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This feature module describes the Class-Based Shaping feature. This document includes the following sections:
Using the Class-Based Shaping feature, you can do the following:
Class-based shaping can be enabled on any interface that supports GTS.
Traffic shaping limits the rate of transmission of data. In addition to using a specifically configured transmission rate, you can use GTS to specify a derived transmission rate based on the level of congestion.
You can specify two types of traffic shaping; average rate shaping and peak rate shaping. Average rate shaping limits the transmission rate to the committed information rate (CIR). Using the CIR ensures that the average amount of traffic being sent conforms to the rate expected by the network.
peak rate = CIR(1+Be/Bc)
where:
Peak rate shaping allows the router to burst higher than average rate shaping. However, using peak rate shaping, the traffic sent above the CIR (the delta) has the potential of being dropped if the network becomes congested.
If your network has additional bandwidth available (over the provisioned CIR) and the application or class can tolerate occasional packet loss, that extra bandwidth can be exploited through the use of peak rate shaping. However, there may be occasional packet drops when network congestion occurs. If the traffic being sent to the network must strictly conform to the configured network provisioned CIR, then you should use average traffic shaping.
Prior to this release, when GTS queues packets that, when sent, cause the traffic flow to violate the configured rate, only flow-based WFQ was supported for the queued packets.
Applying GTS to classes provides greater flexibility for configuring traffic shaping. Previously, this ability was limited to the use of ACLs.
Better Use of Bandwidth
Specifying peak rate shaping allows you to make better use of available bandwidth by allowing more data than the CIR to be sent if the bandwidth is available.
Bandwidth Allocation
CBWFQ allows you to specify the exact amount of bandwidth to be allocated for a specific class of traffic. Taking into account available bandwidth on the interface, you can configure up to 64 classes and control distribution among them, which is not the case with flow-based WFQ.
Flow-based WFQ applies weights to traffic to classify it into conversations and determine how much bandwidth each conversation is allowed relative to other conversations. These weights, and traffic classification, are dependent on and limited to the seven IP Precedence levels.
Coarser Granularity and Scalability
CBWFQ allows you to define what constitutes a class based on criteria that exceed the confines of flow. CBWFQ allows you to use ACLs and protocols or input interface names to define how traffic will be classified, thereby providing coarser granularity. You need not maintain traffic classification on a flow basis. Moreover, you can configure up to 64 discrete classes in a service policy.
Adaptive traffic shaping for Frame Relay networks is not supported using the Class-Based Shaping feature. To configure adaptive GTS for Frame Relay networks, you must use the commands from releases prior to Release 12.1(2) of Cisco IOS software.
For related information on this feature, refer to the following documents:
Standards
None
MIBs
None
RFCs
None
See the following sections for configuration tasks for the Class-Based Shaping feature. Each task in the list is identified as either optional or required.
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)# policy-map policy-map | Specifies the name of the policy map to be created or modified. |
Step2 | Router(config)#class-map class-map-name | Specifies the name of the class map to be created. |
Step3 | Router(config-pmap-c)# shape {average | peak} cir
[bc] [be]
| Specifies average or peak rate shaping. |
Step4 | Router(config-pmap-c)# shape max-buffers number-of-buffers | (Optional) Specifies the maximum number of buffers allowed on shaping queues. |
To display the contents of a specific policy map, a specific class from a specific policy map, or all policy maps configured on an interface, use one of the following commands in global configuration mode:
This section provides the following configuration examples:
The following example defines one class, c1. Class c1 is configured to shape traffic to 384 kbps, with a normal burst size of 15440 bits.
Router(config)# policy-map shape Router(config-pmap)# class c1 Router(config-pmap-c)# shape average 38400 15440 Router(config-pmap-c)# configure terminal Router(config)# interface Serial 3/3 Router(config-if)# service out shape
In this example, two classes are defined---cust1 and cust2. The class cust1 is ensured a bandwidth of 256 kbps, and the output is shaped to 384 kbps. The class cust2 is ensured a bandwidth of 384 kbps, but if enough bandwidth is available on the interface, the class can obtain throughput up to a peak of 512kbps.
