Cisco IOS CMTS Cable Software Configuration Guide, Release 12.2SC - Wideband Modem Resiliency [Cisco uBR10000 Series Universal Broadband Routers]

Table Of Contents

Wideband Modem Resiliency

Finding Feature Information

Contents

Prerequisites for Wideband Modem Resiliency

Restrictions for Wideband Modem Resiliency

Information About Wideband Modem Resiliency

CM Status Messages

RF Channel Event Dampening Time

How a CMTS Responds to RF Impairment Recovery

How to Configure Wideband Modem Resiliency

Specifying Persistence Thresholds for Events

Specifying Persistence Time for RF Channels

Verifying Wideband Modem Resiliency

What to Do Next

Modifying CM Status Reports for Events

Configuration Example for Wideband Modem Resiliency

Additional References

Related Documents

Standards

Technical Assistance

Feature Information for Wideband Modem Resiliency

Wideband Modem Resiliency

First Published: December 17, 2008

Last Updated: November 16, 2009

The Wideband Modem Resiliency feature provides the best possible service in the event of non-primary radio frequency (RF) channel disruptions to ensure that a cable modem (CM) remains operational. With the implementation of this feature, the Cable Modem Termination System (CMTS) does not force a cable modem to perform a MAC reset if the CM loses connectivity to the CMTS on one or all of its non-primary RF channels.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To see a list of the releases in which each feature is supported, see the "Feature Information for Wideband Modem Resiliency" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for Wideband Modem Resiliency

•Restrictions for Wideband Modem Resiliency

•Information About Wideband Modem Resiliency

•How to Configure Wideband Modem Resiliency

•Configuration Example for Wideband Modem Resiliency

•Additional References

•Feature Information for Wideband Modem Resiliency

Prerequisites for Wideband Modem Resiliency

Table 1 shows the hardware compatibility prerequisites for the Wideband Modem Resiliency feature.

Table 1 Cable Hardware Compatibility Matrix for Wideband Modem Resiliency

CMTS Platform

Processor Engine

Cable Interface Line Cards

Cisco uBR10012 Universal Broadband Router

Cisco IOS Release 12.2(33)SCB

•PRE2

•PRE4

Cisco uBR10-MC5X20S/U/H

Restrictions for Wideband Modem Resiliency

The Wideband Modem Resiliency feature has the following restrictions:

•This feature provides resiliency support only for downstream RF channel disruptions in Cisco IOS Release 12.2(33)SCB and later. This feature does not support any upstream-related resiliency.

•The CMTS cannot move a w-online CM to a bonding group that contains an RF channel if the RF channel is not a member of the original Receive Channel Configuration (RCC) for the wideband CM.

Information About Wideband Modem Resiliency

The Wideband Modem Resiliency feature enables the Cisco uBR10012 router to interact with DOCSIS 3.0-compliant cable modems in order to provide the best possible service in the event of non-primary radio frequency channel disruptions such as loss of quadrature amplitude modulation (QAM), forward error correction (FEC) locks, and MAC Domain Descriptor (MDD) time-outs. If a CM loses connectivity to the CMTS on one or all of its non-primary RF channels, the CMTS does not force the CM to perform a MAC reset and enables the CM to remain operational.

A DOCSIS 3.0-qualified CMTS transmits data to one or more DOCSIS 3.0-compliant cable modems using multiple RF channels. For a CM, one of the RF channels is used as the primary RF channel, and the rest of the channels are considered non-primary channels. The primary RF channel is defined to be the downstream (DS) RF channel on which the CM receives DOCSIS MAC messages needed for upstream timing and synchronization.

This feature enables the CMTS to collect and analyze data related to RF channel disruptions per cable modem and identify the impairment.

CM Status Messages

A DOCSIS 3.0-compliant CM does not perform a MAC reset when reporting DS RF channel failures through CM status messages. Cable modems use CM status messages to report events to the CMTS. The CMTS does not send an acknowledgement to the CM when it receives a CM status message. The CMTS might not receive a CM status message, if the message gets corrupted during transmission. In order to protect against this situation, the CMTS sends the following two parameters to the cable modem using the primary MDD message for each event type:

•Maximum reports

•Maximum hold-off time

The maximum reports parameter specifies how many reports should be sent each time a particular event occurs. The maximum hold-off time parameter defines the amount of time (in units of 20 milliseconds) a CM should wait between transmissions of the CM status messages when the maximum reports parameter is greater than one.

RF Channel Event Dampening Time

The Wideband Modem Resiliency feature enables the CMTS to reduce the occurrence of a particular RF channel event by using the cable rf-change-dampen-time command. This command can also be used to prevent premature CM reconfiguration in the event of a prolonged outage. For example, the failover time of a shared port adapter (SPA) may be 10 seconds. Using the cable rf-change-dampen-time command, you can specify the dampening time such that a SPA failover does not inadvertently trigger a mass reconfiguration of wideband cable modems.

