Marco Di Felice NS2: An Overview
Marco Di Felice
Network Modeling and Simulation with Network Simulator 2 (ns2)
Department of Computer Science and Engineering
University of Bologna. Italy
Marco Di Felice NS2: An Overview
Outline
NS2: Architecture and Design
NS2: Use Cases and Features
NS2: Building simple network models
NS2: Demo & Analysis
Marco Di Felice NS2: An Overview
Ns2: An Overview
NS2: A (discrete event) network simulator tool. NS2: A (discrete event) network simulator tool.
Generally speaking, a network simulator is a dedicated software that allows to:
Model the behaviour of network protocols/applications (e.g. TCP protocol).
Reproduce the behaviour of a computer network as a whole (e.g. a wireless LAN).
Quantify the network performance, through well-defined network metrics (e.g. system throughput).
Marco Di Felice NS2: An Overview
Ns2: WHAT
Q. When may I use a network simulator? Q. When may I use a network simulator?
Case 1: Network planningCase 1: Network planning
Need to build a network infrastructure, with coverage and Quality of Service (QoS) issues.
Q1. Where to place the network gateways?
Q2. How many gateways do I really need?
Marco Di Felice NS2: An Overview
Ns2: WHAT
Q. When may I use a network simulator? Q. When may I use a network simulator?
Case 2: Network EvaluationCase 2: Network Evaluation
Need to evaluate the performance of a (possibly large-scale) network infrastructure or network application.
Use an existing testbed BUT …
Q2. Are the experiments easily reproducible?
Q1. What is the cost of setting up the experiments?
An example: Early Collision Detection Systems In VANETs
Marco Di Felice NS2: An Overview
Ns2: WHAT
Q. When may I use a network simulator? Q. When may I use a network simulator?
Case 3: Research on Networking SystemsCase 3: Research on Networking Systems
Need to evaluate the performance of a new network protocol, architecture, or application.
2. Analytical models might be too complex to model all the components of the scenario under study.
1. A real deployment might not be feasible, or might be too costly.
An example: Proposing a new TCP variant for wireless LANs.
Marco Di Felice NS2: An Overview
Ns2: WHAT
Network simulators might be used to model several kinds of networking systems (wired,
wireless, optical, etc).
In practice, simulation constitutes the main evaluation technique for wireless systems.
Possibility to build reproducible experiments (hard to guarantee with wireless testbeds).
Possibility to reproduce wireless propagation phenomena in an accurate way through probabilistic models (e.g. fading)
Possibility to model large-scale wireless networks composed by several interacting nodes.
Marco Di Felice NS2: An Overview
Ns2: WHAT
Simulation is a meaningful evaluation approach only when it produces “trustable” results.
Validation is needed to certify that the simulation models reproduce correctly the characteristics and dynamics of the system under study.
HOW to VALIDATE a NETWORK MODEL?
Compare Simulation vs Analytical Model
Compare Simulation vs Real Measurements
SIM.THROUGPUT
ANALYTICALEXPERIMENTS
Marco Di Felice NS2: An Overview
Ns2: WHAT
NS2: A network simulation tool
Discrete Event simulator (details later …)
NS2: A network simulation tool
Discrete Event simulator (details later …)
NS2 allows to model and evaluate several IP networking systems (LAN/WAN). It includes:
Network protocols model (e.g. MAC, routing, …)
Network applications model (e.g. CBR, FTP, …)
Queue management algorithms (e.g. FIFO, RED, …)
Network link models (e.g. lossy link)…
Marco Di Felice NS2: An Overview
Ns2: WHERE
http://www.isi.edu/nsnam/ns
http://sourceforge.net/projects/nsnam
download ns-allinone
includes several tools (ns2, nam, awk, otcl, …)
mailing list: [email protected]
documentation:
Reference manual and Tutorials on the website
Other tutorials on the Web
Marco Di Felice NS2: An Overview
Ns2: WHEN
The project started from REAL project in 1989
ns-1 by Floyd and McCanne at Lawrance Berkeley National Laboratory (LBNL).
ns-2 by Steve McCanne, within the VINT project involving a consortium of US universities (LBL, PARC,USC, ...)
currently maintained at USC/ISI (University of Southern California), but several forks available.
NS3 relased in 2008 (now NS3.15)
Deployed by a team lead by Tom Henderson and Sally Floyd (University of Washington)
A completely new tool, not a mere extension of Ns2 !
