Date: 23 Mar 1996 23:03:34 -0600 From: "Richard Wackerbarth" <rkw@dataplex.net> To: "Brian Tao" <taob@io.org>, "FREEBSD-HACKERS-L" <freebsd-hackers@freebsd.org> Subject: Re: Changing Ethernet frame size to 576 bytes? Message-ID: <n1384500272.3953@Richard Wackerbarth>
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> Anyone know what this guy is saying? I figured fragmentation and > reassembly would happen between the FTP server's Ethernet interface > and that of the router to the Internet. Is there any validity to this > guy's suggestion? His suggestion is valid. If the MTU is larger than the minimum MTU along the path, each packet that you send out will be broken into sub-packets and reassembled on the far end. If any subpacket gets lost, the whole packet is lost and must be retransmitted. Since tcp knows how to recover lost packets, the file eventually gets through. However, it is more efficient if your packets are not fragmented in transit. > -- > Brian Tao (BT300, taob@io.org) > System and Network Administrator, Internex Online Inc. > "Though this be madness, yet there is method in't" > > ---------- Forwarded message ---------- > Date: Sat, 23 Mar 1996 16:41:22 -0800 > From: Stuart Cheshire <cheshire@DSG.Stanford.EDU> > To: support@io.org > Subject: Suggestion about ftp.io.org > > I was just trying to ftp VRMLEquinox.sea.hqx from /pub/users/ipsys/nps > on your ftp site, and it is very slow. > > Partly this is due to overloaded links, but I also notice that your > ftp server at ftp.io.org seems to be configured to send Ethernet sized > (ie 1536 byte) packets, instead of the normal Internet 576 byte packets. > This means that every IP packet you send has to be fragmented into three > IP fragments as it travels over the Internet, and if any single one of > those fragments is lost, then the other two are useless, even if they do > arrive. In other words, if your link is congested and is losing 20% of > the packets, then those losses make the other two fragments useless too, > giving you an 'effective' loss rate of 60%. > > Of course, I may be wrong. It's just a guess, based on what I noticed from > this end, that the ftp data seemed to be arriving in 1536 byte chunks. > > Stuart Cheshire <cheshire@cs.stanford.edu> > * <A HREF="http://ResComp.Stanford.EDU/~cheshire">World Wide Web Page</A> > * Stanford Operating Systems and Networking Group Research Assistant > * Stanford Residential Computing Associate > * Macintosh Programmer > > > ------------------ RFC822 Header Follows ------------------ > Received: from freefall.freebsd.org (204.216.27.4) by DATAPLEX.NET > with SMTP (MailShare 1.0fc5); Sat, 23 Mar 1996 22:47:23 -0600 > Received: from localhost (daemon@localhost) > by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id TAA22923 > Sat, 23 Mar 1996 19:35:25 -0800 (PST) > Received: (from root@localhost) > by freefall.freebsd.org (8.7.3/8.7.3) id TAA22321 > for hackers-outgoing; Sat, 23 Mar 1996 19:29:35 -0800 (PST) > Received: from cabal.io.org (cabal.io.org [198.133.36.103]) > by freefall.freebsd.org (8.7.3/8.7.3) with ESMTP id TAA22307 > for <freebsd-hackers@freebsd.org>; Sat, 23 Mar 1996 19:29:16 -0800 (PST) > Received: (from taob@localhost) by cabal.io.org (8.7.4/8.7.4) id WAA12295; Sat, 23 Mar 1996 22:27:38 -0500 (EST) > Date: Sat, 23 Mar 1996 22:27:38 -0500 (EST) > From: Brian Tao <taob@io.org> > To: FREEBSD-HACKERS-L <freebsd-hackers@freebsd.org> > Subject: Changing Ethernet frame size to 576 bytes? > Message-ID: <Pine.BSF.3.91.960323222600.8944G-100000@cabal.io.org> > MIME-Version: 1.0 > Content-Type: TEXT/PLAIN; charset=US-ASCII > Sender: owner-hackers@freebsd.org > X-Loop: FreeBSD.org > Precedence: bulk >
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