From owner-freebsd-hackers Fri Dec 7 9:14:54 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from boreas.isi.edu (boreas.isi.edu [128.9.160.161]) by hub.freebsd.org (Postfix) with ESMTP id AE84437B41A for ; Fri, 7 Dec 2001 09:14:51 -0800 (PST) Received: from isi.edu (w5vt2rqcllg415hj@hbo.isi.edu [128.9.160.75]) by boreas.isi.edu (8.11.6/8.11.2) with ESMTP id fB7HEkN29298; Fri, 7 Dec 2001 09:14:46 -0800 (PST) Message-ID: <3C10F906.1020908@isi.edu> Date: Fri, 07 Dec 2001 09:14:46 -0800 From: Lars Eggert User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:0.9.6) Gecko/20011203 X-Accept-Language: en, de MIME-Version: 1.0 To: Steve Ames Cc: Anders Hagman , freebsd-hackers@FreeBSD.ORG Subject: Re: Nat through two DSL References: <5.0.2.1.0.20011207131945.009fe1d0@mail.training.telia.se> <3C10F658.6070001@isi.edu> <20011207170742.GB80922@virtual-voodoo.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Steve Ames wrote: >>>I want to load share between two ADSL modems using a NAT/Firewall. ... >>>The ADSL are 500k links and I want to load share on session by session. >>>Can I do NAT between an inside interface and two outside interfaces >>>acting in a round robin fashion? >>> >>This may not be the good idea you'd think on first glance. If one of the >>paths has a slightly different RTT (and they're pretty much guaranteed >>to), you'll see out-of-order delivery at the receiver. I remember seeing >>some study that showed that TCP doesn't react too nicely under such >>conditions (it works, but not at peak performance). >> > > Is it even possible to do use two upstream paths for redundancy? I tried > (very briefly while I had two broadband connections while switching from > one to the other) to get that to work and wasn't very successful. Redundancy is a different issue from load-sharing. If you want to switch between a primary and a backup link there are a number of ways to do this. However, Anders was trying to stripe packets over both links (not technically a problem) to increase throughtput. When running TCP over a striped link, you may not see the performance gain you'd expect. (I wish I could remember which paper I saw this in. Anyone know?) Lars -- Lars Eggert Information Sciences Institute http://www.isi.edu/larse/ University of Southern California To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message