Marco Di Felice NS2: An Overview
Ns2: WHY
NS2: A network simulation tool
Discrete Event simulator (details later …)
NS2: A network simulation tool
Discrete Event simulator (details later …)
OMNET++ OPNET JiST NS3 GLOMOSIM …
OTHER SIMULATION TOOLS
Q. WHY should I use NS2 for my research?Q. WHY should I use NS2 for my research?
Marco Di Felice NS2: An Overview
Ns2: WHY
MAC LayerMAC Layer
Network LayerNetwork Layer
Transport LayerTransport Layer
Application LayerApplication Layer
Ethernet, 802.11 (WIFI), 802.15.4, Bluetooth, 802.16 (WIMAX), …
Wired routing (RIP), Ad Hoc Routing (AODV, OLSR, DSR), …
UDP, TCP (Reno, NewReno, Vegas, SACK), …
FTP, Telnet, HTTP, Multimedia, Exponential traffic, …
Link Models:Wired Links,Wireless Links,Satellite Links, …
Link Models:Wired Links,Wireless Links,Satellite Links, …
NS2 includes a vast model library of network components. NS2 includes a vast model library of network components.
Marco Di Felice NS2: An Overview
Ns2: WHY
Collaborative deployment environment
possibility to freely modify the existing NS2 code based on each user’s needs.
possibility to share network models for research/education purposes (e.g. a new implementation of
TCP).
possibility to compare his/her own model with models implemented by other research teams.
Multi-platform support
GNU/Linux, MAC OSX, Solaris, Windows, …
NS2 is distributed with GNU General Public Licence (GPL) NS2 is distributed with GNU General Public Licence (GPL)
Marco Di Felice NS2: An Overview
Ns2: WHY
MOBIHOC Conference: Statistics on tools used to produce a simulation study within the papers submitted at the ACM MOBIHOC conference (2000-2006).MOBIHOC Conference: Statistics on tools used to produce a simulation study within the papers submitted at the ACM MOBIHOC conference (2000-2006).
Number of Users: 10KNumber of Users: 10K
Institutes: 1KInstitutes: 1K
% Papers: 44.4%% Papers: 44.4%
NS2 is a popular tool, widely adopted by researchers working on the field of computer networks.
NS2 is a popular tool, widely adopted by researchers working on the field of computer networks.
Marco Di Felice NS2: An Overview
Ns2: WHY
Q. WHY NOT to use NS2 for my research?Q. WHY NOT to use NS2 for my research?
Performance issues Monolithic (basic) scheduler,
scalability constitutes a big issue.
Architectural issues Not really a modular architecture,
difficult to share the code of network models.
Evaluation issues No support for the trace analysis.
#nodes
CP
U t
ime
?
NS2NS2TRACE
Marco Di Felice NS2: An Overview
NS2: HOW
OTCL for simulation setup and execution Quickly define the simulation environment
C++ for model deployment Implement the behaviour of a network component
Two programming languages: C++ and OTCL. Two programming languages: C++ and OTCL.
Marco Di Felice NS2: An Overview
NS2: HOW
The core of the NS2 simulator is the Scheduler The core of the NS2 simulator is the Scheduler
Discrete-event scheduler.
Basic implementation, few optimization.
Event in NS2 IDID TYPETYPE TIMETIME HANDLERHANDLER
TimerEvents
PacketEvents
NS2 Object+ function name
that should be invoked once the
event is fired.
Simulation time of the event
Packet sent
Packet received
Packet dropped
Marco Di Felice NS2: An Overview
NS2: HOW
The Scheduler manages the simulation event list. The Scheduler manages the simulation event list.
The elements are the events of the simulation.
The list is ordered on the basis of the time field.
E1 E2 E3 E4 E5 E6SIMULATION
TIME: t
At each simulation step:
1.The head element of the list is removed2.The simulation time is set to E1.time3.The event handler (E1.handler) is executed.
11 TYPETYPE TIMETIME HANDLERHANDLER
SIMULATION TIME: E1.time
Marco Di Felice NS2: An Overview
NS2: HOW
The Scheduler manages the simulation event list. The Scheduler manages the simulation event list.
The elements are the events of the simulation.
The list is ordered on the basis of the time field.
