From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Heffner <jheffner@psc.edu>
Subject: Re: [PATCH net-2.6 0/3]: Three TCP fixes
Date: Tue, 04 Dec 2007 13:42:41 -0500
Message-ID: <47559FA1.2090104@psc.edu>
References: <11967869303114-git-send-email-ilpo.jarvinen@helsinki.fi>
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Cc: David Miller <davem@davemloft.net>, netdev@vger.kernel.org
To: =?ISO-8859-1?Q?Ilpo_J=E4rvinen?= <ilpo.jarvinen@helsinki.fi>
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Ilpo J=E4rvinen wrote:
> ...I'm still to figure out why tcp_cwnd_down uses snd_ssthresh/2
> as lower bound even though the ssthresh was already halved,=20
> so snd_ssthresh should suffice.

I remember this coming up at least once before, so it's probably worth =
a=20
comment in the code.  Rate-halving attempts to actually reduce cwnd to=20
half the delivered window.  Here, cwnd/4 (ssthresh/2) is a lower bound=20
on how far rate-halving can reduce cwnd.  See the "Bounding Parameters"=
=20
section of <http://www.psc.edu/networking/papers/FACKnotes/current/>.

   -John