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I keep asking the same question everywhere and I never once had a satisfying answer.

What causes CRC erroring to happen?

This is my current DSL log.

DSL LOG

I have examined the wire from the local box to the end. I spotted no single sign of defect. The wire was pretty solid even tho it barely contains any copper in it. I have examined and cleaned the contacts also near the DSL modem and around the splitter.

The SNR margin isn't great, but looks fine. The line attenuation is beyond outstanding. I have 2 phones connected with an ADSL splitter across the line (one near the modem and the other somewhere else [both of them on a splitter]).

I get these CRC errors occasionally and sometimes even DSL interruptions. However I am still getting the same errors with/without phones connected and even without any splitter (just the modem connected and nothing else)

Assuming that the line is connected properly from the start to the end and assuming that the local box have no issues, what could be causing CRC errors on my DSL line?

CRC can be anything from 1 to thousands on upstream or downstream (mostly downstream)

Another thing to mention is that I should be getting 2045 kbps upload, but the current low SNR on the downstream doesn't allow the ISP to activate Annex M modulation which would drop the downstream SNR in order to left the upstream SNR up

Islam Ghunym
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  • All possible reasons for CRC errors to happen on ADSL connection ........ There can be numerous hardware and firmware reasons for getting Cyclic Redundancy Check (CRC) Errors . I guess that is why you are not getting complete and satisfying answers – John May 29 '23 at 13:02
  • @John do you mean if I change the modem or it's firmware, I may solve the problem? – Islam Ghunym May 29 '23 at 13:05
  • That may be something you should do. I just made major and complete patch to the cable coming into my residence (outside construction issues) and that has made an immense improvement. – John May 29 '23 at 13:07
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    First step is to speak to your ISP. – DavidPostill May 29 '23 at 13:10
  • DSL issues have nothing to do with the ISP here. line issues or service delivery are not their responsibility. They only serve by allowing me to access the internet through a gateway placed somewhere by the landlines service. However there is no problem if the modem was placed near the local lines box directly which means it is not their fault either. – Islam Ghunym May 29 '23 at 13:22
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    It could be any number of things. Random line noise that provokes CRC error can be created by any radio or electronic equipment. A badly shielded microwave oven, military radar or radio installations, baby monitors or even just LED lighting can emit noise which can interfere with digital signals. The copper used in phone lines is not particularly high quality and depending on the installer could be worse than bargain basement garbage. *Some* errors are expected, hence ADSL uses error detection and correction, which TCP/IP reinforces. – Mokubai May 29 '23 at 13:32
  • Based on your latest comment (which should be added to the body of the question because it is pertinent) The issue is most likely on your wires and in your house. So replace your wires and if that doesn't solve things start following the wire party and identifying and isolating any other sources of interference. There is no way we can help with this besides the suggestions we've given. – music2myear May 29 '23 at 13:43

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