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    Upstream attenuation halved?

    This is a discussion on Upstream attenuation halved? within the Sky Broadband help forums, part of the Sky Broadband help and support category; Hi folks. Immediately after i had a line fault fixed 29/7/12, i was left with these stats: (full story here: ...

    1. #1
      gymno's Avatar
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      Upstream attenuation halved?

      Hi folks.

      Immediately after i had a line fault fixed 29/7/12, i was left with these stats: (full story here: lift & shift)

      ADSL Link Downstream Upstream
      Connection Speed 19995*kbps 1175*kbps
      Line Attenuation 23.0*dB 14.3*dB
      Noise Margin 7.1*dB 9.0*dB

      Then, over the next 36 hours my downstream noise margin gradually dropped & stabilised at this:

      ADSL Link Downstream Upstream
      Connection Speed 19995*kbps 1175*kbps
      Line Attenuation 23.0*dB 14.3*dB
      Noise Margin 6.1*dB 9.0*dB

      DLM never ran btw. The last time it did was back in february.

      I was slightly peeved, as i assumed that if i ever needed to reboot or disconnect my router, i'd probably lose about 1-1.5mb with that noise margin. No big deal though.
      Downstream noise would fluctuate between 5.8db & 6.2db, upstream would fluctuate between 8.8db & 9.1db.
      No problem...until today.

      I DMZ'd my PS3 for the first time last night, but couldn't detect any improvement (never had a problem with NAT type or anything, just wanted to ensure i was maxing everything).

      Having read that some routers don't fully accept the new settings until after it's been rebooted, i did so today with some trepidation. To my surprise, this happened:

      ADSL Link Downstream Upstream
      Connection Speed 19999*kbps 1175*kbps
      Line Attenuation 23.0*dB 8.0*dB
      Noise Margin 7.4*dB 9.6*dB

      Excellent, i thought. Max speed & healthy noise margins aswell.
      Then i noticed the upstream attenuation. 14.3db down to 8.0db?

      I know i have asked this question before here: ping spikes & upstream attenuation halved & here: lift & shift but i'm just trying to learn about my line & exactly what any of this weirdness might actually mean.
      Last edited by gymno; 14-08-12 at 09:19 PM. Reason: added info


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    3. #2
      gymno's Avatar
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      Re: Upstream attenuation halved?

      Now my pings have shot up:

      PING 212.58.241.131 (212.58.241.131): 56 data bytes
      56 bytes from 212.58.241.131: icmp_seq=0 ttl=247 time=36.6 ms
      56 bytes from 212.58.241.131: icmp_seq=1 ttl=247 time=36.7 ms
      56 bytes from 212.58.241.131: icmp_seq=2 ttl=247 time=36.0 ms
      56 bytes from 212.58.241.131: icmp_seq=3 ttl=247 time=37.3 ms

      They're usually 24ms.
      I don't know what's going on. It's never ending with my line

    4. #3
      gymno's Avatar
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      Re: Upstream attenuation halved?

      Just noticed somebody else getting a random upstream attenuation with each resync:

      Will I get more speed?

      9.8db - 14.1db.
      *EDIT* make that 7.8db - 14.1db.

      Would it be possible that the router simply struggles to report it properly sometimes?

      If so, i can stop worrying, sit tight & just hope that my latency improves.
      It has happened before: high pings & slight drop in throughput
      Last edited by gymno; 17-08-12 at 01:48 PM.

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    6. #4
      gymno's Avatar
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      Re: Upstream attenuation halved?

      double post

    7. #5
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      Re: Upstream attenuation halved?

      replying to subscribe, as i have had the same upstream attenuation fluctuations also, during (and after repair of) problematic line faults - battery contact and split pair

      I was told sky's ISAM in my exchange was overloaded past its capacity and was running at 97.5% (although broadband was fine at any time of day) and it would be fixed in 6 weeks (which has passed) Ive yet to test too see if the phenomenon still exists, it doesn't with current sky router (BCM6361), but I've yet to test my Netgear's again (BCM6348 + BCM6358) which seem to get it worse, i will do so tonight.

      either way it did not affect performance.

