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Re: [PATCH] fix tcp_default_win_scale.

To: bert hubert <ahu@xxxxxxx>
Subject: Re: [PATCH] fix tcp_default_win_scale.
From: "David S. Miller" <davem@xxxxxxxxxx>
Date: Tue, 6 Jul 2004 15:49:07 -0700
Cc: jamie@xxxxxxxxxxxxx, shemminger@xxxxxxxx, netdev@xxxxxxxxxxx, linux-net@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <20040706224453.GA6694@xxxxxxxxxxxxxxx>
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On Wed, 7 Jul 2004 00:44:53 +0200
bert hubert <ahu@xxxxxxx> wrote:

> Not true - the outgoing SYN packet had window scale 7, when it was sent. The
> SYN|ACK had window scale 0, when received by the initiating system.
> 
> Also - even if the remote were to assume a 47 byte window size, would it not
> be able to send small packets? Or does the window size also include
> packet haders?

SWS avoidance makes us not send packets.  See this quote in an email
from John Heffner the other week:

================================
To elaborate on my earlier mail. my hypothesis is that somehow the web
server beleives that we sent a winscale of 0.  In such a case, when we try
to advertise our initial 4*MSS (5840 bytes) of window, with a window scale
of 3 we use a value of 730 in the window field.  All sender SWS avoidance
(RFC1122) tests will fail, most notably 1 (because we already advertised
5840 bytes and 730 < 5840/2) and 3 (because 730 < 1460).  With a winscale
of 2, we will use a value of 1460 in the window field, so both tests will
succeed.
================================

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