DTI Offset

First Published: January 8, 2009

Last Updated: March 20, 2009

 

The Cisco RF Gateway 10 (RFGW-10) Universal Edge Quadrature Amplitude Modulation (UEQAM) supports the DOCSIS Timing Interface (DTI) Offset feature to enable Data Over Cable Service Interface Specification (DOCSIS) timing offset adjustment.

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 find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the “Feature Information for DTI Offset” 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 DTI Offset

  • The QAM mode should be in Downstream External PHY Interface (DEPI) mode to add the offset values per QAM.

Restrictions for DTI Offset

  • The acceptable range of offset value is 0 to 32768 in the unit of 1/10.24 MHz (97.65625 nsec) or ticks.

Information About DTI Offset

The DTI Offset feature enables DOCSIS timing offset adjustment per channel in the Cisco RFGW-10 UEQAM line card. You should measure the actual timing offset adjustment on each QAM channel. To configure all the QAM ports to the same timing offset, use the port range command. With this command, you can configure an entire chassis with the same timing offset.

Redundancy Support

In a line card redundancy scenario, the timing offset command is synchronized to the redundant line card like other QAM configuration commands. The Standby line card will have the same timing offset setting as the Active line card. If the Active and the Standby line cards have different timing offsets in the hardware, then the operator must adjust the timing offset for every QAM.

How to Configure DTI Offset

This section describes how to configure DTI Offset in Cisco RFGW-10 UEQAM:

Setting the Timing Offset Adjustment at the RF Port Level

This section describes how to set the timing offset adjustment at the RF port level using the CLI.

Prerequisites

The prerequisites for setting the timing offset adjustment at RF port level are:

  • For the port level command, all QAM channels in the port should be in DEPI mode.
  • You should measure the offset on the CMTS to measure the offset change required for each QAM.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface qam slot/port

4. cable depi offset n

DETAILED STEPS

Command or Action
Purpose

Step 1
enable
 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2
configure terminal
 
Router# configure terminal

Enters global configuration mode.

Step 3
interface qam slot/port
 
Router(config)# interface qam 3/1

Configures the interface at the port level in the line card and enters interface configuration mode.

Step 4
cable depi offset n
 
Router(config-if)# cable depi offset 950

Adjusts the DOCSIS timing offset.

The offset value ranges from 0 to 32768 in the unit of 1/10.24 MHz (97.65625 nsec) or ticks.

Examples

The following example shows how to configure the timing offset adjustment on slot 7, RF port 3:

Router (config)# interface qam 7/3
Router (config-if)# cable depi offset 950
 

All the QAM channels in RF port 3 in slot 7 (QAM 7/3.1, QAM 7/3.2, QAM 7/3.2, and QAM 7/3.4) are configured with the new offset value.

In the example, the time stamp is reduced by 950 ticks. If the cable modem attached to QAM channel 1 in RF port 3 shows the timing offset as 2000, the new timing offset value is adjusted to 1050. If the cable modem attached to QAM channel 2 in RF port 3 shows the timing offset as 900, then the new timing offset is –50.

Note If the line card is part of the line card redundancy (LCRED) configuration, qam-red should be used instead of qam for the QAM ports in the interface qam command.

Setting the Timing Offset Adjustment at the QAM Level

This section describes how to set the timing offset adjustment at the QAM level using the CLI.

Prerequisites

  • All the QAM channels within the port must be in DEPI mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface qam slot/port.channel

4. cable depi offset n

DETAILED STEPS

Command or Action
Purpose

Step 1
enable
 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2
configure terminal
 
Router# configure terminal

Enters global configuration mode.

Step 3
interface qam slot/port.channel
 
Router(config)# interface qam 3/1.1

Configures the interface on the QAM line card and enters interface configuration mode.

Step 4
cable depi offset n
 
Router(config-if)# cable depi offset 150

Adjusts the DOCSIS timing offset.

The offset value ranges from 0 to 32768 in the unit of 1/10.24 MHz (97.65625 nsec) or ticks.

Examples

The following example shows how to configure the timing offset adjustment on slot 7, RF port 3, channel 1:

Router (config)# interface qam 7/3.1
Router (config)# cable depi offset 150
 

The timing offset value of 7/3.1 channel will only be adjusted.

