DOCSIS3.1 Downstream Resiliency for OFDM channel

This document describes how to configure the DOCSIS3.1 Downstream Resiliency for OFDM channel on the Cisco cBR Series Converged Broadband Router.

Your software release may not support all the features that are documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. The Feature Information Table at the end of this document provides information about the documented features and lists the releases in which each feature is supported.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/. An account on http://www.cisco.com/ is not required.

Hardware Compatibility Matrix for the Cisco cBR Series Routers


Note
The hardware components that are introduced in a given Cisco IOS-XE Release are supported in all subsequent releases unless otherwise specified.
Table 1. Hardware Compatibility Matrix for the Cisco cBR Series Routers

Cisco CMTS Platform

Processor Engine

Interface Cards

Cisco cBR-8 Converged Broadband Router

Cisco IOS-XE Release 16.5.1 and Later Releases

Cisco cBR-8 Supervisor:

  • PID—CBR-SUP-250G

  • PID—CBR-CCAP-SUP-160G

Cisco IOS-XE Release 16.5.1 and Later Releases

Cisco cBR-8 CCAP Line Cards:

  • PID—CBR-LC-8D30-16U30

  • PID—CBR-LC-8D31-16U30

  • PID—CBR-RF-PIC

  • PID—CBR-RF-PROT-PIC

  • PID—CBR-CCAP-LC-40G

  • PID—CBR-CCAP-LC-40G-R

  • PID—CBR-CCAP-LC-G2-R

  • PID—CBR-SUP-8X10G-PIC

  • PID—CBR-2X100G-PIC

Digital PICs:

  • PID—CBR-DPIC-8X10G

  • PID—CBR-DPIC-2X100G

Cisco cBR-8 Downstream PHY Module:

  • PID—CBR-D31-DS-MOD

Cisco cBR-8 Upstream PHY Modules:

  • PID—CBR-D31-US-MOD

Note

Do not use DPICs (8X10G and 2x100G) to forward IP traffic, as it may cause buffer exhaustion, leading to line card reload.

The only allowed traffic on a DPIC interface is DEPI, UEPI, and GCP traffic from the Cisco cBR-8 router to Remote PHY devices. Other traffic such as DHCP, SSH, and UTSC should flow via another router, since DPICs cannot be used for normal routing.

Information about DOCSIS3.1 Downstream Resiliency for OFDM Channel

When DOCSIS3.1 CM reports non-primary RF channel failure for SCQAM or OFDM channel, actions performed by downstream resiliency is the same as DOCSIS3.0 CM. In other words, if RF channel impairment is below the resiliency threshold, CMs service flows are moved to Resiliency Bonding Group (RBG) or Narrow Band (NB) interface. If RF channel impairment is above the resiliency threshold, the impaired RF channel is temporarily removed from the bonding group.

The following table summarizes the CM-STATUS events for OFDM channel, and the action to be taken by the downstream resiliency module:

Table 2. CM-STATUS events for OFDM channel

Event Type Code

Event Description

DS Resiliency Action

1

MDD timeout

Move CM’s service flows to RBG/NB or suspend RF from BG.

2

FEC lock failure

Move CM’s service flows to RBG/NB or suspend RF from BG.

4

MDD recovery

Move CM’s service flows back to original BG.

5

FEC lock recovery

Move CM’s service flows back to original BG.

16

DS OFDM profile failure. A loss of FEC lock on one of the assigned downstream OFDM profiles of a channel.

DS OFDM Profile Manager will handle this event and take action.

20

NCP profile failure. Loss of FEC lock on NCP.

Move CM's service flows to RBG/NB or suspend RF from BG.

21

Loss of FEC lock on the PLC.

Move CM's service flows to RBG/NB or suspend RF from BG.

22

NCP profile recovery.

Move CM's service flows back to original BG.

23

FEC recovery on PLC channel.

Move CM's service flows back to original BG.

24

FEC recovery on OFDM profile.

Recovery of impairment reported by event 16. DS OFDM Profile Manager will handle this event and take action.

How to Configure DOCSIS3.1 Downstream Resiliency for OFDM Channel

Configuring DOCSIS3.1 Downstream Resiliency for OFDM Channel

User must configure the command cable rf-change-trigger percent value count number to enable the downstream resiliency functionality.

To configure the trigger thresholds specific to OFDM RF impairment, follow the steps below:

enable 
configure terminal 
cable ofdm-rf-change-trigger percent value counter number [no-ncp-plc]

Starting from Cisco IOS XE Fuji 16.10.1d release, you can exclude NCP and PLC reports separately by following these steps:


enable 
configure terminal 
cable ofdm-rf-change-trigger percent value counter number [no-ncp] [no-plc]

Trigger thresholds value and number apply globally to the non-primary OFDM RF channels. If this command is not configured, the trigger thresholds configured by the command cable rf-change-trigger percent value count number will be used for the non-primary OFDM channels.

With no-ncp-plc configured in the command, this feature will not take any action when CM reports CM-STATUS-EVENT 20 or 21.


Note

The cable rf-change-trigger percent value count number command is optional and the configured trigger thresholds apply to non-primary OFDM channels only.

