ns2 tutorial for EE566

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Introduction to Ns-2
Zhibin WU WINLAB, ECE Dept. Rutgers
U. zhibinwu_at_winlab.rutgers.edu
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Goals

• Understanding NS-2
• Hands-on Experience with NS2
• Ns-2 by Example
• Write your own scripts
• Extending NS2
• Implementing new functionality

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Schedule

• Presentation (60 min)
• Group Assignments (10 min)
• Practices (1 Hr)
• Q A session (15 min)

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Talk Overview

• What is ns-2? (the evolution)
• Architecture
• Basic Tcl/Otcl commands
• Elements of an ns-2 simulation
• Example
• Online Resources Documentation

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What is ns?

• A discrete event, packet-level simulator
• Targeted at networking research
• Supports the simulation of
• intserv/diffserv, Multicast, Transport,
  Applications, Wireless (fixed, mobile, satellite)
• REAL variant (1989)?DARPA (LBL, Xerox PARC, UCB,
  and USC/ISI) (1995)
• Ns-3 Project (Ongoing)

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Status

• ns-2
• 100K lines of C
• 70K lines of OTcl
• 50K lines of test suite, examples, docs
• Platforms
• Most UNIX and UNIX-like systems (FreeBSD, Linux,
  Sun Solaris)
• Window 95/98/NT with Cygwin
• (Emulation only for FreeBSD for now)

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Remember!

• A simulator model of a real-world system is
  necessarily a simplification. For example, in
  simulating TCP
• No SYN/FIN
• Equal size segments
• No variable window advertisement
• Bugs Users of ns are responsible for verifying
  for themselves that their simulations are not
  invalidated by bugs.

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Architecture Object-Oriented

• C for data
• Per packet action
• OTcl for control
• Periodic or triggered action
• Modularity (), re-usability(), scalability()
• Speed(-), memory(-)

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OTcl and C The Duality
Pure OTcl objects
Pure C objects
C/OTcl split objects
C
OTcl
ns
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Script in interactive mode
linux21 ns set ns new Simulator _o3 ns at
1 puts \Hello World!\ 1 ns at 1.5
exit 2 ns run Hello World! linux21
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A script in batch mode
simple.tcl set ns new Simulator ns at 1 puts
\Hello World!\ ns at 1.5 exit ns
run linux21 ns simple.tcl Hello World! linux21
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Basic Tcl
set a 43 set b 27 proc test a b set c
expr a b set d expr expr a - b
c for set k 0 k lt 10 incr k if
k lt 5 puts k lt 5, pow expr pow(d,
k) else puts k gt 5, mod
expr d k test 43 27
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Basic OTcl
Class Mom Mom instproc greet self instvar
age_ puts age_ years old mom How are you
doing? Class Kid -superclass Mom Kid instproc
greet self instvar age_ puts age_ years
old kid Whats up, dude?
set mom new Mom mom set age_ 45 set kid new
Kid kid set age_ 15 mom greet kid greet
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SIMULATE WIRED NETWORK
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Elements of ns-2 Simulation

• Create the event scheduler
• Turn on tracing
• Create network
• Setup routing
• Insert errors
• Create transport connection
• Create traffic
• Transmit application-level data

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Creating Event Scheduler

• Create event scheduler
• set ns new Simulator
• Schedule events
• ns at lttimegt lteventgt
• lteventgt any legitimate ns/tcl commands
• Start scheduler
• ns run

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Tracing

• Trace packets on all links
• ns trace-all open test.out w
• lteventgt lttimegt ltfromgt lttogt ltpktgt ltsizegt -- ltfidgt
  ltsrcgt ltdstgt ltseqgt ltattrgt
• 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• - 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• Trace packets on all links in nam format
• ns namtrace-all open test.nam w
• Must appear immediately after creating scheduler

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Tracing

• Turn on tracing on specific links
• ns trace-queue n0 n1
• ns namtrace-queue n0 n1

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Creating Network

• Nodes
• set n0 ns node
• set n1 ns node
• Links and queuing
• ns duplex-link n0 n1 ltbandwidthgt ltdelaygt
  ltqueue_typegt
• ltqueue_typegt DropTail, RED, CBQ, FQ, SFQ, DRR