Figure 1 illustrates this example.
The following commands are used to configure this example:
Router(config)# policy-map shape-cbwfq Router(config-pmap)# class cust1 Router(config-pmap-c)# shape average 384000 Router(config-pmap-c)# bandwidth 256 Router(config-pmap)# class cust2 Router(config-pmap-c)# shape peak 512000 Router(config-pmap-c)# bandwidth 384 Router(config-pmap-c)# configure terminal Router(config)# interface Serial 3/3 Router(config-if)# service out shape-cbwfq
This section provides two examples of configuring CBWFQ inside GTS.
The first example uses hierarchical policy maps and configures CBWFQ inside GTS.
In the following example, three policy maps are defined---cust1-classes, cust2-classes, and cust-policy. The policy maps cust1-classes and cust2-classes have three classes defined---gold, silver, and bronze.
For cust1-classes, gold is configured to use 50 percent of the bandwidth. Silver is configured to use 20percent of the bandwidth, and bronze is configured to use 15 percent of the bandwidth.
For cust2-classes, gold is configured to use 30 percent of the bandwidth. Silver is configured to use 15percent of the bandwidth, and bronze is configured to use 10percent of the bandwidth.
The policy map cust-policy specifies average rate shaping of 384 kbps and assigns the service policy cust1-classes to the class cust1. The policy map cust-policy specifies peak rate shaping of 512 kbps and assigns the service policy cust2-classes to the class cust2.
Figure 2 illustrates this example.
Configuration for cust1-classes
Router(config)# policy-map cust1-classes Router(config-pmap)# class gold Router(config-pmap-c)# bandwidth percent 50 Router(config-pmap)# class silver Router(config-pmap-c)# bandwidth percent 20 Router(config-pmap)# class bronze Router(config-pmap-c)# bandwidth percent 15
Configuration for cust2-classes
Router(config)# policy-map cust2-classes Router(config-pmap)# class gold Router(config-pmap-c)# bandwidth percent 30 Router(config-pmap)# class silver Router(config-pmap-c)# bandwidth percent 15 Router(config-pmap)# class bronze Router(config-pmap-c)# bandwidth percent 10
Configuration for Customer Policy and QoS Features
Router(config)# policy-map cust-policy Router(config-pmap)# class cust1 Router(config-pmap-c)# shape average 38400 Router(config-pmap-c)# service-policy cust1-classes Router(config-pmap)# class cust2 Router(config-pmap-c)# shape peak 51200 Router(config-pmap-c)# service-policy cust2-classes Router(config-pmap-c)# interface Serial 3/2 Router(config-if)# service out cust-policy
In this example, the Class-Based Shaping feature is configured for the class named shaped in the policy map named GTS_in_ModCLI. The class shaped is shaped to an average rate of 241,000 bits per second (bps). CBWFQ is also enabled on the class, which guarantees a bandwidth of 241 kbps during times of congestion at the interface.
The shaped class is a congestion point for all the subclasses that comprise that class. Therefore, the subclasses can be further differentiated in the shaped class. All these subclasses are part of the policy map, CBWFQ_in_GTS, that is attached to the shaped class.