Displaying OFDM Specific CM-STATUS Events

To display the statistics of the OFDM specific CM-STATUS events, use the show cable modem wideband rcs-status command as shown in the example below: 

router#show cable modem 4800.33ea.7072 wideband rcs-status verbose 
CM  : 4800.33ea.7072
RF  : 3/0/0 0
  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  : 3/0/0 1
  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  : 3/0/0 159
  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         
  NCP PROF Failure         : 2         May 8  15:14:24
  Dup NCP PROF Failure     : 0         
  NCP PROF Recovery        : 1         May 8  15:15:18
  Dup NCP PROF Recovery    : 0         
  PLC Lock Failure         : 1         May 8  15:14:47
  Dup PLC Lock Failure     : 0         
  PLC Lock Recovery        : 1         May 8  15:15:46
  Dup PLC Lock Recovery    : 0         
  Flaps                    : 0         
  Flap Duration            : 00:00
  OFDM Profile Id : 2
  Status                   : UP
  Profile Failure          : 1         May 8  15:16:18
  DUP Profile Failure      : 0         
  Profile Recovery         : 1         May 8  15:16:44
  DUP Profile Recovery     : 0

Managing Profile Zero CM-STATUS Events

A cable modem sends a CM-STATUS event 16 message to the CMTS to indicate a downstream OFDM profile failure. CMTS would react to CM-STATUS events by either downgrading the profile or changing the cable modem status to partial service.

When a cable modem reports a CM-STATUS event 16 message for profile 0, the profile is neither added to the unfit list, nor any action is taken. As a result, the cable modem continues to send data on OFDM profile 0 which can lead to to packet loss. This can result in FEC errors on profile 0 for the cable modem. Periodic RxMER measurements do not show the problem, which leaves the cBR-8 still scheduling data on an OFDM channel using profile 0. This may cause downgraded performance for the cable modem.

Downstream Resiliency Enhancements for Profile 0

Table 3. Feature History

Feature Name

Release Information

Feature Description

Downstream Resiliency Enhancements

Cisco IOS XE Dublin 17.12.1z

With this release, the CMTS response to a cable modem's CM-STATUS event 16 message is optimized for profile 0.

  • CM-STATUS Event 16 on profile 0 operates as a downstream impairment.

  • CM-STATUS Event 24 on profile 0 operates as a downstream impairment recovery.

Profile 0 is processed in the same way as FEC Loss or MDD timeout and hence experiences the same benefits of better performance and reduced packet loss.

Command introduced: ofdm-rf-change-trigger prof-zero-fail dampen-time seconds recovery-multiplier number .

When a cable modem sends a CM-STATUS event 16 message to the CMTS to indicate a downstream OFDM profile failure, CMTS does not downgrade the profile or change the cable modem status to partial service. Instead, downstream resiliency rules are applied, resulting in a better handling of Profile 0.

Handling CM-STATUS Event 16

When a CMTS handles a CM-STATUS event 16 on profile 0 as a downstream impairment:

  • Downstream resiliency moves the OFDM channel to the Down state after the configured dampen-time .

  • Cable modem enters a downstream partial-service (p-online) state.

  • Cable modem downstream service flows (SF) move to RBG or NB with existing downstream resiliency logic.

Handling CM-STATUS Event 24

When a CMTS handles a CM-STATUS event 24 on profile 0 as a as a downstream impairment recovery:

  • Downstream resiliency uses this event to indicate the recovery of event 16 impairment.

  • CMTS moves the OFDM channel to Up state after the configured duration (dampen time * recovery multiplier).

  • Cable modem moves back to wideband online (w-online) state.

  • Cable modem downstream service flows (SF) move to the original bonding group existing downstream resiliency logic.

See

Configuring Downstream Resiliency for Profile 0

Configuring downstream resiliency for profile 0 is disabled by default. This sample configuration shows how to configure Downstream Resiliency for profile 0: 


Router# configure terminal
Router(config)# cable ofdm-rf-change-trigger prof-zero-fail dampen-time 20 recovery-multiplier 2

  • Use the dampen-time seconds option to specify the time in seconds for a non-primary RF channel to remain in its current state before downstream resiliency processes a CM-STATUS event.

  • Use the recovery-multiplier to set an event specific recovery delay that is equal to the dampen-time in seconds times the recovery-multiplier value.

The following example shows how to disable downstream resiliency for profile 0:


Router# configure terminal
Router(config)# no cable ofdm-rf-change-trigger

Disabling downstream resiliency for profile 0, resets dampen-time and recovery-multiplier values to 0. No resiliency action for CM-STATUS 16 and 24 is performed for profile 0 if this feature is disabled. The following example shows a sample configuration to disable the feature. 


Router# configure terminal
Router(config)# no cable ofdm-rf-change-trigger
Router(config)# end

Router# show run all | sec prof-zero-fail
   cable ofdm-rf-change-trigger prof-zero-fail dampen-time 0 recovery-multiplier 0

Feature Information for DOCSIS3.1 Downstream Resiliency for OFDM Channel

Use Cisco Feature Navigator to find information about the platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to the https://cfnng.cisco.com/ link. An account on the Cisco.com page is not required.


Note

The following table lists the software release in which a given feature is introduced. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Table 4. Feature Information for DOCSIS3.1 Downstream Resiliency for OFDM Channel

Feature Name

Releases

Feature Information

DOCSIS3.1 Downstream Resiliency for OFDM Channel

Cisco IOS XE Everest 16.7.1

This feature was integrated on the Cisco cBR Series Converged Broadband Routers.