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Creating Network LAN

• LAN
• ns make-lan ltnode_listgt ltbandwidthgt ltdelaygt
  ltll_typegt ltifq_typegt ltmac_typegt ltchannel_typegt
• ltll_typegt LL
• ltifq_typegt Queue/DropTail,
• ltmac_typegt MAC/802_3
• ltchannel_typegt Channel

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Inserting Packet Errors

• Creating Error Module
• set loss_module new ErrorModel
• loss_module set rate_ 0.01
• loss_module unit pkt
• loss_module ranvar new RandomVariable/Uniform
• loss_module drop-target new Agent/Null
• Inserting Error Module
• ns lossmodel loss_module n0 n1

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Network Dynamics

• Link failures
• Hooks in routing module to reflect routing
  changes
• Four models
• ns rtmodel-at lttimegt updown n0 n1
• ns rtmodel Trace ltconfig_filegt n0 n1
• ns rtmodel Exponential ltparamsgt n0 n1
• ns rtmodel Deterministic ltparamsgt n0 n1
• Parameter list
• ltstartgt ltup_intervalgt ltdown_intervalgt
  ltfinishgt

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Setup Routing

• Unicast
• ns rtproto lttypegt
• lttypegt Static, Session, DV, cost, multi-path
• Multicast
• ns multicast (right after new Simulator)
• or set ns new Simulator multicast on
• ns mrtproto lttypegt
• lttypegt CtrMcast, DM, ST, BST (centralized,dense
  mode, shared tree

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Creating Connection UDP

• UDP
• set udp new Agent/UDP
• set null new Agent/Null
• ns attach-agent n0 udp
• ns attach-agent n1 null
• ns connect udp null

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Creating Traffic On Top of UDP

• CBR
• set src new Application/Traffic/CBR
• Exponential or Pareto on-off
• set src new Application/Traffic/Exponential
• set src new Application/Traffic/Pareto

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Creating Connection TCP

• TCP
• set tcp new Agent/TCP
• set tcpsink new Agent/TCPSink
• ns attach-agent n0 tcp
• ns attach-agent n1 tcpsink
• ns connect tcp tcpsink

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Creating Traffic On Top of TCP

• FTP
• set ftp new Application/FTP
• ftp attach-agent tcp
• Telnet
• set telnet new Application/Telnet
• telnet attach-agent tcp

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Creating Traffic Trace Driven

• Trace driven
• set tfile new Tracefile
• tfile filename ltfilegt
• set src new Application/Traffic/Trace
• src attach-tracefile tfile
• ltfilegt
• Binary format (native!)
• inter-packet time (msec) and packet size (byte)

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Application-Level Simulation

• Features
• Build on top of existing transport protocol
• Transmit user data, e.g., HTTP header
• Two different solutions
• TCP Application/TcpApp
• UDP Agent/Message

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Script Structure for Wired Scenario
parameters and options set ns new Simulator
Turn on tracing Create topology Setup
packet loss, link dynamics Create routing
agents Create - protocol agents -
application and/or setup traffic sources
Post-processing procs Start simulation
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SIMULATE WIRELESS NETWORK
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Script Structure Wireless
parameters and options set ns new Simulator
Turn on tracing create MobileNode object (PHY
to layer 3 configured) Create topology
create mobility Create Layer 4 and above -
UDP/TCP agents - application and/or setup
traffic sources Post-processing procedures
Start simulation
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Example Wireless Scenario

• 4x4 grid

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240m
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Example Step 1

• Define Parameters
• set cbr_size 500set cbr_interval 0.002set
  num_row 4set time_duration 100

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Example Step 2

• Protocol Options
• set val(chan) Channel/WirelessChannel channel
  typeset val(prop) Propagation/TwoRayGround
  radio-propagation modelset val(netif)
  Phy/WirelessPhy network interface typeset
  val(mac) Mac/802_11 MAC typeset val(ifq)
  Queue/DropTail/PriQueue interface queue
  typeset val(ll) LL link layer typeset
  val(ant) Antenna/OmniAntenna antenna modelset
  val(ifqlen) 50 max packet in ifqset val(rp)
  DSDV routing protocol

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Example Step 3

• Scheduler, Trace, Topo, God
• Initialize nsset ns_ new Simulatorset
  tracefd open simple.tr wns_ trace-all
  tracefd
• set up topography object
• set topo new Topography
• topo load_flatgrid 1000 1000
• create-god expr num_row num_row

