Configuring Cable Modem Registration Timeout; Configuring Dynamic Contention Algorithms (Cable Insertion Interval, Range, And Data Backoff); Cable Insertion-Interval Command Examples - Cisco 7246VXR - uBR Router Software Configuration Manual

Configuring Cable Modem Registration Timeout

Configuring Cable Modem Registration Timeout
By default, registered CMs that have no upstream activity for three minutes are timed out and
disconnected from the Cisco uBR7200 series CMTS. This timeout interval can be decreased to 2 minutes
or increased up to 60 minutes.
To specify the registration timeout interval for CMs connected to the Cisco uBR7200 series CMTS, use
the following command in cable interface configuration mode.
Command
cable registration-timeout n
Configuring Dynamic Contention Algorithms (Cable Insertion
Interval, Range, and Data Backoff)
The Cisco uBR7200 series software includes the following algorithms that control the capacity of the
contention subchannel and control the efficient use of a given contention subchannel capacity:
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In high contention mode, the Cisco uBR7200 series MAC scheduler uses collision statistics and sustains
a high frequency of initial ranging slots until it detects a steady ranging state. The CMTS dynamically
varies the frequency of initial ranging slots using the data grant utilization on the upstream channels. The
CMTS trades upstream bandwidth between data grants and initial ranging slots. The CMTS autodetects
a high collision state and switches to low insertion interval mode after a steady state is achieved where
few collisions occur.
The CMTS is careful when monitoring the ranging channel health to revert to a steady state. In steady
state mode, data grants—grant utilization—receive preference over initial ranging slots.
Although the binary exponential backoff algorithm operates in a distributed fashion at different CMs,
the CMTS provides centralized control for the backoff algorithm. To achieve this, it remotely monitors
traffic load—the backlog developing on the contention channel—and then varies the backoff start and
end specified in the MAPs for that upstream channel. This ensures that colliding CMs are properly
randomized in time.
The following cable interface commands are available to configure the dynamic contention algorithms:
[no] cable insertion-interval [automatic [Imin [Imax]]] | [msecs]
[no] cable upstream port num range-backoff [automatic] | [start end]
[no] cable upstream port num data-backoff [automatic] | [start end]

cable insertion-interval Command Examples

To deviate from system defaults when modifying the dynamic contention algorithm, use one of the
following commands in cable interface configuration mode.
Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
5-6
Algorithm that dynamically controls the rate of upstream contention slots—initial ranging and
bandwidth requests.
Algorithm that varies the backoff parameters that CMs use. Backoff variation falls within each of
the initial ranging and bandwidth request upstream contention subchannels.
Chapter 5 Managing Cable Modems on the Hybrid Fiber-Coaxial Network
Purpose
Specifies the maximum number of minutes allowed to elapse with
no upstream activity before terminating the connection. Valid
range is from 2 to 60 minutes. Default = 3 minutes.
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