NS2 Simulation : Traffic Generators

PART 1

Simulation of Networks
Traffic generation in ns
Traffic generation is described in Chapter 32 of the ns Manual.

Some extracts:

32.5 Applications objects
An application object may be of two types, a traffic generator or a simulated application. Traffic generator objects generate traffic and can be of four types, namely, exponential, pareto, CBR and traffic trace.

Application/Traffic/Exponential objects
Exponential traffic objects generate On/Off traffic. During "on" periods, packets are generated at a constant burst rate. During "off" periods, no traffic is generated. Burst times and idle times are taken from exponential distributions. Configuration parameters are:

PacketSize_
constant size of packets generated.
burst_time_
average on time for generator.
idle_time_
average off time for generator.
rate_
sending rate during on time.

Application/Traffic/Pareto
Application/Traffic/Pareto objects generate On/Off traffic with burst times and idle times taken from pareto distributions. Configuration parameters are:

PacketSize_
constant size of packets generated.
burst_time_
average on time for generator.
idle_time_
average off time for generator.
rate_
sending rate during on time.
shape_
the shape parameter used by pareto distribution.

Application/Traffic/CBR
CBR objects generate packets at a constant bit rate.

$cbr start
Causes the source to start generating packets.

$cbr stop
Causes the source to stop generating packets.

Configuration parameters are:

PacketSize_
constant size of packets generated.
rate_
sending rate.
interval_
(optional) interval between packets.
random_
whether or not to introduce random noise in the scheduled departure times. defualt is off.
maxpkts_
maximum number of packets to send.

Application/Traffic/Trace
Application/Traffic/Trace objects are used to generate traffic from a trace file. $trace attach-tracefile tfile
Attach the Tracefile object tfile to this trace. The Tracefile object specifies the trace file from which the traffic data is to be read. Multiple Application/Traffic/Trace objects can be attached to the same Tracefile object. A random starting place within the Tracefile is chosen for each Application/Traffic/Trace object.

There are no configuration parameters for this object.

TRACEFILE OBJECTS Tracefile objects are used to specify the trace file that is to be used for generating traffic (see Application/Traffic/Trace objects described earlier in this section). $tracefile is an instance of the Tracefile Object.
$tracefile filename trace-input
Set the filename from which the traffic trace data is to be read to trace-input.

There are no configuration parameters for this object. A trace file consists of any number of fixed length records. Each record consists of 2 32 bit fields. The first indicates the interval until the next packet is generated in microseconds. The second indicates the length of the next packet in bytes.


======================================
Link: I found this article at the following Location:
http://www.it.usyd.edu.au/~deveritt/networksimulation/trafficgeneration.html
======================================




PART 2

=============================
Code
=============================
## tg.tcl
## simple example to demonstrate use of traffic generation modules
##
## topology consists of 6 nodes. 4 traffic sources are attached
## to each of 4 'access' nodes. These nodes have links to a single
## 'concentrator' node, which is connected by the bottleneck link
## to the destination node.
##
## there are 4 source agents that generate packets
## 1 generates traffic based on an Exponential On/Off distribution
## 1 generates traffic based on a Pareto On/Off distribution
## 2 generate traffic using the trace file 'example-trace'.
##
set stoptime 10.0
set plottime 11.0

set ns [new Simulator]

set n0 [$ns node]
set n1 [$ns node]

set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
set n5 [$ns node]

set f [open out.tr w]
$ns trace-all $f
set nf [open out.nam w]
$ns namtrace-all $nf

$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail

$ns duplex-link $n0 $n2 10Mb 5ms DropTail
$ns duplex-link $n0 $n3 10Mb 5ms DropTail
$ns duplex-link $n0 $n4 10Mb 5ms DropTail
$ns duplex-link $n0 $n5 10Mb 5ms DropTail

$ns duplex-link-op $n0 $n1 orient right
$ns duplex-link-op $n0 $n2 orient left-up
$ns duplex-link-op $n0 $n3 orient left
$ns duplex-link-op $n0 $n4 orient left-down
$ns duplex-link-op $n0 $n5 orient down