How a CMTS Responds to RF Impairment Recovery

When cable modems report the recovery from downstream RF channel failures and their default downstream service flow has been moved to their primary downstream channel, the response of the CMTS is different between the following two Cisco IOS releases:

•Cisco IOS Release 12.2(33)SCB and later—If a cable modem reports that full service has been restored after downstream RF channel failures, the CMTS forces the CM to perform a MAC reset.

•Cisco IOS Release 12.2(33)SCC and later—If a cable modem reports that full service has been restored, the CMTS does not force the CM to perform a MAC reset, and the CM is kept w-online (the wideband downstream service is restored by the original wideband interface without a MAC reset).

How to Configure Wideband Modem Resiliency

The following tasks describe how to configure the Wideband Modem Resiliency feature on a Cisco uBR10012 router:

•Specifying Persistence Thresholds for Events (required)

•Specifying Persistence Time for RF Channels (optional)

•Verifying Wideband Modem Resiliency (optional)

•Modifying CM Status Reports for Events (optional)

Specifying Persistence Thresholds for Events

Use the cable rf-change-trigger command to configure persistence thresholds (percent and count) for an event before the event triggers an action for the cable modem. When cable modems report downstream RF channel failures and if the configured persistence threshold is not met, the CMTS deals with each CM individually.

If the persistence thresholds for an event are not configured, the state of the non-primary RF channels will always remain up, and the cable modems that report RF failures will be reset after the dampening time specified using the cable rf-change-dampen-time command expires. If both thresholds are configured, then both thresholds must be met before changing the RF channel state to down.

A cable modem that reports impairments will have its downstream service flow(s) modified in order to provide reliable service in the following conditions:

•If the count exceeds the specified number of cable modems but the percent threshold is not met.

•If the percent threshold is met but the count does not reach the specified number of cable modems.

•If all non-primary channels of the cable modem are reported down.

Note In the event of downstream RF channel failures, all downstream service flows (primary and secondary downstream service flows) are moved to the primary DS channel in Cisco IOS Release 12.2(33)SCB and SCB-based releases. In Cisco IOS Release 12.2(33)SCC and later, only the default or primary downstream service flow is moved to the primary DS channel. All secondary downstream service flows remain unchanged.

SUMMARY STEPS

1. enable

2. configure terminal

3. cable rf-change-trigger [percent value] [count seconds]

DETAILED STEPS

Command or Action

Purpose

Step 1

enable
Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 3

cable rf-change-trigger [percent value] [count seconds]
Example:

Router(config)# cable rf-change-trigger percent 50 count 1

Specifies the amount of time an event must persist before it triggers an action for the reporting cable modem.

•percent value—(Optional) Indicates the percentage of cable modems that must report that a particular non-primary (NP) RF channel is down before that channel is removed from the bonding group with that NP RF channel configured. The valid range is from 1 to 100. The default value is 0.

•count seconds—(Optional) Specifies the amount of time in seconds. The valid range is from 1 to 65535. The default value is 0.

Specifying Persistence Time for RF Channels

To configure the amount of time a non-primary RF channel must remain in its current state (either up or down), use the cable rf-change-dampen-time command.

SUMMARY STEPS

1. enable

2. configure terminal

3. cable rf-change-dampen-time seconds

DETAILED STEPS

Command or Action

Purpose

Step 1

enable
Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 3

cable rf-change-dampen-time seconds
Example:

Router(config)# cable rf-change-dampen-time 10

Specifies the amount of time in seconds for a non-primary RF channel to remain in its new state. The default value is 30.

Verifying Wideband Modem Resiliency

Use the following show commands to verify the state of RF channels and the other configuration details:

•show interface rf-status

•show cable rf-status

•show cable modem wideband rcs-status

To verify the logical up and down state for each of the configured RF channels for a wideband interface, use the show interface rf-status command as shown in the following example:
Router# show interface Wideband-Cable1/0/0:3 rf-status
	Logical
RF  Status
--  ------
17  UP
18  UP
19  UP
To verify the logical up and down state of the specified channel number, or the logical state of all RF channels, use the show cable rf-status command as shown in the following example:

