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Network Simulator 2(NS2)
Yingyue Xu04/19/23
Overview:The Network simulator (NS): discrete event simulator for networks. supports wired, wireless, and satellite networks. various routing and multicast protocols. written in C++ and object-oriented tool command
language (OTcl). NS output is a file(s) which contains all packet
information. It can be viewed using network animator (NAM), xgraph, or processed with custom scripts (Perl, Tcl or Awk ).
User view of NS:
Why two languages:C++
Fast in running. Slow and hard to modify (need
to recompile the whole NS ). Used to implement detailed
protocols and algorithms, to manipulate bytes since it can run over large number of data
OTcl Slow in running Can be quickly changed (no
need to recompile). Used to implement the
simulation configuration like # of nodes, simulation topology and the dimensions of test area.
That’s why NS object called split object!
NS via Tclcl (Tcl with classes) provides glue to make objects and variables appear on both languages.
Ns functionalities Wired world
Routing DV, LS, PIM-SM Transportation: TCP and UDP Traffic sources:web, ftp, telnet, cbr, stochastic Queuing disciplines:drop-tail, RED, FQ, SFQ, DRR QoS: IntServ and Diffserv Emulation
Wireless Ad hoc routing and mobile IP Directed diffusion, sensor-MAC
Tracing, visualization, various utilities
Ns Models Traffic models and applications:
Web, FTP, telnet, constant-bit rate, real audio Transport protocols:
unicast: TCP (Reno, Vegas, etc.), UDP Multicast: SRM
Routing and queueing: Wired routing, ad hoc rtg and directed diffusion queueing protocols: RED, drop-tail, etc
Physical media: Wired (point-to-point, LANs), wireless (multiple propagation
models), satellite
NS installation: NS can work on most UNIX platforms, and
also on windows platform.Detailed info for downloading and building NS:
http://www.isi.edu/nsnam/ns/ns-build.html Easier way to download all in one package
and build NS (this will not work on Windows), this package contains Tcl, Tclcl, OTcl, Tk, and NS source codes.
You need to run install from UNIX shell (Bash or C shell).
Basic Tclvariables:set x 10puts “x is $x”
functions and expressions:set y [pow x 2]set y [expr x*x]
control flow:if {$x > 0} { return $x } else {
return [expr -$x] }while { $x > 0 } {
puts $xincr x –1
}
procedures:proc pow {x n} {
if {$n == 1} { return $x }set part [pow x [expr $n-1]]return [expr $x*$part]
}
Also lists, associative arrays, etc.
=> can use a real programming language to build network topologies, traffic models, etc.
Basic otclClass Person# constructor:Person instproc init {age} {
$self instvar age_set age_ $age
}# method:Person instproc greet {} {
$self instvar age_puts “$age_ years old: How are you doing?”
}
# subclass:Class Kid -superclass PersonKid instproc greet {} {
$self instvar age_puts “$age_ years old kid: What’s up, dude?”
}
set a [new Person 45]set b [new Kid 15]$a greet$b greet
=> can easily make variations of existing things (TCP, TCP/Reno)
Ns programming Create the event scheduler Turn on tracing Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data
Creating Event Scheduler Create event scheduler
set ns [new Simulator] Schedule events
$ns at <time> <event> <event>: any legitimate ns/tcl commands
$ns at 5.0 “finish” Start scheduler
$ns run
Ns programming Create the event scheduler Turn on tracing Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data
Tracing and Monitoring Packet tracing:
On all links: $ns trace-all [open out.tr w] On one specific link: $ns trace-queue $n0
$n1$tr<Event> <time> <from> <to> <pkt> <size> -- <fid> <src> <dst>
<seq> <attr>
+ 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
Ns programming Create the event scheduler Turn on tracing Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data
Creating Network Nodes
set n0 [$ns node]
set n1 [$ns node] Links and queuing
$ns <link_type> $n0 $n1 <bandwidth> <delay> <queue_type> <link_type>: duplex-link, simplex-link <queue_type>: DropTail, RED, CBQ, FQ, SFQ,
