Excercise

By now you should know basic commands for creating simple networks. Make a test subdirectory at your home directory. Change your directory to test. Create lab1-ex.tcl Write a tcl script that forms a network consisting of 5 nodes, numbered from 0 to 4, which form a ring. The links have a 128K bandwidht with 10ms delay. Set the routing protocol to DV (Distance vector). Send UDP packets from node 0 to node 2 with the rate of 0.02 seconds per packet. Start transmission at 0.05. Bring down the link between node 1 and node 2 at 0.25. Finish the transmission at 1.000. Then run nam to view the results. What do you see? Will packets be re-routed after the link goes down? Is this what you expect?
	proc finish {} {
	global ns nf nam_file

	$ns flush-trace
	close $nf
	exec nam $nam_file &
	exit 0
	};					# finish

	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
		.....

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


	# Set the routing protocol

	# 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)

	$ns at 1.00 "finish"
	$ns run
    

Nader Salehi
Last modified: Thu Jun 22 19:40:34 PDT 2000