Router# show cable rf-status
          Logical  Flap    Flap
RF        Status   Counts  Time
--------  -------  ------  ----
1/0/0 0   UP       0       
      1   UP       0       
      2   UP       0       
      3   UP       0       
      5   UP       0       
      6   UP       0       
      7   UP       0       
      8   UP       0       
      9   UP       0       
      10  UP       0       
      11  UP       0       
      12  UP       0       
      13  UP       0       
      14  UP       0       
      15  UP       0       
      16  UP       0       
To verify details of events for each RF channel in the cable modem's Receive Channel Configuration (RCC), use the show cable modem wideband rcs-status command as shown in the following example:
Router# show cable modem 0019.474a.c0ba wideband rcs-status
CM  : 0019.474a.c0ba
RF  : 1/0/0 10
  Status                   : UP
  FEC/QAM Failure          : 0         
  Dup FEC/QAM Failure      : 0         
  FEC/QAM Recovery         : 0         
  Dup FEC/QAM Recovery     : 0         
  MDD Failure              : 0         
  Dup MDD Failure          : 0         
  MDD Recovery             : 0         
  Dup MDD Recovery         : 0         
  Flaps                    : 0         
  Flap Duration            : 00:00
RF  : 1/0/0 11
  Status                   : UP
  FEC/QAM Failure          : 0         
  Dup FEC/QAM Failure      : 0         
  FEC/QAM Recovery         : 0         
  Dup FEC/QAM Recovery     : 0         
  MDD Failure              : 0         
  Dup MDD Failure          : 0         
  MDD Recovery             : 0         
  Dup MDD Recovery         : 0         
  Flaps                    : 0         
  Flap Duration            : 00:00
What to Do Next

If you want to modify the default configuration of events for CM status reports, proceed to the "Modifying CM Status Reports for Events" section.

Modifying CM Status Reports for Events

You can enable or modify the following ten CM status events per interface using the cable cm-status enable command:

1. Secondary channel MDD time-out

2. QAM/FEC lock failure

3. Sequence out of range

4. MDD recovery

5. QAM/FEC lock recovery

6. T4 time-out

7. T3 re-tries exceeded

8. Successful ranging after T3 re-tries exceeded

9. CM operating on battery backup

10. CM returned to A/C power

The following events are enabled by default on a cable or modular cable interface:

•Secondary channel MDD time-out

•QAM/FEC lock failure

•MDD recovery

•QAM/FEC lock recovery

SUMMARY STEPS

1. enable

2. configure terminal

3. interface cable slot/subslot/port

4. cable cm-status enable range

DETAILED STEPS

Command or Action

Purpose

Step 1

enable
Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface cable slot/subslot/port
Example:

Router(config)# interface cable8/0/0

Specifies the primary cable interface and enters interface configuration mode. The following are the valid values:

•slot = 5 to 8

•subslot = 0 or 1

•port = 0 to 4 (depending on the cable interface)

Step 4

cable cm-status enable range
Example:

Router(config-if)# cable cm-status enable 6-9

Enables a particular CM status event on a primary cable interface. The valid range is 1 to 10.

The following events are enabled by default on cable and modular cable interfaces:

•Secondary channel MDD time-out

•QAM/FEC lock failure

•MDD recovery

•QAM/FEC lock recovery

To disable a CM status event, use the no form of the cable cm-status enable command.

Configuration Example for Wideband Modem Resiliency

The following example shows how to configure the Wideband Modem Resiliency feature by specifying the dampening time and persistence thresholds for non-primary RF channels:
Router# configure terminal
Router(config)# cable rf-change-dampen-time 40
Router# configure terminal
Router(config)# cable rf-change-trigger percent 50 count 1
Additional References

The following sections provide references related to the Wideband Modem Resiliency feature.

Related Documents

Related Topic

Document Title

Commands on the Cisco CMTS (universal broadband) routers

Cisco IOS CMTS Cable Command Reference

http://www.cisco.com/en/US/docs/ios/cable/command/reference/cbl_book.html

Cisco DOCSIS 3.0 Downstream Solution

Cisco DOCSIS 3.0 Downstream Solution Design and Implementation Guide

http://www.cisco.com/en/US/docs/cable/cmts/wideband/solution/guide/release_2.0/ds_solu.html

Cisco Cable Wideband Solution Design

Cisco Cable Wideband Solution Design and Implementation Guide

http://www.cisco.com/en/US/docs/cable/cmts/wideband/solution/guide/release_1.0/wb_solu.html

Standards

Standard

Title

CM-SP-MULPIv3.0-I08-080522

DOCSIS 3.0 MAC and Upper Layer Protocol Interface Specification

Technical Assistance

Description

Link

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Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport

Feature Information for Wideband Modem Resiliency

Table 2 lists the features in this module and provides links to specific configuration information. Only features that were introduced or modified in Cisco IOS Release 12.2(33)SCB or a later release appear in the table.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 2 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 2 Feature Information for Wideband Modem Resiliency

Feature Name

Releases

Feature Information

Wideband Modem Resiliency

12.2(33)SCB

The Wideband Modem Resiliency feature provides the best possible service in the event of non-primary RF channel disruptions.

The following sections provide information about this feature:

•How to Configure Wideband Modem Resiliency

•Configuration Example for Wideband Modem Resiliency

The following commands were introduced or modified:

•cable rf-change-dampen-time

•cable rf-change-trigger

•cable cm-status enable

•show interface rf-status

•show cable rf-status

•show cable modem wideband rcs-status

•show cable modem summary wb-rf

•clear cable modem cm-status

•clear cable modem rcs-counts

•clear cable rf-status

•debug cable wbcmts resiliency

•show cable flap-list wb-rf

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