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CRC Error's and SNR

Discussion in 'Networks & Internet Connectivity' started by PiKe, 12 Apr 2006.

  1. PiKe

    Caporegime

    Joined: 18 Oct 2002

    Posts: 25,122

    Location: Lake District

    I've had DSL for 3 years or so, for as long as I remember I've always had CRC error's but on services 2mbit and below they didn't effect the speed of my service or cause disconnects. However on Max they're causing me headaches, the SNR margin is above the 6dB limit BT set for Max services all the time however, CRC error's appear to roll in which I cannot understand.

    Why is the data getting corrupted if there is sufficiant signal to noise ratio?

    I can sync at 8mbit and there's margin to spare so I know the line would be able to take it if it wasn't for the CRC Error's. I sometimes receive several hundred in just a few seconds causing the router to drop the connection and resync with the exchange (sometimes at a higher(?) speed). My lines current sat at 5mbit with 15dB SNR and this moment in time I'm getting 2 CRC Errors per minute.

    What's causing the CRC Error's and if it's noise, why isnt it being reflected in the SNR?
     
  2. Bin Boy

    Gangster

    Joined: 3 Nov 2005

    Posts: 217

    Location: N.Ireland

    Anything below 9dB SNR for downstream is going to cause problems, there could be a better pair of wires at your street cabinet which would yield better results, but your line speed will have to drop down to 15dB + - so your modem can handle the CRC error's.

    You can try Test Line Dial - 17070 for a silent test and listen to hear for any noise on the line, then it could be reported has a fault.

    Or try this http://yarwell.blogspot.com/2005_08_01_yarwell_archive.html
     
    Last edited: 12 Apr 2006
  3. PiKe

    Caporegime

    Joined: 18 Oct 2002

    Posts: 25,122

    Location: Lake District

    I've seen people with very marginal stats getting little to no CRC errors on their line, yet me, with plenty of signal, manages to clock up thousands an hour.

    I've already explored the possibility of the phoneline fault, a battery fault was found but fixing it did precisely jack.

    Ring wire trick isnt possible because I have no slave sockets, so theres no ring wire to disconnect in the first place.

    Thanks for your reply though.
     
  4. Bin Boy

    Gangster

    Joined: 3 Nov 2005

    Posts: 217

    Location: N.Ireland

    Well i know about CRC errors comes down to a noisy set of wires and that many modems give out the not so accurate of readings, but good luck dude :)
     
  5. PiKe

    Caporegime

    Joined: 18 Oct 2002

    Posts: 25,122

    Location: Lake District

    Tried 3 routers, 2 DrayTek and 1 Billion, so I can't see it being that.
     
  6. OllyM

    Soldato

    Joined: 16 Aug 2004

    Posts: 6,218

    Location: New Jersey, USA

    Sweeping statement, that.

    Both of my routers are synced at 8128/832, and the SNR on one is 4dB, the other is 6dB. No problems at all. Neither have lost sync since they've been Max'd, apart from when I've been playing around.
     
  7. Bin Boy

    Gangster

    Joined: 3 Nov 2005

    Posts: 217

    Location: N.Ireland

    Well i just got upgraded this week to office max and have lost sync four times today and the down stream SNR is 6.1

    From what have been reading on adslguide and from other users is that after the ten days there will be a - + on what final speed users may get, different lines other than just one line there will be differences, i dare say that for my line that an increase in SNR on the downstream say 9dB may just do the trick, but will give me a slow speed.