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Standard Overhead on a DSL line

Discussion in 'Tech Talk' started by Hauptmann6, Jul 29, 2011.

  1. Hauptmann6


    May 22, 2002
    Portage, MI
    I'm paying for 768 up and down. I barely get 360k on a good day lately(as showed by speedtest sites). I keep getting the that's normal answer.

    It's been a long time since I went through networking classes but that seems absurd.
  2. GIockGuy24

    GIockGuy24 Bring M&M's

    Jul 14, 2005
    With Amber Lamps
    I was getting very close to max speed for a long time. Recently I looked at the available speeds by my provider and they used to say "up to X Mb/s" but now they say "from X Mb/s to X Mb/s" for each price range. My speed has decreased to half max speed or sometimes when I'm lucky, almost 3/4 max speed. Usually half max speed these days. I am getting within the price range I'm paying for but it's not nearly maximum and it used to be. I don't watch streaming movies or streaming TV but the max speed I get is just under the recommended for those services and what I'm getting now wouldn't work without jerky video. I really don't need more speed for just internet surfing but I have noticed a slow down when I download large files.

  3. joeroket


    Mar 25, 2009
    20% is the typical tcp/ip overhead. You also have to take line distance to the CO when talking about DSL. the further away you are the slower your speeds will drop. 18000 feet is the max distance you can transmit over DSL. You also need to take into account network congestion. Speedtest sites can make it look like your actual line speed is slow when in fact it is network congestion causing the slowdown. The only true way to tell line speed is to perform a speed test with your provider.
  4. kc8ykd


    Oct 6, 2005
    joeroket's explanation is pretty good, however i'd consider about 16-18% overhead to be more acceptable for dsl due to pppoe & atm. more than that and i'd start looking at why there's more.

    there's lots of ways to run 'speed tests', basically you just want to try and load up the line as much as possible with data and measure the transfer rate.

    personally, i find those speed test sites generally unreliable. i personal preference is to start a bunch of downloads and see how fast the overall line is. this can be accomplished with as few as one download, depending on the source and it's ability to transfer data.

    an easy way to do this would be to grab a utility like Netmeter for windows, or open the task manager and go to the networking page. netmeter is a little nicer since you don't have to calculate percentages of the nic's capacity or anything like that.

    then, find some stuff to download, like some things from megaupload, filesonic, fileserv, or from where ever. once your d/l's are going, check out the speed.

    it sounds like you're seeing about 50% of advertised speed, which isn't good and could be caused by a number of things.

    if you can, try and get some stats from your dsl modem. look up the make/model of the modem and see if there's a way to see the ATM and the line stats. you could be experiencing a lot of errors due to line noise, low signal to noise ratio or straight atm errors.

    if you're getting low s/n ratio or other line errors, i'd check to make sure you've got all your dsl filters in place (make sure not to put one on the dsl modem).

    you'll also want to check the wiring from the dsl modem to the interface box outside. a bad internal path (like run parallel to your electrical mains) or cable issue can cause significant problems.

    if those all look good, i'd contact the provider and have them see if there's a problem in cables running from your premises to their equipment.

    if you're seeing atm errors and the line looks good, i'd call the dsl provider, they could have a bad interface card on their side.

    make sure to check all your equipment and cables first, they'll probably want to charge you for a truck roll if they come out and find there's nothing wrong between the interface box outside your structure and their equipment.

    here's a good overview explaining dsl (pppoe & atm) overhead:
  5. Hauptmann6


    May 22, 2002
    Portage, MI
    The reason I checked is it is taking 5-10 seconds or more to open a page on GT.

    The net has been slowing down for me bigtime.
  6. Hauptmann6


    May 22, 2002
    Portage, MI
    Up till a month ago my ISP had a T1 into my building. I was the last person using it so they pulled it and went to a standard DSL. Bleh.

    I'm going to be looking into cable.
  7. kc8ykd


    Oct 6, 2005
    cable will probably be faster, assuming it's available (cable co's typically don't use pppoe and atm, thus eliminating that overhead).

    still, i'd try and pull the stats and check the wiring.
  8. GAFinch


    Feb 23, 2009
    GT has been randomly loading slowly for me the past couple weeks...tends to be the ad servers. I think they just switched to a new hosting company. Every other site is loading normal for me.
  9. 361cop


    Jul 5, 2007
    Lone Star State
    Why should there not be a fliter on the line running to the DSL?

    The instructions that came with my wirless one from AT&T stated to put a filter on every telephone jack.

    I once had a jack without a filter and when the phone rang, it kicked off my internet signal. I had to reboot the modem once the phone call was done.
  10. JimmyN


    Sep 29, 2006
    The filter is to block the DSL signal on the line. That's why you don't have one on the line running to your modem, it needs the DSL, but your phones, fax, etc. all need a filter or they'll get confused. :supergrin:
  11. srhoades


    Jul 14, 2000
    Change your DNS servers. AT&T's have always sucked for me.

    Open DNS