From owner-freebsd-stable Sat Jan 4 8:32:25 2003 Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8EF1537B401 for ; Sat, 4 Jan 2003 08:32:24 -0800 (PST) Received: from pit.databus.com (p70-227.acedsl.com [66.114.70.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id A0F9B43EE6 for ; Sat, 4 Jan 2003 08:32:22 -0800 (PST) (envelope-from barney@pit.databus.com) Received: from pit.databus.com (localhost [127.0.0.1]) by pit.databus.com (8.12.6/8.12.6) with ESMTP id h04GWE1N071191; Sat, 4 Jan 2003 11:32:14 -0500 (EST) (envelope-from barney@pit.databus.com) Received: (from barney@localhost) by pit.databus.com (8.12.6/8.12.6/Submit) id h04GWEV1071190; Sat, 4 Jan 2003 11:32:14 -0500 (EST) (envelope-from barney) Date: Sat, 4 Jan 2003 11:32:13 -0500 From: Barney Wolff To: David Magda Cc: Evren Yurtesen , Sten Daniel S?rsdal , "Wright, Michaelx L" , fkittred@gwi.net, Michael Sierchio , freebsd-stable@FreeBSD.ORG, wpaul@ctr.columbia.edu Subject: Re: wi0 and mtu setting [bad idea] Message-ID: <20030104163213.GA70776@pit.databus.com> References: <0AF1BBDF1218F14E9B4CCE414744E70F07DE29@exchange.wanglobal.net> <20030104154328.GA266@number6.magda.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030104154328.GA266@number6.magda.ca> User-Agent: Mutt/1.4i X-Scanned-By: MIMEDefang 2.26 (www . roaringpenguin . com / mimedefang) Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sat, Jan 04, 2003 at 10:43:29AM -0500, David Magda wrote: > > If you want to change this you'll have to hack code. Since this is the > first I've heard about it, I don't think many people share your concern > regarding the issue. Is there any reason why you need this > functionality? Other people do share the concern. Life is much nicer when tunneled packets don't have mysteriously restricted MTUs. PMTU is at best a clumsy solution, albeit the least-awful available. > Messing around with the MTU is fine if you can control all the hosts on > the network, but things can get real messy real quickly if any mistakes > are made. Sure, and setting hosts to different subnets will break things too. I thought the Unix tradition was to give the sysadmin the chainsaw, trusting that it would not be used on human flesh. Where hardware supports jumbo frames software should too, though of course the default remains 1500. It's a really bad idea to infer framing or anything else from MTU. -- Barney Wolff http://www.databus.com/bwresume.pdf I'm available by contract or FT, in the NYC metro area or via the 'Net. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message