outline - ce.aut.ac.irce.aut.ac.ir/~bakhshis/ns-2/ns-2 introduction.pdf · • share code,...

Outline• An introduction to ns-2

• What is ns-2• Fundamentals• Writing ns-2 codes• Wireless support• Traces support and visualization• Emulation• Related work

What is ns-2

• History• What does it support

Ns Goals

• Support networking research and education• Protocol design, traffic studies, etc• Protocol comparison

• Provide a collaborative environment• Freely distributed, open source

• Share code, protocols, models, etc• Allow easy comparison of similar protocols• Increase confidence in results

• More people look at models in more situations• Experts develop models

• Multiple levels of detail in one simulator

Multiple levels of detail in simulations

Consider two nodeson an Ethernet:

A B

simplequeuingmodel:

t=1, A enqueues pkt on LANt=1.01, LAN dequeues pkt

and triggers B

detailedCSMA/CDmodel:

t=1.0: A sends pkt to NICA’s NIC starts carrier sense

t=1.005: A’s NIC concludes cs,starts tx

t=1.006: B’s NIC begins reciving pktt=1.01: B’s NIC concludes pkt

B’s NIC passes pkt to app

Alternatives

• Experimentation• Private lab• Public testbed (e.g.

Planetlab)• Shared labs (e.g.

Utah Emulab)• Analysis• Other simulator

• Custom simulators• Other general

simulators

• Operational details, but• Limited scale• Expensive, limited

flexibility• Higher overhead

• Can provide understanding, but• Limited details

• Important niches• Limited re-use

History of ns-2• History

• Cornell REAL simulator -1989• VINT project (UCB, Xerox ,USC/ISI) – 1995• USC/ISI SAMAN/CONSER project – 1999• Ns-3 project now led by Tom Henderson

• Size• ~220K lines of codes

• 45% C++• 31% OTcl• 23% test suite/example/documents

• ~400 pages of manual• Very steep learning curve for a new user!

• The most popular non-commercial discrete event packet-level simulator• Used by 10000+ users from 1000+ institutes from 50+ countries• 300+ posts to [email protected] every month

ns-2 support

• Platform• FreeBSD, Linux, Solaris, Windows and Mac

• Release• Periodical release: ~6 months

• current release: ns-2.31, Mar 10, 2007

• Daily snapshot• Now has moved to sourceforge

• Validation• 100+ test suites and 100+ examples

What ns-2 can simulate

• Wired network• Traffic model and applications• Transport protocol• Routing and Queuing• QoS• LANs

• Wireless network• Ad hoc routing and mobile IP• Sensor network• Propagation model/Energy model• WLAN (802.11)• Satellite

• Error modules• Tracing, visualization, emulation, various utilities

Wired network• Application

• HTTP, web caching• telnet, FTP, RealAudio• CBR, on-off source

• Transport• UDP, TCP (almost all variants of TCP), RTP• SRM, PLM, LMS, PGM

• Routing• Unicast (DV, LM, etc) and multicast routing (PIM etc)• Hierarchical routing• Manual routing• Broadcasting• MPLS

• Queuing• RED, FIFO, FQ, SFQ, DRR, CBQ• Diffserv and IntServ• ECN

Wireless network• Ad-hoc network routing

• AODV, DSR, TORA, DSDV• Mobile IP• ARP• Radio propagation model

• Friss-space attenuation• Two-ray ground reflection model• Shadowing model

• Sensor network• Direct diffusion• SMAC

• WLAN• Ad-hoc mode• Infrastructure mode

• Satellite• Geostationary• LEO

• Energy model• Omni-directional antenna with unity gain

“Ns” Components

• Ns, the simulator itself• Nam, the network animator

• Visualize ns (or other) output• Nam editor: GUI interface to generate ns scripts

• NSE, the network emulator• Pre-processing:

• Traffic and topology generators• Post-processing:

• Simple trace analysis, often in Awk, Perl, or Tcl

Installation

• Getting the pieces• Tcl/TK 8.x

• http://dev.scriptics.com• OTcl, TclCL, ns-2, nam-1:

http://www.isi.edu/nsnam/dist• Other utilities

• http://www.isi.edu/nsnam/ns/ns-build.html• Tcl-debug, GT-ITM, xgraph, …

Getting Help

• ns-2 build questions• http://www.isi.edu/nsnam/ns/ns-build.html

• [email protected]• [email protected]• “subscribe ns-users” in body• Archive: http://www.isi.edu/nsnam/ns

