Installation guide

5-11
Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 5 Troubleshooting the System
Managing Cable Modems on the HFC Network
Note Before the introduction of this feature, the CMTS would drop bandwidth requests from a CM it detected
as exceeding its configured peak upstream rate. Such request dropping affects the throughput
performance of IP-based protocols such as FTP, TCP, and SMTP. With this feature, the CMTS can shape
(buffer) the grants for a CM that is exceeding its upstream rate, rather than dropping the bandwidth
requests.
CMTS01# show interface c1/0 sid 1 counters
Sid Inpackets Inoctets Outpackets Outoctets Ratelimit Ratelimit
BWReqDrop DSPktDrop
1 67859 99158800 67570 98734862 2579 0
Configuring Spectrum Management
Combining Blind Strategies and Time Scheduled Spectrum Management
Cisco uBR7100 series software supports combined blind and time scheduled spectrum management:
• Using blind spectrum management, the number of lost station management messages exceeding a
configured threshold (default = 10) initiates an upstream channel frequency reassignment. The
Cisco uBR7100 series software moves all CMs on the upstream port by sending UCD messages that
contain the next frequency and input power level defined in the spectrum management group. The
frequency change occurs rapidly without data loss and with minimal latency.
• Using time scheduled spectrum management, the upstream channel frequency reassignment process
is initiated at a configured time of day or week.
With combined blind and time scheduled strategies, blind hop tables are given the capability for
time-variant configuration. The frequency or subband list can change with time. Blind frequency hop is
performed within the spectrum specified to be currently available. An example follows:
uBR(config)# cable spectrum-group 2 time Mon 09:00:00 frequency 10000000
uBR(config)# cable spectrum-group 2 time Tue 09:05:00 delete frequency 10000000
uBR(config)# cable spectrum-group 2 time Tue 09:00:00 frequency 5000000
uBR(config)# cable spectrum-group 4 time Fri 09:00:00 band 15000000 25000000
uBR(config)# cable spectrum-group 4 time Sat 09:00:00 delete band 15000000 25000000
Using Guided Frequency Hop
Using guided frequency hop, the upstream channel frequency is reassigned if a threshold number or
percentage of CMs suddenly go offline. You can adjust the thresholds and assign explicit frequencies or
frequency subbands and associated input power levels in the unified spectrum group table. The
Cisco uBR7100 series CMTS locates the defined channel or a suitable channel and moves all CMs on
the upstream port.
The following example shows that the Cisco uBR7100 series can force the CTMS to change the
upstream to another frequency before the CMTS sends a message to increase output power levels. You
can configure the frequency hop table so that the next entry has the same frequency, but a different power
level:
uBR(config)# cable spectrum-group 2 frequency 20000000
uBR(config)# cable spectrum-group 2 frequency 20000000 2
uBR(config)# cable spectrum-group 2 frequency 20000000 -2
uBR(config)# cable spectrum-group 2 frequency 22000000
uBR(config)# cable spectrum-group 2 frequency 22000000 2