Cisco uBR10-SRP-OC12SML Specifications download pdf (Page 161)

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Cisco uBR10012 Universal Broadband Router Software Configuration Guide

OL-1520-05

Chapter3 Configuring Cable Interface Features for the CiscouBR10012Router

Configuring the Upstream Cable Interface

Router# show interface c5/0/0 sid 1 counters

00:02:23: %ENVM-3-LASTENV: Cannot save environmental data

Sid Req-polls BW-reqs Grants Packets Frag Concatpkts

issued received issued received complete received

1 0 22 22 22 0 0

2 0 3 3 2 0 0

3 0 0 0 0 0 0

Verifying Upstream Traffic Shaping

To determine if upstream traffic shaping is configured and activated, enter the show running-config

command and look for the cable interface configuration information. If upstream traffic shaping is

configured and enabled, a traffic shaping entry appears in the show running-config output. If upstream

traffic shaping is disabled, no cable upstream rate-limit appears in the output.

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

Step1 Configure a low-peak upstream rate limit for the CM in its QoS profile. Either use the command-line

interface (CLI) to modify the modem’s QoS profile, or edit the modem’s TFTP configuration file. refer

to the DOCSIS 1.1 for the Cisco uBR7200 Series Universal Broadband Routers feature module at

http://www.cisco.com/univercd/cc/td/doc/product/cable/cab_r_sw/docsis11.htm.

Step2 Use a regular rate-limiting algorithm on the upstream without rate shaping, and note the drops of the

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

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

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

and backoffs produced by the drop in bandwidth requests. Enter the

showinterfacecx/y serviceflowqos command to see the input rate at CMTS in bps.

Step3 Enable grant shaping on the upstream channel by using the new shaping keyword extension to the

token-bucket algorithm CLI command.

Step4 Make the CM exceed its peak upstream rate by generating upstream traffic, and note the effect of grant

buffering (shaping) at the CMTS. If you use CM-to-CMTS pings, there is a perceivable decrease in the

frequency of the pings.

Let the pings run long enough to allow the averages at the CMTS to settle; then view the upstream rate

received by this single modem. Use the show interface cx/y command and see the input rate in bps. This

value should be close to the modem’s peak upstream rate. Also note the drop counts for the modem’s

SID by using the show interface sid counters command, and verify that the CMTS no longer drops the

bandwidth requests from the CM.

The bandwidth request drop count (from the previous nonshaping test) remains unchanged when

upstream rate shaping is used, indicating that the CMTS is actually shaping (buffering) the grants for the

modem. Verify that the input rate at the CMTS (from the single rate-exceeded CM) stabilizes close to

the configured peak rate of 128 Kbps.

Troubleshooting Tips

Perform these steps if you are having difficulty with verification:

Step1 Ensure that the cable connections are not loose or disconnected.

Step2 Ensure that the cable interface line card is firmly seated in its chassis slot.

Step3 Ensure that the captive installation screws are tight.

Step4 Verify that you have entered the correct slot and port numbers.

Step5 Verify that you selected a valid frequency for your router.

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