      @ Gymno - I wouldnt be too concerned about those ping times, they are still brilliant, mine can change from 32-38ms at times, it just depends on how busy the ISAM is, if you game you could ask for gaming mode to be enabled with 8ms delays via the sky help forum, it could be you had gaming mode on but now its been turned off? possibly anyway
      - Hardware - Netgear DG834Nv1
      - Line Attenuation - 27.5db
      - Sync Rate - 17,600k
      - Noise Margin - 7db
      - Latency - 28ms

    8. #6
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      Re: Upstream attenuation halved?

      Thanks snadge, that's interesting.

      I've just managed to pinpoint exactly when my attenuation started being silly & it was straight after a 'lift & shift' was done (the 2nd time - when it was done properly).
      On the same day, 2 new connectors were fitted at the distribution point outside my property (the cables also needed cleaning due to corrosion).

      As in your case, performance doesn't appear to be affected at all, unless it is related to my ping increase.

      As for that, you're right. 36ms isn't bad but i am a gamer & believe me, i do notice it.

      I'm just going to sit tight & keep an eye on it for now. This jump to 36ms has happened once before in april. Sky said my max delays were still 8ms, then it sorted itself out after exactly 1 week & i was back to 24ms.

      Cheers

    9. #7
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      Re: Upstream attenuation halved?

      OK ive got my Netgear 834N (BCM 6358) in and upstream LA was 13.9db ,

      1st reboot = 12.3db
      2nd reboot = 13.9db

      a small change but nothing substantial yet, the downstream on this router is 28db so upstream should be around 13-14db, it used to go as low as 6db - I will reboot it later tonight and see what it says, but ive a feeling its stopped now.

      I come across another thread on this forum where someone is having ping issues and their upstream attenuation is low, i have asked if it fluctuates too because it may be related, especially because sky told me that their equipment was overloaded when it was happening really badly.. if this is the case then fluctuating upstream attenuation may indicate over-loaded hardware at exchange...just a theory..
      - Hardware - Netgear DG834Nv1
      - Line Attenuation - 27.5db
      - Sync Rate - 17,600k
      - Noise Margin - 7db
      - Latency - 28ms

    10. #8
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      Re: Upstream attenuation halved?

      ...more info - rebooted the 834N tonight and still 13.8db - it would seem this phenomenon has now ended for me, i think its possible it may have summit too do with overloaded ISAM, because mine would have been upgraded by now
      - Hardware - Netgear DG834Nv1
      - Line Attenuation - 27.5db
      - Sync Rate - 17,600k
      - Noise Margin - 7db
      - Latency - 28ms

    11. #9
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      Re: Upstream attenuation halved?

      i think its possible it may have summit too do with overloaded ISAM
      Even though you were told this by Sky I find it hard to believe. An ISAM only has so many ports and it is impossible to plug in more than that number. What has probably happened is that the back haul from the exchange has been overloaded and has now been upgraded. This is happening all over the country and was first observed when Anytime+ came on line. It will effect throughput and pings, but not the sync speed.

      As for Gymno's problem he should do as you say and ask Sky to check his delay. It is possible the line was not reconfigured properly after the lift and shift was done.

      TomD


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    12. #10
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      Re: Upstream attenuation halved?

      Quote Originally Posted by Isitme View Post
      Even though you were told this by Sky I find it hard to believe. An ISAM only has so many ports and it is impossible to plug in more than that number. What has probably happened is that the back haul from the exchange has been overloaded and has now been upgraded. This is happening all over the country and was first observed when Anytime+ came on line. It will effect throughput and pings, but not the sync speed.

      As for Gymno's problem he should do as you say and ask Sky to check his delay. It is possible the line was not reconfigured properly after the lift and shift was done.
      Hi Tom

      could be, all i know is the tech Advisor said the Engineers told him the ISAM was running over its capacity at 97 or 98% (cant remember exact figure) and would take 6 weeks to upgrade, I understand what your saying, it wouldnt make sense to make an ISAM that can be overloaded, unless all the ports were being used more than expected - at the time I just thought it was an excuse to fob me off, I got it escalated and eventually got my problem sorted (with a lot of pushing) and got my sync rate back up...

      ive found another thread on kitz where someone with a sky LLu line had fluctuating upstream attenuation.... wierd eh?

      anyway it seems to be gone for me
      - Hardware - Netgear DG834Nv1
      - Line Attenuation - 27.5db
      - Sync Rate - 17,600k
      - Noise Margin - 7db
      - Latency - 28ms

     

     
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