QoS: Percentage-Based Policing

Table Of Contents

QoS: Percentage-Based Policing

Contents

Prerequisites for QoS: Percentage-Based Policing

Restrictions for QoS: Percentage-Based Policing

Information About QoS: Percentage-Based Policing

Benefits for QoS: Percentage-Based Policing

Defining Class and Policy Maps for QoS: Percentage-Based Policing

Traffic Regulation Mechanisms and Bandwidth Percentages

Specifying Burst Size in Milliseconds Option

How to Configure QoS: Percentage-Based Policing

Configuring a Class and Policy Map

Attaching the Policy Map to an Interface

Verifying the Configuration

Troubleshooting Tips

Configuration Examples for QoS: Percentage-Based Policing

Specifying Traffic Policing on the Basis of a Bandwidth Percentage: Example

Verifying the Configuration: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

police (percent)

shape (percent)

show policy-map

show policy-map interface

QoS: Percentage-Based Policing

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The QoS: Percentage-Based Policing feature allows you to configure traffic policing and traffic shaping on the basis of a percentage of bandwidth available on the interface. This feature also allows you to specify the committed burst (bc) size and the excess burst (be) size (used for configuring traffic policing) in milliseconds (ms). Configuring traffic policing in this manner enables you to use the same policy map for multiple interfaces with differing amounts of bandwidth.

Feature History for QoS: Percentage-Based Policing

Release	Modification
12.2(13)T	This feature was introduced.
12.0(28)S	This feature is based on the Percentage-Based Policing and Shaping feature introduced in Cisco IOS Release 12.2(13)T. The option of specifying committed (conform) burst (bc) and excess (peak) burst (be) sizes in milliseconds was added.
12.2(27)SBA	This feature was integrated into Cisco IOS Release 12.2(27)SBA.

Finding Support Information for Platforms and Cisco IOS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.

Contents

•Prerequisites for QoS: Percentage-Based Policing

•Restrictions for QoS: Percentage-Based Policing

•Information About QoS: Percentage-Based Policing

•How to Configure QoS: Percentage-Based Policing

•Configuration Examples for QoS: Percentage-Based Policing

•Additional References

•Command Reference

Prerequisites for QoS: Percentage-Based Policing

•For input traffic policing on a Cisco 7500 series router, verify that distributed Cisco Express Forwarding (dCEF) is enabled on the interface on which traffic policing is configured.

•For output traffic policing on a Cisco 7500 series router, ensure that the incoming traffic is dCEF-switched. Traffic policing cannot be used on the switching path unless dCEF switching is enabled.

Restrictions for QoS: Percentage-Based Policing

The shape (percent) command, when used in "child" (nested) policy maps, is not supported on the Cisco 7500, the Cisco 7200, or lower series routers. Therefore, the shape (percent) command cannot be configured for use in nested policy maps on these routers.

Information About QoS: Percentage-Based Policing

To configure QoS: Percentage-Based Policing, you need to understand the following concepts:

•Benefits for QoS: Percentage-Based Policing

•Defining Class and Policy Maps for QoS: Percentage-Based Policing

•Traffic Regulation Mechanisms and Bandwidth Percentages

•Specifying Burst Size in Milliseconds Option

Benefits for QoS: Percentage-Based Policing

Increased Flexibility and Ease-of-Use

This feature provides the ability to configure traffic policing and traffic shaping on the basis of a percentage of bandwidth available on an interface, and it allows you to specify burst sizes in milliseconds. Configuring traffic policing and traffic shaping in this manner enables you to use the same policy map for multiple interfaces with differing amounts of bandwidth. That is, you do not have to recalculate the bandwidth for each interface or configure a different policy map for each type of interface.

Defining Class and Policy Maps for QoS: Percentage-Based Policing

To configure the QoS: Percentage-Based Policing feature, you must define a traffic class, configure a policy map, and then attach that policy map to the appropriate interface. These three tasks can be accomplished by using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC).

The MQC is a command-line interface that allows you to define traffic classes, create and configure traffic policies (policy maps), and then attach these traffic 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:

•Defining a traffic class with the class-map command.

•Creating a traffic policy by associating the traffic class with one or more QoS features (using the policy-map command).

•Attaching the traffic policy to the interface with the service-policy command.

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 (that is, match-all or match-any). 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.

Traffic Regulation Mechanisms and Bandwidth Percentages

Cisco IOS quality of service (QoS) offers two kinds of traffic regulation mechanisms—traffic policing and traffic shaping. A traffic policer typically drops traffic that violates a specific rate. A traffic shaper typically delays excess traffic using a buffer to hold packets and shapes the flow when the data rate to a queue is higher than expected.

Traffic shaping and traffic policing can work in tandem and can be configured in a class map. Class maps organize data packets into specific categories ("classes") that can, in turn, receive a user-defined QoS treatment when used in policy maps (sometimes referred to as "service policies").

