1. Network Simulator 2
Tejas Vasavada

2. Contents Simulation of wired networks Simulation of wireless networks
Traffic and movement-pattern files
Trace files
Analyzing trace files using 'awk' script
'gnuplot' – utility to plot graphs

3. Contents (contd.) DSR – A protocol for MANETs
Source code of DSR in NS2
How to change DSR (with examples)
Printing packet header
Configuring nodes to drop packets
Adding a new function in DSR
Calling previous function from Tcl
Passing arguments from Tcl to DSR
Use of timers

4. Contents How to add new package in NS
Simulation of Wired-cum-Wireless Networks

5. Introduction Simulation comes before implementation.
A newly designed protocol is simulated first to test the performance.

6. Simulation Tools OmNet++, NS2, Qualnet, Opnet, GlomoSim etc.
NS2 - an open source tool, widely used in academics for research purpose.

7. How to use NS2 Front end – Tcl (Tool Command Langauage) Back end – C++
Today we will learn Tcl.

8. Wired Network

9. Tcl script set ns [new Simulator]
creates an instance of ‘Simulator’ class.
Output is stored in .nam files (Network AniMator) set nf [open out.nam w]
$ns namtrace-all $nf

10. Tcl script (contd.) proc finish {} { global ns nf $ns flush-trace
close $nf
exec nam out.nam &
exit 0 }
‘finish’ will be called at the end of simulation.

11. Tcl Script (contd.) $ns at 5.0 "finish“
finish() is called at 5th second.
$ns run
Starts simulation.

12. Tcl script (contd.) set n0 [$ns node] set n1 [$ns node]
Creates two nodes - n0 and n1.
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
Connects both the nodes.

13. Tcl script (contd.) #Create a UDP agent and attach it to node n0
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
# Create a CBR traffic source and attach it to udp0
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 500
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0

14. Tcl script (contd.) set null0 [new Agent/Null]
$ns attach-agent $n1 $null0
Creates a null agent and attaches it to n1.
$ns connect $udp0 $null0
Two agents are connected togother.

15. Tcl script (contd.) $ns at 0.5 "$cbr0 start" $ns at 4.5 "$cbr0 stop“
Node n0 will start sending packets at time
0.5 sec and will stop at 4.5 sec.

16. Exercise 1 Read example1.tcl provided to you.
Run it using following command
ns example1.tcl
Read & Run Example2.tcl

17. Example2.tcl $ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns duplex-link-op $n2 $n3 orient right
Creates star shape topology.

18. Example2.tcl (contd.)

19. Example2.tcl (contd.) Nodes n0 and n1 connect to n3 via n2.
Bandwidth n2-n3 < (bandwidth n0-n2 +
bandwidth n1-n2)
Node n2 drops packets.

20. Example2.tcl
To see what is happening at n2, different flows should be coloured differently.
$udp0 set class_ 1
$udp1 set class_ 2
$ns color 1 Blue
$ns color 2 Red

21. Example2.tcl (contd.)

22. Example3.tcl for {set i 0} {$i < 7} {incr i} { set n($i) [$ns node]
Creates 7 nodes.
$ns duplex-link $n($i) $n([expr ($i+1)%7]) 1Mb 10ms DropTail

23. Example3.tcl (contd.)

24. Example3.tcl (contd.)
Node n0 is connected to n3. Packets will pass through n1 and n2 (shortest path).
Break n1-n2 link using following commands.
$ns rtmodel-at 1.0 down $n(1) $n(2)
$ns rtmodel-at 2.0 up $n(1) $n(2)

25. Example3.tcl (contd.)

26. Example3.tcl (contd.) Use following command to use alternate path.
$ns rtproto DV

27. Example3.tcl (contd.)

28. Wireless Network

29. Simple-wireless.tcl Components of a mobile node… Link Layer,
Interface Queue between LL and Network Layer,
MAC Layer
Routing Layer
Parameters of a mobile node
Type of antenna,
Radio propagation model

30. Simple-wireless.tcl (contd.)
set val(chan) Channel/WirelessChannel ;# channel type set val(prop) Propagation/TwoRayGround ;# radio-propagation model set val(ant) Antenna/OmniAntenna ;# Antenna type set val(ll) LL ;# Link layer type set val(ifq) Queue/DropTail/PriQueue ;# Interface queue type set val(ifqlen) 50 ;# max packet in ifq set val(netif) Phy/WirelessPhy ;# network interface type set val(mac) Mac/802_11 ;# MAC type set val(rp) DSDV ;# ad-hoc routing protocol set val(nn) 2 ;# number of mobilenodes

31. Simple-wireless.tcl (contd.)
set ns_ [new Simulator]
Creates new instance of ‘Simulator’.
set tracefd [open simple.tr w]
$ns_ trace-all $tracefd
Creates new instance of trace file.

32. Simple-wireless.tcl (contd.)
set topo [new Topography]
Creates new topology.
$topo load_flatgrid
Sets resolution of topology to 500 x 500.

33. Simple-wireless.tcl (contd.)
# Configure nodes
$ns_ node-config -adhocRouting $val(rp) -llType $val(ll) \
-macType $val(mac) ifqType $val(ifq) \
-ifqLen $val(ifqlen) -antType $val(ant) \
-propType $val(prop)
–phyType $val(netif) \
-topoInstance $topo \
-channelType $val(chan) \
-agentTrace ON \
-routerTrace ON \
-macTrace OFF \
-movementTrace OFF

34. Simple-wireless.tcl (contd.)
for {set i 0} {$i < $val(nn) } {incr i} {
set node_($i) [$ns_ node ]
$node_($i) random-motion 0 }
Random motion is disabled. We will provide initial position and movement parameters.

