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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-05
Chapter1 Overview of Cisco uBR7200 Series Software
cops tcp window-size
Input Power Levels
The input power level, power-level-dBmV, is an option in the cable spectrum-group command. The
option allows you to specify the expected U.S. input power levels on the upstream receivers on the
CMTS when the cable modems are hopping from one fixed frequency to another or from one band to
another. Each upstream frequency has an associated upstream input power level in dBmV. The power
level is the modem transmit power that each spectrum group can use when an upstream frequency change
is necessary. The input power level may be set at the time of the frequency hop.
Specifying an input power level is done so that the cable modems do not have to increase or decrease
their transmit power with every hop. The cable operator can perform minor power equalizations as a
function of frequency. The valid range is -10 to +10dBmV. The power level value should be changed
only if you want to change the power level as part of spectrum management. Some cable plants may want
to change only the input power level and not the frequency on a daily time schedule.
For information on how to configure input power levels, see the “Setting Input Power Level” section in
the Cisco Cable Modem Termination System Feature Guide on Cisco.com.
Spectrum Management Enhancements in Cisco IOS Release 12.3(9a)BC
Cisco IOS Release 12.3(9a)BC introduces enhancements to spectrum management for the
CiscouBR7246VXR router:
• Supports the Cisco Broadband Troubleshooter (CBT) 3.2, page 1-123 (with caveats)
• Supports Subscriber Traffic Management (STM) Version 1.1, page 1-95 (with caveats)
For additional information about CBT 3.2, spectrum management and STM 1.1, refer to the following
documents on Cisco.com:
• Release Notes for Cisco Broadband Troubleshooter Release 3.2
http://www.cisco.com/en/US/products/hw/cable/ps2217/products_command_reference_book0918
6a0080108e88.html
• Spectrum Management for the Cisco CMTS
http://www.cisco.com/en/US/products/hw/cable/ps2217/products_feature_guide_chapter09186a00
8019b586.html
• Subscriber Traffic Management for the Cisco CMTS
http://www.cisco.com/en/US/products/hw/cable/ps2217/products_feature_guide09186a00801b17d0.html
Upstream Traffic Shaping
This feature allows the cable modem termination system (CMTS) to perform upstream rate shaping on
the DOCSIS (Data-Over-Cable Service Interface Specifications) upstream channel.
With traffic shaping, the CMTS can buffer the grants for rate exceeded modems. This grant buffering at
the CMTS avoids TCP-related timeouts and retransmits resulting in an improved TCP throughput
performance for the rate-exceeded modems. Thus, shaping enables the CMTS to enforce the peak
upstream rate for the modem without degrading overall TCP performance for the modem.
When users do not enable the shaping option for upstream rate limiting, the CMTS upstream-rate-policing
code drops bandwidth requests from CMs that are found to have exceeded their configured-peak-upstream
rate (using different local drop policies). The effect of bandwidth requests (eventually upstream packets)
being dropped causes degraded throughput performance of window-based protocols (like TCP) for these
rate-exceeded modems because of the timeouts and retransmits that follow.
For additional information about upstream traffic shaping, refer to the “Setting Upstream Traffic
Shaping” section on page3-26 and to Spectrum Management for the Cisco Cable Modem Termination
System on Cisco.com.