Installation guide

3-17
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 3 Configuring the Cisco Cable Interface
Configuring the Upstream Cable Interface
2. Ensure the cable modem card is firmly seated in its chassis slot.
3. Ensure the captive installation screws are tight.
4. Verify that you have entered the correct slot and port numbers.
5. Verify that you selected a valid frequency for your router.
Activating Upstream Rate Limiting
Upstream rate limiting allows upstream bandwidth requests from rate-exceeding cable modems to be
buffered without incurring TCP-related timeouts and retransmits. This enables the CMTS to enforce the
peak upstream rate for each cable modem without degrading overall TCP performance for the subscriber
CPEs. Upstream grant shaping is per cable interface (SID).
Token bucket policing with shaping is the per-upstream default rate-limiting setting at the CMTS.
Shaping can be enabled or disabled for the token-bucket algorithm.
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 determine if upstream rate limiting is configured and activated, enter the show running-config
command and look for the cable interface configuration information. If upstream rate limiting is
configured and enabled, a rate limiting entry displays in the show running-config output. If upstream
rate limiting is disabled,
no cable upstream rate-limit displays 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
command line interface to modify the modem’s QoS profile, or edit the modem’s TFTP config file.
Command Purpose
CMTS01(config-if)# cable upstream usport
rate-limit
CMTS01(config-if)# cable upstream usport
rate-limit token-bucket
CMTS01(config-if)# cable upstream usport
rate-limit token-bucket shaping
Enable rate limiting for the specified upstream
cable interface.
Enable rate limiting for the upstream cable interface
employing the token bucket policing algorithm.
With this command the Cisco uBR7100 series
CMTS automatically drops packets in violation of
allowable upstream bandwidth.
Default. Enable rate limiting for the upstream cable
interface employing the token bucket policing
algorithm with traffic shaping.
CMTS01(config-if)# ^Z
CMTS01#
Exit back to the EXEC mode so that you can verify
upstream rate limiting.