Resources

• Tcl (Tool Command Language)• http://dev.scriptics.com/scripting

• OTcl (MIT Object Tcl)• ~otcl/doc/tutorial.html (in distribution)

• ns manual• Latex sources are included in distribution: ~ns/doc• http://www.isi.edu/nsnam/ns/ns-documentation.html

Cautions

• Abstraction of the real world is necessary for a simulator

• You must justify the usage of the simulator based on your research goals• What level of details do you need?• What are your models?

Question?


• What is ns-2• Fundamentals• Writing ns-2 codes• Wireless support• Traces support and visualization• Emulation• Related work

Prerequisite

• Some programming experience of object-oriented language (such as C++, Java)

Discrete Event Simulation• Model world as events

• Simulator has list of events• Scheduler: take next one, run it, until done• Each event happens in an instant of virtual

(simulated) time, but takes an arbitrary amount of real time

• Ns uses simple model: single thread of control => no locking or race conditions to worry about

Discrete Event Examples

Consider two nodeson an Ethernet:

A B

simplequeuingmodel:

t=1, A enqueues pkt on LANt=1.01, LAN dequeues pkt

and triggers B

detailedCSMA/CDmodel:

t=1.0: A sends pkt to NICA’s NIC starts carrier sense

t=1.005: A’s NIC concludes cs,starts tx

t=1.006: B’s NIC begins reciving pktt=1.01: B’s NIC concludes pkt

B’s NIC passes pkt to app

Ns Architecture• Object-oriented (C++, OTcl)

• Lots of code reuses (e.g. TCP + TCP variants)• Use TclCl to bind C++ and OTcl together

• Modular approach• Fine-grained object composition

• From the simulator to a single event

• Reusability• Maintenance• Performance (speed and memory)• Careful planning of modularity

TclOTcl

TclCL

ns-2C++

Event Scheduler

Network Components

C++ and OTcl Separation

• “data” / “control” separation• C++ for “data”:

• per packet processing, core of ns• fast to run, detailed, complete control

• OTcl for control:• Simulation scenario configurations• Periodic or triggered action• Manipulating existing C++ objects• fast to write and change

+ running vs. writing speed Learning and debugging (two languages)

Control vs. Data

• Create topology• Setup routing• Create transport

connection• Create traffic

• Details of links and nodes

• Details of a routing protocol

• Details of TCP implementation

• Details of a packet

OTcl C++

24

Creating a link

n0 n1

enqT_ queue_ deqT_

drophead_ drpT_

link_ ttl_

n1 entry_head_

tracing simplex link

duplex link

[ns_ duplex-link $n0 $n1 5Mb 2ms drop-tail]

Details in C++

Octl codes

Otcl and C++: The Duality

• OTcl (object variant of Tcl) and C++ share class hierarchy

• TclCL is glue library that makes it easy to share functions, variables, etc

C++

otcl

C++/OTclsplit objects

ns

user simulation scripts

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.

Compare Otcl to C++

• Object oriented extension of Tcl• C++ constructor/destructor => OTclinit/destroy method

• C++ this => OTcl $self• OTcl methods always “virtual”• C++ static variable => OTcl class

variable• Multiple inheritance is supported

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)

Octl tutorial

ftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/tutorial.html

Using ns

Problem

Simulationmodel

Setup/run simulation

with ns

Resultanalysis

Modifyns

Hello World - Interactive ModeInteractive mode:swallow 71% ns% set ns [new Simulator]_o3% $ns at 1 “puts \“Hello

World!\””1% $ns at 1.5 “exit”2

% $ns runHello World!swallow 72%

Batch mode:simple.tcl

set ns [new Simulator]$ns at 1 “puts \“Hello

World!\””$ns at 1.5 “exit”$ns run

swallow 74% ns simple.tclHello World!swallow 75%

Let’s learn ns-2 by some examples first

• #Create a simulator object• set ns [new Simulator]

• #Open the nam trace file• set nf [open out.nam w]• $ns namtrace-all $nf

• #Define a 'finish' procedure• proc finish {} {• global ns nf• $ns flush-trace• #Close the trace file• close $nf• #Execute nam on the trace file• exec nam out.nam &• exit 0• }

