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Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter 3 Configuring Cable Interface Features for the Cisco uBR10012 Router
Configuring the Upstream Cable Interface
To return the upstream time-adjustment ranging value to the default of 2 seconds, enter the following
command in cable interface configuration mode:
Router(config-if)#
no cable upstream
usport
time-adjust continue
To return the upstream time adjustment threshold value to the default of 1 second, enter the following
command in cable interface configuration mode:
Router(config-if)#
no cable upstream
usport
time-adjust threshold
Verifying Upstream Timing Adjustment
To determine if upstream timing adjustment is configured and activated, enter the
show running-config
command and look for the cable interface configuration information. If upstream timing adjustment is
enabled, either or both of the
continue
and
threshold
timing-adjustment entries appear in the
show
running-config
command output. If both the
continue
and
threshold
upstream timing adjustments are
disabled, no timing adjustment entry appears in the
show running-config
command output.
Tip
Perform the following steps if you are having difficulty with verification:
Step 1
Verify that the cable connections are not loose or disconnected.
Step 2
Verify that the cable interface line card is firmly seated in its chassis slot
Step 3
Verify that the captive installation screws are tight.
Step 4
Confirm that you have entered the correct slot and port numbers.
.
Setting Upstream Backoff Values
The DOCSIS-specified method of contention resolution for CMs wanting to transmit data or requests on
the upstream channel is a truncated binary exponential backoff value, with the initial backoff window
and the maximum backoff window controlled by the CMTS. The Cisco uBR10000 series CMTS
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 configurable on the Cisco uBR10000 series software and 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. You can set fixed start and end values for data backoff on the upstream ports, or you can set
the upstream ports for automatic data backoff. You have the same options for ranging backoff. For both
backoff windows, the default start value is 0; the default end value is 4. Valid values are from 0 to 15.
Note
Cisco does not recommend that you adjust default values, but that you enable the automatic dynamic
backoff algorithm. Refer to the
“Configuring Dynamic Contention Algorithms (Cable Insertion
Interval, Range, and Data Backoff)” section on page 4-7
.
To set data or ranging backoff values for an upstream port, use one or more of the following commands,
in cable interface configuration mode.
