ATM Wide-Area Networks (was: sell shell accounts?)

Paul Ferguson pferguso at
Tue Jul 23 18:28:27 UTC 1996

At 10:22 AM 7/23/96 -0700, Dave Siegel wrote:

>It's difficult to quantify wrt to how ATM plays a role in end-to-end 
>performance on the Internet.  There is very little research to support how
>ATM affects the overall performance.  Even Ameritech and PacBell restricted
>the majority of their performance evaluation on performance in the switch,
>and only extended their scope if they leased an ADSU to a customer.  Even
>with the improved buffering, if you fill your pipe into the ATM switch,
>your ATM switch still becomes a packet shredder, compared to the more
>graceful packet drops seen on a clear channel line.

It depends on what you mean when you say 'performance'. I think
there is more and more interest being vested in ATM inefficiency,
and alternate technologies to better efficiency in the long-haul.

Recall Jerry Scharf's numbers; they're indicative of the issue.


Date: Tue, 18 Jun 1996 23:24:12 -0700 (PDT)
From: scharf at (Jerry Scharf)
X-btw: is also and
To: nanog at
Subject: tilting at windmills discussion 2
Sender: owner-nanog at

In an attempt to reduce the signal to noise ratio of NANOG, I felt like
ATM should get equal time with registry policy for unending discussion of
week award. In Bob Melcalfe's concept that all we care about is working
code, I have included a PERL program for your benefit.

The programs reads a histogram file like the ones kc generates from
mae-west ( and computes
the overhead for various framing methods. Hopefully taking
empirical data from the internet and giving people code will reduce
the discussions of what the "cell tax" for real traffic is. Don't
like my traffic, collect your own. Fighting over conclusions will
be left to others.


Here's the output from the 15 minute collection run on Feb 10th, '96:

% <
total packets seen =     11708789, total payload bytes seen =   3010380871
HDLC framing bytes =   3080633605		HDLC efficiency = 97.72
ATM framing bytes =   3644304857		ATM efficiency = 82.61
ATM w/snap framing bytes =   3862101043		ATM w/snap efficiency = 77.95


- paul

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