CARRIER SENSE MULTIPLE ACCESS

Aim:

To write a ns2 program for implementing carrier sense multiple access.

Algorithm:

Step 1: start the program.

Step 2: declare the global variables ns for creating a new simulator.

Step 3: set the color for packets.

Step 4: open the network animator file in the write mode.

Step 5: open the trace file and the win file in the write mode.

Step 6: transfer the packets in network.

Step 7: create the capable no of nodes.

Step 8: create the duplex-link between the nodes including the delay time,bandwidth and dropping . queue mechanism.

Step 9: give the position for the links between the nodes.

Step 10: set a tcp connection for source node.

Step 11: set the destination node using tcp sink.

Step 12: set the window size and the packet size for the tcp.

Step 13: set up the ftp over the tcp connection.

Step 14:.set the udp and tcp connection for the source and destination.

Step 15: create the traffic generator CBR for the source and destination files.

Step 15: define the plot window and finish procedure.

Step 16: in the definition of the finish procedure declare the global variables.

Step 17: close the trace file and namefile and execute the network animation file.

Step 18: at the particular time call the finish procedure.

Step 19: stop the program.

Program:

set ns [new Simulator]

$ns color 1 blue

$ns color 2 red

set fi1 [open out.tr w]

set winfile [open WinFile w]

$ns trace-all $fi1

set fi2 [open out.nam w]

$ns namtrace-all $fi2

proc finish {} {

global ns fi1 fi2

$ns flush-trace

close $fi1

close $fi2

exec nam out.nam &

exit 0

}

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

set n4 [$ns node]

set n5 [$ns node]

$n1 color red

$n1 shape box

$ns duplex-link $n0 $n2 2Mb 10ms DropTail

$ns duplex-link $n1 $n2 2Mb 10ms DropTail

$ns simplex-link $n2 $n3 0.3Mb 100ms DropTail

$ns simplex-link $n3 $n2 0.3Mb 100ms DropTail

set lan [$ns newLan "$n3 $n4 $n5" 0.5Mb 40ms LL Queue/DropTail MAC/Csma/Cd Channel]

set tcp [new Agent/TCP/Newreno]

$ns attach-agent $n0 $tcp

set sink [new Agent/TCPSink/DelAck]

$ns attach-agent $n4 $sink

$ns connect $tcp $sink

$tcp set fid_ 1

$tcp set window_ 8000

$tcp set packetsize_ 552

set ftp [new Application/FTP]

$ftp attach-agent $tcp

$ftp set type_ FTP

set udp [new Agent/UDP]

$ns attach-agent $n1 $udp

set null [new Agent/Null]

$ns attach-agent $n5 $null

$ns connect $udp $null

$udp set fid_ 2

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set type_ CBR

$cbr set packet_size_ 1000

$cbr set rate_ 0.01mb

$cbr set random_ false

$ns at 0.1 "$cbr start"

$ns at 1.0 "$ftp start"

$ns at 24.0 "$ftp stop"

$ns at 24.5 "$cbr stop"

proc plotwindow { tcpSource file } {

global ns

set time 0.1

set now [$ns now]

set cwnd [$tcpSource set cwnd_]

set wnd [$tcpSource set window_]

puts $file "$now $cwnd"

$ns at [expr $now+$time] "plotwindow $tcpSource $file"

}

$ns at 1.0 "plotwindow $tcp $winfile"

$ns at 5 "$ns trace-annotate \"packet drop\""

$ns at 125.0 "finish"

$ns run