Ns2 Network Simulator- Tutorial for Begineers

Ns2 Network Simulator Tutorial for Beginners’

Udhay Prakash Udhayprakash.blogspot.in Uday3prakash @gmail.com

Presentation Agenda • Introduction to Linux • Importance of Open Source software • Network Simulators • • Ns2 Installation • TCL scripting language • Introduction to NAM and Xgraph • Discussion about trace file format

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udhayprakash.blogspot.in

Outcomes • To get ease with Linux platform

tary • Open Source vs Free ware vs proprietar insigh ghtt abou aboutt a Netw Networ ork k Sim Simulat ulator or • To insi • • Scri Script ptin ing g lang langua uage ge vs prog progra ramm mmin ing g lang langua uage ge • Ability to install ns2, nam and xgraph • Ease in workin king with ith TCL scriptin ting • Insight to NAM and Trace files

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Linux • Developed under GNU project. • Open Source software, except RedHat • Major Linux Families » Debian, Ubuntu, Mint, …. » Fedora » OpenSUSE » ArchLinux » Cent CentOS OS & RedH RedHat at

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Working in Linux • Are you new to Linux Operating System?

Windows or • Are you more habituated to Windows Macintosh Operating Systems ? en, care u y o ow me… (switch on your PCs)

•

– Creating a file – Reading/writing/editing a file – Operating System specific file types

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Why Simulators? • Advantages ☺Com ☺Compl plex ex sce scenari narios os can can be eas easily ily tes tested ted ☺Che ☺Cheap ap-d -doe oess no nott requ requir iree cost costly ly equi equipm pmen entt ☺Results can be quickly obtained-more ideas can be tested in a smalle sm allerr timefr timeframe ame ☺Contr ☺Controlle olled d experim experiment ental al conditi conditions ons ☺Rep ☺Repea eata tabi bili lity ty help helpss aid aid debu debugg ggin ing g

• Disadvantages ☻Not real real ☻Real systems too complex to model ☻Con ☻Consi side dera rati tion on of pract practic ical al cond condit ition ionss l


NS2 Network Simulator Open-s -sou ourc rcee event event-d -dri rive ven n simu simula lato tor r • Open • Designed specifically for research in computer commun communica icatio tion n networ networks. ks. •

onta ns mo u es or numerous networ components such as routing, transport layer protocol, and application.

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Ns2 sources •

http://www.isi.edu/nsnam/ns/ – The source code and documentation is currently maintained by VINT project at ISI

•

http://nsnam.isi.edu/nsnam/index.php/Main_Page –

ep

,

: ns- .

re ease .

–

Mar 10, 2007: ns-2.31 released.

–

July 2, 2006: ns-3 project announced.

•

NS2 is a discrete event simulator targeted targeted at networking research

•

NS2 is an object oriented simulator, written in C++, with an OTcl OTcl interpreter as a frontend

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NS2 related Documentation arcc Gr Grei eis' s'ss tu tuto tori rial al • introductory: Mar reference: Ns Manual (formerly called "ns Notes • reference: Ns and and Docu Docume ment ntat atio ion" n")) • ns y xamp e • Practical Programming in Tcl (http://www.beedub.com/book/ http://www.beedub.com/book/))

and

Tk

• http://hpds.ee.ncku.edu.tw/~smallko/ns2/ns2.htm

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NS2 S2-- Feat atu ure ress • Collection of various protocols various protocols at multiple layers – – – – –

•

tahoe, vegas, sack) MAC(802.11, 802.3, TDMA) Ad-hoc Routing (DSDV, (DSDV, DSR, AODV, AODV, TORA) Sensor Network (diffusion, gaf) Multicast protocols, Satellite protocols, and TCP(reno, many others

Traf raffic fic Mod Models els:: CBR, VBR, Web, …

Uniform orm,, Bust Busty y, … • Error Models: Unif • Misc: Radi Radio o Prop Propag agat atio ion, n, Mo Mobi bili lity ty mod odel els, s, En Ener ergy gy Mo Mode dels ls,, … •

Topo opolog logyy Gen Genera eratio tion n too tools ls (nsg2. (nsg2.1, 1, ..) ..)