E2 E3 E4 E5 E6 E7SIMULATION
TIME: t
At each simulation step:
E1.handler is executed, and it might generate new events (e.g. E7), that are inserted into the event list (at a position denoted by E7.time)
SIMULATION TIME: E1.time
E1.HANDLERE1.HANDLER
Marco Di Felice NS2: An Overview
NS2: HOW
Let’s make an example on a network scenario … Let’s make an example on a network scenario …
NODE A NODE B
APPLICATIONAPPLICATION
MACMAC
APPLICATIONAPPLICATION
MACMACETHERNETLINK
SIMULATION TIME: 0
EVENT LIST
At t=0, the Application module of node A is invoked
Marco Di Felice NS2: An Overview
NS2: HOW
Let’s make an example on a network scenario … Let’s make an example on a network scenario …
NODE A NODE B
APPLICATIONAPPLICATION
MACMAC
APPLICATIONAPPLICATION
MACMACETHERNETLINK
SIMULATION TIME: 0
EVENT LIST
A timer event is scheduled at time 4 by node A
11 SendSend 44 A.APPLICATIONA.APPLICATION
E1
Marco Di Felice NS2: An Overview
NS2: HOW
Let’s make an example on a network scenario … Let’s make an example on a network scenario …
NODE A NODE B
APPLICATIONAPPLICATION
MACMAC
APPLICATIONAPPLICATION
MACMACETHERNETLINK
SIMULATION TIME: 4
EVENT LIST
22 RecvRecv 4.54.5 A.MACA.MAC
E2 E3
33 SendSend 88 A.APPLICATIONA.APPLICATION
Marco Di Felice NS2: An Overview
NS2: HOW
Let’s make an example on a network scenario … Let’s make an example on a network scenario …
NODE A NODE B
APPLICATIONAPPLICATION
MACMAC
APPLICATIONAPPLICATION
MACMACETHERNETLINK
SIMULATION TIME: 4.5
EVENT LIST
44 RecvRecv 5.05.0 B.MACB.MAC
E4 E3
33 SendSend 88 A.APPLICATIONA.APPLICATION
Marco Di Felice NS2: An Overview
NS2: HOW
Let’s make an example on a network scenario … Let’s make an example on a network scenario …
NODE A NODE B
APPLICATIONAPPLICATION
MACMAC
APPLICATIONAPPLICATION
MACMACETHERNETLINK
SIMULATION TIME: 5
EVENT LIST
55 RecvRecv 5.25.2 B.APPLICATIONB.APPLICATION
E5 E3
33 SendSend 88 A.APPLICATIONA.APPLICATION
Marco Di Felice NS2: An Overview
NS2: HOW
Let’s make an example on a network scenario … Let’s make an example on a network scenario …
NODE A NODE B
APPLICATIONAPPLICATION
MACMAC
APPLICATIONAPPLICATION
MACMACETHERNETLINK
SIMULATION TIME: 5.2
EVENT LIST
E3
33 SendSend 88 A.APPLICATIONA.APPLICATION
The message is processed by Node B at time 5.2
Marco Di Felice NS2: An Overview
Ns2: HOW
Two ways of interactions:
Modify/Create a new network model
- Network models: network protocols, applications, queue policies, network architecture models, etc.
- Coding in C++
- Recompile at the end.
Configure/Run a network simulation
- Coding in OTCL
- Executed by an interpreter, no need to recompile.
QUITE EASY
NOT EASY
Marco Di Felice NS2: An Overview
Ns2: HOW
Running an OTCL script:
ns script-file.tcl [parameters]
Initialize the scheduler
Define the simulation parameters (e.g. start time)
Build the network topology
Generate the traffic load
Define the protocol stack used by each node
OTCL scripting language, OO-extension of TCL
Marco Di Felice NS2: An Overview
Ns2: OTCL inside
Assign a value to a variable
set x 0
Keyword $ returns the value of a variable
set y $x
Selection Statements if (if < expr > ... else ...)
if {$x == $y } { puts “Hello world” }
Iterative Statements
for {set i 0; $i < $x ; incr i}{puts “Hello world” }
Function Declaration proc name_FUNCTION {par1, ...parn} {... return
$x}
OTCL OverviewOTCL Overview
Marco Di Felice NS2: An Overview
Ns2: HOW
Running an OTCL script:
ns script-file.tcl [parameters]
Initialize the scheduler
Define the simulation parameters (e.g. start time)
Build the network topology
Generate the traffic load
Define the protocol stack used by each node
OTCL scripting language, OO-extension of TCL
Marco Di Felice NS2: An Overview
Ns2: Initialize the Scheduler
Creating the Event Scheduler
set ns [new Simulator]
Starting the simulation
$ns run
Initializing the random number generator
$ns-random SEED
Scheduling the events
$ns at <time> <event>
Stopping the simulation at time 300
$ns at 300 "finish“
SEED=0 current timestamp
All the random variable used by the current simulation are initialized with this SEED.