DRR, diffserv RED queues
Creating Network: LAN$ns make-lan <node_list> <bandwidth>
<delay> <ll_type> <ifq_type> <mac_type> <channel_type>
<ll_type>: LL
<ifq_type>: Queue/DropTail,
<mac_type>: MAC/802_3
<channel_type>: Channel
Ns programming Create the event scheduler Turn on tracing Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data
Setup Routing Unicast
$ns rtproto <type>
<type>: Static, Session, DV, cost, multi-path
Multicast$ns multicast (right after [new Simulator])
$ns mrtproto <type><type>: CtrMcast, DM, ST, BST
Other types of routing supported: source routing, hierarchical routing
Ns programming Create the event scheduler Turn on tracing Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data
Inserting 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 $n1
Ns programming Create the event scheduler Turn on tracing Create network Setup routing Insert errors Create transport connection Create traffic
Creating Connection and Traffic UDPset udp [new Agent/UDP]set null [new Agent/Null]$ns attach-agent $n0
$udp$ns attach-agent $n1
$null$ns connect $udp $null
CBRset src [new
Application/Traffic/CBR]
Creating Connection and Traffic II
TCPset tcp [new Agent/TCP]
set tcpsink [new Agent/TCPSink]
$ns attach-agent $n0 $tcp
$ns attach-agent $n1 $tcpsink
$ns connect $tcp $tcpsink
FTPset ftp [new Application/FTP]
$ftp attach-agent $tcp
Telnetset telnet [new
Application/Telnet]
$telnet attach-agent $tcp
Summary: Generic Script Structure
set ns [new Simulator]set ns [new Simulator]
# [Turn on tracing]# [Turn on tracing]
# Create topology# Create topology
# Setup packet loss, link dynamics# Setup packet loss, link dynamics
# Create routing agents# Create routing agents
# Create: # Create:
# - multicast groups# - multicast groups
# - protocol agents# - protocol agents
# - application and/or setup traffic sources# - application and/or setup traffic sources
# Post-processing procs# Post-processing procs
# Start simulation# Start simulation
Plumbing: Packet Flow
0
1
n0 n1
Addr Classifier
Port Classifier
entry_
0 Agent/TCP Addr Classifier
Port Classifier
entry_
1
0Link n0-n1
Link n1-n0
0 Agent/TCPSink
dst_=1.0 dst_=0.0Application/FTP
Getting started with nam Turn on nam tracing in your Tcl script
As easy as turning on normal tracing$ns namtrace $file
Specify link orientation (or node position for wireless)$ns duplex-link-op $node1 $node2 orient left
Execute namexec nam $filename
Advanced nam capabilities Node options — color, shape, label
$node color red$node shape hexagon$node label “my text”$node label-color blue$node label-at up
Link options$ns duplex-link-op $n1 $n2 color green$ns duplex-link-op queuePos right$ns duplex-link-op $n1 $n2 label “my text”$ns duplex-link-op $n1 $n2 label-color blue$ns duplex-link-op $n1 $n2 label-at down
Advanced nam capabilities Packet colors
$ns color $n blue
$agent set fid_ $n
Annotation$ns at $time “$ns trace-annotate $text”
Control playback$ns set-animation-rate 3ms
The nam user interface
The nam editor Create simple scenarios graphically Good for those who don’t want to learn
Tcl, but only a limited subset of ns is available
The nam editor
Wireless model Mobilenode at core of mobility model Mobilenodes can move in a given topology,
receive/transmit signals from/to wireless channels Wireless network stack consists of LL, ARP,
MAC, IFQ etc Allows simulations of multi-hop ad hoc networks,
wireless LANs, sensor networks etc
An Example – Step 1# Define Global Variables# create simulatorset ns [new Simulator]
# create a flat topology in a 670m x 670m areaset topo [new Topography] $topo load_flatgrid 670 670
An Example – Step 2# Define standard ns/nam trace
# ns trace
set tracefd [open demo.tr w]
$ns trace-all $tracefd
# nam trace
set namtrace [open demo.nam w]
$ns namtrace-all-wireless $namtrace 670 670
GOD (General Operations Director) Stores smallest number of hops from one
node to another Optimal case to compare routing protocol
