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<H1 ALIGN=CENTER>XI. Generating node-movement and traffic-connection files
for large wireless scenarios</H1>
<P>
[<A HREF="nsscript6.html">Previous section</A>]
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</P>
<P>
We have used traffic-pattern and node-movement files available with the ns
distribution for simulation examples in <A
HREF="nsscript5.html">section IX</A>
and <A HREF="nsscript6.html">section X</A>. In this section we will
discuss
how to use CMU's traffic and scenario generating scripts to create these
files. This section is divided into 2 subsections. The <A HREF="nsscript7.html#first">first subsection</A>
talks about
the traffic-pattern generating script, how it works and the random TCP and/or
CBR flows it produces.
The <A HREF="nsscript7.html#second">second subsection</A> is about CMU's node-movement generator "setdest"
which can be used to create random waypoint node movements for
mobilenodes.
</P>
<P>
<I>IMPORTANT: This tutorial chapter uses a revised version of setdest
which is not available in the ns2.1b5 version. So please download the <A
HREF="http://www.isi.edu/nsnam/dist/vint/ns-src-current.tar.gz">daily
snapshot</A>
unless a release is made for version ns2.1b6 or higher. The current
snapshot version is updated daily, so please check the <A
HREF="http://www.isi.edu/nsnam/ns/ns-tests.html">validation
results</A> for that day before downloading, as these snapshots can
sometimes be unstable due to ongoing changes made by ns-developers.</I>
</P>
<HR>
<A NAME="first"></A>
<P><STRONG>XI.1. Creating random traffic-pattern for wireless
scenarios.</STRONG>
</P>
<P>
Random traffic connections of TCP and CBR can be setup between mobilenodes
using a traffic-scenario generator script.
This traffic generator script is available under
~ns/indep-utils/cmu-scen-gen and is called cbrgen.tcl. It can be used to
create CBR and TCP traffics connections between wireless mobilenodes.
In order to create a traffic-connection file, we need to define the type
of traffic connection (CBR or TCP), the number of nodes and maximum number
of connections to be setup between them, a random seed and incase of CBR
connections, a rate whose inverse value is used to compute the interval
time between the CBR pkts. So the command line looks like the following:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
ns cbrgen.tcl [-type cbr|tcp] [-nn nodes] [-seed seed] [-mc connections]
[-rate rate]
</PRE></CODE></TD></TABLE>
</P>
<P>
The start times for the TCP/CBR connections are randomly generated with a
maximum value set at 180.0s. Go through the tcl script cbrgen.tcl for the
details of the traffic-generator implementation.
</P>
<P>
For example, let us try to create a CBR connection file between 10 nodes,
having maximum of 8 connections, with a seed value of 1.0 and a rate of
4.0. So at the prompt type:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
ns cbrgen.tcl -type cbr -nn 10 -seed 1.0 -mc 8 -rate 4.0 > cbr-10-test
</PRE></CODE></TD></TABLE>
</P>
<P>
From cbr-10-test file (into which the output of the generator is
redirected) thus created, one of the cbr connections looks like the
following:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
#
# 2 connecting to 3 at time 82.557023746220864
#
set udp_(0) [new Agent/UDP]
$ns_ attach-agent $node_(2) $udp_(0)
set null_(0) [new Agent/Null]
$ns_ attach-agent $node_(3) $null_(0)
set cbr_(0) [new Application/Traffic/CBR]
$cbr_(0) set packetSize_ 512
$cbr_(0) set interval_ 0.25
$cbr_(0) set random_ 1
$cbr_(0) set maxpkts_ 10000
$cbr_(0) attach-agent $udp_(0)
$ns_ connect $udp_(0) $null_(0)
$ns_ at 82.557023746220864 "$cbr_(0) start"
</PRE></CODE></TD></TABLE>
Thus a UDP connection is setup between node 2 and 3. Total UDP sources
(chosen between nodes 0-10) and total number of connections setup is
indicated as 5 and 8 respectively, at the end of the file cbr-10-test.
</P>
<P>
Similarly TCP connection files can be created using "type" as tcp.
An example would be:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
ns cbrgen.tcl -type tcp -nn 25 -seed 0.0 -mc 8 > tcp-25-test
</PRE></CODE></TD></TABLE>
A typical connection from tcp-25-test looks like the following:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
#
# 5 connecting to 7 at time 163.0399642433226
#
set tcp_(1) [$ns_ create-connection TCP $node_(5) TCPSink $node_(7) 0]
$tcp_(1) set window_ 32
$tcp_(1) set packetSize_ 512
set ftp_(1) [$tcp_(1) attach-source FTP]
$ns_ at 163.0399642433226 "$ftp_(1) start"
</PRE></CODE></TD></TABLE>
</P>
<A NAME="second"></A>
<P><STRONG> XI.2. Creating node-movements for wireless scenarios.
