From owner-freebsd-net@FreeBSD.ORG Fri Feb 22 03:51:12 2008 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 323B516A400 for ; Fri, 22 Feb 2008 03:51:12 +0000 (UTC) (envelope-from wes@opensail.org) Received: from mail6.dotsterhost.com (mail6.dotsterhost.com [72.5.54.120]) by mx1.freebsd.org (Postfix) with SMTP id 1216013C459 for ; Fri, 22 Feb 2008 03:51:11 +0000 (UTC) (envelope-from wes@opensail.org) Received: (qmail 3080 invoked from network); 22 Feb 2008 03:51:11 -0000 Received: from unknown (HELO scurvy.softweyr.com) (wes@opensail.org@[66.27.90.155]) by 72.5.54.120 with SMTP; 22 Feb 2008 03:51:11 -0000 Message-Id: <1C828D1A-192A-40ED-8391-DA316611E6E2@opensail.org> From: Wes Peters To: Bruce M. Simpson In-Reply-To: <47BCA1AA.7060800@FreeBSD.org> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v919.2) Date: Thu, 21 Feb 2008 19:51:10 -0800 References: <20080219021012.95B1116A4CB@hub.freebsd.org> <8E87DC1A-6EC2-4E53-9FA3-17E694BE7846@opensail.org> <47BCA1AA.7060800@FreeBSD.org> X-Mailer: Apple Mail (2.919.2) Cc: Nick Barnes , freebsd-net@freebsd.org Subject: Re: Multiple default routes on multihome host X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 Feb 2008 03:51:12 -0000 On Feb 20, 2008, at 1:54 PM, Bruce M. Simpson wrote: > Wes Peters wrote: >> I see a number of people have replied to this message offering >> solutions of how to accomplish your migration, using a variety of >> tools available to you in FreeBSD. I've always found this >> community very supportive in this fashion, and I'm glad they've >> jumped in to help you in your transition as well. Please note that >> the variety of solutions presented recognize that your transition >> period is just that, a temporary situation, and that "multiple >> default routes" is not the solution. > > The thing is, in a peer-to-peer or ad-hoc mesh network, not having > access to a single next-hop serving as the gateway of last resort > has a much higher probability of occurring than in a fully converged > network with more deterministic layer 3 behaviour. > > So we're largely arguing apples vs oranges here. Fact of the matter > is, we can't tell people how to run their networks, or which > protocols to run. People want IP everywhere and they want it now. > (Infinite demand for free goods is another story.) > > The argument that functionality "should not" be present because > people "should not" run their networks that way carries no water -- > particularly so when issues of wireless presence and ad-hoc networks > blow the old assumptions out of the water. As much as anything I just object to the semantic dissonance in "multiple" "default". Think about it. I still haven't decided what it means at the packet level to have multiple default routes. Does that mean that, not having found a "better" route, I send the packets out both routes? Choose between them? Doesn't that tend to flap packets in a TCP "connection" back and forth? Does my router have to remember which route it chose for a TCP connection and reuse that one? I know people want to be able to plug in a pair of itty bitty routers and just have their computers be smart enough to use the "best" one, but it's not clear the implementations they are pushing us towards -- Linux and Windows -- actually accomplish that. In fact, what they usually do is screw it up badly and the people only THINK they're getting any enhanced reliability. You're one of the few people who could convince me that they're doing better than my experience says, or that we have a way of doing better. Short of being able to somehow collect information about whether these links are working, I just don't how it would work. I can design a daemon that can such thing abusing ICMP, but that is just a poor man's routing daemon, and still doesn't require multiple default routes, just one that is semi-intelligently managed. -- Where am I, and what am I doing in this handbasket? Wes Peters wes@opensail.org