• #Create two nodes• set n0 [$ns node]• set n1 [$ns node]

• #Create a duplex link between the nodes• $ns duplex-link $n0 $n1 1Mb 10ms DropTail

• #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

• #Create a Null agent (a traffic sink) and attach it to node n1• set null0 [new Agent/Null]• $ns attach-agent $n1 $null0

• #Connect the traffic source with the traffic sink• $ns connect $udp0 $null0

• #Schedule events for the CBR agent• $ns at 0.5 "$cbr0 start"• $ns at 4.5 "$cbr0 stop"• #Call the finish procedure after 5 seconds of simulation time• $ns at 5.0 "finish"

• #Run the simulation• $ns run


• #Define different colors for data flows• $ns color 1 Blue• $ns color 2 Red



• #Create four nodes• set n0 [$ns node]• set n1 [$ns node]• set n2 [$ns node]• set n3 [$ns node]

• #Create links between the nodes• $ns duplex-link $n0 $n2 1Mb 10ms DropTail• $ns duplex-link $n1 $n2 1Mb 10ms DropTail• $ns duplex-link $n3 $n2 1Mb 10ms SFQ

• $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

• #Monitor the queue for the link between node 2 and node 3• $ns duplex-link-op $n2 $n3 queuePos 0.5

• #Create a UDP agent and attach it to node n0• set udp0 [new Agent/UDP]• $udp0 set class_ 1• $ns attach-agent $n0 $udp0


• #Create a UDP agent and attach it to node n1• set udp1 [new Agent/UDP]• $udp1 set class_ 2• $ns attach-agent $n1 $udp1


• #Create a Null agent (a traffic sink) and attach it to node n3• set null0 [new Agent/Null]• $ns attach-agent $n3 $null0

• #Connect the traffic sources with the traffic sink• $ns connect $udp0 $null0 • $ns connect $udp1 $null0

• #Schedule events for the CBR agents• $ns at 0.5 "$cbr0 start"• $ns at 1.0 "$cbr1 start"• $ns at 4.0 "$cbr1 stop"• $ns at 4.5 "$cbr0 stop"• #Call the finish procedure after 5 seconds of simulation time• $ns at 5.0 "finish"



• #Tell the simulator to use dynamic routing• $ns rtproto DV



• #Create seven nodes• for {set i 0} {$i < 7} {incr i} {• set n($i) [$ns node]• }

• #Create links between the nodes• for {set i 0} {$i < 7} {incr i} {• $ns duplex-link $n($i) $n([expr ($i+1)%7]) 1Mb 10ms DropTail• }

• #Create a UDP agent and attach it to node n(0)• set udp0 [new Agent/UDP]• $ns attach-agent $n(0) $udp0


• #Create a Null agent (a traffic sink) and attach it to node n(3)• set null0 [new Agent/Null]• $ns attach-agent $n(3) $null0

• #Connect the traffic source with the traffic sink• $ns connect $udp0 $null0

• #Schedule events for the CBR agent and the network dynamics• $ns at 0.5 "$cbr0 start"• $ns rtmodel-at 1.0 down $n(1) $n(2)• $ns rtmodel-at 2.0 up $n(1) $n(2)• $ns at 4.5 "$cbr0 stop"• #Call the finish procedure after 5 seconds of simulation time• $ns at 5.0 "finish"


OK, now what if I want to create a new protocol?

Ping protocol

• One node will be able to send a packet to another node which will return it immediately, so that the round-trip-time can be calculated

Header file• struct hdr_ping {

char ret; double send_time;};

• class PingAgent : public Agent { public: PingAgent(); int command(int argc, const char*const* argv);void recv(Packet*, Handler*); protected: int off_ping_;};

C++ codes• #include "ping.h"

• static class PingHeaderClass : public PacketHeaderClass {• public:• PingHeaderClass() : PacketHeaderClass("PacketHeader/Ping", • sizeof(hdr_ping)) {}• } class_pinghdr;

• static class PingClass : public TclClass {• public:• PingClass() : TclClass("Agent/Ping") {}• TclObject* create(int, const char*const*) {• return (new PingAgent());• }• } class_ping;

