Skip to main content

Queuing Models in NS2

M/M/1 is a system with poisson arrival time, servicing exponentially and a queue of unlimited capacity and type of FIFO Queue. This is the simplest queuing system.  NS2 supports various distributions like pareto, exponential, constant, unifrom, etc to handle the network dynamics and metrics.
So it is very easy to test the given network link to monitor a given queue using any of these queuing models. The listing 3 and 4 are monitoring the link when DropTail queue is used with a capacity of finite and infinite.
Listing 13.3 uses infinite capacity and Listing 13.4 uses Finite capacity The output screen shot is shown below the scripts for further understanding

Listing 3 – M/M/1 Queuing Model
#new Simulator creation
set ns [new Simulator]
#trace file creation for capturing the UDP data
set tf [open out.tr w]
$ns trace-all $tf

#setting the exponential distribution param
set lambda 30.0
set mu     33.0

#creation of nodes
set n1 [$ns node]
set n2 [$ns node]
#The queue limit is 1Lakh as the capacity is infinite. Simulation will take # more time when the limit is increased.
set link [$ns simplex-link $n1 $n2 100kb 0ms DropTail]
$ns queue-limit $n1 $n2 100000

# generate random interarrival times and packet sizes
set InterArrivalTime [new RandomVariable/Exponential]
$InterArrivalTime set avg_ [expr 1/$lambda]
set pktSize [new RandomVariable/Exponential]
$pktSize set avg_ [expr 100000.0/(8*$mu)]

#create new agent UDP
set src [new Agent/UDP]
$ns attach-agent $n1 $src

# queue monitoring and send the output to queue.out file
set qmon [$ns monitor-queue $n1 $n2 [open queue.out w] 0.1]
$link queue-sample-timeout

proc finish {} {
    global ns tf
    $ns flush-trace
    close $tf
    exit 0
}

proc sendpacket {} {
    global ns src InterArrivalTime pktSize
    set time [$ns now]
    $ns at [expr $time + [$InterArrivalTime value]] "sendpacket"
    set bytes [expr round ([$pktSize value])]
    $src send $bytes
}

set sink [new Agent/Null]
$ns attach-agent $n2 $sink
$ns connect $src $sink
$ns at 0.0001 "sendpacket"
$ns at 1000.0 "finish"

$ns run
To see the output of the above script, execute the following in the terminal
Prompt] gawk '{ print $1, $4, $5, $6, $7, $8, $9, $10, $11 }' queue.out > qm.pre
Prompt] xgraph qm.pre -geometry 500x500 -t “MM1 Queuing Example”
Here is the output screen
Queuing models in ns2
Queuing models in ns2


In the above Listing 13.3, large buffers are used to avoid losses. One can use smaller buffers and observe losses. The way to compute the loss probability from the simulation is simply to divide the total number of losses by the total number of arrivals, both given in the last line of the monitor-queue file. The command
$src set packetSize_ 100000
may be added.
The loss may be computed using the formula
P = pow(p,k)/Pow(p,i);


Listing 4 – M/M/1 with Finite capacity
#create new simulator
set ns [new Simulator]
#open the trace file for capturing UDP
set tf [open out.tr w]
$ns trace-all $tf

#setting the parameters for Exponential distribution
set lambda   30.0
set mu       33.0
set qsize     2
set duration  2000

#creation of new nodes
set n1 [$ns node]
set n2 [$ns node]
#creation of link with queue
set link [$ns simplex-link $n1 $n2 100kb 0ms DropTail]
#setting the queue size as 2
$ns queue-limit $n1 $n2 $qsize

# generate random interarrival times and packet sizes
set InterArrivalTime [new RandomVariable/Exponential]
$InterArrivalTime set avg_ [expr 1/$lambda]
set pktSize [new RandomVariable/Exponential]
$pktSize set avg_ [expr 100000.0/(8*$mu)]

#creation of new UDP Agent
set src [new Agent/UDP]
$src set packetSize_ 100000
$ns attach-agent $n1 $src