35. Simple-wireless.tcl (contd.)
$node_(0) set X_ 5.0
$node_(0) set Y_ 2.0
$node_(0) set Z_ 0.0
$node_(1) set X_ 390.0
$node_(1) set Y_ 385.0
$node_(1) set Z_ 0.0

36. Simple-wireless.tcl (contd.)
# Node_(1) starts to move towards node_(0)
$ns_ at 50.0 "$node_(1) setdest "
$ns_ at 10.0 "$node_(0) setdest “
# Node_(1) then starts to move away from node_(0)
$ns_ at "$node_(1) setdest "

37. Simple-wireless.tcl (contd.)
# TCP connections between node_(0) and node_(1)
set tcp [new Agent/TCP]
$tcp set class_ 2
set sink [new Agent/TCPSink]
$ns_ attach-agent $node_(0) $tcp
$ns_ attach-agent $node_(1) $sink
$ns_ connect $tcp $sink
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ns_ at 10.0 "$ftp start"

38. Simple-wireless.tcl (contd.)
# Tell nodes when the simulation ends for {set i 0} {$i < $val(nn) } {incr i} { $ns_ at "$node_($i) reset"; } $ns_ at "stop" $ns_ at "puts \"NS EXITING...\" ; $ns_ halt" proc stop {} { global ns_ tracefd close $tracefd

39. Simple-wireless.tcl (contd.)
puts "Starting Simulation..."
$ns_ run
Prints the message and starts simulation.

40. Traffic-pattern file and movement-pattern file

41. Wireless-1.tcl set val(cp) “/root/cbr-3-test"
set val(sc) “/root/scen-3-test“
cbr-3-test is connection-pattern file.
scen-3-test is movement-pattern file.

42. Wireless-1.tcl (contd.) set val(x) 670 set val(y) 670
set namtrace [open wireless1-out.nam w]
$ns_ namtrace-all-wireless $namtrace $val(x) $val(y)

43. Wireless-1.tcl (contd.) puts "Loading connection pattern..."
source $val(cp)
Loads connection-pattern file.
puts "Loading scenario file..."
source $val(sc)
Loads movement-pattern(scenario) file.

44. Wireless-1.tcl (contd.) for {set i 0} {$i < $val(nn)} {incr i} {
$ns_ initial_node_pos $node_($i) 20 }
Defines size of node in nam

45. Traffic pattern file
ns cbrgen.tcl [-type cbr|tcp] [-nn nodes] [-seed seed] [-mc connections] [-rate rate] > [filenm]
Generates a traffic pattern. It is saved in file ‘filenm’.
-type : type of connection cbr or tcp
-nn : no. of nodes
-seed : seed value used by random number generator
-mc : no. of connections
-rate : rate at with packets are sent

46. Traffic pattern file (contd.)
ns cbrgen.tcl -type cbr -nn 10 -seed 1.0 -mc 8 -rate 4.0 > cbr-10-test
Generates traffic-pattern and saves in file cbr-10-test.
Create traffice-pattern file for tcp traffic and check how it differs from cbr-10-test

47. Movement-pattern file
‘setdest’ utility available at:
ns-x.xx/indep-utils/cmu-scen-gen/setdest
/setdest –v 1 –n <nodes> -p <pause time> -M <max speed> -t <sim time> -x <maxx> -y <maxy>

48. Movement-pattern file (contd.)
./setdest –v 2 –n <nodes> -s <speed type> -m <min speed> -M <max speed> -t <sim time> -P <pause type> -p <pause time> -x <maxx> -y <maxy>
Speed type: 1 - uniform speed
2 - normal speed

49. Pause type: 1 - constant
2 – uniform [ 0, 2 x pause ]
For e.g.
./setdest –v 2 -n 50 -s 1 -m 1 -M 20 -t 200 -P 1 -p 0 -x 200 -y 200 > /root/Desktop/scen-3-test

50. Trace file format

51. Trace files Output of simulation is in trace format.
Trace file has two formats: old and new
To use new format add following line in tcl script before calling trace-all .
$ns use-newtrace

52. Trace file format
Event type
s send
d drop
r receive
f forward
Time -t

53. Trace file format (contd.)
Node property tag
-Ni Node id
-Nx Node’s x-coordinate
-Ny Node’s y-coordinate
-Nz Node’s z-coordinate
-Ne Node’s energy level
-Nl Trace level (AGT, RTR, MAC)

54. Trace file format (contd.)
-Is source address.source port number
-Id dest address.dest port number
-It packet type
-Il packet size
-If flow id
-Ii unique id
-Iv ttl value

55. Trace file format (contd.)
Next hop information
-Hs id for this node
-Hd id of next node towards destination

56. Awk script

57. Awk script ‘Awk’ is a scripting language used to process text files.
Processes the file row by row.
Columns are identified like $1,$2 etc.
awk –f <.awk file> <.tr> file.
Use the awk file provided to calculate throughput from tracefile.

58. Sample Script - dr.awk
BEGIN {
sent=0
recd=0 }

59. dr.awk event=$1 level=$19 if(event == “s” && level == “AGT”) sent++
if(event == “r” && level == “AGT”)
recd++ }

60. dr.awk
END {
printf("sent %g, recd %g, fwd %g, del. %g\n",sent,recd,fwd,recd/sent); }

61. GnuPlot

62. 'gnuplot'
Syntax:
gnuplot <file.gnu>
Read dr.gnu file to understand use of 'gnuplot' to plot graphs.

63. Adding new Files in NS
Find ns2_ricean_dist folder available with this presentation.
Follow the procedure in “README” file.