• PingAgent::PingAgent() : Agent(PT_PING) { bind("packetSize_", &size_);bind("off_ping_", &off_ping_); }

C++

otcl


ns

Otcl and C++: The Duality

• OTcl (object variant of Tcl) and C++ share class hierarchy

• TclCL is glue library that makes it easy to share functions, variables, etc

C++

otcl


ns

user simulation scripts

• int PingAgent::command(int argc, const char*const* argv){if (argc == 2) {

if (strcmp(argv[1], "send") == 0) {// Create a new packet Packet* pkt = allocpkt(); // Access the Ping header for the new packet: hdr_ping* hdr = (hdr_ping*)pkt->access(off_ping_); // Set the 'ret' field to 0, so the receiving node knows// that it has to generate an echo packet hdr->ret = 0; // Store the current time in the 'send_time' field hdr->send_time = Scheduler::instance().clock(); // Send the packet send(pkt, 0);// return TCL_OK, so the calling function knows that the // command has been processed return (TCL_OK); }}

// If the command hasn't been processed by PingAgent()::command, // call the command() function for the base class return (Agent::command(argc, argv)); }

void PingAgent::recv(Packet* pkt, Handler*) {

// Access the IP header for the received packet: hdr_ip* hdrip = (hdr_ip*)pkt->access(off_ip_); // Access the Ping header for the received packet: hdr_ping* hdr = (hdr_ping*)pkt->access(off_ping_); // Is the 'ret' field = 0 (i.e. the receiving node is being pinged)?if (hdr->ret == 0) {

// Send an 'echo'. First save the old packet's send_timedouble stime = hdr->send_time; // Discard the packet Packet::free(pkt); // Create a new packetPacket* pktret = allocpkt();

// Access the Ping header for the new packet:hdr_ping* hdrret = (hdr_ping*)pktret->access(off_ping_);

// Set the 'ret' field to 1, so the receiver won't send another // echo hdrret->ret = 1;// Set the send_time field to the correct valuehdrret->send_time = stime;// Send the packet send(pktret, 0);

} else {// A packet was received. Use tcl.eval to call the Tcl// interpreter with the ping results. // Note: In the Tcl code, a procedure 'Agent/Ping recv// {from rtt}' // has to be defined which allows the user to react to the // ping result. char out[100]; // Prepare the output to the Tcl interpreter. Calculate the // round trip timesprintf(out, "%s recv %d %3.1f", name(), hdrip->src_.addr_ >> Address::instance().NodeShift_[1], (Scheduler::instance().clock()-hdr->send_time) * 1000); Tcl& tcl = Tcl::instance(); tcl.eval(out); // Discard the packet Packet::free(pkt);

} }

Necessary changes (I): packet.henum packet_t {

PT_TCP,PT_UDP, ...... // insert new packet types here PT_TFRC, PT_TFRC_ACK, PT_PING,// packet protocol ID for our ping-agentPT_NTYPE // This MUST be the LAST one

};

Necessary changes (I)class p_info {

public: p_info() {name_[PT_TCP]= "tcp"; name_[PT_UDP]= "udp"; ...........name_[PT_TFRC]= "tcpFriend"; name_[PT_TFRC_ACK]= "tcpFriendCtl"; name_[PT_PING]="Ping";

name_[PT_NTYPE]= "undefined"; } .....

}

Necessary change (II): tcl/lib/ns-default.tcl

• Agent/Ping set packetSize_ 64

Necessary change (III): 'tcl/lib/ns-packet.tcl'

{ SRMEXT off_srm_ext_} { Ping off_ping_ }} {

set cl PacketHeader/[lindex $pair 0]

Necessary Changes (IV): Makefile

sessionhelper.o delaymodel.o srm-ssm.o \srm-topo.o \ping.o \$(LIB_DIR)int.Vec.o $(LIB_DIR)int.RVec.o \$(LIB_DIR)dmalloc_support.o \

OK, now how to write a tcl script to use the new Ping Agent you

just wrote?

