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    SubjectRe: Raise initial congestion window size / speedup slow start?
    On 14/07/2010 19:15, David Miller wrote:
    > From: Bill Davidsen<>
    > Date: Wed, 14 Jul 2010 11:21:15 -0400
    >> You may have to go into /proc/sys/net/core and crank up the
    >> rmem_* settings, depending on your distribution.
    > You should never, ever, have to touch the various networking sysctl
    > values to get good performance in any normal setup. If you do, it's a
    > bug, report it so we can fix it.

    Just checking the basics here because I don't think this is a bug so
    much as a, less common installation that differs from the "normal" case.

    - When we create a tcp connection we always start with tcp slow start
    - This sets the congestion window to effectively 4 packets?
    - This applies in both directions?
    - Remote sender responds to my hypothetical http request with the first
    4 packets of data
    - We need to wait one RTT for the ack to come back and now we can send
    the next 8 packets,
    - Wait for the next ack and at 16 packets we are now moving at a
    sensible fraction of the bandwidth delay product?

    So just to be clear:
    - We don't seem to have any user-space tuning knobs to influence this
    right now?
    - In this age of short attention spans, a couple of extra seconds
    between clicking something and it responding is worth optimising (IMHO)
    - I think I need to take this to netdev, but anyone else with any ideas
    happy to hear them?


    Ed W

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