In the above example, the time stamp is adjusted by 150 ticks. If the cable modem attached to slot 7, RF port 3, QAM channel 1 shows the timing offset as 1000, the new timing offset value is adjusted to 850. The timing offset value of the cable modems attached to the other QAM channels in slot 7, RF port 3 are not adjusted.

Note If the line card is part of the line card redundancy (LCRED) configuration, qam-red should be used instead of qam for the QAM interfaces in the interface qam command.

Setting the Timing Offset Value for a Chassis

This section describes how to set the same timing offset adjustment at the chassis level using the CLI.

Prerequisites

  • All the line cards must be in DEPI mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface range qam slot/port range, qam slot/port range,...

4. cable depi offset n

DETAILED STEPS

Command or Action
Purpose

Step 1
enable
 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2
configure terminal
 
Router# configure terminal

Enters global configuration mode.

Step 3
interface range qam slot/port range, qam slot/port range,...
 
Router(config)# interface range qam 3/1 - 12, qam 4/1 - 12

Configures the interface at a chassis level for all the line cards and enters interface configuration mode.

Step 4
cable depi offset n
 
Router(config-if)# cable depi offset 100

Adjusts the DOCSIS timing offset.

The offset value ranges from 0 to 32768 in the unit of 1/10.24 MHz (97.65625 nsec) or ticks.

Examples

The following example shows how to configure the timing offset adjustment on line card slots 3 and 5, RF port range 1 to 12:

Router (config)# interface range qam 3/1 - 12, qam 5/1 - 12
Router (config)# cable depi offset 150
 

The timing offset value of line card slots 3 and 5 is adjusted by 150 ticks.

Displaying the Timing Offset Value

To display the timing offset value, use the following command:

show cable depi-sessions offset
 

The following is sample output of the command:

Router# show cable depi-sessions offset
Qam-info Offset
x-----------x-------------------
Qam3/01.1 639
Qam3/01.2 640
Qam3/01.3 641
Qam3/01.4 642
Qam3/02.1 639
Qam3/02.2 640
Qam3/02.3 641
Qam3/02.4 642

Additional References

The following sections provide references related to the DTI Offset feature.

Related Documents

Related Topic
Document Title

Cisco RFGW-10 commands

Cisco RF Gateway 10 Command Reference http://www.cisco.com/en/US/docs/cable/rf_gateway/command/reference/RFGW-10_Book.html

New Software Features in Cisco IOS Release 12.2SQ

Cisco RF Gateway 10 Software Feature and Configuration Guide

http://www.cisco.com/en/US/docs/cable/rf_gateway/feature/guide/rfgw_scg.html

Standards

Standard
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

MIBs

MIB
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC
Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—

Technical Assistance

Description
Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

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

http://www.cisco.com/techsupport

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco RF Gateway 10 Command Reference at http://www.cisco.com/en/US/docs/cable/rf_gateway/command/reference/RFGW-10_Book.html. For information about all Cisco IOS commands, use the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or the Cisco IOS Master Command List, All Releases, at http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html.

  • interface qam slot/port
  • interface qam slot/port.channel
  • interface range qam slot/port range, qam slot/port range,...
  • cable depi offset n
  • show cable depi-sessions offset

Feature Information for DTI Offset

Table 1 lists the release history for this feature.

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, Catalyst OS, and Cisco IOS XE 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 1 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 1 Feature Information for DTI Offset

Feature Name
Releases
Feature Information

DTI Offset

12.2(44)SQ

This feature was introduced in the Cisco IOS Release 12.2(44)SQ to support the Cisco RF Gateway 10.

The following commands were introduced or modified:

  • interface qam slot/port
  • interface qam slot/port.channel
  • interface range qam slot/port range, qam slot/port range,...
  • cable depi offset n
  • show cable depi-sessions offset

Glossary

DEPI—Downstream External PHY Interface

DOCSIS—Data Over Cable Service Interface Specification

DTI—DOCSIS Timing Interface

EQAM—Edge Quadrature Amplitude Modulation. A network element, which receives MPEG-TS frames over a network interface such as Ethernet, and modulates them onto QAM carriers for use on an HFC plant.

LCRED—Line Card Redundancy

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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

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