netdev - Re: [NOT VERY SAFE] [TCP]: Set initial_ssthresh default to zero in Cubic and BIC.

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Message-ID: <20071015085541.48ec63ae@freepuppy.rosehill>
Date:	Mon, 15 Oct 2007 08:55:41 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Komuro <komurojun-mbn@...ty.com>
Cc:	shemminger@...ux.foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [NOT VERY SAFE]     [TCP]: Set initial_ssthresh default to zero
 in Cubic and BIC.

On Mon, 15 Oct 2007 21:59:49 +0900
Komuro <komurojun-mbn@...ty.com> wrote:

> Dear shemminger
> 
> >In which case it is zero because that is the default value.
> 
> The default value of snd_ssthresh is 0x7fffffff, isn't it?
> 
> [linux/net/ipv4/tcp_ipv4.c]
> static int tcp_v4_init_sock(struct sock *sk)
> ...
>         tp->snd_ssthresh = 0x7fffffff;  /* Infinity */
> ...
> 
> Best Regards
> Komuro
> 
> 

Yes that value means that TCP stays in slow start until the first loss.
This makes TCP behave as expected in the RFC's.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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