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    Lots of CRC errors but seems OK

    This is a discussion on Lots of CRC errors but seems OK within the Sky Broadband help forums, part of the Sky Broadband help and support category; I'm on broadband mid with a white Sky Netgear running V1.03.87 (CU3.04) The issue I see is the amount of ...

    1. #1
      starfire's Avatar
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      Lots of CRC errors but seems OK

      I'm on broadband mid with a white Sky Netgear running V1.03.87 (CU3.04)

      The issue I see is the amount of CRC errors (10% of my throughput), along with HEC,ES etc as below.

      I've tried everything, ie direct connection to master socket, disconnected ring wire + all extensions, black sagem router, different ADSL filters etc but still see this.

      The weird thing is, sometimes after a reboot the CRC, ES will stay low for hours/days and then really start clocking up.

      I think its an intermittent line fault myself or an issue with the DSLAM port in the exchange?, or its simply pushing the line too hard at 8MB for my attenuation, but I can reliably download at 800KB/s + with newsbin even with these stats....

      Anyone got any other ideas ?

      adslctl: ADSL driver and PHY status
      Status: ShowtimeRetrain Reason: 0
      Channel: INTR, Upstream rate = 384 Kbps, Downstream rate = 8096 Kbps
      Link Power State: L0
      Mode: G.DMT
      Channel: Interleave
      Trellis: ON
      Line Status: No Defect
      Training Status: Showtime
      Down Up
      SNR (dB): 9.2 14.0
      Attn(dB): 39.0 25.5
      Pwr(dBm): 19.8 0.8
      Max(Kbps): 9504 1248
      Rate (Kbps): 8096 384
      G.dmt framing
      K: 254(0) 13
      R: 12 16
      S: 1 16
      D: 64 8
      ADSL2 framing
      MSGc: 1 1
      B: 254 13
      M: 1 16
      T: 1 1
      R: 12 16
      S: 1.0470 17.1428
      L: 2040 112
      D: 64 8
      Counters
      SF: 7489754 7489830
      SFErr: 781679 8
      RS: 1018606608 31831352
      RSCorr: 83019607 87
      RSUnCorr: 1533369 0

      HEC: 489709 3
      OCD: 0 1
      LCD: 0 0
      Total Cells: 2430469613 0
      Data Cells: 60156318 0
      Drop Cells: 0
      Bit Errors: 0 0

      ES: 89347 0
      SES: 822 0
      UAS: 11 0
      AS: 127327

      INP: 1.50 4.57
      PER: 1.83 1.87
      delay: 16.75 34.28
      OR: 30.56 29.86

      Bitswap: 0 0

      Total time = 1 days 11 hours 22 min 24 sec
      SF = 7489754
      CRC = 781679
      LOS = 0
      LOF = 0
      ES = 89347
      Latest 1 day time = 11 hours 22 min 24 sec
      SF = 2408498
      CRC = 246902
      LOS = 0
      LOF = 0
      ES = 33548
      Latest 15 minutes time = 7 min 24 sec
      SF = 26137
      CRC = 1749
      LOS = 0
      LOF = 0
      ES = 357
      Previous 15 minutes time = 15 min 0 sec
      SF = 52923
      CRC = 5005
      LOS = 0
      LOF = 0
      ES = 763
      Previous 1 day time = 24 hours 0 sec
      SF = 5081256
      CRC = 534777
      LOS = 0
      LOF = 0
      ES = 55799
      15 minutes interval [-30 min to -15 min] time = 15 min 0 sec
      SF = 52982
      CRC = 3921
      LOS = 0
      LOF = 0
      ES = 728
      15 minutes interval [-45 min to -30 min] time = 15 min 0 sec
      SF = 52923
      CRC = 3958
      LOS = 0
      LOF = 0
      ES = 712
      15 minutes interval [-60 min to -45 min] time = 15 min 0 sec
      SF = 52923
      CRC = 4801
      LOS = 0
      LOF = 0
      ES = 752
      Showtime Drop Reason: 0
      Last Retrain Reason: 0


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    3. #2
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      Re: Lots of CRC errors but seems OK

      Your CRC level is absolutely horrendous and must be lowering your throughput. But if your connection is relatively stable, then maybe you should just live with it.

      What is causing it is hard to say. You are on G.DMT so your sync is limited to around 8meg even though your attenuation would, in theory, support a higher sync on ADSL2+.

      Raising your noise margin, either by doing it yourself or asking Sky to cap you would reduce those errors. But if you're happy I'd advise leaving it alone.

    4. #3
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      Re: Lots of CRC errors but seems OK

      I should say I was originally on Max (hence my forum profile) but as it only connected at G.DMT and not ADSL2+ I asked them to drop it to Mid as there was no benefit (apart from unlimited downloads).

      We used to have a problem very occasionally with noise on the line and the modem losing sync but that hasn't happened for some time now.

      Could Sky ascertain what is causing the CRC errors with a linecheck of some type? I personally doubt it but thought I'd ask.

    5. #4
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      Re: Lots of CRC errors but seems OK

      All Sky could do is ask BT to investigate.

