ATM Wide-Area Networks

Mon Jul 29 22:21:43 UTC 1996

On Mon, 29 Jul 1996, Tim Salo wrote:

> > > I am not quite sure how an ATM switch becomes a "packet shredder," or
> > > even what a "packet shredder" is...

> My point was that the term "packet shredder" doesn't seem to have
> any very precise meaning beyond perhaps the writer's desire to
> use a catchy phrase to indicate an attitude towards ATM. 

I have always interpreted it as meaning a protocol below the IP level which
breaks IP packets up into fragments for transport.

> > If an ATM has a 5% loss, i.e. 1 in every 20 cells is lost, then 0%
> > of the IP traffic will get through. ...
> 
> Most anything with 5% loss is broken.

Just a worst case scenario intended to illustrate that in the case of ATM
packet shredding, losses at the lower level (ATM) can have an effect at
the higher level (IP) that is roughly 20 times as great.

By now people have realized this and are attacking the problem many
different ways, but the problem still does exist and is an artifact of
the relationship between IP packet sizes and ATM cell sizes.

Michael Dillon                   -               ISP & Internet Consulting
Memra Software Inc.              -                  Fax: +1-604-546-3049
http://www.memra.com             -               E-mail: michael at memra.com