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cable upstream range-backoff
cable upstream range-backoff
To specify automatic or configured initial ranging backoff calculation, use the cable upstream range-
backoff command in cable interface configuration mode. To set default values, use the no form of this
command.
Syntax Description
n
automatic
start
end
Defaults
Ranging backoff is enabled with the automatic setting
Command Modes
Interface configuration (cable interface only)
Command History
Release
12.1 T
Usage Guidelines
The DOCSIS-specified method of contention resolution for CMs used to send data or requests on the
upstream channel is a truncated binary exponential back-off with the initial backoff window and the
maximum backoff window controlled by the CMTS. The Cisco CMTS router specifies backoff window
values for both data and initial ranging and sends these values downstream as part of the Bandwidth
Allocation Map (MAP) MAC message. The values are power-of-two values. For example, a value of 4
indicates a window between 0 and 15; a value of 10 indicates a window between 0 and 1023.
The automatic setting is optimized for a maximum of 250 CMs per upstream port. Set manual values
for data backoff windows only when operating with more than 250 CMs per upstream port. (The
automatic setting is not supported on Cisco uBR-MC5X20S/U cable interface line cards, which should
use manually configured ranging backoff instead.)
Use the show controllers cable upstream command to display the current Ranging Backoff settings.
Tip
Cisco Broadband Cable Command Reference Guide
2-342
cable upstream n range-backoff {automatic | start end}
no cable upstream n range-backoff
Modification
This command was introduced.
Specifies the upstream port number. Valid values start with 0 for the
first upstream port on the cable interface line card.
Specifies the fixed data backoff start and end values.
The automatic setting is not supported on
Note
Cisco uBR-MC5X20S/U cable interface line cards, which
should use manually configured ranging backoff instead.
Binary exponential algorithm. Sets the start value for initial ranging
backoff. Valid values are from 0 to 15.
Binary exponential algorithm. Sets the end value for initial ranging
backoff. Valid values are from 0 to 15.
Chapter 2
Cisco CMTS Configuration Commands
OL-1581-08
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