In a wireless network, nodes communicate using the communication model that consists of TCP agent, TCPSink agent, and FTP application. The sender node is attached to the TCP agent while the receiver node is attached to the TCPSink agent. The connection between TCP agent and TCPSink agent is established using the keyword “connect”. Transport agent (TCP) and application (FTP) are connected using the keyword “attach-agent”. TCP agent sends data to TCPSink agent. On receiving the data packet, TCPSink agent sends the acknowledgement to the TCP agent that in turn processes the acknowledgements and adjusts the data transmission rate. The lost packets interpreted as a sign of congestion. The tcl script in sample5.tcl demonstrates the communication between the nodes using TCP protocol.
#Filename: sample5.tcl
TCP (Transmission Control Protocol) and FTP (File Transfer
Protocol) ************#
#*****defining Communication between node0 and node1 **********#
# Defining a transport agent for sending
set tcp [new Agent/TCP]
# Attaching transport agent to sender node
$ns attach-agent $node_(0) $tcp
# Defining a transport agent for receiving
set sink [new Agent/TCPSink]
# Attaching transport agent to receiver node
$ns attach-agent $node_(1) $sink
#Connecting sending and receiving transport agents
$ns connect $tcp $sink
#Defining Application instance
set ftp [new Application/FTP]
# Attaching transport agent to application agent
$ftp attach-agent $tcp
# data packet generation starting time
$ns at 1.0 "$ftp start"
# data packet generation ending time
$ns at 6.0 "$ftp stop"
