1 NS Fundamentals

USC INFORMATION SCIENCES INSTITUTE 2 OTcl and C++: The Duality C++ OTcl Pure C++ objects Pure OTcl objects C++/OTcl split objects ns

USC INFORMATION SCIENCES INSTITUTE 3 NS input & output

USC INFORMATION SCIENCES INSTITUTE 4 Basic Tcl Defining a variable. set var1 1 set var2 “Hello“ Variable Reference puts "var1=$var1, var2=$var2" Assign the results of a function set var3 [expr 5*10]

USC INFORMATION SCIENCES INSTITUTE 5 Basic Tcl For Loop for {set i 0} {$i < 100} {incr i} { puts “I = $i " } While Loop set i 0 while {$i < 10} { set n($i) [new Node] incr i } Procedure proc proc1 {} { puts "in procedure proc1" } proc1

USC INFORMATION SCIENCES INSTITUTE 6 Basic OTcl Class 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: What’s up, dude?” } set mom [new Mom] $mom set age_ 45 set kid [new Kid] $kid set age_ 15 $mom greet $kid greet

USC INFORMATION SCIENCES INSTITUTE 7 Simple Simulation Example

USC INFORMATION SCIENCES INSTITUTE 8 Summary: Generic Script Structure set ns [new Simulator] # [Turn on tracing] # Create topology # Setup packet loss, link dynamics # Create routing agents # Create: # - multicast groups # - protocol agents # - application and/or setup traffic sources # Post-processing procs # Start simulation

USC INFORMATION SCIENCES INSTITUTE 9 Creating Event Scheduler Create event scheduler set ns [new Simulator] Schedule events $ns at : any legitimate ns/tcl commands Start scheduler $ns run

USC INFORMATION SCIENCES INSTITUTE 10 Tracing Trace packets on all links $ns trace-all [open out.tr w] tcp tcp r tcp

USC INFORMATION SCIENCES INSTITUTE 11 Creating Network Nodes set n0 [$ns node] set n1 [$ns node] Links and queuing $ns duplex-link $n0 $n1 : DropTail, RED, CBQ, FQ, SFQ, DRR

USC INFORMATION SCIENCES INSTITUTE 12 Setup Routing Unicast $ns rtproto : Static, Session, DV, cost, multi- path Multicast $ns multicast (right after [new Simulator]) $ns mrtproto : CtrMcast, DM, ST, BST

USC INFORMATION SCIENCES INSTITUTE 13 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

USC INFORMATION SCIENCES INSTITUTE 14 Creating Traffic: On Top of UDP CBR set src [new Application/Traffic/CBR] Exponential or Pareto on-off set src [new Application/Traffic/Exponential] set src [new Application/Traffic/Pareto]

USC INFORMATION SCIENCES INSTITUTE 15 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

USC INFORMATION SCIENCES INSTITUTE 16 Creating Traffic: On Top of TCP FTP set ftp [new Application/FTP] $ftp attach-agent $tcp Telnet set telnet [new Application/Telnet] $telnet attach-agent $tcp

USC INFORMATION SCIENCES INSTITUTE 17 Simple Simulation Example

USC INFORMATION SCIENCES INSTITUTE 18 TCL Script Step 1 #Create a simulator object set ns [new Simulator] #Define different colors for data flows (for NAM) $ns color 1 Blue $ns color 2 Red #Open the NAM trace file set nf [open out.nam w] $ns namtrace-all $nf #Open the All trace file Set f [open out.tr w] $ns trace-all $f

USC INFORMATION SCIENCES INSTITUTE 19 TCL Script Step 2 #Create four nodes set n0 [$ns node] set n1 [$ns node] set n2 [$ns node] set n3 [$ns node] #Create links between the nodes $ns duplex-link $n0 $n2 2Mb 10ms DropTail $ns duplex-link $n1 $n2 2Mb 10ms DropTail $ns duplex-link $n2 $n3 1.7Mb 20ms DropTail

USC INFORMATION SCIENCES INSTITUTE 20 TCL Script Step 3 # Set Queue Size of link (n2-n3) to 10 $ns queue-limit $n2 $n3 10 #Give node position (for NAM) $ns duplex-link-op $n0 $n2 orient right-down $ns duplex-link-op $n1 $n2 orient right-up $ns duplex-link-op $n2 $n3 orient right #Monitor the queue for link (n2-n3). (for NAM) $ns duplex-link-op $n2 $n3 queuePos 0.5

USC INFORMATION SCIENCES INSTITUTE 21 TCL Script Step 4 #Setup a TCP connection set tcp [new Agent/TCP] $ns attach-agent $n0 $tcp set sink [new Agent/TCPSink] $ns attach-agent $n3 $sink $ns connect $tcp $sink $tcp set fid_ 1 #Setup a FTP over TCP connection set ftp [new Application/FTP] $ftp attach-agent $tcp

USC INFORMATION SCIENCES INSTITUTE 22 TCL Script Step 5 #Setup a UDP connection set udp [new Agent/UDP] $ns attach-agent $n1 $udp set null [new Agent/Null] $ns attach-agent $n3 $null $ns connect $udp $null $udp set fid_ 2 #Setup a CBR over UDP connection set cbr [new Application/Traffic/CBR] $cbr attach-agent $udp $cbr set packet_size_ 1000 $cbr set rate_ 1mb

USC INFORMATION SCIENCES INSTITUTE 23 TCL Script Step 6 #Schedule events for the CBR and FTP agents $ns at 0.1 "$cbr start" $ns at 1.0 "$ftp start" $ns at 4.0 "$ftp stop" $ns at 4.5 "$cbr stop" #Call the finish procedure after 5 seconds of simulation time $ns at 5.0 "finish" #Print CBR packet size and interval puts "CBR packet size = [$cbr set packet_size_]" puts "CBR interval = [$cbr set interval_]"