• •

Visual isualizat ization ion tools (NAM), (NAM), Tracing racing Codes are contributed from multiple research communities – Good: Large set of simulation modules – Bad: Level of support and documentation varies l


NS2 Chronicle • 1989: REAL by Keshav • 1995: ns by Floyd, McCanne at LBL • 1997: ns-2 by the VINT project (Virtual InterNetwork Testbed at LBL, Xerox PARC, UCB, USC/ISI • Now: ns-2.35 maintained at USC/ISI • Also there there is NS-3, but it has no backward backward compatibility with NS-2. l

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NS2 Chronicle • REAL Simulator →NS (or NS1)→NS2→NS3. • NS-1 – – Developed by the network research group at the Lawrence – Berkeley National Laboratory (1989) – Derived from REAL Simulator – Simulation description language: TCL l


NS2 Chronicle • NS-2 – Object Object Oriented Oriented (OTcl (OTcl instead instead of TCL) – Built in C++ and provides a simulation interface through OTcl – Developed by UC Berkeley – Difficult for the first time users • Very few user friendly manuals. Ex: ns manual • Needs scripting language, queuing theory and modelling modelling techniques knowledge • Complaint about inconsistent results • And BUGS!!!!

• But, large community support l


NS3 • • • • • •

No backward compatibility with NS2 YANS (Yet (Yet Another Network Ne twork Simulator)→NS-3 Simulat or)→NS-3 base NS-3.1 (2008), (2008), NS-3.11(201 NS-3.11(2011), 1), … Built in C++ and python Good support su pport for LTE LTE and Wimax Simple to work with…..and suitable for dumping into and getting data from real-time devices. • No support for some protocols protocols which were supported supported in ns-2. • But, lesser community support l


NS-2 Directory Structure ns-allinone Tcl8.0

TK8.0

OTcl

tclcl

tcl ex examples

test

ns-2

...

lib

C++ code

mcast

validation tests OTcl code

simple.tcl l


nam-1

...

NS-2 Environment Simulation Scenario

1

2

set ns_ [new Simulator]

c

_

cr p

_

set node_(1) [$ns_ node]

C++ Implementation

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clas class s Mobil MobileN eNod ode e : publi public c Node Node { friend class PositionHandler; public: MobileNode(); • • } udhayprakash.blogspot.in

NS2 Architecture

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Why two languages? (Tcl & C+ C++) • C++: Detailed protocol simulations require systems programming

language – byte manipulation, packet processing, algorithm implementation – Run time s eed is im ortant – Turn around time (run simulation, find bug, fix bug, recompile, re-run) is

slower

• Tcl cl:: Si Simu mula lati tion on of sl slig ight htly ly va vary ryin ing g pa para rame mete ters rs or co conf nfig igur urat atio ions ns quic ickl kly y exp xplo lori ring ng a nu num mber ber of scen scenar ario ioss – qu iterat atio ion n tim time (cha (chang ngee the the mod odel el and re-r re-run un)) is more ore impo import rtan antt – iter

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What is Tcl/Tk ? •It is a Scripting language to describe a high-level programming language with relati relativel vely y transp transpare arent nt syn syntax tax •Tools Command Lanuage (TCL) simple le stri string ng base based d scri scripti pting ng langu languag agee for for cont contro rolli lling ng and and exten extendi ding ng appl applica icatio tions ns.. –simp

– provides generic programming facilities such as variables, loops, and rocedures. –Tcl sy synt ntaax is very very much uch sim similar ilar to UNIX UNIX sh shel elll prog progra ram mming ng.. •Tool k it it (TK) – based on X-window system.

– provides facilities (widgets) for building user interfaces.

•Tcl/Tk Rapid pr proto ototyp typing ing.. Exce cell llen entt tool toolss for for Rapid –Ex –Tcl/T Thee inte interp rpre rete terr is in !/opt/bin/wish ) cl/Tk k is inte interp rpre rete ted d rath rather er than than com compile piled. d. ( Th –weak weakly ly type typed d langu languag agee (str (strin ings gs and and inte intege gerr vari variab able less are are inte interc rcha hange ngeab able le). ). l


Basic Tcl variables: set x 10 puts “x is $x”

procedures: proc pow {x n} { if {$n == 1} { return $x } set set part part [pow [pow x [expr [expr $n $n-1 -1]] ]] re urn expr x par }

functions and expressions: set set y [po [pow w x 2] set y [expr [expr x*x x*x]] control flow: if {$x > 0} { return $x } else { return return [expr [expr -$x] } while { $x > 0 } { puts $x incr incr x –1 } l

Also lists, associative arrays, etc. => can use a real programming language to build network topologies, traffic models, etc.


