netdev - Re: [PATCH] tcp: Expose the initial RTO via a new sysctl.

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Date:	Wed, 18 May 2011 15:26:53 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	tsunanet@...il.com
Cc:	kuznet@....inr.ac.ru, pekkas@...core.fi, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org, kaber@...sh.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp: Expose the initial RTO via a new sysctl.

From: Benoit Sigoure <tsunanet@...il.com>
Date: Wed, 18 May 2011 03:43:04 -0700

> Instead of hardcoding the initial RTO to 3s and requiring
> the kernel to be recompiled to change it, expose it as a
> sysctl that can be tuned at runtime.  Leave the default
> value unchanged.
> 
> Signed-off-by: Benoit Sigoure <tsunanet@...il.com>

If you read the ietf draft that reduces the initial RTO down to 1
second, it states that if we take a timeout during the initial
connection handshake then we have to revert the RTO back up to 3
seconds.

This fallback logic conflicts with being able to only change the
initial RTO via sysctl, I think.  Because there are actually two
values at stake and they depend upon eachother, the initial RTO and
the value we fallback to on initial handshake retransmissions.

So I'd rather get a patch that implements the 1 second initial
RTO with the 3 second fallback on SYN retransmit, than this patch.

We already have too many knobs.
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