Before this feature, traffic policing and traffic shaping were configured on the basis of a user-specified amount of bandwidth available on the interface. Policy maps were then configured on the basis of that specific amount of bandwidth, meaning that separate policy maps were required for each interface.

This feature provides the ability to configure traffic policing and traffic shaping on the basis of a percentage of bandwidth available on the interface. Configuring traffic policing and traffic shaping in this manner enables customers to use the same policy map for multiple interfaces with differing amounts of bandwidth.

Configuring traffic policing and shaping on the basis of a percentage of bandwidth is accomplished by using the police (percent) and shape (percent) commands. For more information about these commands, see the "Command Reference" section later in this document.

Specifying Burst Size in Milliseconds Option

The purpose of the burst parameters (bc and be) is to drop packets gradually, as is done with Weighted Random Early Detection (WRED), and to avoid tail drop. Setting sufficiently high burst values helps to ensure good throughput.

This feature allows you the option of specifying the committed burst (bc) size and the extended burst (be) as milliseconds (ms) of the class bandwidth when you configure traffic policing. The number of milliseconds is used to calculate the number of bytes that will be used by the QoS: Percentage-Based Policing feature.

Specifying these burst sizes in milliseconds is accomplished by using the bc and be keywords (and their associated arguments) of the police (percent) and shape (percent) commands.

For more information about these commands, see the "Command Reference" section later in this document.

How to Configure QoS: Percentage-Based Policing

See the following sections for configuration tasks for the QoS: Percentage-Based Policing and Shaping feature. Each task in the list is identified as either required or optional.

•Configuring a Class and Policy Map (required)

•Attaching the Policy Map to an Interface (required)

•Verifying the Configuration (optional)

Configuring a Class and Policy Map

A class map is used to organize traffic into specific categories or classes. These categories or classes of traffic are associated with a traffic policy or policy map. In turn, the policy map is used in conjunction with the class map to apply a specific QoS feature to the traffic. In this instance, the QoS feature of percentage-based policing will be applied.

To configure a class map and associate the class map with a specific policy map, perform the following steps.

SUMMARY STEPS

1. enable

2. configure terminal

3. policy-map policy-name

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

5. police cir percent percentage [burst-in-ms] [bc conform-burst-in-msec ms] [be peak-burst-in-msec ms] [pir percent percent]

6. exit

DETAILED STEPS

	Command	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-name Example: Router(config)# policy-map policy1	Specifies the name of the policy map to be created. Enters policy-map configuration mode. •Enter 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 or specify the default class (class-default).
Step 5	police cir percent percentage [burst-in-ms] [bc conform-burst-in-msec ms] [be peak-burst-in-msec ms] [ pir percent percent] Example: Router(config-pmap-c)# police cir percent 20 bc 300 ms be 400 ms pir percent 40	Configures traffic policing on the basis of the specified bandwidth percentage and optional burst sizes. Enters policy-map class police configuration mode. •Enter the bandwidth percentage and optional burst sizes.
Step 6	exit Example: Router(config-pmap-c-police)# exit	Exits policy-map class police configuration mode.

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 or output direction of the interface.

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Note Depending on the needs of your network, you may need to attach the policy map to a subinterface, an ATM PVC, a Frame Relay DLCI, or other type of interface.

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To attach the policy map to an interface, perform the following steps.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number

4. pvc [name] vpi/vci [ilmi | qsaal | smds]

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

6. 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 Example: Router(config)# interface s4/0	Configures an interface (or subinterface) type and enters interface configuration mode. •Enter the interface type number.
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 and specifies the encapsulation type on an ATM PVC. Enters ATM VC configuration mode. 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, skip this step and proceed with Step 5.
Step 5	service-policy {input | output} policy-map-name Example: Router(config-if)# service-policy input policy1	Specifies the name of the policy map to be attached to the input or output direction of the interface. 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. •Enter the policy map name.
Step 6	exit Example: Router(config-if)# exit	(Optional) Exits interface configuration mode.

Verifying the Configuration

To verify the configuration, perform the following steps.

SUMMARY STEPS

1. enable

2. show class-map [class-map-name]

or

show policy-map interface interface-name

3. 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 class-map [class-map-name] Example: Router# show class-map class1	Displays all information about a class map, including the match criterion. •Enter class map name.
	or
	show policy-map interface interface-name Example: Router# show policy-map interface s4/0	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 name.
Step 3	exit Example: Router# exit	(Optional) Exits EXEC mode.

Troubleshooting Tips

The commands in the "Verifying the 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 the feature is not functioning as expected, perform these operations:

If the configuration is not the one you intended, complete the following procedures:

1. Use the show running-config command and analyze the output of the command.

2. If the policy map does not appear in the output of the show running-config command, enable the logging console command.

