[2436] in North American Network Operators' Group
Re: ATM overhead
daemon@ATHENA.MIT.EDU (Kent W. England)
Fri Apr 5 20:14:59 1996
Date: Fri, 05 Apr 1996 17:12:44 -0800
To: Paul Ferguson <pferguso@cisco.com>
From: "Kent W. England" <kwe@6SigmaNets.com>
Cc: nanog@merit.edu
At 11:41 PM 3/24/96 -0500, Paul Ferguson wrote:
>Kent,
>
>Have you done any statistical gathering on the overhead required to route
>IP traffic in the Pac Bell ATM NAP? I'd be interested in seeing this, for
>certain. :-)
>
>- paul
>
That's difficult to do on the ATM switch, and not really necessary since we
can measure IP packet size any number of places and compute the ATM overhead.
I have been doing some more arithmetic on the "ATM cell tax" to see if I can
find out how folks get from 10% (which is the 5/53 overhead) to 35%
overhead. I would really really like to see some backup for those sort of
numbers -- I can't make the arithmetic work out to anything near 35% for
what I think are useful assumptions. Of course, if you want to posit 100%
of IP traffic with 49 bytes, but that doesn't seem realistic and you
shouldn't forget that 40 of those are TCP/IP overhead. :-)
What traffic mix do you use to calculate ATM overhead and what results do
you get?
--Kent
