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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.
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If the incoming high priority traffic exceeds the bandwidth percentage calculated by the priority percentcommand, and there is congestion in the network, the excess traffic is dropped. This is identical to the behavior demonstrated when the prioritycommand 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.
By default, when the bandwidth percentand 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 75 percent of the total bandwidth available on the interface.
The remaining 25 percent of the total bandwidth available on the interface is kept in reserve for the unclassified traffic and routing traffic, if any, and proportionally divided among the defined traffic classes. To override the 75 percent limitation, use the max-reserved bandwidth command in interface configuration mode.
![]() Note | The max-reserved bandwidth command is intended for use on main interfaces only; it has no effect on virtual circuits (VCs) or ATM permanent virtual circuits (PVCs). |
This feature allows the Cisco 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.
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 percentand bandwidth remaining percent.
The bandwidth percent command configures bandwidth as an absolute percentage of the total bandwidth on the interface.
The bandwidth remaining percentcommand 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.
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 percentcommand.
Unlike the bandwidth command, the priority command provides a strict priority to the traffic class, which ensures low latency to high priority traffic classes.
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.
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
1.
enable
2.
show
policy-map
policy-map
3.
show
policy-map
policy-map
class
class-name
4.
show
policy-map
interface
type
number
5.
exit
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.
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
The following sample output from the show policy-map interfacecommand shows that 50 percent of the interface bandwidth is guaranteed for the class called class1, and 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 Serial3/2 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, interface s3/2 has a total bandwidth of 1544 kbps. During periods of congestion, 50 percent (or 772 kbps) of the 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.
![]() Note | The counters displayed for classes configured with bandwidth or priority after using the show policy-map interface command are updated only if congestion is present on the interface. |
The following sections provide references related to the Low Latency Queueing with Priority Percentage Support feature.
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 |
Congestion management concepts and related topics |
"Congestion Management Overview" module |
LLQ, bandwidth allocation |
"Configuring Weighted Fair Queueing" module |
Standards |
Title |
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No new or modified standards are supported, and support for existing standards has not been modified. |
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MIBs |
MIBs Link |
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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 releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs |
Title |
---|---|
No new or modified RFCs are supported, and support for existing RFCs has not been modified. |
-- |
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. |
The following table provides release information about the feature or features described in this module. This table 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.
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 Name |
Releases |
Feature Information |
---|---|---|
Low Latency Queueing with Priority Percentage Support |
12.2(2)T 12.0(28)S 12.2(28)SB |
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. In 12.2(2)T, this feature was introduced. In 12.0(28)S, this feature was integrated into Cisco IOS Release 12.0(28)S. In 12.2(28)SB, this feature was integrated into Cisco IOS Release 12.2(28)SB. The following commands were introduced or modified: bandwidth (policy-map class), priority. |