Ns2 Introduction

Introduction to Ns-2Zhibin WU WINLAB, ECE Dept. Rutgers U. zhibinwu@winlab.rutgers.edu

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Goals

Understanding NS-2 Hands-on Experience with NS2

Ns-2 by Example Write your own scripts Implementing new functionality

Extending NS2

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Schedule

Presentation (60 min) Group Assignments (10 min) Practices (1 Hr) Q & A session (~15 min)

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Talk Overview

What is ns-2? (the evolution) Architecture Basic Tcl/Otcl commands Elements of an ns-2 simulation Example Online Resources & Documentation

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What is ns?

A discrete event, packet-level simulator Targeted at networking research Supports the simulation of intserv/diffserv, Multicast, Transport, Applications, Wireless (fixed, mobile, satellite) REAL variant (1989)DARPA (LBL, Xerox PARC, UCB, and USC/ISI) (1995) Ns-3 Project (Ongoing)

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Status

ns-2

100K lines of C++ 70K lines of OTcl 50K+ lines of test suite, examples, docs

Platforms

Most UNIX and UNIX-like systems (FreeBSD, Linux, Sun Solaris) Window 95/98/NT with Cygwin (Emulation only for FreeBSD for now)

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Remember!

A simulator model of a real-world system is necessarily a simplification. For example, in simulating TCP

No SYN/FIN Equal size segments No variable window advertisement

Bugs: Users of ns are responsible for verifying for themselves that their simulations are not invalidated by bugs.7

Architecture: Object-Oriented

C++ for data

Per packet action Periodic or triggered action

OTcl for control

Modularity (+), re-usability(+), scalability(+) Speed(-), memory(-)8

OTcl and C++: The DualityPure C++ objectsPure OTcl objects

C++/OTcl split objects

C++

OTcl

ns9

Script in interactive modelinux21% ns % set ns [new Simulator] _o3 % $ns at 1 puts \Hello World!\ 1 % $ns at 1.5 exit 2 % $ns run Hello World! linux21%10

A script in batch mode#simple.tclset $ns $ns $ns ns [new Simulator] at 1 puts \Hello World!\ at 1.5 exit run

linux21% ns simple.tcl Hello World! linux21%

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Basic Tclset a 43 set b 27 proc test { a b } { set c [expr $a + $b] set d [expr [expr $a - $b] * $c] for {set k 0} {$k < 10} {incr k} { if {$k < 5} { puts k < 5, pow = [expr pow($d, $k)] } else { puts k >= 5, mod = [expr $d % $k] } } } test 43 2712

Basic OTclClass Mom Mom instproc greet {} { $self instvar age_ puts $age_ years old mom: How are you doing? } Class Kid -superclass Mom Kid instproc greet {} { $self instvar age_ puts $age_ years old kid: Whats up, dude? } set mom [new Mom] $mom set age_ 45 set kid [new Kid] $kid set age_ 15

$mom greet $kid greet

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SIMULATE WIRED NETWORK

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Elements of ns-2 Simulation

Create the event scheduler [Turn on tracing] Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data15

Creating Event Scheduler

Create event scheduler

set ns [new Simulator] $ns at : any legitimate ns/tcl commands $ns run

Schedule events

Start scheduler

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Tracing

Trace packets on all links

$ns trace-all [open test.out w]-- 0 0 3.1 0 0

+ 1 0 2 cbr 210 ------- 0 0.0 3.1 0 - 1 0 2 cbr 210 ------- 0 0.0 3.1 0 r 1.00234 0 2 cbr 210 ------- 0 0.0

Trace packets on all links in nam format

$ns namtrace-all [open test.nam w]

Must appear immediately after creating scheduler17

Tracing

Turn on tracing on specific links

$ns trace-queue $n0 $n1 $ns namtrace-queue $n0 $n1

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Creating Network

Nodes

set n0 [$ns node] set n1 [$ns node] $ns duplex-link $n0 $n1 : DropTail, RED, CBQ, FQ, SFQ, DRR19

Links and queuing

Creating Network: LAN

LAN

$ns make-lan : LL : Queue/DropTail, : MAC/802_3 : Channel20

Inserting Packet Errors

Creating Error Module

set loss_module [new ErrorModel] $loss_module set rate_ 0.01 $loss_module unit pkt $loss_module ranvar [new RandomVariable/Uniform] $loss_module drop-target [new Agent/Null] $ns lossmodel $loss_module $n0 $n121

Inserting Error Module

Network Dynamics

Link failures

Hooks in routing module to reflect routing changesrtmodel-at up|down $n0 $n1 rtmodel Trace $n0 $n1 rtmodel Exponential {} $n0 $n1 rtmodel Deterministic {} $n0 $n1

Four models$ns $ns $ns $ns

Parameter list[] []

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Setup Routing

Unicast

$ns rtproto : Static, Session, DV, cost, multi-path $ns multicast (right after [new Simulator])

Multicast

or set ns [new Simulator multicast on]

$ns mrtproto : CtrMcast, DM, ST, BST (centralized,dense mode, shared tree

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Creating Connection: UDP

UDP

set udp [new Agent/UDP] set null [new Agent/Null] $ns attach-agent $n0 $udp $ns attach-agent $n1 $null $ns connect $udp $null

