netdev - Re: [PATCH] tcp-illinois: incorrect beta usage

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Message-ID: <20071129141254.GC9145@gondor.apana.org.au>
Date:	Fri, 30 Nov 2007 01:12:55 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	Julian Shao Liu <shaoliu@...c.edu>,
	"David S. Miller" <davem@...emloft.net>,
	'Lachlan Andrew' <lachlan.andrew@...il.com>,
	shaoliu@...nceton.EDU, 'Douglas Leith' <doug.leith@...m.ie>,
	'Robert Shorten' <robert.shorten@...m.ie>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] tcp-illinois: incorrect beta usage

On Wed, Nov 28, 2007 at 03:47:25PM -0800, Stephen Hemminger wrote:
> Lachlan Andrew observed that my TCP-Illinois implementation uses the
> beta value incorrectly:
>   The parameter  beta  in the paper specifies the amount to decrease
>   *by*:  that is, on loss,
>      W <-  W -  beta*W
>   but in   tcp_illinois_ssthresh() uses  beta  as the amount
>   to decrease  *to*: W <- beta*W
> 
> This bug makes the Linux TCP-Illinois get less-aggressive on uncongested network,
> hurting performance. Note: since the base beta value is .5, it has no
> impact on a congested network.
> 
> Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>

Applied to net-2.6.  Thanks Stephen!
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