ATM overhead

Kent W. England kwe at
Sat Apr 6 01:12:44 UTC 1996

At 11:41 PM 3/24/96 -0500, Paul Ferguson wrote:
>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?


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