Basic oTcl Class Person # constructor: Person instproc init {age} { self inst instvar var age_ $self set age_ $age } # method: Person instproc greet {} { self inst instvar var age_ $self puts “$age_ years old: How are you doing?” } Person a 45 Kid b 15 a greet b greet l

# subclass: Class Kid -superclass Person Kid instproc greet {} { self inst instva varr age_ $self puts “$age_ years old kid: What’s What’s up , u e } set a [new Person 45] set b [new Kid 15] $a greet $b greet # “new” in ns2 only

=> can easily make variations of existing things (TCP, (TCP, TCP/Reno) udhayprakash.blogspot.in

Split Object Model •

Split Object Model with shared class hierarchy –

•

TclCL provides ‘glue library’ to “easily” share functions, variables, etc – –

•

Control (OTcl) vs. Data (C++) OTcl OTcl into C++: command(), tcl.result() tcl.result() C++ into OTcl: OTcl: tcl.eval()

Not all classes are mirrored mirrored exactly

OTcl

OTcl script OTcl s cript describing simulation

C++

L C l c T

C+++ an C+ and d OT OTcl cl Li Link nkag agee • Class Tcl: Tcl: instance instance of OTcl OTcl interpreter interpreter Tcl& tcl = Tcl::in Tcl::instanc stance(); e(); tcl.evalc( tcl.evalc(“puts “puts stdout hello world”) world”);; tcl.result() and tcl.error()

• Class TclOb TclObject ject and TclCl TclClass ass ariabl e bindings bind ings – Variable bind(“rtt_”, &t_rtt_) – Invoking command method in shadow class

$tcp $tcp adva advanc nceb eby y 10

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Callin Cal lingg Otcl Otcl fun functi ctions ons fro from m C++ C++ • OTcl Agent/TCP instproc advance {num} { set set wind window_ ow_ [expr [expr $windo $window_ w_ + $num $num] ] return $window_ }

• C++ Tcl& Tcl& tcl = Tcl::i Tcl::inst nstanc ance() e(); ; char *result;

tcl.evalf(“%s advance %d”, name_, size); result = tcl.result(); wnd_ = atoi(result);

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EmbeddedTcl • How it works – tcl2c++: provided by TclCL, TclCL, converts tcl scripts

into a C++ static character array –

.

tclsh8.0 bin/tcl-expand.tcl tcl/lib/ns-lib.tcl | tcl2c+ tcl2c++ + et_ns_ et_ns_lib lib > gen/n gen/ns_t s_tcl cl.cc .cc

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C++ and OT OTcl cl Se Sepa para rati tion on • “data” / control separation – C++ for “data”: core of ns • per packet processing, core • fast to run, detailed, complete control

OTcl for cont control: rol: – OTcl • • • •

Simulation scenario configurations Periodic or triggered action Manipulating existing C++ objects fast to write and change

+ runni running ng vs vs.. wri writi ting ng sp spee eed d – Learning and debugging (two languages) l


Object Granularity Tips • Functionality – Per-packet processing  C++ – Hooks, frequently changing code

•



OTcl

a a ma manage agemen Complex/large data structure str ucture  C++ – Complex/large – One-time configuration variables

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

OTcl

Ns2 Installation Procedure • Linux Installation (preferred): – Go to udhayprakash.blogspot.in – Search for ns2 installation procedure –

…..

• Windows Installation – Go to http://nsnam.isi.edu/nsnam/index.php/Running_Ns _and_Nam_Under_Windows_9x/2000/XP_Using_ _and_Nam_Under_W indows_9x/2000/XP_Using_ Cygwin l


Where to find…/ns-2/tcl/lib find…/ns-2/tcl/lib • ns-lib.tcl: – The simulator class and most of its member function definitions

• ns-default.tcl: –

• ns-packet.tcl: – Th Thee pack packet et head header er form format at init initia iali liza zati tion on impl implem emen enta tati tion on

othe herr OT OTcl cl fi file les: s: • ot – implementation of compound network objects or the front end (con (conttrol rol part part)) of netw networ ork k ob obje ject ctss

