ATM Hierarchical Shaping—ATM VC into VP Shaping
First Published: March 18, 2011
Last Updated: March 18, 2011
Traffic shaping is a quality of service (QoS) mechanism that is used to manage the network traffic by shaping the traffic to a specified rate. Traffic shaping enables the network administrator to:
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Control access to the available bandwidth.
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Ensure that the traffic conforms to the policies.
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Regulate the flow of traffic to avoid congestion that can occur when the transmitted traffic exceeds the access speed of its remote target interface.
Traffic shaping uses queues to constrain data bursts, limit peak data rate, and smooth jitters so that traffic will fit within the promised envelope. Traffic shaping limits the throughput by buffering excess traffic instead of dropping packets.
ATM VP/VC hierarchical shaping provides two levels of traffic shaping—per-VC and per-VP—to control or modify the flow of traffic on an interface. The shaping function also ensures that the traffic from one VC does not adversely impact another VC, thus preventing the loss of data. The traffic is shaped first at the VC level and then at the VP level.
Finding Feature Information
Your software release may not support all the features documented in this module. 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 ATM Hierarchical Shaping" section.
Use Cisco Feature Navigator to find information about platform support and Cisco 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
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Restrictions for ATM Hierarchical Shaping
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Information About ATM Hierarchical Shaping
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How to Configure ATM Hierarchical Shaping
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Configuration Examples for ATM Hierarchical Shaping
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Additional References
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Feature Information for ATM Hierarchical Shaping
Restrictions for ATM Hierarchical Shaping
All virtual channels (VCs) within a given virtual path (VP) must belong to the same ATM service category.
Information About ATM Hierarchical Shaping
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ATM Hierarchical Shaping
ATM Hierarchical Shaping
If a service (or an application) wants to use an ATM network to transport a particular kind of traffic, it must first inform the network about what kind of traffic is to be transported, and the performance requirements of that traffic. The ATM service categories provide a method to relate traffic characteristics and QoS requirements to network behavior. Hierarchical shaping requires that all VCs belonging to a given VP have the same ATM service category. This hierarchy ensures that packets are shaped first at the VC level and then at the VP level. At the interface level, the priority is based on the ATM service category. The service category is determined by the first PVC that is configured under a VP. The priority is in the following order:
1.
Constant Bit Rate (CBR)
2.
Unspecified Bit Rate (UBR)
3.
Variable Bit Rate Non Real-Time (VBR-nRT)
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Real-time Variable Bit Rate (VBR-RT)
If no service category is specified at the VC level, the default is unshaped UBR. The ATM Hierarchical Shaping feature is supported for the following ATM traffic service categories:
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VBR-nRT
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UBR
For VBR-nRT traffic the output sustainable cell rate (SCR) value that is configured will be taken into account for VC shaping. For UBR traffic, the output peak cell rate (PCR) value that is configured will be taken into account for VC shaping.
The ATM Hierarchical Shaping feature supports over-subscription. Over-subscription occurs when the sum of the configured rate of UBR and VBR PVCs exceeds the line rate.
How to Configure ATM Hierarchical Shaping
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Configuring ATM Hierarchical Shaping (required)
Configuring ATM Hierarchical Shaping
Perform this task to configure ATM hierarchical shaping.
SUMMARY STEPS
1.
enable
2.
configure terminal
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interface atm interface-number [.subinterface-number {mpls | multipoint | point-to-point}]
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atm pvp vpi [peak-rate]
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pvc vpi/vci
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exit
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range [range-name] pvc [start-vpi/]start-vci [end-vpi/]end-vci
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ubr output-pcr
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exit
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atm pvp vpi [peak-rate]
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pvc vpi/vci
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vbr-nrt output-pcr output-scr [output-maxburstsize]
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create on-demand
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end
15.
show atm pvc
16.
show atm vp
DETAILED STEPS
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Step 1 |
enable
Router> enable |
Enables privileged EXEC mode. • Enter your password if prompted. |
Step 2 |
configure terminal
Router# configure terminal |
Enters global configuration mode. |
Step 3 |
interface atm interface-number [.subinterface-number {mpls | multipoint | point-to-point}]
Router(config)# interface atm 0/3/2.1 multipoint |
Configure an ATM interface and enters subinterface configuration mode. |
Step 4 |
atm pvp vpi [peak-rate]
Router(config-subif)# atm pvp 2 |
Creates a permanent virtual path (PVP) used to multiplex (or bundle) one or more VCs. |
Step 5 |
pvc vpi/vci
Router(config-subif)# pvc 2/200 |
Creates or assigns a name to an ATM PVC and enters ATM virtual circuit configuration mode. |
Step 6 |
exit
Router(config-if-atm-vc)# exit |
Exits ATM virtual circuit configuration mode and returns to subinterface configuration mode. |
Step 7 |
range [range-name] pvc [start-vpi/]start-vci [end-vpi/]end-vci
Router(config-subif)# range range1 pvc 2/100 2/102 |
Defines a range of ATM PVCs. |
Step 8 |
ubr output-pcr
Router(config-if-atm-vc)# ubr 4000 |
Configures UBR QoS and specifies the output PCR for an ATM PVC, PVC range, switched virtual circuit (SVC), VC class, or VC bundle member. |
Step 9 |
exit
Router(config-if-atm-vc)# exit |
Exits ATM virtual circuit configuration mode and returns to subinterface configuration mode. |
Step 10 |
atm pvp vpi [peak-rate]
Router(config-subif)# atm pvp 3 |
Creates a PVP used to multiplex (or bundle) one or more VCs. |
Step 11 |
pvc vpi/vci
Router(config-subif)# pvc 3/150 |
Creates or assigns a name to an ATM PVC and enters ATM virtual circuit configuration mode. |
Step 12 |
vbr-nrt output-pcr output-scr [output-maxburstsize]
Router(config-if-atm-vc)# vbr-nrt 1000 1000 |
Configures the VBR-nRT QoS and specifies output PCR, output SCR, and output maximum burst cell size for an ATM PVC, PVC range, SVC, VC class, or VC bundle member. |
Step 13 |
create on-demand
Router(config-if-atm-vc)# create on-demand |
Configures ATM PVC autoprovisioning, which enables a PVC or range of PVCs to be created automatically on demand. |
Step 14 |
end
Router(config-if-atm-vc)# end |
Exits ATM virtual circuit configuration mode and returns to privileged EXEC mode. |
Step 15 |
show atm pvc
Router# show atm pvc |
(Optional) Displays the statistics for all VPs on an interface or for a specific VP. |
Step 16 |
show atm vp
Router# show atm vp |
(Optional) Displays all ATM PVCs and traffic information. |
Configuration Examples for ATM Hierarchical Shaping
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Example: Configuring ATM Hierarchical Shaping
Example: Configuring ATM Hierarchical Shaping
The following example shows how to configure ATM hierarchical shaping:
interface atm 0/3/2.1 multipoint
range range1 pvc 2/100 2/102
Additional References
Related Documents
Standards
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
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MIBs
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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 software releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs |
RFCs
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No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
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Technical Assistance
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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 ATM Hierarchical Shaping
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 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 software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Table 1 Feature Information for ATM Hierarchical Shaping
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ATM Hierarchical Shaping—ATM VC into VP Shaping |
Cisco IOS XE Release 3.3S |
ATM VP/VC hierarchical shaping provides two levels of traffic shaping—per-VC and per-VP—to control or modify the flow of traffic on an interface. The shaping function also ensures that traffic from one VC does not adversely impact another VC, thus preventing loss of data. The traffic is shaped first at the VC level and then at the VP level. |
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