Configuration for Policy Map GTS_in_ModCLI
Router(config)# policy-map GTS_in_ModCLI
Router(config-pmap)# class shaped
Router(config-pmap-c)# bandwidth 241
Router(config-pmap-c)# shape average 241000
Router(config-pmap-c)# service-policy CBWFQ_in_GTS
Configuration for Policy Map CBWFQ_in_GTS
The policy map, CBWFQ_in_GTS, has four CBWFQ classes:
Router(config)# policy-map CBWFQ_in_GTS Router(config-pmap)# class cust_A Router(config-pmap-c)# bandwidth percent 25 Router(config-pmap)# class cust_B Router(config-pmap-c)# bandwidth percent 25 Router(config-pmap)# class cust_C Router(config-pmap-c)# bandwidth percent 25 Router(config-pmap)# class class-default Router(config-pmap-c)# fair
The output of the show policy-map command for GTS_in_ModCLI displays an expanded configuration, including the subclasses:
Router# show policy-map GTS_in_ModCLI Policy Map GTS_in_ModCLI Class shaped Weighted Fair Queueing Bandwidth 241 (kbps) Max Threshold 64 (packets) Traffic Shaping Average Rate Traffic Shaping CIR 241000 (bps) Max. Buffers Limit 1000 (Packets) Policy Map CBWFQ_in_GTS Class cust_A Weighted Fair Queueing Bandwidth 25 (%) Max Threshold 64 (packets) Class cust_B Weighted Fair Queueing Bandwidth 25 (%) Max Threshold 64 (packets) Class cust_C Weighted Fair Queueing Bandwidth 25 (%) Max Threshold 64 (packets) Class class-default Weighted Fair Queueing Flow based Fair Queueing
The policy map GTS_in_ModCLI can be attached to any logical interface that provides a congestion point. Run-time statistics after attaching to interface Serial 3/0 are shown.
Router# show policy interface Serial 3/0 Serial3/0 output: GTS_in_ModCLI Class shaped Weighted Fair Queueing Output Queue: Conversation 267 Bandwidth 241 (kbps) Max Threshold 64 (packets) (pkts matched/bytes matched) 3852/947384 (pkts discards/bytes discards/tail drops) 0/0/0 Traffic Shaping Target Byte Sustain Excess Interval Increment Adapt Rate Limit bits/int bits/int (ms) (bytes) Active 241000 1928 7712 7712 32 964 - Queue Packets Bytes Packets Bytes Depth Delayed Delayed Active 41 3980 978872 3967 975686 yes Class cust_A Weighted Fair Queueing Output Queue: Conversation 41 Bandwidth 25 (%) Max Threshold 64 (packets) (pkts matched/bytes matched) 0/0 (pkts discards/bytes discards/tail drops) 0/0/0 Class cust_B Weighted Fair Queueing Output Queue: Conversation 42 Bandwidth 25 (%) Max Threshold 64 (packets) (pkts matched/bytes matched) 0/0 (pkts discards/bytes discards/tail drops) 0/0/0 Class cust_C Weighted Fair Queueing Output Queue: Conversation 43 Bandwidth 25 (%) Max Threshold 64 (packets) (pkts matched/bytes matched) 0/0 (pkts discards/bytes discards/tail drops) 0/0/0 Class class-default Weighted Fair Queueing Flow Based Fair Queueing Maximum Number of Hashed Queues 32
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.1 command reference publications.
Syntax Description
policy-map The name of a service policy map (created using the policy-map command) to be attached.
Defaults
No service policy is specified.
Command Modes
Class-map configuration within policy map
Command History
12.1(2)T This command was introduced.
Release
Modification
Usage Guidelines
You can attach a single policy map to one or more classes to specify the service policy for those classes. This command is only available for the output interface, which is assumed.
Examples
For cust1-classes, gold is configured to use 50 percent of the bandwidth. Silver is configured to use 20percent of the bandwidth, and bronze is configured to use 15 percent of the bandwidth.
For cust2-classes, gold is configured to use 30 percent of the bandwidth. Silver is configured to use 15percent of the bandwidth, and bronze is configured to use 10 percent of the bandwidth.
The policy map cust-policy specifies average rate shaping of 384 kbps and assigns the service policy cust1-classes to the policy map cust1-classes. The policy map cust-policy specifies peak rate shaping of 512 kbps and assigns the service policy cust2-classes to the policy map cust2-classes.