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A Simple Topology Application

n0

n1

Agent

Agent

0

0 1

0

head_

enqT_ queue_ deqT_ link_

drophead_

drpT_

Link n1 – n0

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ttl_

rcvT_

N1

N2 Node

Node

C l a s s i i e r

Local

C l a s s i f i e r

C l a s s i i e r

Agent

Port

Local

C l a s s i f i e r

Agent

Port

Addr

Addr Link Enq Trace

Queue

Link

Drop head

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Deq Trace

Delay

Drp Tr Trace ace


TTL

Rcv Trace

Using ns Problem

Result analysis

Simulation model Setup/run simulation with ns

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Modify ns

NS-2 Generic Script Structure set ns [new Simulator] # [Turn on tracing] # [Turn on visualizer visualizer] ] # Create topology # Setup packet loss, link dynamics # Create: # - m multicast ulti ultica cas st groups grou roups # - protocol protocol agents ag agents # - applic app application licati ation on and/or and/ and/or or setup setu setup p traffic traff traffic ic sources sour sources ces # PostPost-processing -processing procs # Start simulation

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Event Scheduler Creation •

Event is a packet ID that is unique for a packet, which constitutes: – Scheduled time – The pointer to an object that handles the event

•

An event scheduler – Keeps track of simulation time – Fires all the events in the event queue

• Create event scheduler: set ns [new simulator] • Schedule an event: $ns at – Event is any legitim legitimate ate ns/tcl ns/tcl function function – $ns at 5.0 “finish”

• Start scheduler – $ns run l


Tracing

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Tracing • Packet tracing and event tracing – Objects that are inserted between nodes – Insert Insert from from OTcl OTcl using using trace{} method • $ns trace-all $file , or • [$ns link $n0 $n1] trace $file

• Monitoring – Record counters of interest for all packets or on a per-flow basis

• …or roll your own l

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Tracing •

and nam trace file formats

ns

–

•

also supports show_tcphdr_ variable controlling display of TCP flags ns

format

ns

op op

ts

+

prevho pre prevhop vhop

.

nextho nex next ne xtho thop hop p

type ty pe

s size si iz ze e

c cp p

flags

flow fl flowid owid id

––––––

• Enque [+], dequeue [-], receive receive [r], drop drop [d] • Types are • Flags are – ECN-CE [E], -ECT -ECT [N], -CE [C], -CWR [A]; plus – priority [P] and TCP fast start start [F] l

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s src sr rc

dst

.

.

seqn se seqno qno

pkti pk pktid tid d

Visualization (nam) set nf [open out.nam w] $ns namtrace-all $nf Proc finish {} { global ns nf close $nf exec nam out.nam & exit 0 }

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Topology Creation

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Sending Data

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Sending Data

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Creating TCP Connections • Create TCP agent and attach it to the node 

set tcp0 [new Agent/TCP] Agent/TCP]



$ns attach-agent $n0 $tcp0



Set null0 [new Agent/TCPSink] Agent/TCPSink]



$ns attach-agent $n1 $null0

•

• Connect the agents 

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$ns connect $tcp0 $null0


Traffic on top of TCP • FTP – set ftp [new Application/FTP] Application/FTP] – $ftp attach-agent $tcp0

• Telnet – Set telnet [new Application/Telnet] – $telnet attach-agent $tcp0

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NS2 NS 2 prepre- and po post st proc proces essi sing ng • pre-processing: – traffic and topology generators – NSG 2.1 (for more details, go to udhayprakash.blogspot.in ) – tclTutor

• post-processing: – simple trace analysis, often in Awk, Perl, or Tcl. – Awk scripting scripting is preferred. preferred.

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Summary • Simulators help in easy verification of protocols in less less tim time, mon oneey. • NS2 offers support for simulating a variety of protocols suites and scenarios • Front end is oTCL, back end is C++ • NS2 is on-going effort of research and development.

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Reference 1)

ns2 website: http://www.isi.edu/nsnam/ns

2)

Marc Greis' tutorial

3)

Jae Chung tutorial

4)

Ns manual –

.

.

6)

Nsnam web pages – http://www.isi.edu/nsnam/ – http://www.isi.edu/nsnam/

7)

NS by example – http://nile.wpi.edu/NS/ – http://nile.wpi.edu/NS/

8)

Tutorial – Mar Marcc Greis' Greis'ss tuto tutoria riall

9)

Disc Discre rete te-e -eve vent nt simu simula lati tion on so soft ftwa ware re – http://www.topology.org/soft/sim.html

10) Introd Introducti uction on to to NS2(P NS2(PPT) PT),, Prepar Prepared ed by Changyo Changyong ng Jun Jung g l


Ns2 Network Simulator- Tutorial for Begineers

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