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Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter 1 Overview of Cisco uBR10012 Universal Broadband Router Software
Supported Software Features for the Cisco uBR10012 Router
CBT 3.2 Spectrum Management Support with the Cisco uBR10-MC5X20S/U BPE
Cisco IOS Release 12.3(9a)BC introduces support for remote spectrum management for the Cisco
uBR10012 router. Cisco uBR10012 spectrum management supports interoperability with these
enhancements to the Cisco CMTS in Cisco IOS 12.3(9a)BC:
•
Cisco Broadband Troubleshooter 3.2, page 1-89
, supporting the Cisco uBR10-MC5X20S/U
Broadband Processing Engine (BPE)
•
Subscriber Traffic Management (STM) Version 1.1, page 1-80
Additional supported spectrum management functions are available on the Cisco uBR10012 router. For
a complete list, and the latest information about Spectrum Management on the Cisco uBR10012 router,
refer to the following document on Cisco.com:
•
Release Notes for Cisco Broadband Troubleshooter Release 3.2
http://www.cisco.com/en/US/products/sw/netmgtsw/ps819/prod_release_notes_list.html
Dynamic Ranging
Dynamic ranging is the Cisco patent-pending troubleshooting feature that supports quick restoration of
service following a catastrophic plant failure. With dynamic ranging, hundreds of cable interfaces can
come back online quickly, because the time that cable interfaces spend deferring contention-ranging
slots is minimized. This reduces cable interface reinitialization time.
This results from use of Cisco uBR10012 router algorithms that vary the number of contention
bandwidth-request minislots and request slots. Software converts unallocated minislots in the current
MAC allocation and management messages—known as MAPs—into request minislots as needed. At low
upstream loads, most of the MAPs of that upstream have no grants to serve, and the scheduler converts
all unallocated (ungranted) minislots into request minislots. This helps ensure a low access delay for
CMs at low loads due to the abundance of request opportunities. At high upstream loads, the scheduler
has data grants to be served before allocating the next request region, and automatically reduces the
number of request minislots.
The initial ranging slots—also called initial maintenance slots—are each about 2 msecs wide. These
slots are used by CMs joining the cable network, and thus, are subject to ranging collisions. CMs use
these slots for initial connectivity with the CMTS only. After the initial ranging message from the CM
is received successfully, the CM no longer uses such contention-ranging slots for subsequent operations.
The CMTS periodically polls CMs with unicast station maintenance slots. Any action that involves a
simultaneous bringing up of many CMs on an upstream channel—service restoration after a catastrophic
power failure, online insertion and removal (OIR) for CMTS cable interface line cards, or fiber node
servicing—gives rise to an impulse-ranging contention state on each of the affected upstream channels.
Rebooted CMs on the upstream attempt to send initial ranging MAC messages using broadcast initial
ranging slots at roughly the same time. Without theCisco uBR10012 router algorithms enabled, CMs can
repeatedly collide and back off a random number of initial ranging slots independently before trying
again.
With Cisco uBR10012 router algorithms enabled, the CMTS can detect such high-contention scenarios,
and can increase the frequency of initial ranging slots to assist in quick resolution of ranging contention.
After the high collision state is over—few persistent ranging collisions occur on the upstream—the
CMTS detects this condition and switches back to the steady state mode. In the steady state mode, the
frequency of initial ranging slots is a function of the upstream channel utilization. If extra upstream
bandwidth is available, the CMTS allocates more initial upstream ranging slots. As soon as the MAC
scheduler needs the upstream bandwidth for data grants, the MAC scheduler reduces the frequency of
initial ranging slots.