$ns duplex-link-op $n0 $n1 queuePos 0.5

#$ns trace-queue $n0 $n1 $f

## set up the exponential on/off source, parameterized by packet size,
## ave on time, ave off time and peak rate

set s1 [new Agent/UDP]
$ns attach-agent $n2 $s1

set null1 [new Agent/Null]
$ns attach-agent $n1 $null1

$ns connect $s1 $null1

set exp1 [new Application/Traffic/Exponential]
$exp1 set packetSize_ 210
$exp1 set burst_time_ 500ms
$exp1 set idle_time_ 500ms
$exp1 set rate_ 100k

$exp1 attach-agent $s1

## set up the pareto on/off source, parameterized by packet size,
## ave on time, ave off time, peak rate and pareto shape parameter

set s2 [new Agent/UDP]
$ns attach-agent $n3 $s2

set null2 [new Agent/Null]
$ns attach-agent $n1 $null2

$ns connect $s2 $null2

set pareto2 [new Application/Traffic/Pareto]
$pareto2 set packetSize_ 210
$pareto2 set burst_time_ 500ms
$pareto2 set idle_time_ 500ms
$pareto2 set rate_ 200k
$pareto2 set shape_ 1.5

$pareto2 attach-agent $s2

## initialize a trace file
set tfile [new Tracefile]
$tfile filename example-trace

## set up a source that uses the trace file

set s3 [new Agent/UDP]
$ns attach-agent $n4 $s3

set null3 [new Agent/Null]
$ns attach-agent $n1 $null3

$ns connect $s3 $null3

set tfile [new Tracefile]
#$tfile filename /tmp/example-trace
$tfile filename example-trace

set trace3 [new Application/Traffic/Trace]
$trace3 attach-tracefile $tfile

$trace3 attach-agent $s3

## attach a 2nd source to the same trace file

set s4 [new Agent/UDP]
$ns attach-agent $n5 $s4

set null4 [new Agent/Null]
$ns attach-agent $n1 $null4

$ns connect $s4 $null4

set trace4 [new Application/Traffic/Trace]
$trace4 attach-tracefile $tfile

$trace4 attach-agent $s4

$ns at 1.0 "$exp1 start"
$ns at 1.0 "$pareto2 start"
$ns at 1.0 "$trace3 start"
$ns at 1.0 "$trace4 start"

$ns at $stoptime "$exp1 stop"
$ns at $stoptime "$pareto2 stop"
$ns at $stoptime "$trace3 stop"
$ns at $stoptime "$trace4 stop"

$ns at $plottime "close $f"
$ns at $plottime "finish tg"

proc finish file {

set f [open temp.rands w]
puts $f "TitleText: $file"
puts $f "Device: Postscript"

exec rm -f temp.p1 temp.p2 temp.p3 temp.p4
exec touch temp.p1 temp.p2 temp.p3 temp.p4
#
#
exec awk {
{
if (($1 == "+") && ($3 != 0) && ($9 == 2.0)) \
print $2, 2
}
} out.tr > temp.p1
exec awk {
{
if (($1 == "+") && ($3 != 0) && ($9 == 3.0)) \
print $2, 3
}
} out.tr > temp.p2
exec awk {
{
if (($1 == "+") && ($3 != 0) && ($9 == 4.0)) \
print $2, 4
}
} out.tr > temp.p3
exec awk {
{
if (($1 == "+") && ($3 != 0) && ($9 == 5.0)) \
print $2, 5
}
} out.tr > temp.p4

puts $f [format "\n\"ExpOnOff"]
flush $f
exec cat temp.p1 >@ $f
flush $f
puts $f [format "\n\"ParetoOnOff"]
flush $f
exec cat temp.p2 >@ $f
flush $f
puts $f [format "\n\"Trace1"]
flush $f
exec cat temp.p3 >@ $f
flush $f
puts $f [format "\n\"Trace2"]
flush $f
exec cat temp.p4 >@ $f
flush $f

close $f
exec rm -f temp.p1 temp.p2 temp.p3 temp.p4
exec xgraph -bb -tk -nl -m -x time -y "source node" temp.rands &

puts "running nam..."
exec nam out.nam &

exec rm -f out.tr

}

$ns run


exit 0


====================================
Link: Found the above code at the following link:
http://www.it.usyd.edu.au/~deveritt/networksimulation/tg.tcl
====================================