Ping.tcl#Create a simulator objectset ns [new Simulator]#Open a trace fileset nf [open out.nam w]$ns namtrace-all $nf#Define a 'finish' procedureproc finish {} {

global ns nf$ns flush-traceclose $nfexec nam out.nam &exit 0

}

#Create three nodesset n0 [$ns node]set n1 [$ns node]set n2 [$ns node]#Connect the nodes with two links$ns duplex-link $n0 $n1 1Mb 10ms DropTail$ns duplex-link $n1 $n2 1Mb 10ms DropTail#Define a 'recv' function for the class 'Agent/Ping'Agent/Ping instproc recv {from rtt} {

$self instvar node_puts "node [$node_ id] received ping answer from \

$from with round-trip-time $rtt ms."}

#Create two ping agents and attach them to the nodes n0 and n2

set p0 [new Agent/Ping]$ns attach-agent $n0 $p0set p1 [new Agent/Ping]$ns attach-agent $n2 $p1#Connect the two agents$ns connect $p0 $p1#Schedule events$ns at 0.2 "$p0 send"$ns at 0.4 "$p1 send"$ns at 0.6 "$p0 send"$ns at 0.6 "$p1 send"$ns at 1.0 "finish"#Run the simulation$ns run

C++/OTcl Linkage

Root of ns-2 object hierarchy

bind(): link variable values between C++ and OTcl TclObject

command(): link OTcl methods to C++ implementations

TclClass Create and initialize TclObject’s

Tcl C++ methods to access Tcl interpreter

TclCommand Standalone global commands

EmbeddedTcl ns script initialization

TclObject

• Basic hierarchy in ns for split objects• Mirrored in both C++ and OTcl• Example

•• set set tcptcp [new Agent/TCP][new Agent/TCP]

•• $$tcptcp set set packetSizepacketSize_ 1024_ 1024

•• $$tcptcp advancebyadvanceby 50005000

TclObject: Hierarchy and Shadowing

TclObject

Agent

Agent/TCP

Agent/TCP OTclshadow object

_o123Agent/TCP C++

object

*tcp

TclObject

Agent

TcpAgent

OTcl classhierarchy

C++ classhierarchy

TclObject::bind()

• Link C++ member variables to OTclobject variables

• C++• TcpAgent::TcpAgent() {

• bind(“window_”, &wnd_);• … …

• }

• OTcl•• set set tcptcp [new Agent/TCP][new Agent/TCP]•• $$tcptcp set window_ 200set window_ 200

TclObject::command()

• Implement OTcl methods in C++• Trap point: OTcl method cmd{}

• Access the shadow object• Send all arguments after cmd{} call to



$tcp send TclObject::unknown{} $tcp cmd sendno suchprocedure

TcpAgent::command()

match “send”?

Invoke parent: return Agent::command()

process and return

Yes No

OTcl space

C++ space

TclObject::command()• OTcl

set tcp [new Agent/TCP]$tcp send 10

• C++int TcpAgent::command(int argc,

const char*const* argv) {if (argc == 3) {

if (strcmp(argv[1], “send”) == 0) {int newseq = atoi(argv[2]);……return(TCL_OK);

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

}

TclObject: Creation and Deletion

• Global procedures: new{}, delete{}• Example

•• set set tcptcp [new Agent/TCP][new Agent/TCP]

•• ……

•• delete $delete $tcptcp

C++

OTcl

TclObject: Creation and Deletion

invoke parentconstructor

Agent/TCPconstructor

Parent(Agent)constructor


TclObjectconstructor

create C++object

AgentTCPconstructor



parent (Agent)constructor

do nothing,return

TclObject (C++)constructor

bind variablesand return

bind variablesand return

create OTclshadow object

complete initialization

complete initialization

which C++ object to create? – TclClass

TclClass

TclObject

Agent

Agent/TCP

TclObject

Agent

TcpAgent

NsObject ??

OTclC++ mirroringStatic class TcpClass : public TclClass {public:

TcpClass() : TclClass(“Agent/TCP”) {}TclObject* create(int, const char*const*) {

return (new TcpAgent());}

} class_tcp;

Static class TcpClass : public TclClass {public:

TcpClass() : TclClass(“Agent/TCP”) {}TclObject* create(int, const char*const*) {

return (new TcpAgent());}

} class_tcp;

NsObject• Other important objects:

• NsObject: has recv() method• Connector: has target() and drop()• BiConnector: uptarget() &

downtarget()• Class hierarchy

• NsObject• Connector

• PingAgent• BiConnector

• Mac802_11PHY

MAC

NETWORK

TRANSPORT

SESSION

PRESENTATION

APPLICATION

Class Tcl• Singleton class with a handle to Tcl interpreter

• Tcl& tcl = Tcl::instance();• Usage

• Invoke OTcl procedure• tcl.evalc(“callbackX”);

