From owner-freebsd-hackers Fri Jun 19 19:17:49 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id TAA23615 for freebsd-hackers-outgoing; Fri, 19 Jun 1998 19:17:49 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from super-g.inch.com (super-g.com [207.240.140.161]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id TAA23603 for ; Fri, 19 Jun 1998 19:17:45 -0700 (PDT) (envelope-from spork@super-g.com) Received: from localhost (localhost [127.0.0.1]) by super-g.inch.com (8.8.8/8.8.5) with SMTP id WAA04769; Fri, 19 Jun 1998 22:17:10 -0400 (EDT) Date: Fri, 19 Jun 1998 22:17:09 -0400 (EDT) From: spork X-Sender: spork@super-g.inch.com To: Joel Ray Holveck cc: opsys@mail.webspan.net, root@bmccane.maxbaud.net, hackers@FreeBSD.ORG Subject: Re: TweakDUN In-Reply-To: <199806200006.TAA10769@detlev.UUCP> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Fri, 19 Jun 1998, Joel Ray Holveck wrote: > > Okay, I'm a bit confused here. How does the broken stack affect this > issue? I thought it was a network design issue, since (if I > understand correctly) many ISPs' uplinks use an MTU of 576, so any > system using an MTU of 1500 (which includes the FreeBSD default) is > going to have their packets broken into three packets of 576, 576, and > 348 bytes. So, to reduce overhead, the MTU is set to 576 originally > (why not 1152 I don't know) and life goes on. I can't think of anywhere this is true. I'll use our dialup pools as an example: modem-> dialup PPP 1500 -> term server -> ethernet 1500 -> router -> T1(s) HDLC 1500 -> core router -> fast ethernet 1500 -> upstream's border router -> FDDI 40?? -> upstream core router -> ATM/SONET/whatever ? Generally, one avoids small MTUs on big links, I beleive. ATM's small cell size makes *every* packet get fragmented at layer 2, but I'm not sure that's even relevant. Anyone else? I've never heard of the oft quoted "Internet standard MTU of 576"... Charles > > Am I mistaken? > > Best, > joelh > > -- > Joel Ray Holveck - joelh@gnu.org - http://www.wp.com/piquan > Fourth law of programming: > Anything that can go wrong wi > sendmail: segmentation violation - core dumped > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message