Integrated Network Simulator: Introduction to NS and Discrete Event Simulation

Network Simulator - NS

Introduction • Discrete Event Simulator • Research on networks • Wired, wireless • TCP, UDP, multicast, unicast • Web, telnet, ftp

Discrete Event Simulations • Real world is modeled by the occurance of events • List of events • List of events is visited sequentially • Virtual time • Single control thread

Ns Architecture • Object Oriented (C++, OTcl) • C++ for the objects: • Packet processing, NS kernel • Fast execution • OTcl for control: • Configuration of scenarios • Deals with objects in C++ • Fast to write and execute

Ns Architecture • OTcl (object Tcl) and C++share class hierarchy. • TclCL is the library which allows the sharing of functions and variables C++ C++/OTcl split objects otcl

variables: set x 10 puts “x é $x” Functions and expressions: set y [pow x 2] set y [expr x*x] control: if {$x > 0} { return $x } else { return [expr -$x] } while { $x > 0 } { puts $x incr x –1 } procedures: proc pow {x n} { if {$n == 1} { return $x } set part [pow x [expr $n-1]] return [expr $x*$part] } Lists, vectors, etc. Tcl

Class Person # constructor: Person instproc init {age} { $selfinstvar age_ set age_ $age } # method: Person instproc greet {} { $selfinstvar age_ puts “$age_ years old: How are you doing?” } # subclass: Class Kid -superclass Person Kid instproc greet {} { $selfinstvar age_ puts “$age_ years old kid: What’s up, dude?” } set a [new Person 45] set b [new Kid 15] $a greet $b greet OTCL

C++ and OTCL class ControleAdmissao{ public: ControleAdmissao(); private: int fluxos_admitidos; int fluxos_rejeitados; int tam_janela; int admitir_fluxo(Pacote *, int); int computar_estatisticas(); }

C++ and OTCL static class ControleAdmissaoClass: public TclClass{ public: ControleAD():TclClass(“CAdmissao”){ } TclObject * create(int argc, const char*cons*argv){ return(new ControleAdmissao()); } }class_controleadmissao;

C++ and OTCL C++ Admission_Control(){ ….. ….. bind(“tam_janela_”,&tam_janela); ….. } Script OTCL set cad [new CAdmissao] $cad set tam_janela_ 1s

Utilizando o ns Problem Output Analysis Modify Ns Simulation Model Run Simulation in Ns

Using Ns • Criate Event scheduler • Use trace • Design the network • Define Routing • Insert errors • Create transport connection • Create traffic

Event Scheduler • Create event scheduler set ns [new Simulator] • Schedule events $ns at <time> <event> • <event>: qualquer comando ns/tcl $ns at 5.0 “finish” • Initiate Scheduler $ns run

Trace and Monitoring • Trace of packets: • In every channel: $ns trace-all [open out.tr w] • In a specific channel: $ns trace-queue $n0 $n1 $tr <Event> <time> <from> <to> <pkt> <size> -- <fid> <src> <dst> <seq> <attr> + 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0 - 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0 r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0 + 0.94176 2 3 tcp 1000 ------- 0 0.0 3.0 26 41 d 0.94176 2 3 tcp 1000 ------- 0 0.0 3.0 26 41 + 0.95072 2 0 ack 40 ------- 0 3.0 0.0 14 29

Monitoring • Queue monitoring set qmon [$ns monitor-queue $n0 $n1 $q_f $sample_interval] • Collect statistical data $qmon set pdrops_ • Record a trace 29.000000000000142 0 1 0.0 0.0 4 4 0 1160 1160 0 • Flow monitoring set fmon [$ns_ makeflowmon Fid] $ns_ attach-fmon $slink $fmon $fmon set pdrops_

Trace and Monitoring • Visualize the trace in nam (network animator) $ns namtrace-all [open test.nam w] $ns namtrace-queue $n0 $n1

Creating the network • Nodes set n0 [$ns node] set n1 [$ns node] • Channels and queues $ns <link_type> $n0 $n1 <bandwidth> <delay> <queue_type> • <link_type>: duplex-link, simplex-link • <queue_type>: DropTail, RED, CBQ, FQ, SFQ, DRR, diffserv RED queues

Creating a LAN $ns make-lan <node_list> <bandwidth> <delay> <ll_type> <ifq_type> <mac_type> <channel_type> <ll_type>: LL <ifq_type>: Queue/DropTail, <mac_type>: MAC/802_3 <channel_type>: Channel

Routing • Unicast $ns rtproto <type> <type>: Static, Session, DV, cost, multi-path • Multicast $ns multicast (right after [new Simulator]) $ns mrtproto <type> <type>: CtrMcast, DM, ST, BST

Errors • Error Modulo 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 $n1

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 CBR set src [new Application/Traffic/CBR] Exponential ou Pareto on-off set src [new Application/Traffic/Exponential] set src [new Application/Traffic/Pareto] Conection and Traffic

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

Traffic • Trace driven set tfile [new Tracefile] $tfile filename <file> set src [new Application/Traffic/Trace] $src attach-tracefile $tfile <file>: • Binary format • Interarrival time (msec) and packet size (byte)

An Example #Create a simulator object set ns [new Simulator] #Open the nam trace file set nf [open out.nam w] $ns namtrace-all $nf #Define a 'finish' procedure proc finish {} { global ns nf #Close the trace file close $nf #Execute nam on the trace file exec nam out.nam & exit 0 }

Na Example #Create two nodes set n0 [$ns node] set n1 [$ns node] #Create a duplex link between the nodes $ns duplex-link $n0 $n1 1Mb 10ms DropTail #Create a UDP agent and attach it to node n0 set udp0 [new Agent/UDP] $ns attach-agent $n0 $udp0 # Create a CBR traffic source and attach it to udp0 set cbr0 [new Application/Traffic/CBR] $cbr0 set packetSize_ 500 $cbr0 set interval_ 0.005 $cbr0 attach-agent $udp0 0 1

An Example #Create a Null agent (a traffic sink) and attach it to node n1 set null0 [new Agent/Null] $ns attach-agent $n1 $null0 #Connect the traffic source with the traffic sink $ns connect $udp0 $null0 #Schedule events for the CBR agent $ns at 0.5 "$cbr0 start" $ns at 4.5 "$cbr0 stop" #Call the finish procedure after 5 seconds of simulation time $ns at 5.0 "finish" #Run the simulation $ns run

Documents • http://www.isi.edu/nsnam/ns/ • ns Notes and Documentation • Tutorials (ns by Example) • Trace Graph – analysis of trces

Integrated Network Simulator: Introduction to NS and Discrete Event Simulation