# Create event scheduler
set ns [new Simulator]

# Turn on tracing
set nam_file lab-ex-2.nam
set nf [open $nam_file w]
$ns namtrace-all $nf

# Create the topology

# First the nodes
	......

# Make the links
	......

# Define the topology layout in nam
$ns duplex-link-op $n(0) $n(1) orient right
$ns duplex-link-op $n(1) $n(2) orient right
$ns duplex-link-op $n(2) $n(3) orient right
$ns duplex-link-op $n(1) $n(3) orient down
$ns duplex-link-op $n(1) $n(4) orient up

# Create the multicast group.  Use the following line
	......

# Choose the routing protocol
	......

# Create the UDP agent and tie it to the multicast group
	......

# Set the timing and run the script.
	......

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

	$ns flush-trace
	close $nf
	exec nam $nam_file &
	exit 0
}
$ns at 5.0 "finish"

# Start the simulator
$ns run