user manual

Configuring Headend Broadband Access Router Features

Configuring the Upstream Cable Interface

MC-554

Cisco IOS Multiservice Applications Configuration Guide

To enable upstream rate limiting for an upstream port on a Cisco cable modem card, use one of the

following commands in cable interface configuration mode:

To disable upstream traffic shaping for an upstream port, enter the following command in cable interface

configuration mode:

CMTS01(config-if)# no cable upstream usport rate-limit

Verifying Upstream Rate Limiting

To verify whether or not upstream rate limiting has been configured and activated, enter the show

running-config command and look for the cable interface configuration information. If upstream rate

limiting has been configured and enabled, a rate limiting entry will be displayed in the show

running-config output. If upstream rate limiting is disabled,

no cable upstream rate-limit will be

displayed in the output.

You can also perform the following tasks to verify that rate limiting is enabled on the upstream channel:

Step 1 Configure a low-peak upstream rate limit for the cable modem in its QoS profile. Either use the CLI to

modify the QoS profile, or edit the TFTP configuration file.

Step 2 Use a regular rate-limiting algorithm on the upstream without rate shaping and see the drops of the

excess bandwidth requests from this cable modem when it exceeds its peak upstream rate.

Use the show interface cx/y sid counters command to see the bandwidth request drops. See that the

upstream rate received by that modem is in fact less than its configured peak rate due to the timeouts and

backoffs produced by the drop in bandwidth requests. To see the input rate at the CMTS in bps, enter the

show interface cx/y sid command.

Step 3 Enable grant shaping on the upstream channel by using the new shaping keyword extension to the token

bucket algorithm CLI command.

Command Purpose

Step 1

CMTS01(config-if)# cable upstream usport rate-limit

token-bucket

CMTS01(config-if)# cable upstream usport rate-limit

token-bucket shaping

Enables rate limiting for the specified upstream cable

interface.

Enables rate limiting for the upstream cable interface

employing the token bucket policing algorithm. With

this command the Cisco uBR7200 series will

automatically drop packets in violation of allowable

upstream bandwidth.

Default. Enables rate limiting for the upstream cable

interface employing the token bucket policing

algorithm with traffic shaping.

Step 2

CMTS01(config-if)# ^Z CMTS01#

Exits to EXEC mode so that you can verify upstream

rate limiting.