Create a simulator object

set ns [new Simulator]

Create two nodes (node1 and node2)

set node1 [$ns node] set node2 [$ns node]

Create a link between the nodes with bandwidth, delay, and queue size

$ns duplex-link$node1 $node2 1Mb 10ms DropTail

Create a TCP connection from node1 to node2

set tcp [new Agent/TCP]
$ns attach-agent$node1 $tcp

Create a sink (receiver) on node2

set sink [new Agent/TCPSink]
$ns attach-agent$node2 $sink

Set up a TCP connection between the nodes

$ns connect$tcp $sink

Set the start and stop times for the simulation

$ns at 0.5 "start-traffic$tcp $sink"$ns at 5.0 "finish"

Run the simulation

$ns run

Define the traffic pattern (for example, a simple TCP flow)

proc start-traffic {tcp sink} {
$tcp send 1000
}