- Policing and Shaping Overview
- IPv6 QoS: MQC Traffic Policing
- Configuring Traffic Policing
- IPv6 QoS: MQC Traffic Shaping
- Two-Rate Policer
- Policer Enhancement - Multiple Actions
- Percentage-Based Policing and Shaping
- Modular QoS CLI Three-Level Hierarchical Policer
- ATM Policing by Service Category for SVC and SoftPVC
- Modular QoS CLI Unconditional Packet Discard
- Control Plane Policing
- Control Plane Protection
- Control Plane Logging
- Management Plane Protection
- Class-Based Policing
- QoS Percentage-Based Policing
- Overhead Accounting
- Adaptive QoS over DMVPN
Contents
- Percentage-Based Policing and Shaping
- Finding Feature Information
- Feature Overview
- Benefits
- Restrictions
- Related Features and Technologies
- Related Documents
- Supported Standards MIBs and RFCs
- Prerequisites
- Configuration Tasks
- Configuring Policing and Shaping Based on Bandwidth Percentage
- Attaching the Policy Map to an Interface or a VC
- Verifying the Policing and Shaping Bandwidth Percentage Setting
- Troubleshooting Tips
- Configuration Examples
- Example Specifying Traffic Policing Based on a Bandwidth Percentage
- Example Specifying Traffic Shaping Based on a Bandwidth Percentage
- Example Verifying That CEF Is Enabled
Percentage-Based Policing and Shaping
Feature History
|
Release |
Modification |
|---|---|
|
12.2(13)T |
This feature was introduced. |
|
Supported Platforms |
|
|
For platforms supported in Cisco IOS Release 12.2(13)T, consult Cisco Feature Navigator. |
This document describes the Percentage-Based Policing and Shaping feature in Cisco IOS Release 12.2(13)T. It includes the following sections:
- Finding Feature Information
- Feature Overview
- Supported Standards MIBs and RFCs
- Prerequisites
- Configuration Tasks
- Configuration Examples
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Overview
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 based on 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.
This feature also provides the option of specifying burst sizes in milliseconds (ms) when configuring traffic policing and shaping based on a percentage of bandwidth.
Benefits
Increased Flexibility
This feature provides the ability to configure traffic policing and traffic shaping based on a percentage of bandwidth available on an 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.
Restrictions
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.
Related Features and Technologies
Modular QoS command-line interface (CLI) (Modular QoS CLI)
Class-based weighted fair queueing (CBWFQ)
Class-based packet marking
Cisco Express Forwarding (CEF) and Distributed CEF (dCEF)
Traffic policing
Two-rate policing
Traffic shaping
Related Documents
"Applying QoS Features Using the MQC" module
"Configuring Weighted Fair Queueing" module
"Marking Network Traffic" module
"Policing and Shaping Overview" module
"Traffic Policing" module
"Two-Rate Policer" module
"Policer Enhancements-Multiple Actions" module
"Cisco Express Forwarding Overview" module
Cisco IOS Quality of Service Solutions Command Reference
Cisco IOS Switching Services Command Reference
RFC 2697, A Single Rate Three Color Marker
RFC 2698, A Two Rate Three Color Marker
Supported Standards MIBs and RFCs
Standards
None
MIBs
None
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
http://tools.cisco.com/ITDIT/MIBS/servlet/index
If Cisco MIB Locator does not support the MIB information that you need, you can also obtain a list of supported MIBs and download MIBs from the Cisco MIBs page at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
To access Cisco MIB Locator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions found at this URL:
RFCs
RFC 2697, A Single Rate Three Color Marker
RFC 2698, A Two Rate Three Color Marker
Prerequisites
On a Cisco 7500 series router, Distributed Cisco Express Forwarding (dCEF) must be configured on the interface before you can use the Percentage-Based Policing and Shaping feature.