3. Attach the policy map to the interface again.

If the packets are not being matched correctly (for example, the packet counters are not incrementing correctly), complete the following procedures:

1. Run the show policy-map command and analyze the output of the command.

2. Run the show running-config command and analyze the output of the command.

3. Use the show policy-map interface command and analyze the output of the command. Check the the following findings:

a. If a policy map applies queueing, and the packets are matching the correct class, but you see unexpected results, compare the number of the packets in the queue with the number of the packets matched.

b. If the interface is congested, and only a small number of the packets are being matched, check the tuning of the transmission (tx) ring, and evaluate whether the queueing is happening on the tx ring. To do this, use the show controllers command, and look at the value of the tx count in the output of the command.

Configuration Examples for QoS: Percentage-Based Policing

This section provides the following configuration examples:

•Specifying Traffic Policing on the Basis of a Bandwidth Percentage: Example

•Verifying the Configuration: Example

Specifying Traffic Policing on the Basis of a Bandwidth Percentage: Example

The following example configures traffic policing using a committed information rate (CIR) and a peak information rate (PIR) on the basis of a percentage of bandwidth. In this example, a CIR of 20 percent and a PIR of 40 percent have been specified. Additionally, an optional bc value and be value (300 ms and 400 ms, respectively) have been specified.

Router> enable

Router# configure terminal

Router(config)# policy-map policy1

Router(config-pmap)# class class1

Router(config-pmap-c)# police cir percent 20 bc 300 ms be 400 ms pir percent 40 

Router(config-pmap-c-police)# exit 

After the policy map and class maps are configured, the policy map is attached to interface as shown in the following example.

Router> enable

Router# configure terminal

Router(config-if)# interface s4/0 

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

Router(config-if)# exit

Verifying the Configuration: Example

This section contains sample output from the show policy-map interface command and the show policy-map command. The output from these commands can be used to verify and monitor the feature configuration on your network.

The following is sample output from the show policy-map command. This sample output displays the contents of a policy map called "policy1." In policy 1, traffic policing on the basis of a CIR of 20 percent has been configured, and the bc and be have been specified in milliseconds. As part of the traffic policing configuration, optional conform, exceed, and violate actions have been specified.

Router# show policy-map policy1

  Policy Map policy1

    Class class1

     police cir percent 20 bc 300 ms pir percent 40 be 400 ms

       conform-action transmit 

       exceed-action drop 

       violate-action drop 

The following is sample output from the show policy-map interface command. This sample displays the statistics for the serial 2/0 interface on which traffic policing has been enabled. The committed burst (bc) and excess burst (be) are specified in milliseconds (ms).

Router# show policy-map interface s2/0

 Serial2/0 

  Service-policy output: policy1 (1050)

    Class-map: class1 (match-all) (1051/1)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: ip precedence 0  (1052)

      police:

          cir 20 % bc 300 ms

          cir 409500 bps, bc 15360 bytes

          pir 40 % be 400 ms

          pir 819000 bps, be 40960 bytes

        conformed 0 packets, 0 bytes; actions:

          transmit 

        exceeded 0 packets, 0 bytes; actions:

          drop 

        violated 0 packets, 0 bytes; actions:

          drop 

        conformed 0 bps, exceed 0 bps, violate 0 bps

    Class-map: class-default (match-any) (1054/0)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: any  (1055)

        0 packets, 0 bytes

        5 minute rate 0 bps

In this example, the CIR and PIR are displayed in bps, and both the committed burst (bc) and excess burst (be) are displayed in bits.

The CIR, PIR bc, and be are calculated on the basis of the formulas described below.

Formula for Calculating the CIR

When calculating the CIR, the following formula is used:

•CIR percentage specified (as shown in the output of the show policy-map command) * bandwidth (BW) of the interface (as shown in the output of the show interfaces command) = total bits per second

On the serial 2/0 interface, the bandwidth (BW) is 2048 kbps. To see the bandwidth of the interface, use the show interfaces command. A sample is shown below:

Router # show interfaces s2/0

Serial2/0 is administratively down, line protocol is down  
  Hardware is M4T 
  MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec, rely 255/255, load 1/255 

The following values are used for calculating the CI:.

20 % * 2048 kbps = 409600 bps

Formula for Calculating the PIR

When calculating the PIR, the following formula is used:

•PIR percentage specified (as shown in the output of the show policy-map command) * bandwidth (BW) of the interface (as shown in the output of the show interfaces command) = total bits per second

On the serial 2/0 interface, the bandwidth (BW) is 2048 kbps. To see the bandwidth of the interface, use the show interfaces command. A sample is shown below:

Router # show interfaces s2/0 
Serial2/0 is administratively down, line protocol is down  
  Hardware is M4T 
  MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec, rely 255/255, load 1/255 

The following values are used for calculating the PIR:

40 % * 2048 kbps = 819200 bps

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Note Discrepancies between this total and the total shown in the output of the show policy-map interface command can be attributed to a rounding calculation or to differences associated with the specific interface configuration.

