From owner-freebsd-hackers@FreeBSD.ORG  Tue Nov  2 19:38:39 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id D733E16A4CE
	for <freebsd-hackers@freebsd.org>;
	Tue,  2 Nov 2004 19:38:39 +0000 (GMT)
Received: from mx1.z-axis.com (z.axis28.z.subnet.rcn.com [209.122.82.156])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 7C08843D49
	for <freebsd-hackers@freebsd.org>;
	Tue,  2 Nov 2004 19:38:37 +0000 (GMT)
	(envelope-from justin@z-axis.com)
Received: (qmail 2168 invoked by uid 89); 2 Nov 2004 19:38:37 -0000
Received: from unknown (HELO ?127.0.0.1?) (justin@209.122.82.179)
  by mx1.z-axis.com with SMTP; 2 Nov 2004 19:38:37 -0000
Message-ID: <4187E23C.7000900@z-axis.com>
Date: Tue, 02 Nov 2004 11:38:36 -0800
From: Justin Bennett <justin@z-axis.com>
Organization: Z-Axis, Ltd.
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US;
	rv:1.7.3) Gecko/20040910
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: FreeBSD Hackers <freebsd-hackers@freebsd.org>
X-Enigmail-Version: 0.86.0.0
X-Enigmail-Supports: pgp-inline, pgp-mime
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Subject: ipfw pipes: theoretical speed vs. reality
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 02 Nov 2004 19:38:39 -0000

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

All,

I have recently been setting up pipes to shape bandwidth on our local net.

However, unless I am missing something, the TCP overhead seems quite large.

If I configure the following pipe:

$IPFW pipe 1 config bw 64Kbit/s
$IPFW add 31 pipe 1 ip from 192.168.0.1/24 to any
$IPFW add 32 pipe 1 ip from any to 192.168.0.1/24

The run traffic from my machine (192.168.0.2) through it, I get less
than half the expected bandwidth (3.9KB/s). I tried another test with a
512Kbit/s pipe, and got around 30KB/s.

I know on most ATM/FR lines, you can expect about 10% overhead, but 50%
seems high.

When I remove the pipe, my T1 comes back to life, and I can pull the
same data at 160+KB/s.

Am I missing something?

Thanks,

Justin
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.5 (MingW32)

iD8DBQFBh+I8lNUG+Ne1CZMRAl95AJ973J3YiUIStcyJ5c5gM+i2lrebTACfUE83
4V9bl8bR9GxjHsKqL764hJk=
=gc51
-----END PGP SIGNATURE-----