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Lol packets are moving like Bullet So here is Question? How i did this :p. it’s really simple i made a small script in TCL language, which is basically design to stimulate UDP packet’s from node 0 to node 1 via one Link. Let me explain you..but Before check Below Fundamental’s for writing tcl script for Network simulator-2 I have devided this codes into 6 parts with each explanation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 set ns [new Simulator] set nf [open out.nam w] $ns namtrace-all $nf proc finish {} {         global ns nf         $ns flush-trace         close $nf         exec nam out.nam &         exit 0 } $ns at 3.0 "finish" set n0 [$ns node] set n1 [$ns node] $ns duplex-link $n0 $n1 1Mb 10ms DropTail $ns run 1. we need to create a simulator object something like this. 1 set ns [new Simulator] 2.Now we need to open a file for writing that is going to be used for the nam trace data.First line open a file ‘out.nam’ for writing and give it to file handle ‘nf’ 1 set nf [open out.nam w] In this code we are telling simulator object that we created above to write all simulation data that is going to be relevant for nam into this file 1 $ns namtrace-all $nf 3.This is to add a ‘finish’ procedure that closes the trace file and start nam 1 2 3 4 5 6 7 proc finish {} {         global ns nf         $ns flush-trace         close $nf         exec nam out.nam &         exit 0 } 4.This one tell simulator object to execute the ‘finish’ procedure after 3.0 seconds of simulation time 1 $ns at 3.0 "finish" 5. This code tells the simulator object to connects the nodes n0 and n1 with duplex link with a bandwidth 1 Megabit,a delay of 10ms Drop tail (A simple queue management algorithm used by internet routers to decides when to drop packets  ) 1 $ns duplex-link $n0 $n1 1Mb 10ms DropTail 6.This is a last line finally starts the simulation 1 $ns run Now save the above script with .tcl extansion, and Open a terminal type 1 ns filename.tcl You will se something like this NOW to send a data on two nodes via one link, we need to do certaine things 1.Create a UDP agent. 2.Create a CBR traffic source. 3.Create NULL agent which act as a traffic sink 4.Connect the two agent with each other. 5.Fixe the time when to send and stop a data. 1.Create a UDP agent and attach it to node n0 1 2 set udp0 [new Agent/UDP] $ns attach-agent $n0 $udp0 2.Create a CBR traffic source and attach it to udp0 1 2 3 4 set cbr0 [new Application/Traffic/CBR] $cbr0 set packetsize_ 500 $cbr0 set interval_ 0.005 $cbr0 attach-agent $udp0 3.The next lines creates a null agent which acts as traffic sink and attach it to node n1 1 2 set null0 [new Agent/null] $ns attach-agent $n1 $null0 4. Now we are going to connect two agents with each other 1 $ns connect $udp0 $null0 5 NOw to fix a time by telling CBR agent when to send data and when to stop sending a data by following code 1 2 $ns at 0.5 "$cbr0 start" $ns at 4.5 "$cbr0 stop" So here is a complete code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 #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         $ns flush-trace     #Close the trace file         close $nf     #Execute nam on the trace file         exec nam out.nam &         exit 0 } #Create two nodes set n0 [$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_ 0.05 $cbr0 attach-agent $udp0 #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 Now save it with some name with .tcl extension,and again Open a terminal Type 1 ns filename.tcl