To configure classes for cust1-classes, use the following commands:
Router(config)# policy-map cust1-classes Router(config-pmap)# class gold Router(config-pmap-c)# bandwidth percent 50 Router(config-pmap)# class silver Router(config-pmap-c)# bandwidth percent 20 Router(config-pmap)# class bronze Router(config-pmap-c)# bandwidth percent 15
To configure classes for cust2, use the following commands:
Router(config)# policy-map cust2-classes Router(config-pmap)# class gold Router(config-pmap-c)# bandwidth percent 30 Router(config-pmap)# class silver Router(config-pmap-c)# bandwidth percent 15 Router(config-pmap)# class bronze Router(config-pmap-c)# bandwidth percent 10
To define the customer policy with cust1-classes and cust2-classes and QoS features, use the following commands:
Router(config)# policy-map cust-policy Router(config-pmap)# class cust1 Router(config-pmap-c)# shape average 38400 Router(config-pmap-c)# service-policy cust1-classes Router(config-pmap)# class cust2 Router(config-pmap-c)# shape peak 51200 Router(config-pmap-c)# service-policy cust2-classes Router(config-pmap-c)# interface Serial 3/2 Router(config-if)# service out cust-policy
Related Commands
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 Displays the configuration for the specified class of the specified policy map.
Command
Description
To specify average or peak rate traffic shaping, use the shape class-map configuration command. To remove traffic shaping, use the no form of this command,
shape {average | peak} cir [bc] [be]
Syntax Description
average Specifies average rate shaping. peak Specifies peak rate shaping. cir Specifies the committed information rate (CIR) in bits per second (bps). bc Specifies the Committed Burst rate in bits. be Specifies the Excess Burst rate in bits.
Defaults
No default behavior or values.
Command Modes
Class-map configuration within policy map
Command History
12.1(2)T This command was introduced.
Release
Modification
Usage Guidelines
Traffic shaping limits the rate of transmission of data. In addition to using a specifically configured transmission rate, you can use generic traffic shaping (GTS) to specify a derived transmission rate based on the level of congestion.
You can specify two types of traffic shaping; average rate shaping and peak rate shaping. Average rate shaping limits the transmission rate to the CIR. Using the CIR ensures that the average amount of traffic being sent conforms to the rate expected by the network.
Peak rate shaping configures the router to send more traffic than the CIR. To determine the peak rate, the router uses the following formula:
peak rate = CIR(1+Be/Bc)
where:
Peak rate shaping allows the router to burst higher than average rate shaping. However, using peak rate shaping, the traffic sent above the CIR (the delta) has the potential of being dropped if the network becomes congested.
If your network has additional bandwidth available (over the provisioned CIR) and the application or class can tolerate occasional packet loss, that extra bandwidth can be exploited through the use of peak rate shaping. However, there may be occasional packet drops when network congestion occurs. If the traffic being sent to the network must strictly conform to the configured network provisioned CIR, then you should use average traffic shaping.
Examples
The following example sets the uses average rate shaping to ensure a bandwidth of 256 kbps:
shape average 256000
The following example uses peak rate shaping to ensure a bandwidth of 300 kbps, but allow throughput up to 512 kbps if enough bandwidth is available on the interface:
bandwidth 300 shape peak 512000
Related Commands
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. 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 max-buffers Specifies the maximum number of buffers allowed on shaping queues.
Command
Description
To specify the maximum number of buffers allowed on shaping queues, use the shape max-buffers class-map configuration command. To remove the maximum number of buffers, use the no form of this command.
shape max-buffers number-of-buffers
Syntax Description
number-of-buffers Specifies the maximum number of buffers. The minimum number of buffers is 1, the maximum number of buffers is 4096.
Defaults
The default setting is 1000 buffers.
Command Modes
Class-map configuration within policy map
Command History
12.1(2)T This command was introduced.
Release
Modification
Usage Guidelines
You can specify the maximum number of buffers allowed on shaping queues for each class configured to use generic traffic shaping (GTS).
Examples
The following example configures shaping and sets the maximum buffer limit to 100:
shape average 350000 shape max-buffers 100
Related Commands
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. 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 Specifies average or peak rate traffic shaping.
Command
Description
Posted: Tue Jun 20 14:21:40 PDT 2000
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