set ns [new Simulator]

set nam_file lab-ex.nam
set nf [open $nam_file w]
$ns namtrace-all $nf

# Create the topology

# Frist, the nodes
	......

# Then create the links
	......
	
# Set the routing protocol
	......

# Now create agents and attach them to the appropriate nodes
	......

# Start transmitting packets from 0 to 2
	......

# Bring down the link between 1 and 2 using this command
$ns rtmodel-at 0.25 down $n(0) $n(1)

# Final wrapup
proc finish {} {
	global ns nf nam_file

	$ns flush-trace
	close $nf
	exec nam $nam_file &
	exit 0
}
$ns at 1.00 "finish"

# Start simulator
$ns run