Configuration Tasks
- Configuring Policing and Shaping Based on Bandwidth Percentage
- Attaching the Policy Map to an Interface or a VC
- Verifying the Policing and Shaping Bandwidth Percentage Setting
- Troubleshooting Tips
Configuring Policing and Shaping Based on Bandwidth Percentage
1. Router (config)# policy-mappolicy-name
2. Router(config-pmap)# class-mapclass-map-name
3. Router(config-pmap-c)# police cir percent percent[bcconform-burst-in-msec ] [ pir percent percent ] [bepeak-burst-in-msec ]
4. Router(config-pmap-c)# shape {average | peak} percentpercent [bc ] [be ]
5. Router (config-pmap-c)# service-policypolicy-map-name
6. Router(config-pmap-c)# exit
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | Router (config)# policy-mappolicy-name |
Specifies the name of the policy map to be created. Enters policy-map configuration mode. |
| Step 2 | Router(config-pmap)# class-mapclass-map-name |
Specifies the name of the class map to be created. Enters policy-map class configuration mode. |
| Step 3 | Router(config-pmap-c)# police cir percent percent[bcconform-burst-in-msec ] [ pir percent percent ] [bepeak-burst-in-msec ] |
Configures traffic policing. |
| Step 4 | Router(config-pmap-c)# shape {average | peak} percentpercent [bc ] [be ] |
Configures traffic shaping using either an average or peak traffic shaping rate based on a percentage of available bandwidth. |
| Step 5 | Router (config-pmap-c)# service-policypolicy-map-name |
Specifies the name of a policy map to be used as a child policy map for this class. |
| Step 6 | Router(config-pmap-c)# exit |
Exits policy-map class configuration mode. |
Attaching the Policy Map to an Interface or a VC
Verifying the Policing and Shaping Bandwidth Percentage Setting
|
Command |
Purpose |
|---|---|
Router# show class-map
|
Displays all information about a class map, including the match criterion. |
Router# show policy-map
|
Displays all configured policy maps. |
Router# show policy-map interface interface-name |
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 permanent virtual circuit (PVC) on the interface. |
Troubleshooting Tips
For input traffic policing on a Cisco 7500 series router, verify that 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.
Configuration Examples
- Example Specifying Traffic Policing Based on a Bandwidth Percentage
- Example Specifying Traffic Shaping Based on a Bandwidth Percentage
- Example Verifying That CEF Is Enabled
Example Specifying Traffic Policing Based on a Bandwidth Percentage
The following example configures traffic policing using a committed information rate (CIR) and a peak information rate (PIR) based on 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 (config)# policy-map policy1
Router(config-pmap)# class-map class1
Router(config-pmap-c)# police cir percent 20 bc 300 ms pir percent 40 be 400 ms
Router (config-pmap-c)# service-policy child-policy1
Router(config-pmap-c)# exit
Router(config-pmap-c)# interface serial 3/1
Router(config-if)# service-policy output policy1
The purpose of the burst parameters (bc and be values) 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.
Example Specifying Traffic Shaping Based on a Bandwidth Percentage
The following example configures traffic shaping using an average shaping rate based on a percentage of bandwidth. In this example, 25 percent of the bandwidth has been specified. Additionally, an optional bc value and be value (300 ms and 400 ms, respectively) have been specified.
Router (config)# policy-map policy1
Router(config-pmap)# class-map class1
Router(config-pmap-c)# shape average percent 25 300 ms 400 ms
Router (config-pmap-c)# service-policy child-policy1
Router(config-pmap-c)# exit
Router(config-pmap-c)# interface serial 3/1
Router(config-if)# service-policy output policy1
The purpose of the bc and be values is to drop packets gradually, as is done with WRED, and to avoid tail drop. Setting sufficiently high burst values helps to ensure good throughput.
Example Verifying That CEF Is Enabled
On a Cisco 7500 series router, dCEF must be configured on the interface before you can use the Percentage-Based Policing and Shaping feature. The show ip cef summary command can be used to confirm that dCEF is enabled and is being used for IP switching. In rare instances, this command displays "IP Distributed CEF without switching" in the command output. This indicates that dCEF is disabled. The following sample output of the show ip cef summary command indicates that dCEF is disabled:
Router# show ip cef summary
IP Distributed CEF with switching (Table Version 36), flags=0x0
18 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 3
18 leaves, 19 nodes, 22136 bytes, 45 inserts, 27 invalidations
0 load sharing elements, 0 bytes, 0 references
universal per-destination load sharing algorithm, id 680E93E2
3(0) CEF resets, 1 revisions of existing leaves
Resolution Timer:Exponential (currently 1s, peak 1s)
0 in-place/0 aborted modifications
refcounts: 5136 leaf, 5120 node
When you configure a feature that requires special handling or is not yet supported in the dCEF switching paths, packets are forwarded to the next switching layer for handling. In this instance, the output of the show cef interface command displays "Packets switched to this interface on line card are dropped to next slow path" as shown in the following sample output.
Router# show cef interface Serial 10/0/0:28
Serial10/0/0:28 is up (if_number 38)
Internet address is 90.0.0.1/8
ICMP redirects are never sent
Per packet loadbalancing is disabled
Inbound access list is not set
Interface is marked as point to point interface
Packets switched to this interface on linecard are dropped to next slow path Hardware idb is Serial10/0/0:28
Fast switching type 4, interface type 20
IP Distributed CEF switching enabled
Fast flags 0x0. ifindex 37(37)
Slot 10 Slot unit 0 VC 28
Hardware transmit queue ptr 0x48001AE0 (0x48001AE0)
Transmit limit accumulator 0x48000102 (0x48000102)
IP MTU 1500