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Cisco Broadband Cable Command Reference Guide
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Chapter 2 Cisco CMTS Configuration Commands
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.
cable upstream
n
range-backoff
{
automatic
|
start end
}
no cable upstream
n
range-backoff
Syntax Description
Defaults
Ranging backoff is enabled with the
automatic
setting
Command Modes
Interface configuration (cable interface only)
Command History
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.)
Tip
Use the
show controllers cable upstream
command to display the current Ranging Backoff settings.
n
Specifies the upstream port number. Valid values start with 0 for the
first upstream port on the cable interface line card.
automatic
Specifies the fixed data backoff start and end values.
Note
The
automatic
setting is not supported on
Cisco uBR-MC5X20S/U cable interface line cards, which
should use manually configured ranging backoff instead.
start
Binary exponential algorithm. Sets the start value for initial ranging
backoff. Valid values are from 0 to 15.
end
Binary exponential algorithm. Sets the end value for initial ranging
backoff. Valid values are from 0 to 15.
Release
Modification
12.1 T
This command was introduced.