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Formula for Calculating the Committed Burst (bc)

When calculating the bc, the following formula is used:

•The bc in milliseconds (as shown in the show policy-map command) * the CIR in bits per seconds = total number bytes

The following values are used for calculating the bc:

300 ms * 409600 bps = 15360 bytes

Formula for Calculating the Excess Burst (be)

When calculating the bc and the be, the following formula is used:

•The be in milliseconds (as shown in the show policy-map command) * the PIR in bits per seconds = total number bytes

The following values are used for calculating the be:

400 ms * 819200 bps = 40960 bytes

Additional References

The following sections provide references related to the QoS: Percentage-Based Policing feature.

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, Release 12.3 T
Modular QoS Command-Line Interface (CLI) (MQC)	Cisco IOS Quality of Service Solutions Configuration Guide
Information about attaching policy maps to interfaces	Cisco IOS Quality of Service Solutions Configuration Guide
Traffic shaping	Cisco IOS Quality of Service Solutions Configuration Guide
Traffic policing	Cisco IOS Quality of Service Solutions Configuration Guide
dCEF	Cisco IOS Switching Services Configuration Guide
Commands related to dCEF	Cisco IOS Switching Services Command Reference, Release 12.3 T

Standards

Standards	Title
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.	—

MIBs

MIBs	MIBs Link
No new or modified MIBS are supported by this feature, and support for existing MIBs has not been modified by this feature.	To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs

RFCs

RFCs	Title
RFC 2697	A Single Rate Three Color Marker
RFC 2698	A Two Rate Three Color Marker

Technical Assistance

Description	Link
Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.	http://www.cisco.com/public/support/tac/home.shtml

Command Reference

This section documents modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.3 command reference publications.

•police (percent)

•shape (percent)

•show policy-map

•show policy-map interface

police (percent)

To configure traffic policing on the basis of a percentage of bandwidth available on an interface, use the police command in policy-map class configuration mode. To remove traffic policing from the configuration, use the no form of this command.

police cir percent percentage [burst-in-msec] [bc conform-burst-in-msec ms] [be peak-burst-in-msec ms] [pir percent percentage]

no police cir percent percentage [burst-in-msec] [bc conform-burst-in-msec ms] [be peak-burst-in-msec ms] [pir percent percentage]

Syntax Description

cir	Committed information rate. Indicates that the CIR will be used for policing traffic.
percent	Specifies that percent of bandwidth will be used for calculating the CIR.
percentage	Specifies the bandwidth percentage. Valid range is a number from 1 to 100.
burst-in-msec	(Optional) Burst in milliseconds. Valid range is a number from 1 to 2000.
bc	(Optional) Conform burst (bc) size used by the first token bucket for policing traffic.
conform-burst-in-msec	(Optional) Specifies the bc value in milliseconds (ms). Valid range is a number from 1 to 2000.
ms	(Optional) Indicates that the burst value is specified in milliseconds.
be	(Optional) Peak burst (be) size used by the second token bucket for policing traffic.
peak-burst-in-msec	(Optional) Specifies the be size in ms. Valid range is a number from 1 to 2000.
pir	(Optional) Peak information rate. Indicates that the pir will be used for policing traffic.
percent	(Optional) Specifies that a percentage of bandwidth will be used for calculating the pir.

Defaults

The default bc and be is 4 ms.

Command Modes

Policy-map class configuration

Command History

Release	Modification
11.1 CC	The rate-limit command was introduced.
12.0(5)XE	This police command, which was closely related to the rate-limit command, was introduced.
12.1(1)E	This command was integrated into Cisco IOS Release 12.2(1)E.
12.1(5)T	This command was integrated into Cisco IOS Release 12.1(5)T.
12.2(13)T	This command was modified for the Percentage-Based Policing and Shaping feature.
12.0(28)S	The command was integrated into Cisco IOS Release 12.0(28)S.
12.2(27)SBA	The command was integrated into Cisco IOS Release 12.2(27)SBA.

Usage Guidelines

This command calculates the cir and pir on the basis of a percentage of the maximum amount of bandwidth available on the interface. When a policy map is attached to the interface, the equivalent cir and pir values in bits per second (bps) are calculated on the basis of the interface bandwidth and the percent value entered with this command. The show policy-map interface command can then be used to verify the bps rate calculated.

The calculated cir and pir bps rates must be in the range of 8000 and 2000000000 bps. If the rates are outside this range, the associated policy map cannot be attached to the interface. If the interface bandwidth changes (for example, more is added), the bps values of the cir and the pir are recalculated on the basis of the revised amount of bandwidth. If the cir and pir percentages are changed after the policy map is attached to the interface, the bps values of the cir and pir are recalculated.

Conform Burst and Peak Burst Sizes in Milliseconds

This command also allows you to specify the values for the conform burst size and the peak burst size in milliseconds. If you want bandwidth to be calculated as a percentage, the conform burst size and the peak burst size must be specified in milliseconds (ms).

