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Cisco 6000 Series IP DSL Switches

Field Notice: ATUC-1-4DMT to ATUC-8-DMT-1 Migration May Require Profile Changes


June 28, 2001


Products Affected

Product

Comments

ATUC-1-4DMT

800-05262-03

ATUC-8-DMT-1

800-06778-03

Problem Description

Some customers may experience degraded performance, training difficulties, or reliability issues when migrating from the ADI-based ATUC-1-4DMT Line Card to the GlobeSpan (GSI)-based ATUC-8-DMT-1 Line Card.

Background

Profile changes are recommended for customers encountering performance, training, or reliability issues when upgrading from the ATUC-1-4DMT to the ATUC-8-DMT-1. These changes address chip set interoperability with third party ADI-based Customer Premises Equipment (CPE), Alcatel-based CPE, and Cisco CPE.

Problem Symptoms

After migrating to ATUC-8-DMT-1, the following issues may be observed:

  • Cisco 677 or Third Party CPE using ADI firmware drop train, lose connections, or retrain.

  • Performance issues affecting ADI-based and GSI-based CPE

Workaround/Solution

  1. If you are using a Cisco 677 or Third Party CPE which use the ADI firmware and experience loss of connection or retraining, please note that this issue has been addressed in Cisco IOS® software release 12.1(7)DA2 and later. If you are currently unable to upgrade to this Cisco IOS software level, the following short-term workaround is provided as an alternative:

    1. Set the downstream interleave max bit rate to 768 Kbps or higher

    2. Set the downstream interleave delay to 16 ms

    3. Disable trellis (see point 2 below)

    Testing has shown that different combinations of interleave delay, downstream bit rate, and loop length can cause the CPE not to maintain connection or to retrain in an ATUC-8-DMT-1 environment when using the Cisco 677 or any Third Party CPE with ADI firmware 2.0(BE2D) and 2.2(BE04). The above configuration changes reflect the most stable settings for most environments, but as a long-term solution, customers are advised to upgrade to Cisco IOS software release 12.1(7)DA2, scheduled for release in July 2001.

  2. If you are experiencing performance issues after upgrading to the ATUC-8-DMT-1, please verify that trellis is correctly enabled or disabled (as required by the CPE chip set). These settings are independent of the Cisco IOS software revision used.

    1. For ADI-based CPE (Cisco 677 or Third Party CPE), it is recommended that you DISABLE trellis. Testing has shown performance issues with trellis enabled on ADI chip sets.

    2. For Alcatel-based CPE (Cisco 827, Cisco 1417, SOHO 77, ADSL WIC, or Third Party CPE), it is recommended that you ENABLE trellis. Alcatel algorithms are maximized for trellis encoding. Alcatel-based CPE will not hold train with trellis disabled and maximum downstream rates below 1Mbps.

  3. If you are experiencing issues with your ADI-based CPE dropping train after upgrading from ATUC-1-4DMT to ATUC-8-DMT-1, set the subscriber profile downstream between 3dB (minimum) and 6dB (preferred).

    In an ATUC-1-4DMT environment using the Cisco 677 or Third Party CPE with ADI firmware 2.0(BE2D), 2.2(BE04), and 3.0(BE70), it is possible to set the subscriber profile downstream margin to 0dB. The actual value used by the ADI chipset with a 0dB setting was 3dB. With the GSI-based ATUC-8-DMT-1 line card, the card will attempt to use the 0dB setting, resulting in train drops. To achieve performance levels similar to the ATUC-1-4DMT, the margin on the ATUC-8-DMT-1 must be set to a minimum of 3dB.

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:

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