From: jamin@caldera.usc.edu (Sugih Jamin)
Newsgroups: comp.protocols.tcp-ip
Subject: Bug fix for tcplib, a library of TCP traffic model
Date: 15 Oct 1992 09:14:33 -0700
Organization: University of Southern California, Los Angeles, CA
Distribution: world
NNTP-Posting-Host: caldera.usc.edu

Hello,

This is a bug fix message for tcplib, a library of TCP traffic models.
We apologize for any inconvenience that this message may cause you.

Vern Paxson of LBL noticed that "there's a rather huge spike in the UCB 
ftp-data connections [of the trace data used in tcplib].  During that 
particular day [when the traces was collected,] there were 2312 
connections of 74 bytes each between the same two UCB and remote hosts.  
[Ninety five percent] of these connections came between 30 and 45 seconds
apart.  None of the other datasets showed this sort of traffic so it
clearly appears to be anomalous."

Fortunately for us...the anomaly did not show up in either our SIGCOMM or 
Journal of Internetworking papers because of the way we grouped multiple 
ftp-data connections into one conversation.

We have taken out the anomalous data from the two data files:
  ftp.nitems
  ftp.itemsize.
Both are available on jerico.usc.edu (128.125.11.6) for anonymous ftp,
in the directory pub/jamin/tcplib.  These files are meant to replace 
their namesakes in the tcplib/data.  To update your libtcp.a, remember 
to do a make in your tcplib directory after you replaced the two files.

Alternatively, you can get the new library or the whole set of sources 
from jerico.usc.edu:pub/jamin/tcplib as described below.  The papers 
[Caceres91] and [Danzig92] cited in the tech report are also available
for anonymous ftp from jerico.usc.edu:~ftp/pub/jamin/traffic. The file
traffic.ps.Z is for [Caceres91] and the files journal.part[1-4].ps.Z 
are for [Danzig92].
=======================================================================
The following technical report and the source library it describes are
available for anonymous ftp from jerico.usc.edu:~ftp/pub/jamin/tcplib.
(Jerico's IP address is 128.125.51.6.) The directory contains the 
following files:

  README
  libtcp_ds31_ultrix41.a.Z
  libtcp_hp90_hpux847.a.Z   /* not supported anymore because we 
                               lost access to our hp machine. */
  libtcp_sun3_sunos411.a.Z
  libtcp_sun4_sunos411.a.Z
  brkdn_dist.h
  tcpapps.h
  tcplib.1
  tcplib.tar.Z
  tcplibtr.ps.Z

All you need to transfer to use the library are: README, brkdn_dist.h, 
tcpapps.h, tcplib.1, and one of libtcp* that matches your setup.  You
need tcplib.tar.Z only if you must generate the library yourself.  
The file tcplibtr.ps.Z is the PostScript version of the tech. report 
which is introduced below:


    tcplib: A Library of TCP Internetwork Traffic Characteristics

                 Peter B. Danzig       Sugih Jamin

                    Computer Science Department, 
                 University of Southern California,
                 Los Angeles, California 90089-0781

                     traffic@excalibur.usc.edu

                            USC-CS-91-495

1. Introduction
  When simulating computer networks, it is necessary to specify the 
traffic between network nodes.  Typically, simulation studies of 
wide-area tcp/ip networks model traffic as a combination of Poisson 
processes and maximal rate streams--corresponding to telnet traffic 
and large file transfers respectively.  Such traffic models are 
justified when the modeler wants to show, for example, that his flow 
control or gateway scheduling algorithm responds well to worst case 
traffic or when essentially nothing is known about the real network
traffic.  However, such models do not reveal how similarly robust 
algorithms respond to the common case load.
  This paper describes tcplib, a library to help generate realistic 
tcp/ip network traffic.  Tcplib is motivated by our observation that 
present-day wide-area tcp/ip traffic cannot be accurately modeled with 
simple analytical expressions, but instead requires a combination of 
detailed knowledge of the end-user applications responsible for the 
traffic and certain measured probability distributions [Caceres91].  
We collected three-day traces of wide-area Internet traffic at UC 
Berkeley, University of Southern California, and Bell Communications 
Research.  Our study identified that out of more than 35 different 
application programs, ftp, smtp, nntp, vmnet, telnet, and rlogin are
responsible for 96% of wide-area tcp/ip bytes.  Two related studies, 
one at University College London and the other at Lawrence Berkeley 
Laboratory, identified a subset of these six applications as 
responsible for most of their wide-area tcp traffic [Crowcroft91] 
[Paxson91]. Tcplib models five of these six applications.  It excluded 
vmnet, an IBM mail exchange application , because it was absent from 
three of the five traces.  Furthermore, since telnet and rlogin have 
essentially the same characteristics, we have included in tcplib only 
routines describing telnetUs.  Additionally, we included characteristics 
of phone conversations based on the study reported in [Brady65] and a 
distribution of conversations composition breakdown derived from several 
stub-network traces.
-- 
sugih                                              Use email, save a tree.