Hierarchical Policy Maps

Policy maps can be configured in two-level (nested) hierarchies; a top (or "parent") level and a secondary (or "child") level. The police (percent) command can be configured for use in either a parent or child policy map.

Notes About Bandwidth and Hierarchical Policy Maps

The police (percent) command uses the maximum rate of bandwidth available as the reference point for calculating the bandwidth percentage. When the police (percent) command is configured in a child policy map, the police (percent) command uses the bandwidth amount specified in the next higher-level policy (in this case, the parent policy map). If the parent policy map does not specify the maximum bandwidth rate available, the police (percent) command uses the maximum bandwidth rate available on the next higher level (in this case, the physical interface, the highest point in the hierarchy) as the reference point. The police (percent) command always looks to the next higher level for the bandwidth reference point. The following sample configuration illustrates this point:

Policymap parent_policy

 class parent

  shape average 512000

  service-policy child_policy

Policymap child_policy

 class normal_type

  police cir percent 30

In this sample configuration, there are two hierarchical policies; one called parent_policy and one called child_policy. In the policy map called child_policy, the police command has been configured in the class called normal_type. In this class, the percentage specified by for the police (percent) command is 30 percent. The command will use 512 kbps, the peak rate, as the bandwidth reference point for class parent in the parent_policy. The police (percent) command will use 512 kbps as the basis for calculating the cir rate (512 kbps * 30 percent).

interface serial 4/0

 service-policy output parent_policy

Policymap parent_policy

 class parent

  bandwidth 512

  service-policy child_policy

In the above example, there is one policy map called parent_policy. In this policy map, a peak rate has not been specified. The bandwidth command has been used, but this command does not represent the maximum rate of bandwidth available. Therefore, the police (percent) command will look to the next higher level (in this case Serial interface 4/0) to get the bandwidth reference point. Assuming the bandwidth of the Series interface s4/0 is 1.5 Mbps, the police (percent) command will use 1.5 Mbps as the basis for calculating the cir rate (1500000 * 30 percent).

How Bandwidth Is Calculated

The police (percent) command is often used in conjunction with the bandwidth and priority commands. The bandwidth and priority commands can be used to calculate the total amount of bandwidth available on an entity (for example, a physical interface). 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 permanent virtual circuit (PVC), the total bandwidth is calculated as follows:

–For a variable bit rate (VBR) virtual circuit (VC), the sustained cell rate (SCR) is used in the calculation.

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

For more information on bandwidth allocation, refer to the"Congestion Management Overview" chapter in the Cisco IOS Quality of Service Solutions Configuration Guide.

Examples

The following example configures traffic policing using a CIR and a PIR on the basis of a percentage of bandwidth. In this example, a CIR of 20 percent and a PIR of 40 percent have been specified. Additionally, an optional bc value and be value (300 ms and 400 ms, respectively) have been specified.

Router> enable

Router# configure terminal

Router (config)# policy-map policy1

Router(config-pmap)# class class1

Router(config-pmap-c)# police cir percent 20 bc 300 ms be 400 ms pir percent 40 

Router(config-pmap-c-police)# exit 

After the policy map and class maps are configured, the policy map is attached to interface as shown in the following example.

Router> enable

Router# configure terminal

Router(config-if)# interface s4/0 

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

Router(config-if)# exit

Related Commands

Command	Description
policy-map	Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.
service-policy	Attaches a policy map to an input interface or VC, or an output interface or VC, to be used as the service policy for that interface or VC.
shape (percent)	Specifies average or peak rate traffic shaping on the basis of a percentage of bandwidth available on an interface.
show policy-map	Displays the configuration of all classes for a specified service policy map or all classes for all existing policy maps.
show policy-map interface	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.

shape (percent)

To specify average or peak rate traffic shaping on the basis of a percentage of bandwidth available on an interface, use the shape command in policy-map class configuration mode. To remove traffic shaping, use the no form of this command.

shape {average | peak} percent percentage [sustained-burst-in-msec ms] [be excess-burst-in-msec ms] [bc committed-burst-in-msec ms]

no shape {average | peak} percent percentage [sustained-burst-in-msec ms] [be excess-burst-in-msec ms] [bc committed-burst-in-msec ms]

Syntax Description

average	Specifies average rate traffic shaping.
peak	Specifies peak rate traffic shaping.
percent	Specifies that percent of bandwidth will be used for either the average rate or peak rate traffic shaping.
percentage	Specifies the bandwidth percentage. Valid range is a number from 1 to 100.
sustained-burst-in-msec	(Optional) Sustained burst size used by the first token bucket for policing traffic. Valid range is a number from 4 to 200.
ms	(Optional) Indicates that the burst value is specified in milliseconds.
be	(Optional) Excess burst (be) size used by the second token bucket for policing traffic.
excess-burst-in-msec	(Optional) Specifies the be size in ms. Valid range is a number from 0 to 200.
bc	(Optional) Committed burst (bc) size used by the first token bucket for policing traffic.
committed-burst-in-msec	(Optional) Specifies the bc value in milliseconds (ms). Valid range is a number from 1 to 2000.

