple policy maps, however, which in turn can use different bandwidth units.

The following sample configuration contains three policy maps—policy1, policy2, and policy3. In the policy map called policy1 and the policy map called policy2, the bandwidth is specified by percentage. However, in the policy map called policy3, bandwidth is specified in kbps. 

Router> enable

Router# configure terminal

Router(config)# policy-map policy1

Router(config-pmap)# class voice-percent

Router(config-pmap-c)# priority percent 10

Router(config-pmap-c)# exit

Router(config-pmap)# class data1

Router(config-pmap-c)# bandwidth percent 30

Router(config-pmap-c)# exit

Router(config-pmap)# class data2

Router(config-pmap-c)# bandwidth percent 20

Router(config-pmap-c)# exit

Router(config-pmap)# exit

Router(config)# policy-map policy2

Router(config-pmap)# class voice-percent

Router(config-pmap-c)# priority percent 10

Router(config-pmap-c)# exit

Router(config-pmap)# class data1

Router(config-pmap-c)# bandwidth remaining percent 30

Router(config-pmap-c)# exit

Router(config-pmap)# class data2

Router(config-pmap-c)# bandwidth remaining percent 20

Router(config-pmap-c)# exit

Router(config-pmap)# exit

Router(config)# policy-map policy3

Router(config-pmap)# class voice-percent

Router(config-pmap-c)# priority 500

Router(config-pmap-c)# exit

Router(config-pmap)# class data1

Router(config-pmap-c)# bandwidth 30

Router(config-pmap-c)# exit

Router(config-pmap)# class data2

Router(config-pmap-c)# bandwidth 20

Router(config-pmap-c)# end

Example: Verifying the Bandwidth Percentage

The following sample output from the show policy-map interface command shows that 50 percent of the interface bandwidth is guaranteed for the class called class1 and that 25 percent is guaranteed for the class called class2. The output displays the amount of bandwidth as both a percentage and a number of kbps. 

Router# show policy-map interface serial3/2/0


 Serial3/2/0


  Service-policy output:policy1


    Class-map:class1 (match-all)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match:none

      Weighted Fair Queueing

        Output Queue:Conversation 265

        Bandwidth 50 (%)

        Bandwidth 772 (kbps) Max Threshold 64 (packets)

        (pkts matched/bytes matched) 0/0

        (depth/total drops/no-buffer drops) 0/0/0


Class-map:class2 (match-all)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match:none

      Weighted Fair Queueing

        Output Queue:Conversation 266

        Bandwidth 25 (%)

        Bandwidth 386 (kbps) Max Threshold 64 (packets)

        (pkts matched/bytes matched) 0/0

        (depth/total drops/no-buffer drops) 0/0/0


    Class-map:class-default (match-any)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match:any

In this example, serial interface s3/2/0 has a total bandwidth of 1544 kbps. During periods of congestion, 50 percent (or 772 kbps) of the link bandwidth is guaranteed to the class called class1, and 25 percent (or 386 kbps) of the link bandwidth is guaranteed to the class called class2.

Additional References

Related Documents

Related Topic
Document Title

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

Cisco IOS Quality of Service Solutions Command Reference

LLQ

"Applying QoS Features Using the MQC" module


Standards

Standards
Title

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

—


MIBs

MIBs
MIBs Link

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

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

RFCs
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 LLQ with Priority Percentage Support

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 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.

Table 1 Feature Information for Low Latency Queueing with Priority Percentage Support 

Feature Name
Releases
Feature Information

Low Latency Queueing with Priority Percentage Support

Cisco IOS XE Release 2.1

This feature allows you to configure bandwidth as a percentage within low latency queueing (LLQ). Specifically, you can designate a percentage of the bandwidth to be allocated to an entity (such as a physical interface, a shaped ATM permanent virtual circuit [PVC], or a shaped Frame Relay PVC to which a policy map is attached). Traffic associated with the policy map will then be given priority treatment.

This feature was implemented on the Cisco ASR 1000 Series Routers.

The following commands were introduced or modified: bandwidth (policy-map class), priority.


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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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