Specifications

3-26
Cisco Cable Modem Termination System Feature Guide
0L-1467-02
Chapter 3 Spectrum Management for the Cisco Cable Modem Termination System
Configuration Tasks
• Configuring Dynamic Upstream Modulation, page 3-32
• Setting Input Power Level, page 3-34
• Verifying Frequency Hopping, page 3-35
Setting 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
customer premises equipment (CPE) devices. Upstream grant shaping is per 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 interface line 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
For examples of upstream rate limiting, see the “Upstream Traffic Shaping and Rate Limiting Examples”
section on page 3-56.
Note For more information on the cable upstream rate-limit command, see the Cisco Broadband Cable
Command Reference Guide on Cisco.com and on the Documentation CD-ROM.
Command Purpose
Step 1
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
Enables rate limiting for the specified upstream
port.
Enables rate limiting for the upstream port
employing the token-bucket policing algorithm.
With this command the CMTS automatically drops
packets in violation of allowable upstream
bandwidth.
Default. Enables rate limiting for the upstream port
employing the token-bucket policing algorithm
with traffic shaping. Use of the default value (the
upstream port’s rate limit) enforces strict
DOCSIS-compliant rate limiting. The default
setting of token-bucket with the shaping option is
recommended.
Step 2
CMTS01(config-if)# ^Z
CMTS01#
Exits back to the EXEC mode so that you can
verify upstream rate limiting.