Table Of Contents

Configuring Rate Limiting and Traffic Shaping

Rate Limiting

Restrictions

Configuring Rate Limiting

Traffic Shaping

Features

Restrictions

Configuring Traffic Shaping

Displaying the Configurations

Configuring Rate Limiting and Traffic Shaping

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This chapter describes rate limiting features and configuration procedures for your Catalyst 8500 switch router.

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Note For further information about the commands used in this chapter, refer to the ATM and Layer 3 Switch Router Command Reference and the Cisco IOS Quality of Service Solutions Command Reference.

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This chapter includes the following sections:

• Rate Limiting

• Traffic Shaping

• Displaying the Configurations

Rate Limiting

Rate limiting is available on the Catalyst 8540 MSR, Catalyst 8510 MSR, Catalyst 8540 CSR, and Catalyst 8510 CSR. This feature is similar to the IOS committed access rate (CAR) feature. You can deploy rate limiting on your switch router to ensure that a packet, or data source, adheres to a stipulated contract, and to determine the QoS for a packet.

Rate limiting can be applied to individual interfaces. When an interface is configured with this feature, the traffic rate will be monitored by the Ethernet processor interface ucode to verify conformity. Non-conforming traffic is dropped, conforming traffic passes through without any changes.

Features Supported

The following features are supported for rate limiting on the Catalyst 8500 switch router:

•This feature is supported on the following interface modules:

–Eight-Port 10/100BASE-T Fast Ethernet Interface Modules

–16-Port 10/100BASE-T Fast Ethernet Interface Modules

–Eight-Port 100BASE-FX Fast Ethernet Interface Modules

–16-port 100BASE-FX Fast Ethernet Interface Modules

•This feature can be applied on a per-physical-port basis.

•This feature is available for input traffic and output traffic.

Restrictions

Restrictions for rate limiting on the Catalyst 8500 switch router include the following:

•This feature is not supported on the LightStream 1010.

•IPX and rate limiting cannot be configured at the same time. If rate limiting is configured on an interface, IPX will be automatically disabled on that interface. In addition, IPX will be automatically disabled on any of the three other interfaces which are controlled by the same hardware micro-controller as the configured interface. For example, if rate limiting is configured on Fast Ethernet slot 0, IPX will not work on slots 0, 1, 2, and 3.

•The QoS mapping ratio might be disrupted by the rate limiting configuration.

•Due to additional processing, when rate limiting is enabled, switching might not be at wire speed.

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Note Broadcast packets, dropped ACL packets, packets dropped due to expiration of the designed Time To Live, and bad CRC packets are included in the rate limit calculation. This might cause a problem if the policed port is not part of a point-to-point connection and is connected via a hub rather than a layer 2 switch.

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Configuring Rate Limiting

Enter the following command in interface configuration mode to configure rate limiting on your switch router:

Command	Purpose
rate-limit {input | output} rate burst	Configures rate limiting on an interface.

For more detailed configuration information, refer to the "Policing and Shaping Overview" section of the Cisco IOS Quality of Service Solutions Configuration Guide.

Example

The following is an example of how to configure rate limiting on your switch router:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z

Router(config)# interface f0/0/0

Router(config-if)# rate-limit input 1000000 20000

Router(config-if)# rate-limit output 100000 30000

Router(config-if)# exit

Traffic Shaping

Traffic shaping allows you to shape output traffic (egress traffic) on a per-physical port basis. Ucode monitors output traffic to verify that it conforms to the rate configured on the switch router. When excess traffic comes into the switch, the output side of the processor interface applies back pressure and queues the excess traffic in the switch fabric. If the switch fabric queues overflow, the traffic is dropped. This feature is similar to the IOS GTS feature.

Features

Traffic shaping on the Catalyst 8500 switch router includes the following features:

•This feature is supported on the following interface modules:

–Eight-Port 10/100BASE-T Fast Ethernet Interface Modules

–16-Port 10/100BASE-T Fast Ethernet Interface Modules

–Eight-Port 100BASE-FX Fast Ethernet Interface Modules

–16-port 100BASE-FX Fast Ethernet Interface Modules

•Per-physical port traffic shaping

•Back pressure and traffic queues

•Egress traffic traffic shaping

Restrictions

Restrictions for traffic shaping on the Catalyst 8500 switch router include the following:

•This feature is not supported on the LightStream 1010.

•IPX and traffic shaping cannot be configured at the same time. If traffic shaping is configured on an interface, IPX will be automatically disabled on that interface. In addition, IPX will be automatically disabled on any of the three other interfaces which are controlled by same hardware micro-controller as the configured interface. For example, if traffic shaping is configured on Fast Ethernet slot 0, IPX will not work on slots 0, 1, 2, and 3.

•The QoS mapping ratio might be disrupted by the rate limiting configuration.

•This feature is not available for ingress traffic.

Configuring Traffic Shaping

Enter the following command in interface configuration mode to configure traffic shaping on your switch router:

Command	Purpose
traffic-shape rate {target-bit-rate | bit per interval }	Configures traffic shaping on a port.

Example

The following is an example of how to configure rate limiting on your switch router:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z

Router(config)# interface f0/0/0

Router(config-if)# traffic-shape rate 1000000 20000

Router(config-if)# exit

Displaying the Configurations

To display the rate limiting and traffic shaping configurations, enter the following commands in Privileged EXEC mode:

Command	Purpose
show epc port-qos	Displays the port configurations.
show epc port qos interface	Displays the QoS configuration.
show epc port-qos interface card/subcard/port out	Displays the output for port QoS parameters for a particular interface.

Example

The following is an example of how to display the port configuration on your switch router:

Router# show epc port-qos

Interface Type Input/ Target-Rate Burst-Size

Output (bits/sec) (bytes)

---------------------------------------------------------------------

FastEthernet0/0/0 Rate-Limit Input 1000000 20000

Rate-Limit Output 100000 30000

Example

The following is an example of how to display the QoS configuration on your switch router:

Router# show epc port-qos

Interface            Type            Input/ Target-Rate    Burst-Size

                                     Output  (bits/sec)       (bytes)

---------------------------------------------------------------------

FastEthernet9/0/3    Rate-Limit      Input     10000000         64000

                     Rate-Limit      Output    10000000         64000

Example

The following is an example of how to display the port QoS input parameters for an interface:

Router# show epc port-qos interface f9/0/3 in

Input Port QoS Parameters:

Current number of tokens                    (tokens):  65352

Configured burst size                    (burstsize):  65352

Token update interval (ticks)                (time1):   7789

Tokens added per interval          (tokens_in_time1):   1556

Time to fill bucket (ticks)     (time_to_fill_burst): 327138

Example

The following is an example of how to display the QoS output parameters for an interface:

Router# show epc port-qos interface f9/0/3 out

Output Port QoS Parameters:

Current number of tokens                    (tokens):  65352

Configured burst size                    (burstsize):  65352

Token update interval (ticks)                (time1):   7789

Tokens added per interval          (tokens_in_time1):   1556

Time to fill bucket (ticks)     (time_to_fill_burst): 327138