Description:

         This network consists of 4 nodes (Client1, Router1, Endserver1 and Endserver2). The duplex link between Client1and Router1 has 2 Mbps of bandwidth and 100 ms of delay. The duplex link between Router1 and Endserver1 has 100Kbps of bandwidth and 100 ms of delay. The duplex link between Router1 and Endserver2 has 200Kbps of bandwidth and 100 ms of delay. Each node uses a DropTail queue. A "TCP" agent is attached to Client1. "TCPSink" agent is attached to Endserver1 and Endserver2. TCP and TCPSink agent is connected. As default, the maximum size of a packet that a "TCP" agent can generate is 1000bytes. A tcp "sink" agent generates and sends ACK packets to the sender (tcp agent) and frees the received packets. The ftp is set to start at 0.50 sec and stop at 8.5 sec.

File name: “tcpred1.tcl”

#-------Event scheduler object creation--------#
set ns [new Simulator]

#----------creating nam objects----------------#

set nf [open tcpred1.nam w]
$ns namtrace-all $nf

#open the trace file
set nt [open tcpred1.tr w]
$ns trace-all $nt

set proto rlm

$ns color 1 blue
$ns color 2 yellow
$ns color 3 red
 
 #------- creating client- router- end server node-----------#

set Client1 [$ns node]
set Router1 [$ns node]
set Endserver1 [$ns node]
set Endserver2 [$ns node]

#---creating duplex link---------#

$ns duplex-link $Client1 $Router1 2Mb 100ms DropTail
$ns duplex-link $Router1 $Endserver1 100Kb 100ms DropTail
$ns duplex-link $Router1 $Endserver2 200Kb 100ms DropTail

#----------------creating orientation------------------#

$ns duplex-link-op $Client1 $Router1 orient right
$ns duplex-link-op $Router1 $Endserver1 orient up-right
$ns duplex-link-op $Router1 $Endserver2 orient down-right

#------------Labeling----------------#

$ns at 0.0 "$Client1 label Client1"
$ns at 0.0 "$Router1 label Router1"
$ns at 0.0 "$Endserver1 label Endserver1"
$ns at 0.0 "$Endserver2 label Endserver2"

#-----------Configuring nodes------------#

$Endserver1 shape hexagon
$Endserver2 shape hexagon
$Router1 shape square

#----------------Establishing queues---------#
 
#$ns duplex-link-op $Client1 $Router1 queuePos 0.1
#$ns duplex-link-op $Client2 $Router1 queuePos 0.1
#$ns duplex-link-op $Router1 $Router2 queuePos 0.1
#$ns duplex-link-op $Router2 $Endserver1 queuePos 0.5

#---------Establishing communication-------------#

#-------------Client1 to Endserver1---#

set tcp0 [new Agent/TCP]
$tcp0 set maxcwnd_ 16
$tcp0 set fid_ 1
$ns attach-agent $Client1 $tcp0
set sink0 [new Agent/TCPSink]
$ns attach-agent $Endserver1 $sink0
$ns connect $tcp0 $sink0
set ftp0 [new Application/FTP]
$ftp0 attach-agent $tcp0
$ns add-agent-trace $tcp0 tcp
$tcp0 tracevar cwnd_
$ns at 0.50 "$ftp0 start"
$ns at 8.5 "$ftp0 stop"

#-------------Client1 to Endserver2---#

set tcp1 [new Agent/TCP]
$tcp1 set maxcwnd_ 16
$tcp1 set fid_ 2
$ns attach-agent $Client1 $tcp1
set sink1 [new Agent/TCPSink]
$ns attach-agent $Endserver2 $sink1
$ns connect $tcp1 $sink1
set ftp1 [new Application/FTP]
$ftp1 attach-agent $tcp1
$ns add-agent-trace $tcp1 tcp
$tcp0 tracevar cwnd_
$ns at 0.50 "$ftp1 start"
$ns at 8.5 "$ftp1 stop"

#---------finish procedure--------#
 
proc finish {} {
         global ns nf nt
         $ns flush-trace
         close $nf
         puts "running nam..."
         exec nam Tcpred1.nam &
         exit 0
      }

#Calling finish procedure
$ns at 10.0 "finish"
$ns run

#--------- how to execute the program-----------#
$ ns tcpred1.tcl

 #--------------output---------------#