Poor Internet downloads - Setup

This is a discussion on Poor Internet downloads - Setup ; Since some time I cannot download large files, the transfer often stalls after receiving as few as 1 MB. Using Windows on the same machine, downloading the same files works at full bandwidth, and for files over 1 GB in ...

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Thread: Poor Internet downloads

  1. Poor Internet downloads

    Since some time I cannot download large files, the transfer often stalls
    after receiving as few as 1 MB. Using Windows on the same machine,
    downloading the same files works at full bandwidth, and for files over 1
    GB in size, so that I suspect a Linux driver or configuration problem.

    Any ideas for a diagnosis and possible cure of that behaviour?

    DoDi


  2. Re: Poor Internet downloads

    Hans-Peter Diettrich wrote:
    > Since some time I cannot download large files, the transfer often stalls
    > after receiving as few as 1 MB. Using Windows on the same machine,
    > downloading the same files works at full bandwidth, and for files over 1
    > GB in size, so that I suspect a Linux driver or configuration problem.
    >
    > Any ideas for a diagnosis and possible cure of that behaviour?
    >
    > DoDi
    >

    This may be that MTU and TCP window thing.


    First try setting the MTU to < 1500 bytes.

    Then google 'linux tcp window' - theres a load of stuff out there on
    that issue.

    Essentially some older kit on the net is broken and Linux default window
    sizes don't play nice with it.

  3. Re: Poor Internet downloads

    Hans-Peter Diettrich wrote:

    > Since some time I cannot download large files, the transfer often stalls
    > after receiving as few as 1 MB. Using Windows on the same machine,
    > downloading the same files works at full bandwidth, and for files over 1
    > GB in size, so that I suspect a Linux driver or configuration problem.
    >
    > Any ideas for a diagnosis and possible cure of that behaviour?
    >
    > DoDi


    Try turning off tcp window scaling, it is enabled by default in 2.6.x
    kernels, some broken routers have a problem with window scaling turning it
    off will fix this.

    as root do:

    echo 0 > /proc/sys/net/ipv4/tcp_window_scaling

    If it works for you then add the line to /etc/rc.local or equiv. so it is
    turned off on boot.

    --
    Tayo'y Mga Pinoy

  4. Re: Poor Internet downloads

    The Natural Philosopher schrieb:

    > First try setting the MTU to < 1500 bytes.


    Shouldn't it be the MRU, for problems with downloads?

    ifconfig says:

    wlan0 Link encap:Ethernet...
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:63408 errors:0 dropped:0 overruns:0 frame:0
    TX packets:36779 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:1000
    RX bytes:90812278 (86.6 Mb) TX bytes:3257748 (3.1 Mb)

    I wonder why no errors were detected. But fortunately all the downloads
    finished now, after running for some hours in the background :-)


    Here is what I found in /etc/ppp/options:

    # Set the MRU [Maximum Receive Unit] value to for negotiation. pppd
    # will ask the peer to send packets of no more than bytes. The
    # minimum MRU value is 128. The default MRU value is 1500. A value of
    # 296 is recommended for slow links (40 bytes for TCP/IP header + 256
    # bytes of data). The value 1492 is for DSL connections (PPP Default -
    # PPPoE Header: 1500 - 8 = 1492)
    # mru 1492

    # Set the MTU [Maximum Transmit Unit] value to . Unless the peer
    # requests a smaller value via MRU negotiation, pppd will request that
    # the kernel networking code send data packets of no more than n bytes
    # through the PPP network interface. The value 1492 is for DSL connections
    # (PPP Default - PPPoE Header: 1500 - 8 = 1492)
    # mtu 1492

    Removing the comment markers may affect autotuning?

    I couldn't use the MTU Discovery Server yet, because I'm unable to
    install the required plugin :-(


    > Then google 'linux tcp window' - theres a load of stuff out there on
    > that issue.


    Thanks, a good key :-)

    > Essentially some older kit on the net is broken and Linux default window
    > sizes don't play nice with it.


    I have kernel 2.6.22, where autotuning may be active (dunno?), in which
    case manual optimizations are said to be discouraged.

    Applying some changes to the buffer sizes (sysctl.conf) improved the
    behaviour a bit, but not much. The Firefox download progress shows some
    100KB chunks received at maximum speed (120KB/sec), followed by pauses
    of several seconds, until the downloads stall after 5-15MB transferred.


    Just a few questions about VMWare:

    Does the VMWare (Player) affect networking, i.e. should I search for
    conflicts or corrections in that direction?

    Currently I'm using NAT in my VMs, with the same poor behaviour as in
    the host system. Could a switch to briged networking allow to bypass the
    poor behaviour of the host system?

    DoDi

  5. Re: Poor Internet downloads

    Hans-Peter Diettrich schrieb:

    > Since some time I cannot download large files, the transfer often stalls
    > after receiving as few as 1 MB...


    For the curious:

    It seems to be a driver problem. After switching from WLAN to USB (such
    a cable was already lying around) my Internet connection works as
    expected - at least for now :-)

    DoDi

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