Defaults

The default bc and be is 4 ms.

Command Modes

Policy-map class configuration

Command History

Release	Modification
12.1(2)T	This command was introduced.
12.2(13)T	This command was modified for the Percentage-Based Policing and Shaping feature.
12.0(28)S	The command was integrated into Cisco IOS Release 12.0(28)S.
12.2(27)SBA	The command was integrated into Cisco IOS Release 12.2(27)SBA.

Usage Guidelines

This command calculates the committed information rate (CIR) on the basis of a percentage of the available bandwidth on the interface. Once a policy map is attached to the interface, the equivalent cir value in bits per second (bps) is calculated on the basis of the interface bandwidth and the percent value entered with this command. The show policy-map interface command can then be used to verify the cir bps value calculated.

The calculated cir bps rate must be in the range of 8000 and 154400000 bps. If the rate is less than 8000 bps, the associated policy map cannot be attached to the interface. If the interface bandwidth changes (for example, more is added), the cir bps values are recalculated on the basis of the revised amount of bandwidth. If the cir percentage is changed after the policy map is attached to the interface, the bps value of the cir is recalculated.

Conform Burst and Peak Burst Sizes in Milliseconds

This command also allows you to specify the values for the conform burst size and the peak burst size in milliseconds. If you want bandwidth to be calculated as a percentage, the conform burst size and the peak burst size must be specified in milliseconds (ms).

Hierarchical Policy Maps

The shape (percent) command, when used in "child" (hierarchical) policy maps, is not supported on the Cisco 7500, the Cisco 7200, or lower series routers. Therefore, the shape (percent) command cannot be configured for use in hierarchical policy maps on these routers.

How Bandwidth Is Calculated

The shape (percent) command is often used in conjunction with the bandwidth and priority commands. The bandwidth and priority commands can be used to calculate the total amount of bandwidth available on an entity (for example, a physical interface). 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 permanent virtual circuit (PVC), the total bandwidth is calculated as follows:

–For a variable bit rate (VBR) virtual circuit (VC), the sustained cell rate (SCR) is used in the calculation.

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

For more information on bandwidth allocation, refer to the "Congestion Management Overview" chapter in the Cisco IOS Quality of Service Solutions Configuration Guide.

Examples

The following example configures traffic shaping using an average shaping rate on the basis of a percentage of bandwidth. In this example, 25 percent of the bandwidth has been specified. Additionally, an optional be value and bc value (300 ms and 400 ms, respectively) have been specified.

Router> enable

Router# configure terminal

Router (config)# policy-map policy1

Router(config-pmap)# class class1

Router(config-pmap-c)# shape average percent 25 20 ms be 300 ms bc 400 ms

Router(config-pmap-c)# exit 

After the policy map and class maps are configured, the policy map is attached to interface as shown in the following example.

Router> enable

Router# configure terminal

Router(config)# interface s4/0 

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

Router(config-if)# exit

Related Commands

Command	Description
bandwidth	Specifies or modifies the bandwidth allocated for a class belonging to a policy map.
class (policy-map)	Specifies the name of the class whose policy you want to create or change, and the default class (commonly known as the class-default class) before you configure its policy.
police (percent)	Configures traffic policing on the basis of a percentage of bandwidth available on an interface.
policy-map	Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.
priority	Gives priority to a class of traffic belonging to a policy map.
service-policy	Attaches a policy map to an input interface or VC, or an output interface or VC, to be used as the service policy for that interface or VC.
shape max-buffers	Specifies the maximum number of buffers allowed on shaping queues.

show policy-map

To display the configuration of all classes for a specified service policy map or all classes for all existing policy maps, use the show policy-map command in EXEC mode.

show policy-map [policy-map]

Syntax Description

policy-map

(Optional) Name of the service policy map whose complete configuration is to be displayed.

Defaults

All existing policy map configurations are displayed.

Command Modes

EXEC

Command History

Release	Modification
12.0(5)T	This command was introduced.
12.0(5)XE	This command was integrated into Cisco IOS Release 12.0(5)XE.
12.0(7)S	This command was integrated into Cisco IOS Release 12.0(7)S.
12.1(1)E	This command was integrated into Cisco IOS Release 12.1(1)E.
12.2(13)T	The output of this command was modified for the Percentage-Based Policing and Shaping feature and includes the bandwidth percentage used when calculating traffic policing and shaping.
12.0(28)S	The output of this command was modified for the QoS: Percentage-Based Policing feature to display the committed (conform) burst (bc) and excess (peak) burst (be) sizes in milliseconds (ms).
12.2(27)SBA	This command was integrated into Cisco IOS Release 12.2(27)SBA.