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Creating Traffic: On Top of UDP

CBR

set src [new Application/Traffic/CBR] set src [new Application/Traffic/Exponential] set src [new Application/Traffic/Pareto]

Exponential or Pareto on-off

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Creating Connection: TCP

TCP

set tcp [new Agent/TCP] set tcpsink [new Agent/TCPSink] $ns attach-agent $n0 $tcp $ns attach-agent $n1 $tcpsink $ns connect $tcp $tcpsink

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Creating Traffic: On Top of TCP

FTP

set ftp [new Application/FTP] $ftp attach-agent $tcp set telnet [new Application/Telnet] $telnet attach-agent $tcp

Telnet

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Creating Traffic: Trace Driven

Trace driven

set tfile [new Tracefile] $tfile filename set src [new Application/Traffic/Trace] $src attach-tracefile $tfile Binary format (native!) inter-packet time (msec) and packet size (byte)

:

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Application-Level Simulation

Features

Build on top of existing transport protocol Transmit user data, e.g., HTTP header TCP: Application/TcpApp UDP: Agent/Message

Two different solutions

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Script Structure for Wired Scenario# parameters and options set ns [new Simulator] # [Turn on tracing] # Create topology # Setup packet loss, link dynamics # Create routing agents # Create: # - protocol agents # - application and/or setup traffic sources # Post-processing procs # Start simulation

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SIMULATE WIRELESS NETWORK

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Script Structure: Wireless# parameters and options set ns [new Simulator] # [Turn on tracing] # create MobileNode object (PHY to layer 3 configured) # Create topology # create mobility # Create Layer 4 and above # - UDP/TCP agents # - application and/or setup traffic sources # Post-processing procedures # Start simulation32

Example: Wireless Scenario

4x4 grid240m

11 13 14

8 4 2 3

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Example: Step 1

Define Parametersset set set set cbr_size 500 cbr_interval 0.002 num_row 4 time_duration 100

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Example: Step 2

Protocol Optionsset val(chan) Channel/WirelessChannel ;# channel type set val(prop) Propagation/TwoRayGround ;# radiopropagation model set val(netif) Phy/WirelessPhy ;# network interface type set val(mac) Mac/802_11 ;# MAC type set val(ifq) Queue/DropTail/PriQueue ;# interface queue type set val(ll) LL ;# link layer type set val(ant) Antenna/OmniAntenna ;# antenna model set val(ifqlen) 50 ;# max packet in ifq set val(rp) DSDV ;# routing protocol

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Example: Step 3

Scheduler, Trace, Topo, God# # Initialize ns # set ns_ [new Simulator] set tracefd [open simple.tr w] $ns_ trace-all $tracefd # set up topography object set topo [new Topography] $topo load_flatgrid 1000 1000

create-god [expr $num_row * $num_row ]

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Example: Step 4

Create Node Object with protocols$ns_ node-config -adhocRouting $val(rp) -llType $val(ll) \ -macType $val(mac) -ifqType $val(ifq) \ -ifqLen $val(ifqlen) -antType $val(ant) \ -propType $val(prop) -phyType $val(netif) \ -channel $chan1 -topoInstance $topo \ -agentTrace ON -routerTrace OFF\ -macTrace ON \ -movementTrace OFF for {set i 0} {$i < [expr $num_row*$num_row]} {incr i} { set node_($i) [$ns_ node] }37

Example: Step 5

Create Topology

set k 0; while {$k < $num_row } { for {set i 0} {$i < $num_row } {incr i} { set m [expr $i+$k*$num_row]; $node_($m) set X_ [expr $i*240]; $node_($m) set Y_ [expr $k*240+20.0]; $node_($m) set Z_ 0.0 } incr k; };

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Example: Step 6

Create Mobility

#Move node 11 from its original place to top-right corner $ns_ at 60.0 "$node_(11) setdest 990.0 990.0 15.0

Example: Step 7

Set up transport layer (UDP)

for {set i 0} {$i < $num_row } {incr i} { set udp_($i) [new Agent/UDP] set null_($i) [new Agent/Null] } $ns_ attach-agent $node_(8) $udp_(0) $ns_ attach-agent $node_(4) $udp_(1) $ns_ attach-agent $node_(13) $udp_(2) $ns_ attach-agent $node_(14) $udp_(3) $ns_ attach-agent $node_(11) $null_(0) $ns_ attach-agent $node_(7) $null_(1) $ns_ attach-agent $node_(2) $null_(2) $ns_ attach-agent $node_(3) $null_(3) for {set i 0} {$i < $num_row } {incr i} { $ns_ connect $udp_($i) $null_($i) } 40

Example: Step 8

Define Traffic Scenario

for {set i 0} {$i < $num_row } {incr i} { set cbr_($i) [new Application/Traffic/CBR] $cbr_($i) set packetSize_ $cbr_size $cbr_($i) set interval_ 0.5 $cbr_($i) attach-agent $udp_($i) } $ns_ at 11.0234 "$cbr_(0) start" $ns_ at 10.4578 "$cbr_(1) start" $ns_ at 12.7184 "$cbr_(2) start" $ns_ at 12.2456 "$cbr_(3) start"

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Example: Step 9

End-of-simulation wrapper (as usual)# Te