Lab I: ns Basics

By now you should know basic commands for creating simple networks. Go to the ns-test subdirectory under your home directory that you have made earlier in this lab. Create lab1c.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? 

	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
		......
	
	# 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(1) $n(2)

	# 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"

	$ns run

Exercise 2

Create a network which looks like the following: 
			4
			|
			|
	  0-------------1----------2---------5
			|
			|
			3
Choose CtrMcast as the multicast routing protocol for the experiment. Node 0 is a UDP source for this group. The source will start transmission at time 0.05. Nodes 3 and 4 will join the multicast group at times 0.10 and 0.12, respectively. Node 3 will leave the multicast group at 0.5, and the execution will terminate at 0.6

Stay in the ns-test directory, create lab1d.tcl: 

	# Create event scheduler
	set ns [new Simulator]

	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
	......

	# Use the following to make the orientation right.
	$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

References: