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>
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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?
--
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
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