Cisco Systems uBR7200 manual Setting Downstream Rate Limiting, MC-542

Configuring Headend Broadband Access Router Features

Configuring the Downstream Cable Interface

•If the cable modems acquire an RF and a DHCP, but fail on TOD or TFTP: check DHCP options and the IP address of the TOD server; ping the TOD server using the source IP address option (the primary IP address of a cable interface); check IP routing; verify that the TFTP filename is correct, the TFTP file is in the correct directory on the TFTP server, and that the TFTP file has read privileges for all; ping the TFTP server using the source IP address option (the primary IP address of a cable interface); check IP routing, and so on.

Setting Downstream Rate Limiting

Downstream rate limiting enables you to use the token bucket policing algorithm with traffic shaping options or the weighted discard policing algorithm to buffer, shape, or discard packets that exceed a set bandwidth. Downstream rate limiting is disabled by default.

To enable downstream rate limiting for a downstream port on a Cisco cable modem card, use one of the following commands in cable interface configuration mode:

	Command	Purpose
Step 1	CMTS01(config-if)#cable downstream rate-limit	Enables rate limiting on the downstream port using
	token-bucket	the token bucket policing algorithm. With this
	or	command, the Cisco uBR7200 series will
		automatically drop packets in violation of the
	CMTS01(config-if)#cable downstream rate-limit	allowable bandwidth.
	token-bucket shaping	Enables rate limiting on the downstream port using
	or	the token bucket policing algorithm with traffic
		shaping.
	CMTS01(config-if)#cable downstream rate-limit
	token-bucket shaping granularity 8
	or	Enables rate limiting on the downstream port using
		the token bucket policing algorithm with specific
	CMTS01(config-if)#cable downstream rate-limit	traffic shaping time granularity. Acceptable values
		are 1, 2, 4, 8, or 16 milliseconds (ms).
	token-bucket shaping max-delay 256
		Enables rate limiting on the downstream port using
		the token bucket policing algorithm with specific
		maximum traffic shaping buffering delay. Acceptable
		values are 128, 256, 512, or 1028 ms.
Step 2
	CMTS01(config-if)#cable downstream rate-limit	Enables rate limiting on the downstream port using
	weighted-discard 3	the weighted packet discard policing algorithm and
		assign a weight for exponential moving average of
		loss rate. Acceptable values are 1 to 4.

Step 3 CMTS01(config-if)# ^ZCMTS01#

Exits to EXEC mode so that you can verify the steps.

Cisco IOS Multiservice Applications Configuration Guide

MC-542