Usage Guidelines

The show policy-map command displays the configuration of a service policy map created using the policy-map command. You can use the show policy-map command to display all class configurations comprising any existing service policy map, whether or not that service policy map has been attached to an interface.

Examples

The following is sample output from the show policy-map command. This sample output displays the contents of a policy map called "policy1." In policy 1, traffic policing on the basis of a committed information rate (CIR) of 20 percent has been configured, and the bc and be have been specified in milliseconds. As part of the traffic policing configuration, optional conform, exceed, and violate actions have been specified.

Router# show policy-map policy1

  Policy Map policy1

    Class class1

     police cir percent 20 bc 300 ms pir percent 40 be 400 ms

       conform-action transmit 

       exceed-action drop 

       violate-action drop 

Table 1 describes the significant fields shown in the display.

Table 1 show policy-map Field Descriptions 

Field	Description
Policy Map	Name of policy map displayed.
Class	Name of class configured in policy map displayed.
police	Indicates that traffic policing on the basis of specified percentage of bandwidth has been enabled. The committed burst (bc) and excess burst (be) sizes have been specified in milliseconds (ms), and optional conform, exceed, and violate actions have been specified.

Related Commands

Command	Description
policy-map	Creates or modifies a policy map that can be attached to one or more interfaces to specify a service policy.
show policy-map class	Displays the configuration for the specified class of the specified policy map.
show policy-map interface	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.

show policy-map interface

To display the packet statistics of all classes that are configured for all service policies either on the specified interface or subinterface or on a specific permanent virtual circuit (PVC) on the interface, use the show policy-map interface command in EXEC mode.

show policy-map interface interface-name [vc [vpi/] vci][dlci dlci] [ input | output]

Syntax Description

interface-name	Name of the interface or subinterface whose policy configuration is to be displayed.
vc	(Optional) For ATM interfaces only, shows the policy configuration for a specified PVC. The name can be up to 16 characters long.
vpi/	(Optional) ATM network virtual path identifier (VPI) for this PVC. On the Cisco 7200 and 7500 series routers, this value ranges from 0 to 255. The absence of both the forward slash (/) and a vpi value defaults the vpi value to 0. If this value is omitted, information for all virtual circuits (VCs) on the specified ATM interface or subinterface is displayed. The vpi and vci arguments cannot both be set to 0; if one is 0, the other cannot be 0.
vci	(Optional) ATM network virtual channel identifier (VCI) for this PVC. This value ranges from 0 to 1 less than the maximum value set for this interface by the atm vc-per-vp command. Typically, the lower values 0 to 31 are reserved for specific traffic (F4 Operation, Administration, and Maintenance (OAM), switched virtual circuit (SVC) signaling, Integrated Local Management Interface (ILMI), and so on) and should not be used. The VCI is a 16-bit field in the header of the ATM cell. The VCI value is unique only on a single link, not throughout the ATM network, because it has local significance only. The vpi and vci arguments cannot both be set to 0; if one is 0, the other cannot be 0.
dlci	(Optional) Indicates a specific PVC for which policy configuration will be displayed.
dlci	(Optional) Specific data-link connection identifier (DLCI) number used on the interface. Policy configuration for the corresponding PVC will be displayed when a DLCI is specified.
input	(Optional) Indicates that the statistics for the attached input policy will be displayed.
output	(Optional) Indicates that the statistics for the attached output policy will be displayed.

Defaults

No default behavior or values

Command Modes

EXEC

Command History

Release	Modification
12.0(5)T	This command was introduced.
12.0(5)XE	This command was integrated into Cisco IOS Release 12.0(5)XE.
12.0(7)S	This command was integrated into Cisco IOS Release 12.0(7)S.
12.1(1)E	This command was integrated into Cisco IOS Release 12.1(1)E.
12.1(2)T	This command was modified to display information about the policy for all Frame Relay PVCs on the interface, or, if a DLCI is specified, the policy for that specific PVC. This command was also modified to display the total number of packets marked by the QoS set action.
12.1(3)T	This command was modified to display per-class accounting statistics.
12.2(4)T	This command was modified to display burst parameters and associated actions.
12.2(8)T	This command was modified to display the multiple actions configured for packets conforming to, exceeding, or violating a specific rate.
12.0(28)S	The output of this command was modified for the QoS: Percentage-Based Policing feature to include milliseconds when calculating the committed (conform) burst (bc) and excess (peak) burst (be) sizes.
12.2(27)SBA	This command was integrated into Cisco IOS Release 12.2(27)SBA.

Usage Guidelines

The show policy-map interface command displays the configuration for classes on the specified interface or the specified PVC only if a service policy has been attached to the interface or the PVC.

Examples

The following is sample output from the show policy-map interface command. This sample displays the statistics for the serial 2/0 interface on which traffic policing has been enabled. The committed (conform) burst (bc) and excess (peak) burst (be) are specified in milliseconds (ms).