Marco Di Felice NS2: An Overview
Ns2: HOW
Running an OTCL script:
ns script-file.tcl [parameters]
Initialize the scheduler
Define the simulation parameters (e.g. start time)
Build the network topology
Generate the traffic load
Define the protocol stack used by each node
OTCL scripting language, OO-extension of TCL
Marco Di Felice NS2: An Overview
Ns2: Building the network (WIRED)
Define the nodes of the network
set n0 [$ns node]set n1 [$ns node]
Define the Links among nodes
#Nodes connected with an Ethernet cable, 10 Mb/s $ns duplex-link $n0 $n1 10Mb 100ms DropTail
Specifies bandwidth, delay, and queue policy:DropTail, RED, CBQ, FQ, SFQ, DRR
CASE 1. Modeling a wired network.CASE 1. Modeling a wired network.
Marco Di Felice NS2: An Overview
Ns2: Building the network (WIRED)
Define the error model on wired links
set loss_module [new ErrorModel]$loss_module set rate_ 0.1$loss_module ranvar [new RandomVariable/Uniform]$loss_module drop-target [new Agent/Null]$ns lossmodel $loss_module $n0 $n1
Lossy link between node 0 and node 1, with error rate equal to 0.1. Packets with errors are sent
to Agent/Null, i.e. they are discarded.
CASE 1. Modeling a wired network.CASE 1. Modeling a wired network.
Marco Di Felice NS2: An Overview
Ns2: Building the network (WIRED)
Define the nodes of the network
set n0 [$ns node]set n1 [$ns node]
Define the position
set topograpy [new Topography]$topography load_flatgrid 400 400
Define the position
$n0 set X_ 300$n0 set Y_ 400$n0 set Z_ 0
CASE 1. Modeling a wireless network.CASE 1. Modeling a wireless network.
Set node 0 at position <300,400,0>
Set simulation areato 400mx400m
Marco Di Felice NS2: An Overview
Ns2: Building the network (WIRED)
Define the mobility of wireless nodes
NS_OBJ at TIME “NODE setdest X_COOR Y_COOR SPEED” $ns at 10.5 “$node(0) setdest 100 100 5.0”
CASE 1. Modeling a wireless network.CASE 1. Modeling a wireless network.
At time 10.5, node 0 will move towardposition (100,100) with speed equal to 5 m/s (constant speed)
Utilize the General Object Director (GOD)
set $god [new God] Object that stores global information about the state of the environment (e.g. the matrix of connectivity among nodes)
Marco Di Felice NS2: An Overview
Ns2: Building the network (WIRED)
The mobility traces of wireless nodes can be pre-generated by using the setdest tool (random waypoint model)
./setdest [-n num_of_nodes] [-p pausetime] [-maxspeed]
[-t simtime] [-x][-y] > [fileOutput]
In the TCL script: source “fileOutput”
CASE 1. Modeling a wireless network.CASE 1. Modeling a wireless network.
Any mobility simulator can be used for trace generation.
MOB.TRACE
MOBILITYSIMULATOR
MOBILITYSIMULATOR
OTCLSCRIPT
NS2NS2
e.g. SUMO SOURCE
Marco Di Felice NS2: An Overview
Ns2: HOW
Running an OTCL script:
ns script-file.tcl [parameters]
Initialize the scheduler
Define the simulation parameters (e.g. start time)
Build the network topology
Generate the traffic load
Define the protocol stack used by each node
OTCL scripting language, OO-extension of TCL
Marco Di Felice NS2: An Overview
Ns2: Creating connections (UDP/TCP)
Define the end-points of the communication
TCP Connections:
set src [new Agent/TCP] set dst [new Agent/TCPSink]
UDP Connections:
set src [new Agent/UDP] set dst [new Agent/Null]
Connect sender and receiver
$ns attach-agent $n0 $src $ns attach-agent $n1 $dst $ns connect $src $dst
Several TCP variants:
TCP TahoeTCP RenoTCP NewRenoTCP VegasTCP SACK…
Marco Di Felice NS2: An Overview
Ns2: Attaching Applications
Define the application and attach it to the sender
FTP Agent
set ftp [new Application/FTP] $ftp attach-agent $src $ns at TIME “$ftp start”
CBR Agent
set cbr [new Application/Traffic/CBR] $cbr attach-agent $src $ns at TIME “$cbr start”
Exponential Traffic Generator
set exp [new Application/Traffic/Exponential]
Marco Di Felice NS2: An Overview
Ns2: HOW
Running an OTCL script:
ns script-file.tcl [parameters]
Initialize the scheduler
Define the simulation parameters (e.g. start time)
Build the network topology
Generate the traffic load
Define the protocol stack used by each node
OTCL scripting language, OO-extension of TCL
Marco Di Felice NS2: An Overview
Ns2: HOW
A wireless environment can be modeled by configuring the protocol stack of each node.
