Very complicated network bw problem, ISP ?

Discussion in 'Linux Networking' started by Roman Tatarowski, Oct 19, 2008.

  1. Hello

    I have a very complicated network transfer problem:

    I have a 20mbps / 2mbps internet connection. modem is connected to a linux
    router, then there's a WiFi router
    and on the end my PC.
    For testing i've used http and ftp connections,

    When i download this file on the linux router i hjave 2.2MB/s, when i
    download it from
    the router through WiFi onto my PC i have ~3MB/s
    But when i connect directly to the website i have only 0.8MB/s
    i've tried also downloading onto the router from I-net and downloading from
    the router onto my PC
    and i still had max speeds (2.2MB/s and ~3MB/s) so Hardware is no the limit.

    tc qdisc show gives me this:
    qdisc pfifo_fast 0: dev eth0 [Unknown qdisc, optlen=20]
    qdisc pfifo_fast 0: dev eth1 [Unknown qdisc, optlen=20]

    and IPtables are clean:

    Any ideas whats wrong?! I've also tried connecting:
    Without linux router (modem to WiFi router)
    Without WiFi router (UTP cable)

    And i still didn't get my 20mbps.
    By the process of elimination i think that the ISP is somehow limiting
    traffic to PCs behind router...
    How can this be fixed?

    Best regards

    Roman Tatarowski, Oct 19, 2008
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  2. Roman Tatarowski

    Thad Floryan Guest

    Not very likely (though nothing's impossible :)
    Ask to get a better connection to the 'Net.

    The fastest you can download will be the slowest of your
    connection and the remote connection and further decreased by
    whatever network logjams are occurring between you and the
    remote connection.

    In other words, even if *your* connection is GigE (1000Mbps)
    but the remote end is on, say, a T1 line, the fastest possible
    download transfer speed you could see is 1.5Mbps.
    Thad Floryan, Oct 20, 2008
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  3. Not very likely (though nothing's impossible :)

    Hm, maybe i wasn't clear, i've tested my connection and from
    i have 2.2 mega bytes / s, so its max of my 20mbps connection.
    Roman Tatarowski, Oct 20, 2008
  4. Roman Tatarowski

    Thad Floryan Guest

    OK, as best I could piece-together from your original
    description, the following seems to be the 6 tests you did:

    [WS] = website
    [M] = modem
    [R] = Router
    [WiFi] = WAP
    [PC] = PC

    1. [WS] -> [M] -> [R] 2.2 MB/S

    2. [R] -> [WiFi] -> [PC] 3 MB/S

    3. [WS] -> [M] -> [R] -> [WiFi] -> [PC] 0.8 MB/S

    4. [R] -----------> [PC] 2.2 MB/S

    5. [WS] -> [M] --------> [WiFi] -> [PC] (?slow?)

    6. [WS] -> [M] -> [R] -----------> [PC] (?slow?)

    Is the above diagram correct? What are the speeds
    for (5) and (6)?

    If so, note that (5) omits your primary router, so
    your original speculation the ISP messes with your
    router has no basis, especially considering (1).

    Can you connect to your modem and see its config?
    Assuming it's a cable modem, its IP (typically)
    should be (like mine which is also
    at 20Mbps).

    Are the tests run multiple times to eliminate the
    possibility of heavy traffic affecting the results?

    Note: cable internet is a shared resource and you
    will be competing with probably 500 to 1000 other
    subscribers (check the subnet mask; mine is, for
    example, == 512 nodes on this leg).

    From your description and the fact you downloaded the
    100MB file to your router, I'm inferring the router
    is a Linux box. What is the "ifconfig -a" showing
    both of the Ethernet interfaces?

    It looks like the only things common to the "slow"
    transfers are the remote web site and the modem in
    the above diagram.
    Thad Floryan, Oct 20, 2008
  5. Roman Tatarowski

    Thad Floryan Guest

    That's for sure. Any possibility of a nicked/kinked UTP cable?

    This might prove useful:


    as would reposting your query (feel welcome to use my diagram) in
    the comp.dcom.modems.cable group.

    I wish you success for a problem resolution.
    Thad Floryan, Oct 22, 2008
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