Router# show policy-map interface s2/0

 Serial2/0 

  Service-policy output: policy1 (1050)

    Class-map: class1 (match-all) (1051/1)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: ip precedence 0  (1052)

      police:

          cir 20 % bc 300 ms

          cir 409500 bps, bc 15360 bytes

          pir 40 % be 400 ms

          pir 819000 bps, be 40960 bytes

        conformed 0 packets, 0 bytes; actions:

          transmit 

        exceeded 0 packets, 0 bytes; actions:

          drop 

        violated 0 packets, 0 bytes; actions:

          drop 

        conformed 0 bps, exceed 0 bps, violate 0 bps

    Class-map: class-default (match-any) (1054/0)

      0 packets, 0 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: any  (1055)

        0 packets, 0 bytes

        5 minute rate 0 bps

In this example, the CIR and PIR are displayed in bps, and both the committed burst (bc) and excess burst (be) are displayed in bits.

The CIR, PIR bc, and be are calculated on the basis of the formulas described below.

Formula for Calculating the CIR

When calculating the CIR, the following formula is used:

•CIR percentage specified (as shown in the output of the show policy-map command) * bandwidth (BW) of the interface (as shown in the output of the show interfaces command) = total bits per second

According to the output of the show interfaces command for the serial 2/0 interface, the interface has a bandwidth (BW) of 2048 kbps.

Router # show interfaces s2/0 
Serial2/0 is administratively down, line protocol is down  
  Hardware is M4T 
  MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec, rely 255/255, load 1/255 

The following values are used for calculating the CIR:

20 % * 2048 kbps = 409600 bps

Formula for Calculating the PIR

When calculating the PIR, the following formula is used:

•PIR percentage specified (as shown in the output of the show policy-map command) * bandwidth (BW) of the interface (as shown in the output of the show interfaces command) = total bits per second

According to the output of the show interfaces command for the serial 2/0 interface, the interface has a bandwidth (BW) of 2048 kbps.

Router # show interfaces s2/0 
Serial2/0 is administratively down, line protocol is down  
  Hardware is M4T 
  MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec, rely 255/255, load 1/255 

The following values are used for calculating the PIR:

40 % * 2048 kbps = 819200 bps

---

Note Discrepancies between this total and the total shown in the output of the show policy-map interface command can be attributed to a rounding calculation or to differences associated with the specific interface configuration.

---

Formula for Calculating the Committed Burst (bc)

When calculating the bc, the following formula is used:

•The bc in milliseconds (as shown in the show policy-map command) * the CIR in bits per seconds = total number bytes

The following values are used for calculating the bc:

300 ms * 409600 bps = 15360 bytes

Formula for Calculating the Excess Burst (be)

When calculating the bc and the be, the following formula is used:

•The be in milliseconds (as shown in the show policy-map command) * the PIR in bits per seconds = total number bytes

The following values are used for calculating the be:

400 ms * 819200 bps = 40960 bytes

Table 2 describes the significant fields shown in the display.

Table 2 show policy-map interface Field Descriptions¹  

Field	Description
Service-policy output	Name of the output service policy applied to the specified interface or VC.
Class-map	Class of traffic being displayed. Output is displayed for each configured class in the policy. The choice for implementing class matches (for example, match-all or match-any) can also appear next to the traffic class.
packets and bytes	Number of packets (also shown in bytes) identified as belonging to the class of traffic being displayed.
offered rate	Rate, in kbps, of packets coming in to the class.
drop rate	Rate, in kbps, at which packets are dropped from the class. The drop rate is calculated by subtracting the number of successfully transmitted packets from the offered rate.
Match	Match criteria specified for the class of traffic. Choices include criteria such as the Layer 3 packet length, IP precedence, IP differentiated services code point (DSCP) value, Multiprotocol Label Switching (MPLS) experimental value, access groups, and quality of service (QoS) groups. For more information about the variety of match criteria options that are available, refer to the "Configuring the Modular Quality of Service Command-Line Interface" chapter of the Cisco IOS Quality of Service Solutions Configuration Guide.
police	Indicates that traffic policing has been enabled. Display includes the CIR, PIR (in both a percentage of bandwidth and in bps) and the bc and be in bytes and milliseconds. Also displays the optional conform, exceed, and violate actions, if any, and the statistics associated with these optional actions.

1 A number in parentheses may appear next to the service-policy output name, class-map name, and match criteria information. The number is for Cisco internal use only and can be disregarded.

Related Commands

Command	Description
police (percent)	Configures traffic policing on the basis of a percentage of bandwidth available on an interfaces.
shape (percent)	Specifies average or peak rate traffic shaping on the basis of a percentage of bandwidth available on an interface.
show frame-relay pvc	Displays statistics about PVCs for Frame Relay interfaces.
show interfaces	Displays statistics for all interfaces configured on the router or access server.
show policy-map	Displays the configuration of all classes for a specified service policy map or all classes for all existing policy maps.
show policy-map class	Displays the configuration for the specified class of the specified policy map.

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