#queue monitoring
set qmon [$ns monitor-queue $n1 $n2 [open queue1.out w] 0.1]
$link queue-sample-timeout

proc finish {} {
    global ns tf
    $ns flush-trace
    close $tf
    exit 0
}

proc sendpacket {} {
    global ns src InterArrivalTime pktSize
    set time [$ns now]
    $ns at [expr $time + [$InterArrivalTime value]] "sendpacket"
    set bytes [expr round ([$pktSize value])]
    $src send $bytes
}

set sink [new Agent/Null]
$ns attach-agent $n2 $sink
$ns connect $src $sink
$ns at 0.0001 "sendpacket"
$ns at $duration "finish"

$ns run
To see the output of the above script, execute the following in the terminal
Prompt] gawk '{ print $1, $4, $5, $6, $7, $8, $9, $10, $11 }' queue1.out > qm1.pre
Prompt] xgraph qm1.pre -geometry 500x500 -t “MM1 Queuing Example”
Here is the output screen
 
Queuing models in ns2
Queuing models in ns2

T S Pradeep Kumar

Comments

Popular posts from this blog

Installing ns-3.34 in Ubuntu 20.04

This post shows how to install ns 3.34 in Ubuntu 20.04 LTS Prerequisites: Fresh installation of Ubuntu Version 20.04 LTS  ns3.34 can be downloaded from here Follow the video link for complete step by step instructions on the installation.  This version fixes the compilation issues of vanet-routing-compare.cc (bug in ns3.33)  Issue the following commands after opening a terminal  $ sudo apt update $ sudo apt install g++ python3 python3-dev python-dev pkg-config sqlite3 python3-setuptools git qt5-default gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar openmpi-bin openmpi-common openmpi-doc libopenmpi-dev tcpdump wireshark libxml2 libxml2-dev Unzip or untar the ns-allinone-3.34.tar.bz2 in the home folder (in my case its /home/pradeepkumar) $ cd ns-allinone-3.34/ $ ./build.py --enable-examples --enable-tests  Once the installation is completed, you may get an output show

Installation of ns3 in Windows 10 and Windows 11 OS using WSL (Windows Subsystem for Linux)

This post shows how to install ns-3.33 in Windows 10 through WSL (Windows Subsystem for Linux) This posts works for Windows 11 also (I have tested it on a Windows 11 ISO and it works the Same way as mentioned in the following post.) This post will work for ns-3.3x version. Prerequisites : Install Windows Subsystem for Linux with GUI: Please refer the following video  System Information: OS used: Windows 10 and WSL (Ubuntu 20.04) GUI: XServer for Windows NS3 Version: ns-3.33 See the following complete video on how to install ns3 in Windows 10 Step 0 : Open XLaunch Step 1 :  Open WSL using PowerShell and open it as Administrator Command:/  wsl $ xfce4-session The GUI of Ubuntu Opens within Windows 10 OS. Step 2 : Download ns3 from nsnam.org website through Mozilla Firefox browser Step 3: Open a Terminal  $ sudo apt update $ sudo apt install build-essential autoconf automake libxmu-dev python3-pygraphviz cvs mercurial bzr git cmake p7zip-full python3-matplotlib python-tk python3-dev qt5-q

Installing NS-3.32 in Ubuntu 20.04

This is about installing ns version 3.32 in Ubuntu 20.04 LTS. #ns3 #ns3 .32 #networksimulation The commands used in the video are given here. $] sudo apt update $] sudo apt install build-essential autoconf automake libxmu-dev python3-pygraphviz cvs mercurial bzr git cmake p7zip-full python3-matplotlib python-tk python3-dev qt5-qmake qt5-default gnuplot-x11 wireshark Download the ns-allinone-3.32.tar.bz2 package from nsnam.org and copy it to /home/ folder See the full video for detailed instructions Extract it either in GUI or using command $] tar jxvf ns-allinone-3.32.tar.bz2 $] cd ns-allinone-3.32/ $] ./build.py --enable-examples --enable-tests The above command will take some time to install all the packages  You can see the output as shown below ns3 To check whether ns3 installed successfully, use the following commands. $] cd ns-3.32/ $] ./waf --run hello-simulator You should get the output as Hello Simulator $] ./waf --run first This is the example from the ns-3.32/exa