Introduction to ns-2

Noun Choi

Oct. 11, 2007

Outline

• Background

• ns-2 Internals

• Short demo

• Troubleshooting

• Reference links

• Q & A

History and Status

• UCB REAL network simulator

• VINT from LBL, PARC, UCB, & USC

• ns-1

• ns-2, currently maintained by USC/ISI– 100K lines of C++– 70K lines of OTcl– 30K lines of test suite– 20K lines of documentation

Platforms

• Most UNIX and UNIX-like systems

- FreeBSD or *BSD

- Linux

- Sun Solaris

- HP, SGI

• WINDOWS

– Under Cygwin

Components of ns-2

• Tcl/TK: ns-2 is an extended Tcl interpreter

• OTcl: Object Tcl

• TclCL: Tcl with classes library

• ns-2

• nam-1: Network Animator

• xgraph: Plotting and Graphing

• And more….

Installation

• Latest version: 2.31 (Mar 10, 2007)

• Download ns-allinone – http://www.isi.edu/nsnam/ns/ns-build.html#allino

ne

• ./install will configure, compile, & install

• Problem?– http://www.isi.edu/nsnam/ns/ns-problems.html

What is ns-2

• Discrete-event driven network simulation

• Object Oriented

• ns-2 is an extended Tcl (OTcl) interpreter

• ns-2 is written in C++ and OTcl– OTcl = Tcl + OO– C++ implements the code that executed

frequently– OTcl configures the system

Pros & Cons

• Free• Almost all network

components are implemented

• Active contributions from researchers

• Easy to modify and/or add new functions

• Unreliable

• Real Object

Oriented?

• Hard to troubleshoot

• Unrealistic abstraction

OTcl and C++: The Duality

C++

otcl

OTcl Linkage

set tcp [new Agent/TCP]

init

Agent/TCP

init

Agent

Create Otcl shadow object

TclObject

Create C++ object

constructor

TclObject (C++)

constructor

parent

constructor

TcpAgent

OTcl

C++

static class TcpClass : public TclClass {

public:

TcpClass() : TclClass("Agent/TCP") {}

TclObject* create(int, const char*const*) {

return (new TcpAgent);}

} class_tcp;

OTcl Linkage (II)

Command()• Otcl$tcp advance 10

• C++int Agent::command(int argc, const char*const* argv){

if (argc == 3) {if (strcmp(argv[1], “advance") == 0) {

int newswq = atoi(argv[2]);return (TCL_OK);

} }

return (Agent::command(argc, argv);}

OTcl Linkage (III)

bind(): link C++ member variables to Otcl object variables

• C++TcpAgent::TcpAgent() {

bind(“window_”, &wnd_);}

// bind_time(), bind_bool(), bind_bw()

• Otcl$tcp set window_ 200

You must setting the initial values of variants in ~ns/tcl/lib/ns-default.tcl

OTcl Linkage (IV)

• Invoking Otcl procedure and obtaining its resultsTcl::instance().evalf("%s Lookup_CIP_RT %d", name(), iph-

>dst().addr_);

nextHop = Tcl::instance().result();

Classifier/Addr/Cip instproc Lookup_CIP_RT { m_addr }

{ return … }

• Passing a results string to OtclTcl::instance().result(“………”)

Buffer

How ns-2 works

Scheduler

Event QueueTarget object

Event (Packet)

Time

Object BObject A

Deque

Dispatch Dispatch

Register Event

Source code in Scheduler.ccvoid Scheduler::schedule(Handler* h, Event* e, double delay) {

e->uid_ = uid_++;e->handler_ = h;double t = clock_ + delay;

e->time_ = t;insert(e);

}

void Scheduler::run() {instance_ = this;Event *p;while (!halted_ && (p = deque())) {

dispatch(p, p->time_);}

}

void Scheduler::dispatch(Event* p, double t) {clock_ = t;p->uid_ = -p->uid_; // being dispatchedp->handler_->handle(p); // dispatch

}

An Example

A B

CBR

Transport

Network

LL

IFQ

MAC

NetIF

CBR Sink

Transport

Network

LL

IFQ

MAC

NetIF

Scheduler

Wireless Channel

Demonstration

BaseStation

MobileNode

MobileNode

MobileNode

Wireless

Wired Wired

Demonstration (Contd.)• set opt(chan) Channel/WirelessChannel ;# channel type• set opt(prop) Propagation/TwoRayGround ;# radio-propagation model• set opt(netif) Phy/WirelessPhy ;# network interface type• set opt(mac) Mac/802_11 ;# MAC type• set opt(ifq) Queue/DropTail/PriQueue ;# interface queue type• set opt(ll) LL ;# link layer type• set opt(ant) Antenna/OmniAntenna ;# antenna model• set opt(ifqlen) 50 ;# max packet in ifq• set opt(adhocRouting) DSDV ;# routing protocol

• set opt(cp) "" ;# connection pattern file• set opt(sc) "./scen/scen-3-test" ;# node movement file.

