From owner-freebsd-net@FreeBSD.ORG  Wed Feb 13 18:37:54 2013
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: net@freebsd.org
Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115])
 by hub.freebsd.org (Postfix) with ESMTP id 9AEBD558;
 Wed, 13 Feb 2013 18:37:54 +0000 (UTC)
 (envelope-from adrian.chadd@gmail.com)
Received: from mail-we0-x235.google.com (mail-we0-x235.google.com
 [IPv6:2a00:1450:400c:c03::235])
 by mx1.freebsd.org (Postfix) with ESMTP id C0C0088B;
 Wed, 13 Feb 2013 18:37:53 +0000 (UTC)
Received: by mail-we0-f181.google.com with SMTP id t44so1258374wey.12
 for <multiple recipients>; Wed, 13 Feb 2013 10:37:52 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:x-received:sender:in-reply-to:references:date
 :x-google-sender-auth:message-id:subject:from:to:cc:content-type;
 bh=F/vkrkgr+YDTI5/tM/T7TO0B639XDYvG4zmOC3S1d8Y=;
 b=J8HdYiTl2dUCUFxOE4KMETFfbQnjfphl4u3QxindgP7bQuCZJQ4vHCg7VOs/TF2j2p
 C3kGVxwUL8FivA/BPvWRZ82YVLnENIyRl7flgwLUhpwrNUGVm4JjcAoKlwTseZztENBe
 MsT16IzJJCOWhSn9lO7USvWZjaviusAUq8q/RA7w9bHS/ivdnm3G62Zle8ceRdtFPN3X
 daD2NZZ1fEsgdh4YNHUnrf40PbqRgI/qedixlUn50MJJS3P6NNe/c4/ru7EKXJbCdEa6
 0fcuCQLwvBJcZ8vjHI1Z8n/t6Z1bIIs1cX0BnSkRZBbwes3zcUIO/CEFL8mGEbH0GURZ
 1ljg==
MIME-Version: 1.0
X-Received: by 10.194.161.135 with SMTP id xs7mr40180707wjb.41.1360780672062; 
 Wed, 13 Feb 2013 10:37:52 -0800 (PST)
Sender: adrian.chadd@gmail.com
Received: by 10.216.236.88 with HTTP; Wed, 13 Feb 2013 10:37:51 -0800 (PST)
In-Reply-To: <511B6A87.5060000@freebsd.org>
References: <201301221511.02496.jhb@freebsd.org> <511B4DEF.8000500@freebsd.org>
 <511B6A87.5060000@freebsd.org>
Date: Wed, 13 Feb 2013 10:37:51 -0800
X-Google-Sender-Auth: HOGjc5jmeggVz5EVsGVZYjwM4Tc
Message-ID: <CAJ-Vmo=hi_i=JfF7i1fT+8Yh+PxqwFNq3sOqnHhfnoLCN1iMkg@mail.gmail.com>
Subject: Re: [PATCH] Add a new TCP_IGNOREIDLE socket option
From: Adrian Chadd <adrian@freebsd.org>
To: Andre Oppermann <andre@freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1
Cc: Lawrence Stewart <lstewart@freebsd.org>, John Baldwin <jhb@freebsd.org>,
 net@freebsd.org
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 13 Feb 2013 18:37:54 -0000

On 13 February 2013 02:27, Andre Oppermann <andre@freebsd.org> wrote:

> Again I'd like to point out that this sort of modification should
> be implemented as a congestion control module.  All the hook points
> are already there and can readily be used instead of adding more special
> cases to the generic part of TCP.  The CC algorithm can be selected per
> socket.  For such a special CC module it'd get a nice fat warning that
> it is not suitable for Internet use.
>
> Additionally I speculate that for the use-case of John he may also be
> willing to forgo congestion avoidance and always operate in (ill-named)
> "slow start" mode.  With a special CC module this can easily be tweaked.

There are some cute things that could be done here - eg, having an L3
route table entry map to a congestion control (like having an MSS in
the L3 entry too.)

But I'd love to see some modelling / data showing competing congestion
control algorithms on the same set of congested pipes. Doubly so on
multiple congested pipes (ie, modelling a handful of parallel
user<->last-mile<->IX<->various transit feeds with different levels of
congestion/RTT<->IX<->last mile<->user connections.) You all know much
more about this than I do. :-)

Thanks,


Adrian