</STRONG><BR>
</P>
<P>
The node-movement generator is available under
~ns/indep-utils/cmu-scen-gen/setdest
directory and consists of setdest{.cc,.h} and Makefile.
CMU's version of setdest used system dependent /dev/random and made
calls to library functions initstate() for generating random numbers. That
was replaced with a more portable random number generator (class RNG)
available in ns. In order to compile the revised setdest.cc do the
following:
<BR>1. Go to ns directory and run "configure" (you probably have done that
already while building ns). This creates a makefile for setdest.
<BR>2.Go to indep-utils/cmu-scen-gen/setdest. Run "make" , which first
creates a stand-alone object file for ~ns/rng.cc (the stand-alone
version doesnot use Tclcl libs) and then creates the executable setdest.
<BR>3. Run setdest with arguments as shown below:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
./setdest [-n num_of_nodes] [-p pausetime] [-s maxspeed] [-t simtime] \
[-x maxx] [-y maxy] > [outdir/movement-file]
</PRE></CODE></TD></TABLE>
</P>
<P>
Lets say we want to create a node-movement scenario consisting of 20
nodes moving with maximum speed of 10.0m/s with an average pause between
movement being 2s. We want the simulation to stop after 200s and the
topology boundary is defined as 500 X 500. So our command line will look
like:
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
./setdest -n 20 -p 2.0 -s 10.0 -t 200 -x 500 -y 500 > scen-20-test
</PRE></CODE></TD></TABLE>
</P>
<P>
The output is written to stdout by default. We redirect the output to
file scen-20-test. The file begins with the initial position
of the nodes and goes on to define the node movements.
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
$ns_ at 2.000000000000 "$node_(0) setdest 90.441179033457 44.896095544010
1.373556960010"
</PRE></CODE></TD></TABLE>
This line from scen-20-test defines that node_(0) at time 2.0s starts
to move toward destination
(90.44, 44.89) at a speed of 1.37m/s. These command lines can be used to change
direction and speed of movement of mobilenodes.
</P>
<P>
Directives for GOD are present as well in node-movement file.
The General Operations Director (GOD) object is used to store global
information about the state of the environment, network, or nodes that
an omniscent observer would have, but that should not be made known to
any participant in the simulation.
</P>
<P>
Currently, the god object is used only to store an array of the
shortest number of hops required to reach from one node to an other.
The god object does not calculate this on the fly during simulation runs,
since it can be quite time consuming. The information is loaded into
the god object from the movement pattern file where lines of the form
<TABLE BGCOLOR="#eeeeee" CELLPADDING=5><TD><CODE><PRE>
$ns_ at 899.642 "$god_ set-dist 23 46 2"
</PRE></CODE></TD></TABLE>
are used to load the god object with the knowledge that the shortest
path between node 23 and node 46 changed to 2 hops at time 899.642.
</P>
<P>
The setdest program generates node-movement files
using the random waypoint algorithm. These files already include the
lines to load the god object with the appropriate information at the
appropriate time.
</P>
<P>
Another program calcdest (also available in ~ns/indep-utils/cmu-scen-gen/setdest)
can be used to annotate movement pattern files generated by other means with
the lines of god
information. calcdest makes several assumptions about the
format of the lines in the input movement pattern file which will
cause it to fail if the file is not formatted properly. If
calcdest rejects a movement pattern file you have created, the
easiest way to format it properly is often to load it into
ad-hockey and then save it out again. If ad-hockey can
read your input correctly, its output will be properly formatted for
calcdest.
</P>
<P>
Both calcdest and setdest calculate the shortest number
of hops between nodes based on the nominal radio range, ignoring any
effects that might be introduced by the propagation model in an actual
simulation. The nominal range is either provided as an argument to
the programs, or extracted from the header on the movement pattern
file.
</P>
<P>
The path length information was used by the Monarch Project to analyze
the path length optimality of ad hoc network routing protocols, and so
was printed out as part of the CMUTrace output for each packet.
</P>
<P>
Other uses that CMU found for the information:
<LI>Characterizing the rate of topology change in a movement pattern.
<LI>Identifying the frequency and size of partitions.
<LI>Experimenting with the behavior of the routing protocols if the
god information is used to provide them with ``perfect'' neighbor
information at zero cost.
</P>
<P>
Thus at the end of the node-movement file are listed information like number
of destination unreachable,
total number of route and connectivity changes for mobilenodes and the same
info for each mobilenode.
</P>
<P>
The revised (more portable)
version of setdest ( files revised are: setdest{.cc,.h}, ~ns/rng{.cc,.h},
~ns/Makefile.in ) should be available from the latest ns distribution.
If not, you could download the daily snapshot version of ns from
<A HREF="http://www.isi.edu/nsnam/ns/ns-build.html"> ns-build
page</A>.
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VINT <BR>
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