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Re: [tcpm] TCP tuning

John Heffner <johnwheffner@gmail.com> Wed, 03 February 2010 20:50 UTC

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Date: Wed, 03 Feb 2010 15:51:03 -0500
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From: John Heffner <johnwheffner@gmail.com>
To: Jerry Chu <hkchu@google.com>
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Subject: Re: [tcpm] TCP tuning
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On Wed, Feb 3, 2010 at 3:44 PM, Jerry Chu <hkchu@google.com> wrote:
> Hi John,
>
> On Wed, Feb 3, 2010 at 12:32 PM, John Heffner <johnwheffner@gmail.com> wrote:
>> A couple thoughts:
>> - A large initial window should probably only be used by mutual
>> agreement.  Maybe via a TCP option during the handshake?
>
> This may not be needed. A receiver can effectively constrain the
> sender's window by advertising a smaller initial receive window.
>
> Obviously this works for only the initial window, not the restart window.
> (Oh, on a second thought this can be made to work for the restart
> window too.)

A good point, though most receivers (Linux 2.4 and later being the
exception) advertise all available window space, not expecting a large
initial burst from the sender.  I think you need a negotiation for
opt-in rather than opt-out.

  -John

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