From owner-freebsd-hackers Fri Jun 19 21:17:25 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id VAA06070 for freebsd-hackers-outgoing; Fri, 19 Jun 1998 21:17:25 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from mail.camalott.com (root@[208.203.140.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id VAA06065 for ; Fri, 19 Jun 1998 21:17:23 -0700 (PDT) (envelope-from joelh@gnu.org) Received: from detlev.UUCP (tex-62.camalott.com [208.229.74.62] (may be forged)) by mail.camalott.com (8.8.7/8.8.5) with ESMTP id XAA03063; Fri, 19 Jun 1998 23:16:16 -0500 Received: (from joelh@localhost) by detlev.UUCP (8.8.8/8.8.8) id XAA11637; Fri, 19 Jun 1998 23:16:45 -0500 (CDT) (envelope-from joelh) Date: Fri, 19 Jun 1998 23:16:45 -0500 (CDT) Message-Id: <199806200416.XAA11637@detlev.UUCP> To: spork@super-g.com CC: opsys@mail.webspan.net, root@bmccane.maxbaud.net, hackers@FreeBSD.ORG In-reply-to: (message from spork on Fri, 19 Jun 1998 22:17:09 -0400 (EDT)) Subject: Re: TweakDUN From: Joel Ray Holveck Reply-to: joelh@gnu.org References: Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >> 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"... Okay. I don't know much about ATM, etc, so I'll take your word for it. Happy hacking, 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