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Cisco 6100 Series IP DSL Switches

Field Notice: Trellis Coding Enable Default Recommendations


August 7, 2000



Products Affected

Product

Comments

ATUC-1-4DMT

Leave default for trellis setting to Disable

ATUC-4-FLX-2

Change trellis default setting from Disable to Enable

ATUC-4-FLX-1

Change trellis default setting from Disable to Enable

Problem Description

Trellis Coding is disabled by default on the NI-2 because it is not supported on the ATUC-1-4xDMT card. Trellis coding, however, is supported on the 4xFlexi line card. Additionally, it is preferred that trellis coding be enabled for the 4xFlexi line card, and therefore it should be manually enabled for the 4xFlexi card.

Problem Symptoms

On the 4xDMT ADI-based line card, having trellis coding enabled will decrease link reliability by causing problems training and/or passing data. For some trains on some loops the result is continuous errored seconds, as well as corrupted data in the upstream direction. There is no way to accurately predict when links will be reliable, and therefore, trellis coding is disabled by default on the NI-2 to ensure that it is not accidentally enabled with the 4xDMT line card. Trellis Coding needs to be manually enabled when using the 4xFlexi line card.

Background

Due to a lack of complete support for trellis coding in the firmware from ADI/Aware, Trellis Coding is not supported on the 4xDMT ADI-based line card.

Workaround/Solution

For all 4xDMT (ATUC-1-4DMT) ports in the Digital Subscriber Line Access Multiplexer (DSLAM), make sure that Trellis Coding is disabled in the dsl-profile for those ports. For all 4xFlexi (ATUC-1-4FLX-1 or ATUC-1-4FLX-2) ports in the DSLAM, make sure that Trellis Coding is enabled in the dsl-profile for those ports.

See the documentation at the following location for details on the commands used to change Trellis coding settings on the NI-2:

Enabling and Disabling Trellis Coding

DDTS

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DDTS

Description

CSCdm73343 (registered customers only)

Although turning trellis coding on will work reliably on most loops and most trains. It will not work reliably 100% of the time. For some trains on some loops the result is continuous errored seconds, as well as, corrupted data in the upstream direction. There is no way to accurately predict when it will be reliable. Therefore the recommendation is that Trellis coding should be disabled on the 6260. This will prevent Trellis coding from being used on the link. This will be fixed in a later release.

Cisco IOS Versions Affected

Upgrade Program

How To Identify Hardware Levels

How To Upgrade Software

Physical Replacement of Parts

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: