From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] tcp: Implement a two-level initial RTO as per draft RFC 2988bis-02. Date: Thu, 19 May 2011 00:14:26 -0400 (EDT) Message-ID: <20110519.001426.2119532755281545481.davem@davemloft.net> References: <1305771744-83951-1-git-send-email-tsunanet@gmail.com> <20110518.223622.1525088601595365235.davem@davemloft.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kuznet@ms2.inr.ac.ru, pekkas@netcore.fi, jmorris@namei.org, yoshfuji@linux-ipv6.org, kaber@trash.net, hagen@jauu.net, eric.dumazet@gmail.com, alexander.zimmermann@comsys.rwth-aachen.de, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: tsunanet@gmail.com Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org =46rom: tsuna Date: Wed, 18 May 2011 20:56:33 -0700 > On Wed, May 18, 2011 at 7:36 PM, David Miller w= rote: >> From: Benoit Sigoure >> Date: Wed, 18 May 2011 19:22:24 -0700 >> >>> Prior to this patch, Linux would always use 3 seconds (compile-time >>> constant) as the initial RTO. =A0Draft RFC 2988bis-02 proposes to t= une >>> this down to 1 second and, in case of a timeout during the TCP 3WHS= , >>> revert the RTO back up to 3 seconds when data transmission begins. >> >> We just had a discussion where it was determined that changes to >> these settings are "network specific" and therefore that if it >> is appropriate at all (I'm still not convinced) it is only suitable >> as a routing metric. >=20 > Fair enough. I'll take another stab at it and see if I can change > this to be on a per network basis. Do I need any patch that's not ye= t > in Linus' tree? I'm referring to this: Keep in mind another thing I do not like about this knob. The IETF draft has a requirement that we fallback to 3 seconds if the initial RTO is 1 second. Nothing in your facilities ensure this, or provide a way for the kernel to make sure this is the case. And for other values of initial RTO, what fallback is appropriate? As a result of all of this, I do not really think this is something the user should control at all. I really would rather see the initial RTO be static and be set to 1 with fallback RTO of 3.