• set opt(x) 670 ;# x coordinate of topology• set opt(y) 670 ;# y coordinate of topology• set opt(seed) 0.0 ;# seed for random number

gen.• set opt(stop) 250 ;# time to stop simulation

• set opt(ftp1-start) 100• set opt(ftp2-start) 150

• set num_wired_nodes 2• set num_bs_nodes 1

Demonstration (Contd.)• #

================================================================• # accpet input parameter• set opt(nn) [lindex $argv 0]• set outfile_ [lindex $argv 1]

• # ================================================================

• # check for boundary parameters and random seed• if { $opt(x) == 0 || $opt(y) == 0 } {• puts "No X-Y boundary values given for wireless topology\n"• }

• if {$opt(seed) > 0} {• puts "Seeding Random number generator with $opt(seed)\n"• ns-random $opt(seed)• }

Demonstration (Contd.)• # create simulator instance• set ns_ [new Simulator]

• # set up for hierarchical routing• $ns_ node-config -addressType hierarchical• AddrParams set domain_num_ 2 ;# number of domains• lappend cluster_num 2 1 ;# number of clusters in each domain• AddrParams set cluster_num_ $cluster_num• lappend eilastlevel 1 1 4 ;# number of nodes in each cluster • AddrParams set nodes_num_ $eilastlevel ;# of each domain

• set tracefd [open $outfile_.tr w]• set namtrace [open $outfile_.nam w]• $ns_ trace-all $tracefd• $ns_ namtrace-all-wireless $namtrace $opt(x) $opt(y)

Demonstration (Contd.)• # Create topography object• set topo [new Topography]

• # define topology• $topo load_flatgrid $opt(x) $opt(y)

• # create God• create-god [expr $opt(nn) + $num_bs_nodes]

• #create wired nodes• set temp {0.0.0 0.1.0} ;# hierarchical addresses for wired

domain• for {set i 0} {$i < $num_wired_nodes} {incr i} {• set W($i) [$ns_ node [lindex $temp $i]] • }

Demonstration (Contd.)• # configure for base-station node• $ns_ node-config -adhocRouting $opt(adhocRouting) \• -llType $opt(ll) \• -macType $opt(mac) \• -ifqType $opt(ifq) \• -ifqLen $opt(ifqlen) \• -antType $opt(ant) \• -propType $opt(prop) \• -phyType $opt(netif) \• -channelType $opt(chan) \• -topoInstance $topo \• -wiredRouting ON \• -agentTrace OFF \• -routerTrace OFF \• -macTrace OFF

• #create base-station node• set temp {1.0.0 1.0.1 1.0.2 1.0.3} ;# hier address to be used for wireless• ;# domain• set BS(0) [$ns_ node [lindex $temp 0]]• $BS(0) random-motion 0 ;# disable random motion

• #provide some co-ord (fixed) to base station node• $BS(0) set X_ 1.0• $BS(0) set Y_ 2.0• $BS(0) set Z_ 0.0

Demonstration (Contd.)• #configure for mobilenodes• $ns_ node-config -wiredRouting OFF

• for {set j 0} {$j < $opt(nn)} {incr j} {• set node_($j) [ $ns_ node [lindex $temp \• [expr $j+1]] ]• $node_($j) base-station [AddrParams addr2id \• [$BS(0) node-addr]]• }

• #create links between wired and BS nodes

• $ns_ duplex-link $W(0) $W(1) 5Mb 2ms DropTail• $ns_ duplex-link $W(1) $BS(0) 5Mb 2ms DropTail

• $ns_ duplex-link-op $W(0) $W(1) orient down• $ns_ duplex-link-op $W(1) $BS(0) orient left-down

Demonstration (Contd.)• # setup TCP connections• set tcp1 [new Agent/TCP]• $tcp1 set class_ 2• set sink1 [new Agent/TCPSink]• $ns_ attach-agent $node_(0) $tcp1• $ns_ attach-agent $W(0) $sink1• $ns_ connect $tcp1 $sink1• set ftp1 [new Application/FTP]• $ftp1 attach-agent $tcp1• $ns_ at $opt(ftp1-start) "$ftp1 start"

• set tcp2 [new Agent/TCP]• $tcp2 set class_ 2• set sink2 [new Agent/TCPSink]• $ns_ attach-agent $W(1) $tcp2• $ns_ attach-agent $node_(2) $sink2• $ns_ connect $tcp2 $sink2• set ftp2 [new Application/FTP]• $ftp2 attach-agent $tcp2• $ns_ at $opt(ftp2-start) "$ftp2 start"

Demonstration (Contd.)• # Tell all nodes when the simulation ends• for {set i } {$i < $opt(nn) } {incr i} {• $ns_ at $opt(stop).0 "$node_($i) reset";• }• $ns_ at $opt(stop).0 "$BS(0) reset";

• $ns_ at $opt(stop).0002 "puts \"NS EXITING...\" ; $ns_ halt"• $ns_ at $opt(stop).0001 "stop"• proc stop {} {• global ns_ tracefd namtrace• # $ns_ flush-trace• close $tracefd• close $namtrace• }

• puts "Starting Simulation..."• $ns_ run

Trace File Format

Event Abbreviation Type Value

Normal Event

r: Receive

d: Drop

e: Error

+: Enque

-: Deque

%g %d %d %s %d %s %d %d.%d %d.%d %d %d

double Time

Int Source Node

int Destination Node

string Packet Name

int Packet Size

string Flags

Int Flow ID

Int Source Address

Int Destination Address

Int Sequence Number

Int Unique Packet ID

Troubleshooting

• Problem while installing– Compiler may complain– http://www.isi.edu/nsnam/ns/ns-problems.html

• Program crashes– Use gdb

• Unexpected results

• Hidden problem– Slice & dice the trace log

Reference Links• http://www.isi.edu/nsnam/ns/• Manual & Tutorial

– http://www.isi.edu/nsnam/ns/ns-documentation.html– http://www.isi.edu/nsnam/ns/tutorial/index.html– http://www-sop.inria.fr/maestro/personnel/Eitan.Altman/COURS-NS/n3.

pdf• Mailing List

– http://www.isi.edu/nsnam/ns/ns-lists.html• Tcl

– http://www.tcl.tk/man/tcl8.5/tutorial/tcltutorial.html• OTcl

– http://bmrc.berkeley.edu/research/cmt/cmtdoc/otcl/tutorial.html• tclCL

– http://www.openmash.org/lxr/source/tclcl/tclcl.tcl?c=tutorials