netdev - Re: [PATCH] tcp: Increase the initial congestion window to 10.

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Message-ID: <AANLkTimWHAz0SX_u42guHp2KNyQESsH6ysNwRoe7ZVJ=@mail.gmail.com>
Date:	Thu, 3 Feb 2011 13:17:19 -0800
From:	"H.K. Jerry Chu" <hkjerry.chu@...il.com>
To:	Hagen Paul Pfeifer <hagen@...u.net>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	dccp@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH] tcp: Increase the initial congestion window to 10.

On Thu, Feb 3, 2011 at 6:00 AM, Hagen Paul Pfeifer <hagen@...u.net> wrote:
>
> On Wed, 02 Feb 2011 17:07:50 -0800 (PST), David Miller wrote:
>
>> +/* TCP initial congestion window */
>> +#define TCP_INIT_CWND                10
>> +
>
> Davem, there is _no_ research how this huge IW will behave in environments
> with a small BDP. Belief it or not, but there are networks out there with a
> BDP similar to ~1980. Why for heaven's sake should this work in these
> environments? There are only _two_ extensive analysis one from Cherry and
> and one from Ilpo. Both analysis focus on current mainstream BDP. I started

It's more than that. We have also conducted extensive, large scale
experiments covering
all BDP/RTT combinations and the result was documented in details in a
SIGCOMM/CCR paper that can be found from a summary page
http://code.google.com/speed/protocols/tcpm-IW10.html covering all our
IW10 work.

> to setup a ns-2 environment but due to lack of time I am a little bit
> behind schedule. Anyway, why not make this a tunable per route knob so that
> it is easier to fix things, e.g. set IW back to 3.

You've seemed to get this backwards. Shouldn't we set the default for the normal
cases and leave the corner cases to the initcwnd and initrwnd knobs to cover?

Jerry

>
> HGN
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