Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752723Ab1ESES0 (ORCPT ); Thu, 19 May 2011 00:18:26 -0400 Received: from shards.monkeyblade.net ([198.137.202.13]:60960 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927Ab1ESESZ convert rfc822-to-8bit (ORCPT ); Thu, 19 May 2011 00:18:25 -0400 Date: Thu, 19 May 2011 00:14:26 -0400 (EDT) Message-Id: <20110519.001426.2119532755281545481.davem@davemloft.net> To: tsunanet@gmail.com 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 Subject: Re: [PATCH] tcp: Implement a two-level initial RTO as per draft RFC 2988bis-02. From: David Miller In-Reply-To: References: <1305771744-83951-1-git-send-email-tsunanet@gmail.com> <20110518.223622.1525088601595365235.davem@davemloft.net> X-Mailer: Mew version 6.3 on Emacs 23.2 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (shards.monkeyblade.net [198.137.202.13]); Wed, 18 May 2011 21:14:31 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1712 Lines: 41 From: tsuna Date: Wed, 18 May 2011 20:56:33 -0700 > On Wed, May 18, 2011 at 7:36 PM, David Miller wrote: >> 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. ?Draft RFC 2988bis-02 proposes to tune >>> 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. > > 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 yet > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/