Mailing List Archive

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 (http://www.nlanr.net/NA/Learn/packetsizes.html) 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.

Jerry

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

% packettax.pl < packetsizes.data
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

and here's the crude but working code (copyright courtesy of the ISC)

#! /usr/bin/perl

# Copyright (c) 1996 by Internet Software Consortium.
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
# ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
# CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
# DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
# PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
# SOFTWARE.
#
# Jerry Scharf, 5/96

# perl script to take a packet histogram and compute framing efficiency
# the expected format is:
# packetsize count rest
# for each packetsize, the program computes the frame size for HDLC
# and, ATM/AAL5 with and without SNAP, and multiplies them by count and
# adds them to running totals. At the end, it prints the 3 totals, and the
# efficiency of each framing method (payload/framedsize).
# (I had done PPP, but there are too many possible header sizes.)
#
# this was specifically designed to take data from the NLANR project to
# generate traffic studies, courtesy of k claffy. Kent England checked the
# ATM cell calcualtions.
#

$payload = 0.0;
$hdlcload = 0.0;
# $pppload = 0.0;
$atmload = 0.0;
$atmsnapload = 0.0;
$numpackets = 0.0;

while (<>) {
chop;
($packetsize,$packetcount,@rest) = split;
$hdlcframe = $packetsize + 6;
# $pppframe = $packetsize + 8;
$atmframe = int(($packetsize+8+47)/48) * 53;
$atmsnapframe = int(($packetsize+16+47)/48) * 53;
$payload += $packetsize*$packetcount;
$hdlcload += $hdlcframe*$packetcount;
# $pppload += $pppframe*$packetcount;
$atmload += $atmframe*$packetcount;
$atmsnapload += $atmsnapframe*$packetcount;
$numpackets += $packetcount;
}

printf("total packets seen = %12.0f, total payload bytes seen = %12.0f\n",
$numpackets, $payload);
printf("HDLC framing bytes = %12.0f HDLC efficiency = %2.2f\%\n",
$hdlcload, 100*$payload/$hdlcload);
# printf("PPP framing bytes = %12.0f PPP efficiency = %2.2f\%\n",
# $pppload, 100*$payload/$pppload);
printf("ATM framing bytes = %12.0f ATM efficiency = %2.2f\%\n",
$atmload, 100*$payload/$atmload);
printf("ATM w/snap framing bytes = %12.0f ATM w/snap efficiency = %2.2f\%\n",
$atmsnapload, 100*$payload/$atmsnapload);
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