    6. #5
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      Re: Lots of CRC errors but seems OK

      Just as a followon I forced the SNR to 12 in the GUI and looks like this has sorted it (so far), guess trying to push the line at 8Mbps was too much and the slightly slower speed helps:-

      adslctl: ADSL driver and PHY status
      Status: ShowtimeRetrain Reason: 0
      Channel: INTR, Upstream rate = 384 Kbps, Downstream rate = 7616 Kbps
      Link Power State: L0
      Mode: G.DMT
      Channel: Interleave
      Trellis: ON
      Line Status: No Defect
      Training Status: Showtime
      Down Up
      SNR (dB): 12.0 13.0
      Attn(dB): 39.0 26.0
      Pwr(dBm): 19.8 0.6
      Max(Kbps): 8448 1184
      Rate (Kbps): 7616 384
      G.dmt framing
      K: 239(0) 13
      R: 16 16
      S: 1 16
      D: 64 8
      ADSL2 framing
      MSGc: 1 1
      B: 239 13
      M: 1 16
      T: 1 1
      R: 16 16
      S: 1.0666 17.1428
      L: 1920 112
      D: 64 8
      Counters
      SF: 3320813 3320777
      SFErr: 6 0
      RS: 225815350 14113302
      RSCorr: 273319 2
      RSUnCorr: 25 0

      HEC: 6 0
      OCD: 0 0
      LCD: 0 0
      Total Cells: 1014021316 0
      Data Cells: 123220420 0
      Drop Cells: 0
      Bit Errors: 0 0

      ES: 4 0
      SES: 0 0
      UAS: 11 0
      AS: 56454

      INP: 2.13 4.57
      PER: 1.86 1.87
      delay: 17.06 34.28
      OR: 30.00 29.86

      Bitswap: 0 0

      Total time = 15 hours 41 min 11 sec
      SF = 3320813
      CRC = 6
      LOS = 0
      LOF = 0
      ES = 4
      Latest 1 day time = 15 hours 41 min 11 sec
      SF = 3320813
      CRC = 6
      LOS = 0
      LOF = 0
      ES = 4
      Latest 15 minutes time = 11 min 11 sec
      SF = 39530
      CRC = 0
      LOS = 0
      LOF = 0
      ES = 0
      Previous 15 minutes time = 15 min 0 sec
      SF = 52864
      CRC = 0
      LOS = 0
      LOF = 0
      ES = 0
      Previous 1 day time = 0 sec
      SF = 0
      CRC = 0
      LOS = 0
      LOF = 0
      ES = 0
      15 minutes interval [-30 min to -15 min] time = 15 min 0 sec
      SF = 52982
      CRC = 0
      LOS = 0
      LOF = 0
      ES = 0
      15 minutes interval [-45 min to -30 min] time = 15 min 0 sec
      SF = 52923
      CRC = 0
      LOS = 0
      LOF = 0
      ES = 0
      15 minutes interval [-60 min to -45 min] time = 15 min 0 sec
      SF = 52923
      CRC = 0
      LOS = 0
      LOF = 0
      ES = 0
      Showtime Drop Reason: 0
      Last Retrain Reason: 0

    7. #6
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      Re: Lots of CRC errors but seems OK

      looking good
      -------------------------------------------



      Useful Sticky: - How To Obtain Your Router Stats, BT Speed Test, Check For Test Socket

    8. #7
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      Re: Lots of CRC errors but seems OK

      Quote Originally Posted by Saturday View Post
      Your CRC level is absolutely horrendous and must be lowering your throughput.
      You think thats bad you gotta check this out




      There is no change in throughput and no connection faults at all
      Dont ask me how this is still going but it is

    9. #8
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      Re: Lots of CRC errors but seems OK

      Quote Originally Posted by Steven_Belfast View Post
      There is no change in throughput
      There must be. Effectively, every CRC was a piece of data which was corrupted and therefore (assuming TCP packets) will have been retransmitted. You can't retransmit data and not be impacting throughput. Whether you notice it or not is a different matter though.

      That level of errors on the upstream would make the connection seem a bit "laggy" (i.e. a bit slow to react when surfing) compared to a side-by-side comparison with a connection without those errors, whereas, a similar level of errors on the downstream would impact measured download speed. Both may not be very noticeable on an IPStream connection which is prone to throughput and latency variations.

      A high level of upstream errors as shown in the stats you posted may indicate a filter problem as the upstream uses frequencies just above those used for voice.

    10. #9
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      Re: Lots of CRC errors but seems OK

      Seriously man there is no change in the speed,
      I know what you mean i cant get over this connect and how its still going

      Na its no a filter i have changed this and i am in the test socket and there is no change,
      But i think the distribution box out side my front door mite have some thing to do with it,
      How ever i am not giving off i just cant get over its still working,

      BT speed tester site findings :

      Your DSL connection rate: 4704 kbps(DOWN-STREAM), 448 kbps(UP-STREAM)
      IP profile for your line is - 4000 kbps
      Actual IP throughput achieved during the test was - 3720 kbps

      I know i should call them to get the profile changed as its been the same from day 1 but cant get the time,

      How messed up is this lol

    11. #10
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      Re: Lots of CRC errors but seems OK

      Quote Originally Posted by Steven_Belfast View Post
      I know i should call them to get the profile changed as its been the same from day 1 but cant get the time
      There's no change anyone could/would make - that's how BT IPStream works.

      Your profile of 4000kbps is exactly right for your sync of 4704kbps, lying as it does, in the range of 4544-5219kbps. Your sync would need to be 5220kbps or above for a period of 3 consecutive days before your profile could rise (4500kbps is the next level up).

     

     
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