• Obtain OTcl evaluation results• clock_ = atof(tcl.result());

• Pass a result string to OTcl•tcl.resultf(“%g”, clock())

• Return success/failure code to OTcl• tcl.error(“command not found”);

Class TclTcl& tcl = Tcl::instance();if (argc == 2) {

if (strcmp(argv[1], “now”) == 0) {tcl.resultf(“%g”, clock());return TCL_OK;

}tcl.error(“command not found”);return TCL_ERROR;

} else if (argc == 3) {tcl.eval(argv[2]);clock_ = atof(tcl.result());return TCL_OK;

}

Class TclCommand

• How to implement an OTcl command “ns-random” in C++

class RandomCommand : public TclCommand {public:

RandomCommand() : TclCommand("ns-random") {}virtual int command(int argc, const char*const* argv);

};

int RandomCommand::command(int argc, const char*const* argv){

Tcl& tcl = Tcl::instance();if (argc == 1) {

sprintf(tcl.buffer(), "%u", Random::random());tcl.result(tcl.buffer());

}

Brief summary

• TclObject• Unified interpreted (OTcl) and compiled (C++)

class hierarchies• Seamless access (procedure call and variable

access) between OTcl and C++• TclClass

• Establish interpreted hierarchy• Shadowing objects

• Tcl: primitives to access Tcl interpreter

Question?

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

Event Scheduler• Event: at-event and packet• List scheduler: default (FIFO)

• Heap: good for many events (O(log n) • Calendar queue

• A priority queue having N buckets each with width w. An item with priority p goes in bucket (p/w)%N

• Real-time scheduler• Synchronize with real-time• Network emulation

• set ns_ [new Simulator]• $ns_ use-scheduler Heap• $ns_ at 300.5 “$self halt”

Some scheduler-related commands

• Set now [$ns now]• $ns cancel <event>• $ns after <delay> <event>

• Execute <event> after <delay>• $ns dumpq

• Dump all events in the scheduler queue

Discrete Event Scheduler

time_, uid_, next_, handler_head_ ->

handler_ -> handle()

time_, uid_, next_, handler_insert

head_ ->

Tracing and Monitoring I

• 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

• Event tracing (support TCP currently)• Record “event” in trace file: $ns eventtrace-all• E 2.267203 0 4 TCP slow_start 0 210 1

Tracing and Monitoring II

• Queue monitor • set qmon [$ns monitor-queue $n0 $n1 $q_f $sample_interval]

• Get statistics for a queue $qmon set pdrops_

• Record to trace file as an optional

• Flow monitorset fmon [$ns_ makeflowmon Fid]$ns_ attach-fmon $sink $fmon$fmon set pdrops_

Tracing and Monitoring III

• Visualize trace in nam$ns namtrace-all [open test.nam w] $ns namtrace-queue $n0 $n1

• Variable tracing in namAgent/TCP set nam_tracevar_ true$tcp tracevar srtt_$tcp tracevar cwnd_

• Monitor agent variables in nam$ns add$ns add--agentagent--trace $trace $tcptcp$ns monitor$ns monitor--agentagent--trace $trace $tcptcp$srm0 $srm0 tracevartracevar cwndcwnd__…………$ns delete$ns delete--agentagent--trace $trace $tcptcp

Ns Internals

• Tcl commands translates into • series of object creation • plumbing of these objects

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

Components of Nodeid_

Address of nodeMonotonically increasing by 1

neighbor_A list of neighbors

agent_A list of agents

nodetype_A node type identifier

A routing module

Unicast node

• Address classifier• Distribute incoming packets to the correct link

• Port classifier• Distribute incoming packets to the correct

agent• First element that handles incoming

packet at the node• unicast: entry_• multicast: switch_

Network Topology: Node

n0 n1

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

Node entry

Unicast Node

Multicast Classifier

classifier_

dmux_

entry_

Node entry

Multicast Node

multiclassifier_

set n0 [ns_ node] Set ns_ [new Simulator –multicast on]Set n1 [ns_ node]