$ns_ node-config –phyType $val(netif) -propType $val(prop) -antType $val(type) -llType $val(ll)
-macType $val(mac) -ifqType $val(ifq)
-ifqLen $val(ifqlen) -adhocRouting $val(rp) -topoInstance $topo -channel $chan_
PHY LAYERPHY LAYER
ANTENNA PROPAGATION
MAC LAYERMAC LAYER
NET LAYERNET LAYER
QUEUEQUEUE
LL LAYERLL LAYER
Marco Di Felice NS2: An Overview
Ns2: HOW
A wireless environment can be modeled by configuring the protocol stack of each node.
$ns_ node-config –phyType $val(netif) -propType $val(prop) -antType $val(type) -llType $val(ll)
-macType $val(mac) -ifqType $val(ifq)
-ifqLen $val(ifqlen) -adhocRouting $val(rp) -topoInstance $topo -channel $chan_
PHY LAYERPHY LAYER
ANTENNA PROPAGATION
MAC LAYERMAC LAYER
NET LAYERNET LAYER
QUEUEQUEUE
LL LAYERLL LAYER
Marco Di Felice NS2: An Overview
Ns2: HOW
Configuring the PHY Layer
set val(netif) Phy/WirelessPhy[Ext]
Some parameters to be tuned:
Phy/WirelessPhy set Pt 2.07983391e-01Phy/WirelessPhy set RXThresh 2.591168e-08Phy/WirelessPhy set CSThresh 3.497734e-09
Functionalities offered by the PHY Layers
Signal capture Modulation & Bit-rate setting Modeling of collision/transmission errors …
Marco Di Felice NS2: An Overview
Ns2: HOW
A wireless environment can be modeled by configuring the protocol stack of each node.
$ns_ node-config –phyType $val(netif) -propType $val(prop) -antType $val(type) -llType $val(ll)
-macType $val(mac) -ifqType $val(ifq)
-ifqLen $val(ifqlen) -adhocRouting $val(rp) -topoInstance $topo -channel $chan_
PHY LAYERPHY LAYER
ANTENNA PROPAGATION
MAC LAYERMAC LAYER
NET LAYERNET LAYER
QUEUEQUEUE
LL LAYERLL LAYER
Marco Di Felice NS2: An Overview
Ns2: HOW
Configuring the Propagation model
set val(prop) Propagation/TwoRayGroundset val(prop) Propagation/FreeSpace
FREE SPACE
TWORAY
SENDER RECEIVER
Configuring the Antenna model
set val(antType) Antenna/OmniAntennaset val(antType) Antenna/Directional
DIRECTIONAL OMNIDIRECTIONAL
Marco Di Felice NS2: An Overview
A wireless environment can be modeled by configuring the protocol stack of each node.
$ns_ node-config –phyType $val(netif) -propType $val(prop) -antType $val(type) -llType $val(ll)
-macType $val(mac) -ifqType $val(ifq)
-ifqLen $val(ifqlen) -adhocRouting $val(rp) -topoInstance $topo -channel $chan
Ns2: HOW
PHY LAYERPHY LAYER
ANTENNA PROPAGATION
MAC LAYERMAC LAYER
NET LAYERNET LAYER
QUEUEQUEUE
LL LAYERLL LAYER
Marco Di Felice NS2: An Overview
Ns2: HOW
Configuring the LL layer
set val(ll) LL
Configuring the MAC model
set val(mac) Mac/802_11
Include ARP protocol
Select a MAC protocol:802.11 (Wifi)802.15.4 (Sensors)CSMA/CA… Configuring the Queue Layer
set val(ifq) Queue/DropTail/PrimaryQueueset val(ifqlen) 50
Define the queue policy:PrimaryQueueRED Queue…
Set the queue length
Marco Di Felice NS2: An Overview
Ns2: HOW
A wireless environment can be modeled by configuring the protocol stack of each node.
