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What are CRC errors on DSL lines and how can I fix them on a T5 switch?

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TitleWhat are CRC errors on DSL lines and how can I fix them on a T5 switch?
Objective
What are CRC Errors, also referred to as "Uncorrected Errors" on the DSL ports of a T5 switch, and how can I fix or limit them?
Environment
  • T5 PowerBroadband Switch
  • TS-524
  • TS-0524
  • PBN
  • Private Broadband Networks
  • T5 Switch
  • TW-522
  • TW-511
  • TW-510
  • T5 Wi-Fi over VDSL2
Procedure
If you have a DSL port that is experiencing many Uncorrected Errors, you can make several configuration changes on the T5 switch to help alleviate or limit them.  Use one or all of the following configuration options to help reduce or remove CRC errors:
  1. Enable Interleaver - Interleaver is another layer of error correction that can be configured to help reduce CRCs.  It adds a very small amount of latency to the DSL, but should not impact most applications. 
  2. Lower the configured maximum DSL speed - lowering the speed will allow the DSL line to have more margin and makes the line more resilient to the effects of induced noise.
  3. Raise the link margin - raising the link margin basically accomplishes the same thing as lowering the maximum link speed.  
All of these options can be configured on the T5 GUI.  Go to Configure -> DSL screen.
Additional notes
  • CRC (Uncorrected Errors) are usually caused by Induced Noise on the DSL lines.  The noise can be from a large motor, fluorescent lights,  adjacent DSL lines and various other sources that are close to the DSL lines or blocks.
  • CRC errors occur during transmission of a DSL packet and are not recoverable at the receiving end, so the packet is dropped. 
  • FEC errors refer to Forward Error Correction which are packets that had errors during transmission, but the packet was repairable at the receiving end, so the packet was not dropped.

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