performance Automatically generated by scenario file set god [create-god <no of mnodes>] $god set-dist <from> <to> <#hops>
Example –Step 3 Create God
set god [create-god 3]
$ns at 900.00 “$god setdist 2 3 1”
An Example – Step 4# Define how a mobile node is configured$ns node-config \
-adhocRouting DSDV \-llType LL \-macType Mac/802_11 \-ifqLen 50 \-ifqType Queue/DropTail/PriQueue \-antType Antenna/OmniAntenna \-propType Propagation/TwoRayGround \-phyType Phy/WirelessPhy \-channelType Channel/WirelessChannel \-topoInstance $topo-agentTrace ON \-routerTrace OFF \-macTrace OFF
An Example – Step 5# Next create a mobile node, attach it to the channel set node(0) [$ns node]# disable random motion $node(0) random-motion 0
# Use “for” loop to create 3 nodes:
for {set i < 0} {$i < 3} {incr i} {
set node($i) [$ns node]
$node($i) random-motion 0
}
Mobilenode Movement Node position defined in a 3-D model However z axis not used
$node set X_ <x1>$node set Y_ <y1>$node set Z_ <z1>$node at $time setdest <x2> <y2>
<speed> Node movement may be logged
Scenario Generator: Movement
Mobile Movement Generatorsetdest -n <num_of_nodes> -p pausetime setdest -n <num_of_nodes> -p pausetime
-s <maxspeed> -t <simtime> -x <maxx> -s <maxspeed> -t <simtime> -x <maxx> -y <maxy>-y <maxy>
Source: ns-2/indep-utils/cmu-scen-gen/setdesns-2/indep-utils/cmu-scen-gen/setdest/t/
Random movement $node random-motion 1 $node start$node start
A Movement File$node_(2) set Z_ 0.000000000000$node_(2) set Y_ 199.373306816804$node_(2) set X_ 591.256560093833$node_(1) set Z_ 0.000000000000$node_(1) set Y_ 345.357731779204$node_(1) set X_ 257.046298323157$node_(0) set Z_ 0.000000000000$node_(0) set Y_ 239.438009831261$node_(0) set X_ 83.364418416244$ns_ at 50.000000000000 "$node_(2) setdest 369.463244915743 170.519203111152 3.371785899154"$ns_ at 51.000000000000 "$node_(1) setdest 221.826585497093 80.855495003839 14.909259208114"$ns_ at 33.000000000000 "$node_(0) setdest 89.663708107313 283.494644426442 19.153832288917"
Scenario Generator: Traffic Generating traffic pattern files
CBR trafficns cbrgen.tcl [-type cbr|tcp] [-nn ns cbrgen.tcl [-type cbr|tcp] [-nn nodes] [-seed seed] [-mc connections] nodes] [-seed seed] [-mc connections] [-rate rate][-rate rate]
TCP trafficns tcpgen.tcl [-nn nodes] [-seed seed]ns tcpgen.tcl [-nn nodes] [-seed seed]
Source: ns-2/indep-utils/cmu-scen-ns-2/indep-utils/cmu-scen-gen/gen/
A Traffic Scenarioset udp_(0) [new Agent/UDP]
$ns_ attach-agent $node_(0) $udp_(0)
set null_(0) [new Agent/Null]
$ns_ attach-agent $node_(2) $null_(0)
set cbr_(0) [new Application/Traffic/CBR]
$cbr_(0) set packetSize_ 512
$cbr_(0) set interval_ 4.0
$cbr_(0) set random_ 1
$cbr_(0) set maxpkts_ 10000
$cbr_(0) attach-agent $udp_(0)
$ns_ connect $udp_(0) $null_(0)
$ns_ at 127.93667922166023 "$cbr_(0) start"
…….
An Example – Step 6# Define node movement model source <movement-scenario-files>
# Define traffic modelsource <traffic-scenario-files>
An Example – Step 7
# Tell ns/nam the simulation stop time $ns at 200.0 “$ns nam-end-wireless 200.0”$ns at 200.0 “$ns halt”
# Start your simulation $ns run
nam Visualization Replace
$ns namtrace-all $fd$ns namtrace-all $fd
with$ns namtrace-all-wireless $fd$ns namtrace-all-wireless $fd
At the end of simulation, do
$ns nam-end-wireless [$ns now]$ns nam-end-wireless [$ns now]
Wireless Trace Support Original cmu trace format A separate wireless trace format developed
later at ISI Current ongoing effort to have ONE format
to combine all wired and wireless formats
Useful links: Tutorials:
http://www.isi.edu/nsnam/ns/tutorial/index.html http://nile.wpi.edu/NS/
NS2-Manualhttp://www.isi.edu/nsnam/ns/ns-man.html
Network Animator (NAM ): http://www.isi.edu/nsnam/nam/
OTcl Tutorial:
http://bmrc.berkeley.edu/research/cmt/cmtdoc/otcl
Help and Resources Ns and nam build questions
http://www.isi.edu/nsnam/ns/ns-build.html Ns mailing list: [email protected] TCL: http://dev.scriptics.com/scripting Otcl tutorial (in distribution):
ftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/tutorial.html