Re: Comparing an old flow snapshot with some packet size data

Jeremy Porter <> Fri, 09 August 1996 01:56 UTC

Received: from by id aa25466; 8 Aug 96 21:56 EDT
Received: from cnri by id aa25461; 8 Aug 96 21:56 EDT
Received: from by CNRI.Reston.VA.US id aa18234; 8 Aug 96 21:56 EDT
Received: from mailing-list by (8.6.9/1.0) id LAA13795; Fri, 9 Aug 1996 11:36:01 +1000
Received: from munnari.OZ.AU by (8.6.9/1.0) with SMTP id LAA13766; Fri, 9 Aug 1996 11:24:33 +1000
Received: from [] by munnari.OZ.AU with SMTP (5.83--+1.3.1+0.56) id BA09690; Fri, 9 Aug 1996 11:24:30 +1000 (from
Received: from ( []) by (8.6.12/8.6.6) with ESMTP id UAA06782; Thu, 8 Aug 1996 20:24:04 -0500
Message-Id: <>
To: Andrew Partan <>
Cc: Paul Ferguson <>,,,
Subject: Re: Comparing an old flow snapshot with some packet size data
In-Reply-To: Your message of "Thu, 08 Aug 1996 15:58:00 EDT." <>
Date: Thu, 08 Aug 1996 20:24:03 -0500
From: Jeremy Porter <>
Precedence: bulk

I remember arguing this about 6-9 months ago.  Except from an
exchange point  point of view.  Based on current traffic
patterns I ended up recommend switched full duplex ethernet as
the most cost effective and least complex protocol to run.
FDDI has as lot of unneeded overhead.

So unless you expect to see FDDI deployment to exceed X% of total
LANs then total FDDI MTUs will be less than X%.  (Assuming
relativlity equal data volumes from ethernet and FDDI (which
may not be true due to larger pipes at FDDI sites)).  However
some straight forward market research should be possible to determin
relative sizes.  And unless people start scrapping all that old
technology we are going to have to design for lots of smaller packets
rather than fewer large MTU packets.

I would prefere to have fast packet switches and routers, than
having to fragment packets inside my network.  But that depends
on the cost between packet fragmentation v. carrying more packets.

Someone really should just design a larger MTU for 100BaseTX, i.e.
100BaseTX-BIG.  With a MTU of 4470 say.

In message <>om>, Andrew Partan writes:
>This is all interesting stuff.
>One question that I have been trying to figure out is 
>	What size MTU should an ISP support on its backbone?
>If we view the future where lots of hosts are connected via ethernet
>and fast ethernet & the like, then a MTU of 1500 would be 'correct'.
>If we think that the future will have lots of hosts connected via
>Fddi or similar, then a MTU of 4470 would be 'better'.
>Any ideas?
> (Andrew Partan)

Jeremy Porter, Freeside Communications, Inc.
PO BOX 80315 Austin, Tx 78708  |  1-800-968-8750  |  512-458-9816