USC INFORMATION SCIENCES INSTITUTE 24 TCL Script Step 7 #Define a 'finish' procedure proc finish {} { global ns nf $ns flush-trace #Close the NAM trace file close $nf #Execute NAM on the trace file exec nam out.nam & exit 0 } #Run the simulation $ns run

USC INFORMATION SCIENCES INSTITUTE 25 NS Directory map

USC INFORMATION SCIENCES INSTITUTE 26 ns Primer – Wired World Basic ns A complete example Multicast routing Visualization

USC INFORMATION SCIENCES INSTITUTE 27 G2 time 1.3s G2 time 1.2s G1 G2 time 1.35s Example: Multicast Routing Dynamic group membership under Dense Mode n0 n1 n2 n3 1.5Mb, 10ms G1 time 1.25s G2 1.5Mb, 10ms

USC INFORMATION SCIENCES INSTITUTE 28 Multicast: Step 1 Scheduler, tracing, and topology # Create scheduler set ns [new Simulator] # Turn on multicast $ns multicast # Turn on Tracing set fd [new “mcast.nam” w] $ns namtrace-all $fd

USC INFORMATION SCIENCES INSTITUTE 29 Multicast: Step 2 Topology # Create nodes set n0 [$ns node] set n1 [$ns node] set n2 [$ns node] set n3 [$ns node] # Create links $ns duplex-link $n0 $n1 1.5Mb 10ms DropTail $ns duplex-link $n0 $n2 1.5Mb 10ms DropTail $ns duplex-link $n0 $n3 1.5Mb 10ms DropTail

USC INFORMATION SCIENCES INSTITUTE 30 Multicast: Step 3 Routing and group setup # Routing protocol: let’s run distance vector $ns mrtproto DM # Allocate group addresses set group1 [Node allocaddr] set group2 [Node allocaddr]

USC INFORMATION SCIENCES INSTITUTE 31 Multicast: Step 4 Sender 0 # Transport agent for the traffic source set udp0 [new Agent/UDP] $ns attach-agent $n1 $udp0 $udp0 set dst_addr_ $group1 $udp0 set dst_port_ 0 # Constant Bit Rate source #0 set cbr0 [new Application/Traffic/CBR] $cbr0 attach-agent $udp0 # Start at time 1.0 second $ns at 1.0 "$cbr0 start"

USC INFORMATION SCIENCES INSTITUTE 32 Multicast: Step 5 Sender 1 # Transport agent for the traffic source set udp1 [new Agent/UDP] $ns attach-agent $n3 $udp1 $udp1 set dst_addr_ $group2 $udp1 set dst_port_ 0 # Constant Bit Rate source #0 set cbr1 [new Application/Traffic/CBR] $cbr1 attach-agent $udp1 # Start at time 1.1 second $ns at 1.1 "$cbr1 start"

USC INFORMATION SCIENCES INSTITUTE 33 Multicast: Step 6 Receiver with dynamic membership # Can also be Agent/Null set rcvr [new Agent/LossMonitor] # Assign it to node $n2 $ns at 1.2 "$n2 join-group $rcvr $group2" $ns at 1.25 "$n2 leave-group $rcvr $group2" $ns at 1.3 "$n2 join-group $rcvr $group2" $ns at 1.35 "$n2 join-group $rcvr $group1"

USC INFORMATION SCIENCES INSTITUTE 34 Multicast: Step 7 End-of-simulation wrapper (as usual) $ns at 2.0 "finish" proc finish {} { global ns fd close $fd $ns flush-trace puts "running nam..." exec nam out.nam & exit 0 } $ns run

USC INFORMATION SCIENCES INSTITUTE 35 ns Primer – Wired World Basic ns Two examples TCP, multicast routing Visualization

USC INFORMATION SCIENCES INSTITUTE 36 Visualization Tools nam-1 (Network AniMator Version 1) Packet-level animation Well supported by ns xgraph Conversion from ns trace to xgraph format

USC INFORMATION SCIENCES INSTITUTE 37 nam Interface: Color Color mapping $ns color 40 red $ns color 41 blue $ns color 42 chocolate Color  flow id association $tcp0 set fid_ 40;# red packets $tcp1 set fid_ 41;# blue packets

USC INFORMATION SCIENCES INSTITUTE 38 Multicast: Define nam color # Colors for packets from two mcast groups $ns color 10 blue $ns color 11 red # Prune packets (predefined) $ns color 30 purple # Graft packets $ns color 31 green

USC INFORMATION SCIENCES INSTITUTE 39 Tracefile for cwnd, rtt # trace file for RTT set f3 [open rtt.tr w] set tcp0 [new Agent/TCP] $tcp0 attach $f3 $tcp0 trace rtt_ # trace file for Congestion Window Size set f4 [open cwnd.tr w] set tcp0 [new Agent/TCP] $tcp0 attach $f4 $tcp0 trace cwnd_

USC INFORMATION SCIENCES INSTITUTE 40 GNUPLOT #simple.gnu set term x11 set xrange [0:200] set yrange [0:0.4] set xlabel 'Time (s)' set ylabel 'Throughput (Mbit/s)' plot 'blm.tr' title 'blm' with l 1, 'tcp.tr' title 'tcp' with l 5 set term postscript set output 'blm.ps' rep %gnuplot simple.gnu

USC INFORMATION SCIENCES INSTITUTE 41