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Table Of Contents
Restrictions for Ethernet Overhead Accounting
Information About Ethernet Overhead Accounting
Benefits of Ethernet Overhead Accounting
Subscriber Line Encapsulation Types
Overhead Calculation on the Router
Overhead Accounting and Hierarchical Policies
How to Configure Ethernet Overhead Accounting
Configuring Ethernet Overhead Accounting in a Hierarchical Policy
Configuration Examples for Ethernet Overhead Accounting
Example: Enabling Ethernet Overhead Accounting
Example: Verifying Ethernet Overhead Accounting Using show running-config
Example: Verifying Ethernet Overhead Accounting with User-Defined Option
Feature Information for Ethernet Overhead Accounting
Ethernet Overhead Accounting
First Published: June 30, 2009Last Updated: March 23, 2011
The Ethernet Overhead Accounting feature enables the router to account for downstream Ethernet frame headers when applying shaping to packets.
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 Ethernet Overhead Accounting" 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://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.
Contents
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Restrictions for Ethernet Overhead Accounting
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Restrictions for Ethernet Overhead Accounting
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Information About Ethernet Overhead Accounting
Benefits of Ethernet Overhead Accounting
The Ethernet Overhead Accounting feature enables the router to account for downstream Ethernet frame headers when applying shaping to packets. A user-defined offset specifies the number of overhead bytes that the router is to use when calculating the overhead per packet. Valid offset values are from +63 bytes to -63 bytes of overhead. Before applying shaping, the router calculates the overhead.
Ethernet interfaces and subinterfaces support overhead accounting. Using the shape or bandwidth command, you can configure accounting per VLAN and per port.
Subscriber Line Encapsulation Types
The subscriber-encap option of the shape and bandwidth commands specifies the encapsulation type at the subscriber line. The router supports the following subscriber line encapsulation types:
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Overhead Calculation on the Router
When calculating overhead for traffic shaping, the router considers the encapsulation type used between the BRAS and the DSLAM and between the DSLAM and the CPE.
Table 1 describes the fields that the router uses for the various encapsulation types when calculating ATM overhead.
Overhead Accounting and Hierarchical Policies
In hierarchical policies, you can enable overhead accounting for shaping and bandwidth on top-level parent policies, middle-level child policies, and bottom-level child policies. If you enable overhead accounting on a:
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The parent and child classes must specify the same encapsulation type when enabling overhead accounting and configuring an offset using the user-defined offset [atm] command option.
Table 2 summarizes the configuration requirements for overhead accounting. For example, if overhead accounting is currently enabled for a parent policy, then accounting can be disabled or enabled on a child policy.
How to Configure Ethernet Overhead Accounting
Configuring Ethernet Overhead Accounting in a Hierarchical Policy
SUMMARY STEPS
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Step 1
enable
Example:Router> enable
Enables privileged EXEC mode.
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Step 2
configure terminal
Example:Router# configure terminal
Enters global configuration mode.
Step 3
policy-map policy-map-name
Example:Router(config)# policy-map Business
Creates or modifies the child policy. Enters policy-map configuration mode.
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class class-map-name
Example:Router(config-pmap)# class video
Assigns the traffic class you specify to the policy map. Enters policy-map class configuration mode.
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bandwidth {bandwidth-kbps | percent percentage | remaining percent percentage} [account {{qinq | dot1q} {aal5} {subscriber-encapsulation}} | {user-defined offset [atm]}]
Example:Router(config-pmap-c)# bandwidth 8000 account dot1q aal5 snap-pppoa
Enables class-based fair queueing and overhead accounting.
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exit
Example:Router(config-pmap-c)# exit
Exits policy-map class configuration mode.
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policy-map policy-map-name
Example:Router(config-pmap)# policy-map Test
Creates or modifies the top-level parent policy.
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class class-default
Example:Router(config-pmap)# class class-default
Configures or modifies the parent class-default class.
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shape [average] rate [account {{qinq | dot1q} [aal5] {subscriber-encap}} | {user-defined offset [atm]}]
Example:Router(config-pmap-c)# shape 8000 account qinq aal5 snap-dot1-rbe
Shapes traffic to the indicated bit rate and enables overhead accounting.
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service-policy policy-map-name
Example:Router(config-pmap-c)# service-policy policy-map-name
Applies a child policy to the parent class-default class.
policy-map-name—Specifies the name of a previously configured child policy map.
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end
Example:Router(config-pmap-c)# end
DETAILED STEPS
Verifying Overhead Accounting
SUMMARY STEPS
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Configuration Examples for Ethernet Overhead Accounting
Example: Enabling Ethernet Overhead Accounting
The following configuration example shows how to enable Ethernet overhead accounting. In the example, the configuration of the policy map named ethernet_ovrh shapes class-default traffic at a rate of 200,000 kbps and enables overhead accounting with a user-defined value of 18. The ethernet_ovrh policy is attached to Gigabit Ethernet subinterface 1/0/0.100, thereby enabling overhead accounting on the subinterface.
Router# configure-terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# policy-map ethernet_ovrhRouter(config-pmap)# class class-defaultRouter(config-pmap-c)# shape average 200000 account user-defined 18!Router(config)# interface GigabitEthernet1/0/0.100Router(config-subif)# service-policy output ethernet_ovrh!Router# show running-config | begin 1/0/0.100interface GigabitEthernet1/0/0.100encapsulation dot1Q 101pppoe enable group group_ptaservice-policy output ethernet_ovrhExample: Verifying Ethernet Overhead Accounting Using show running-config
The following partial sample output from the show running-config command indicates that ATM overhead accounting is enabled for shaping. The BRAS-DSLAM encapsulation is dot1q and the subscriber line encapsulation is snap-rbe based on the AAL5 service.
subscriber policy recording rules limit 64no mpls traffic-eng auto-bw timers frequency 0call rsvp-sync!controller T1 2/0framing sflinecode ami!controller T1 2/1framing sflinecode ami!!policy-map unit-testclass class-defaultshape average 10 account dot1q aal5 snap-rbeExample: Verifying Ethernet Overhead Accounting with User-Defined Option
The following sample output for the policy map named ethernet_ovrh indicates that Ethernet overhead accounting is enabled for shaping and that the user-defined offset is 18 bytes. The sample output from the show policy-map interface command indicates that the ethernet_ovrh policy map is attached to the Gigabit Ethernet subinterface 1/0/0.100, enabling overhead accounting on the subinterface.
Router# show policy-map ethernet_ovrhPolicy Map ethernet_ovrhClass class-defaultAverage Rate Traffic Shapingcir 200000 (bps) account user-defined 18Router# show policy-map interface GigabitEthernet1/0/0.100GigabitEthernet1/0/0.100Service-policy output: ethernet_ovrhClass-map: class-default (match-any)0 packets, 0 bytes30 second offered rate 0 bps, drop rate 0 bpsMatch: any0 packets, 0 bytes30 second rate 0 bpsQueueingqueue limit 8 packets(queue depth/total drops/no-buffer drops) 0/0/0(pkts output/bytes output) 0/0shape (average) cir 200000, bc 800, be 800target shape rate 200000Overhead Accounting EnabledAdditional References
Related Documents
QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples
Policing and Shaping.
Class maps
Policy maps
Standards
No new or modified standards are supported, and support for existing standards has not been modified.
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MIBs
RFCs
No new or modified RFCs are supported, and support for existing RFCs has not been modified.
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Technical Assistance
Feature Information for Ethernet Overhead Accounting
Table 3 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.
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