$ns_ node-config –phyType $val(netif) -propType $val(prop) -antType $val(type) -llType $val(ll)
-macType $val(mac) -ifqType $val(ifq)
-ifqLen $val(ifqlen) -adhocRouting $val(rp) -topoInstance $topo -channel $chan
PHY LAYERPHY LAYER
ANTENNA PROPAGATION
MAC LAYERMAC LAYER
NET LAYERNET LAYER
QUEUEQUEUE
LL LAYERLL LAYER
Marco Di Felice NS2: An Overview
Ns2: HOW
Configuring the routing protocol
set val(adhocrouting) AODV
Select a routing protocol for multi-hop networks:AODV, DSDV, DSR, TORA, ….
SOURCE
DESTINATIONROUTING PATH
Marco Di Felice NS2: An Overview
Ns2: HOW
Two ways of interactions:
Modify/Create a new network model
- Network models: network protocols, applications, queue policies, network architecture models, etc.
- Coding in C++
- Recompile at the end.
Configure/Run a network simulation
- Coding in OTCL
- Executed by an interpreter, no need to recompile.
QUITE EASY
NOT EASY
Marco Di Felice NS2: An Overview
Ns2: HOW
In C++, each model extends the class NSObject.
Each NSObject has a correspective in OTCL.
Marco Di Felice NS2: An Overview
Ns2: HOW
When creating a new model in C++:
Extend the NSObject class
Create the corresponding OTCL class
Implement these methods
recv(Packet* p, Handler* h) Callback once a packet is received from the upper layer.
command(int argc, const char*const* argv) Binding between C++ and OTCL for the parameter passing from the TCL script.
Marco Di Felice NS2: An Overview
Ns2: Simulation Output (TRACE)
The output of the simulation is a trace file, containing the description of the events occurred during the simulation.
s 10.00000 0 MAC --- 0 RTS 44 [253e 1 0 0]r 10.00041 1 MAC --- 0 RTS 44 [253e 1 0 0]s 10.00042 1 MAC --- 0 CTS 38 [2404 0 0 0]r 10.00075 0 MAC --- 0 CTS 38 [2404 0 0 0]s 10.00076 0 MAC --- 100 cbr 1112 [13a 1 0 800]r 10.00982 1 MAC --- 100 cbr 1112 [13a 1 0 800]
Simulation Time
Event Type
NodePacket
ID
Traffictype
Packetsize
MAC Header
Marco Di Felice NS2: An Overview
Ns2: Simulation Output (TRACE)
Depending on the length of the simulation, the trace file might occupy lots of bytes on the disk.
$ns_ node-config –agentTrace ON/OFF -routerTrace ON/OFF
-macTrace ON/OFF -mobilityTrace ON/OFF
Configure the granularity of the tracing process …
s 10.00078 1 AGT --- 100 cbr 1112 [13a 1 0 800]s 10.00078 1 MAC --- 100 cbr 1112 [13a 1 0 800]r 10.00078 0 MAC --- 100 cbr 1112 [13a 1 0 800]r 10.00078 0 AGT --- 100 cbr 1112 [13a 1 0 800]
Marco Di Felice NS2: An Overview
Ns2: Simulation Output (NAM)
The output of the simulation can be visualized by using the Network Animator (NAM) tool.
Marco Di Felice NS2: An Overview
Ns2: Analysis of Simulation Results
NS2 does NOT provide any specific support for the data analysis/validation and for the computation of performance metrics (e.g. throughput, delay).
Run multiple simulations with different seeds
Remove the transient phase from the trace file
Extract the performance metrics from the trace file
Compute the average and confidence intervals
Plot the results
External data processing tools must be used.
AWK, PERL, …GNUPLOT
Marco Di Felice NS2: An Overview
Ns2: Analysis of Simulation Results
Example: Computing the system throughput in AWK.
BEGIN {recvByte=sim_time=transient=0.0
}
($1==‘r’) && ($4==‘AGT’) && ($2>transient) {
recvByte+=$8sim_time=$2
}
END {print recvByte/(sime_time-transient)
}
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