[15004] in North American Network Operators' Group
Re: MTU of the Internet?
daemon@ATHENA.MIT.EDU (Eric Osborne)
Thu Feb 5 09:32:47 1998
From: Eric Osborne <osborne@notcom.com>
To: jdd@vbc.net (Jim Dixon)
Date: Thu, 5 Feb 1998 09:11:46 -0500 (EST)
Cc: perry@piermont.com, nanog@merit.edu
In-Reply-To: <Pine.BSI.3.91.980205130258.6407D-100000@avon-gw.uk1.vbc.net> from "Jim Dixon" at Feb 5, 98 01:04:13 pm
>
> On Thu, 5 Feb 1998, Perry E. Metzger wrote:
>
> > Eric Osborne writes:
> > > The problem with anything Microsoft may put forth is that it'll read
> > > like "576 is good. It is the best. We do it. So should everybody.
> > > If 576 is good, all else must be bad." And that's simply not the
> > > case.
> >
> > I must admit that I'm very worried about what will happen to the
> > internet if they do this. Why?
> >
> > This will effectively triple the number of packets that routers have
> > to do processing on, that's why.
>
> Packets going through our border routers have an average packet size
> in the region of 200 to 250 bytes. How would this triple the average
> packet size?
>
I think that "triple" is perhaps an oversimplification. This assumes that
without a 576-byte MTU, all packets would be 1500-byte MTUs. 1500/576 ~=~ 3.
Remember, there's three kinds of average: mean, median, mode. While the mean
packet size may be 200-250 bytes, the mode and median are probably different.
I don't have any statistics on this, but I'd be willing to guess that if you
plotted the packet sizes frequency you'd see something like a bimodal curve,
with a small peak at around 64 (ping) and a larger one near 1500 (10Mbit
Ethernet/T1 MTU). As to median packet size, I have no idea. It's probably
somewhere in the middle. :)
eric