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Example Step 4

• Create Node Object with protocols
• 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) \
• -channel chan1 -topoInstance topo \
• -agentTrace ON -routerTrace OFF\
• -macTrace ON \
• -movementTrace OFF
• for set i 0 i lt expr num_rownum_row
  incr i
• set node_(i) ns_ node

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Example Step 5

• Create Topology
• set k 0
• while k lt num_row
• for set i 0 i lt num_row incr i
• set m expr iknum_row
• node_(m) set X_ expr i240
• node_(m) set Y_ expr k24020.0
• node_(m) set Z_ 0.0
• incr k

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Example Step 6

• Create Mobility
• Move node 11 from its original place to
  top-right corner
• ns_ at 60.0 "node_(11) setdest 990.0 990.0
  15.0

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Example Step 7

• Set up transport layer (UDP)
• for set i 0 i lt num_row incr i
• set udp_(i) new Agent/UDP
• set null_(i) new Agent/Null
• ns_ attach-agent node_(8) udp_(0)
• ns_ attach-agent node_(4) udp_(1)
• ns_ attach-agent node_(13) udp_(2)
• ns_ attach-agent node_(14) udp_(3)
• ns_ attach-agent node_(11) null_(0)
• ns_ attach-agent node_(7) null_(1)
• ns_ attach-agent node_(2) null_(2)
• ns_ attach-agent node_(3) null_(3)
• for set i 0 i lt num_row incr i
• ns_ connect udp_(i) null_(i)

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Example Step 8

• Define Traffic Scenario
• for set i 0 i lt num_row incr i
• set cbr_(i) new Application/Traffic/CBRcb
  r_(i) set packetSize_ cbr_sizecbr_(i) set
  interval_ 0.5cbr_(i) attach-agent udp_(i)
• ns_ at 11.0234 "cbr_(0) start"ns_ at 10.4578
  "cbr_(1) start" ns_ at 12.7184 "cbr_(2)
  start"ns_ at 12.2456 "cbr_(3) start"

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Example Step 9

• End-of-simulation wrapper (as usual)
• Tell nodes when the simulation endsfor
  set i 0 i lt expr num_rownum_row incr
  i ns_ at expr time_duration 10.0
  "node_(i) reset"ns_ at expr
  time_duration 10.0 "finish"ns_ at expr
  time_duration 10.01 "puts \"NS Exiting...\"
  ns_ halt"proc finish global ns_
  tracefdns_ flush-traceclose tracefdputs
  "Starting Simulation..."ns_ run

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Auxiliary Tools

• setdest
• used to generate the positions of nodes and their
  moving speed and moving directions.setdest -v 1
  -n 50 -p 0 -M 20 -t 900 -x 1500 -y 300
• cbrgen.tclns cbrgen.tcl -type cbrtcp -nn
  nodes -seed seed -mc connections -rate
  rate
• Use source ltfilenamegt.tcl to add the generated
  file to scipts

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Resources

• http//www.isi.edu/nsnam/ns
• http//www.winlab.rutgers.edu/zhibinwu
• Tutorials
• Marc Greiss Tutorial (http//www.isi.edu/nsnam/ns
  /tutorial/index.html)
• Ns by example (http//nile.wpi.edu/NS/)
• Wireless Tutorial (http//www.isi.edu/nsnam/ns/ns-
  tutorial/wireless.ppt )

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Documentation

• Tcl (Tool Command Language)
• http//dev.scriptics.com/scripting
• OTcl (MIT Object Tcl)
• otcl/doc/tutorial.html (in distribution)
• ns manual
• Included in distribution ns/doc
• http//www.isi.edu/salehi/ns_doc.ps.gz

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Advanced Topics

• Trace analysis
• Architecture of Mobilenode Object
• Extending NS-2 with new protocols and algorithms
• More complex changes
• Hybrid Node
• A node with multiple interfaces

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Group Assignments

• Download simple.tcl
• http//www.winlab.rutgers.edu/zhibinwu/simple.tcl
  
• Modifications
• Node-Configure changes
• Random topology generation 40-node within
  1000x1000 area
• Random Node Mobility
• Changeprotocol from UDP to TCP
• Dynamic Traffic change

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