0 0

1

Node Addressing

• Two basic address styles available: flat and hierarchical

• Default flat address: 32 bits each for node and port id

• Default hier address: • 3 levels of hierarchy• 10 11 11 or 1 9 11 11 if mcast specified

• Different bit allocation possible for specific hier addresses

88

Hierarchical Node

n2

Nodeentry

Level 1Level 2

Level 3

Addressclassifier To Port

demux

ns_ node-config –addressing hier

Classifiers• Table of n slots• When a packet is received

• classify() identifies the slot to forward the packets• Address Classifiers

• Parse address in packet• Methods

• Install{}: • Elements{}• Clear{}

90

Network Topology: Link

n0 n1

enqT_ queue_ deqT_

drophead_ drpT_

link_ ttl_

n1 entry_head_

tracing simplex link

duplex link

[ns_ duplex-link $n0 $n1 5Mb 2ms drop-tail]

Connectors

• Connectors • Receive incoming packets, and transmit them to their target_

• Different types of connectors• Queue

• Holds a certain number of packets. Packets exceeding their queue-size are sent to the queue’s drop-target_

• LinkDelay• Model delay/bandwidth of the link

• TTLChecker• Decrements TTL on each packet, drops the packet if the TTL

becomes 0• DynaLink

• Transmit packets if the link is up, drop packet otherwise• Trace

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

Local area network• Link layer

• Queue: interface queue• LL: simulate a link layer protocol (e.g. ARQ)

• Mac layer• Must simulate some MAC protocol CS/CD/CA• Sending: follow a MAC protocol before transmitting packets to

Channel• Receiving: pass packets to link layer

• Physical layer• Channel

• Sending side: simulate the shared medium• Classifier/Mac

• Receiving side: delivering and optionally replicating packets to the receiving MAC objects

Routing module

• Routing agent• Exchange routing packets with neighbors

• Route logic• Use information gathered by routing agent (or

topology database) to perform route computation

• Classifier• Use computed routing table to perform packet

forwarding

Setup Routing

• Unicast$ns rtproto <type><type>: Static, Session, DV, cost, multi-path, Manual

• Multicast$ns multicast (right after [new Simulator])$ns mrtproto <type><type>: CtrMcast, DM, ST, BST

• Other types of routing supported: source routing, hierarchical routing

Examples

$ns rtproto Static ; default, use the Dijkstra’s all-pairs SPF algorithm$ns rtproto Session ; recompute route when topology changes$ns rtproto DV $n1 $n2 $n3 $ns rtproto LS $n1 $n2

set n1 [$ns Node] ; only enable $n1 to use multiPaths where applicable$n1 set multiPath_ 1 ; only DV routing can generate multipath routes

$ns cost $n1 $r1 2$ns cost $n2 $r2 2$ns cost $r1 $n2 3

Routing..

n0 n1

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

Node entry 01 enqT_ queue_ deqT_

drophead_ drpT_

link_ ttl_

n1 entry_

head_

..Routing

n0 n1

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

01

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

10

Link n0-n1

Link n1-n0

Class RouteLogic

• Route configuration• rtproto{} -> configure{} -> compute-routes{}

• Query nexthop•[$ns get-routelogic] lookup $n1 $2

• Recompute route on topology change• [$ns get-routelogic] notify

Inserting Errors

• Creating Error Moduleset 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

Network Dynamics

• Link failures• Hooks in routing module to reflect routing

changes• Four models

$ns $ns rtmodelrtmodel Trace <Trace <config_fileconfig_file> $n0 $n1> $n0 $n1$ns $ns rtmodelrtmodel Exponential {<Exponential {<paramsparams>} $n0 $n1>} $n0 $n1$ns $ns rtmodelrtmodel Deterministic {<Deterministic {<paramsparams>} $n0 $n1>} $n0 $n1$ns $ns rtmodelrtmodel--at <time> up|down $n0 $n1at <time> up|down $n0 $n1

• Parameter list[<start>] <up_interval> <down_interval> [<finish>][<start>] <up_interval> <down_interval> [<finish>]

• 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]• Exponential or Pareto

on-offset src [new

Application/Traffic/Exponential]set src [new

Application/Traffic/Pareto]$src attach-agent $udp

Creating Connection and Traffic I

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

Creating Traffic: Trace Driven

• Trace drivenset tfile [new Tracefile]$tfile filename <file>set src [new Application/Traffic/Trace]$src attach-tracefile $tfile<file>:

