My 'Slow Broadband' - what should I expect?

Discussion in 'NZ Computing' started by canon paora, Sep 25, 2006.

  1. canon paora

    canon paora Guest

    It's 256/128 which gives me a speed of 30kB/s up and 15kB/s down. The
    question is should I be able to have maximum up speed and down speed
    simultaneously or will a maximum up speed at 15kB/s affect my down
    canon paora, Sep 25, 2006
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  2. canon paora

    ~misfit~ Guest

    If you're downloading from multiple sources such as bittorrent then full
    upload will most certainly cripple your download as the ack packets won't
    get through. I'd suggest setting a max of 6kB/s up for your connection when
    downloading a torrent, unthrottled when just uploading.

    Ignore that it it doesn't apply. :)
    ~misfit~, Sep 25, 2006
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  3. I believe ADSL is a full-duplex channel, which means in principle you should
    be able to hit both limits simultaneously. Depending on what bottlenecks
    you may hit elsewhere, of course.
    Lawrence D'Oliveiro, Sep 25, 2006
  4. canon paora

    juicyjuice Guest

    wouldn't that be nice, but no. They didn't stick the A in front of DSL for
    juicyjuice, Sep 25, 2006
  5. Hi there,

    As Lawrence D says it is able to do both simultaneously. In
    practice you lose a bit of performance either way while doing
    both, due to checksumming etc...

    I tested this with a simultaneous 100MB download and 15MB
    upload to/from local servers that I can max out my ADSL2+
    on. I got just over 1.2 MB/sec download on a 12600 kbps
    downstream link and just over 100 kByte/sec on the 1020 kbps
    upstream link, at the same time. In both cases thats quite
    close to my theoretical maximum down and up speeds. If I
    paused one transfer the other did speed up, but only a little.

    So yes you will get very close to maximum up and down at the
    same time...

    ~misfits~ advice re torrents is very good, but also limit the
    number of simultaneous peers to connect to, because some ADSL
    modems are limited in the number they can reliably handle (my
    old D-Link DSL-502T used to sometimes bomb starting download
    of torrents with many seeds, or running Limewire).

    Kind regards,

    Chris Wilkinson, Brisbane, Australia.
    Anyone wishing to email me directly can remove the obvious
    spamblocker, and replace it with t p g <dot> c o m <dot> a u
    Chris Wilkinson, Sep 25, 2006
  6. canon paora

    David Guest

    No, they didn't, they stuck it there to signify the fact that the
    downstream rate is much higher than upstream.

    "The distinguishing characteristic of ADSL over other forms of DSL is
    that the volume of data flow is greater in one direction than the other,
    i.e. it is asymmetric."
    David, Sep 25, 2006
  7. canon paora

    Mark C Guest

    Yes, using the maximum up speed of ~16kB/s will affect your down

    When downloading stuff you are receiving packets. Every packet
    received (or every second packet...) must be acknowledged in a timely
    manner, or else the sending host will stop sending (until an
    acknowledgement is received).
    The acknowledgements are sent as packets back to the host you are
    downloading from.

    If you are uploading at the same time as downloading, your upload can
    cause the outgoing acknowledgments to get delayed or wait in a queue
    (for a short while), and this delay can cause your downloads to stall
    or slow.

    If you can limit your upload speed to a few kB/s less than max, this
    will leave some upload room for the acknowledgements to be sent
    without delays, and your download will not be affected.
    (I suggest limiting upload to ~13kB/s)

    You can use bandwidth software such as Netlimiter (I use) or CFos to
    limit upload and/or download speeds.

    Many bittorrent programs also have bandwidth limiting features, but I
    have found that uTorrent (for example) does not do as good a job at
    limiting bandwidth as Netlimiter does.


    (BTW, 256kbps = ~32kB/s, 12kbps =~16kB/s)
    Mark C, Sep 26, 2006
  8. TCP does in fact allow acknowledgements to be "piggybacked" on packets
    carrying outgoing data.
    Lawrence D'Oliveiro, Sep 26, 2006
  9. canon paora

    David Empson Guest

    Yes, but only if you are sending and receiving data on the same TCP
    connection. I believe the assumption here is that you are doing
    independent uploads and downloads at the same time.
    David Empson, Sep 27, 2006
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