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Re: [PATCH] fix tcp_default_win_scale.

To: Jamie Lokier <jamie@xxxxxxxxxxxxx>
Subject: Re: [PATCH] fix tcp_default_win_scale.
From: Stephen Hemminger <shemminger@xxxxxxxx>
Date: Tue, 6 Jul 2004 13:05:49 -0700
Cc: netdev@xxxxxxxxxxx, linux-net@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <20040706194034.GA11021@mail.shareable.org>
Organization: Open Source Development Lab
References: <32886.63.170.215.71.1088564087.squirrel@www.osdl.org> <20040629222751.392f0a82.davem@redhat.com> <20040630152750.2d01ca51@dell_ss3.pdx.osdl.net> <20040630153049.3ca25b76.davem@redhat.com> <20040701133738.301b9e46@dell_ss3.pdx.osdl.net> <20040701140406.62dfbc2a.davem@redhat.com> <20040702013225.GA24707@conectiva.com.br> <20040706093503.GA8147@outpost.ds9a.nl> <20040706114741.1bf98bbe@dell_ss3.pdx.osdl.net> <20040706194034.GA11021@mail.shareable.org>
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On Tue, 6 Jul 2004 20:40:34 +0100
Jamie Lokier <jamie@xxxxxxxxxxxxx> wrote:

> Stephen Hemminger wrote:
> > Recent TCP changes exposed the problem that there ar lots of really
> > broken firewalls that strip or alter TCP options.  When the options
> > are modified TCP gets busted now.  The problem is that when we
> > propose window scaling, we expect that the other side receives the
> > same initial SYN request that we sent.  If there is corrupting
> > firewalls that strip it then the window we send is not correctly
> > scaled; so the other side thinks there is not enough space to send.
> 
> If a firewall strips the window scaling option in both directions,
> then window scaling is disabled (RFC 1323 section 2.2).
> 
> Are you saying there are broken firewalls which strip TCP options in
> one direction only?

It appears so.

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