• inter-packet time (msec) and packet size (byte)

Transport

n0 n1

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

Agent/TCP

agents_

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

Agent/TCPSink

agents_

dst_=1.0 dst_=0.0

set tcp [new Agent/TCP]ns_ attach-agent $n0 $tcp

set tcpsink [new Agent/TCPSink]ns_ attach-agent $n1 $tcpsink

ns_ connect $tcp $tcpsink

0

0

1

0

Application

n0 n1

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

Agent/TCP

agents_

Addr Classifier

Port Classifier

classifier_

dmux_

entry_

Agent/TCPSink

agents_

dst_=1.0 dst_=0.0Application/FTP

set ftp [new Application/FTP]$ftp attach-agent $tcp$ns at 1.2 “$ftp start”

0

0

1

0

Packet Flow

01

n0 n1

Addr Classifier

Port Classifier

entry_

0 Agent/TCP Addr Classifier

Port Classifier

entry_

10

Link n0-n1

Link n1-n0

0 Agent/TCPSink

dst_=1.0 dst_=0.0Application/FTP

Application objects I

• Exponential• packetSize_• burst_time_• idle_time_• rate_

• CBR• packetSize_• rate_• interval_• random_• maxpkts_

Application objects II• Pareto

• packetSize_• burst_time_• idle_time_• rate_• shape_

• Telnet• interval_

• FTP• maxpkts_

• Default values in ns/tcl/lib/ns-default.tcl• All above are virtual applications

• focus only on “size” and “time” when data are transferred

Application-Level Simulation• Simulate applications that actually transfer their

own data• e.g. simulate various webcaching algorithms

• Features• Build on top of existing transport protocol• Transmit user data, e.g., HTTP header

• Examples• TCP: Application/HttpApp• UDP: Agent/Message

Application-Level Simulationa representation of a uniform application-level data unit (ADU)a common interface to pass data between applicationsmechanisms to pass data between applications and transport agents.

ADUfunctionality of an ADU is similar to that of a Packetpack user data into an arraythen included in the user data area of an nspacketUser must derive new agents to acceptuser data from applications, or use an wrapper like TcpApp

Passing data between applications

class Process {public:Process() : target_(0) {}inline Process*& target() { return target_; }

virtual void process_data(int size, char* data) = 0;virtual void send_data(int size, char* data = 0);

protected:Process* target_;};

Compare to Real World

• More abstract (much simpler):• No addresses, just global variables• Connect them rather than name

lookup/bind/listen/accept• Easy to change implementation

Set tsrc2 [new agent/TCP/Newreno]Set tsrc3 [new agent/TCP/Vegas]

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 groupsmulticast groups

# # -- protocol agentsprotocol agents

# # -- application and/or setup traffic sourcesapplication and/or setup traffic sources

# Post# Post--processing processing procsprocs

# Start simulation# Start simulation

Question?

Two examples

• Multicast• Web traffic

G2time1.3s

G2time1.2s

G1G2

time1.35s

Example: Multicast Routing

• Dynamic group membership

n0 n1

n2

n3

1.5Mb, 10ms

1.5Mb, 10ms

G1

time1.25s

G2

1.5Mb, 10ms

Multicast: Step 1

• Scheduler, tracing, and topology

# Create scheduler# Create scheduler

set ns [new Simulator]set ns [new Simulator]

# Turn on multicast# Turn on multicast

$ns multicast$ns multicast

# Turn on Tracing# Turn on Tracing

set set fdfd [new [new ““mcast.nammcast.nam”” w]w]

$ns $ns namtracenamtrace--all $all $fdfd

Multicast: Step 2

• Topology

# Create nodes# Create nodes





# Create links# Create links

$ns duplex$ns duplex--link $n0 $n1 1.5Mb 10ms link $n0 $n1 1.5Mb 10ms DropTailDropTail



Multicast: Step 3

• Routing and group setup

# Routing protocol: let# Routing protocol: let’’s run distance vectors run distance vector

$ns $ns mrtprotomrtproto DMDM

# Allocate group addresses# Allocate group addresses

set group1 [Node set group1 [Node allocaddrallocaddr]]

set group2 [Node set group2 [Node allocaddrallocaddr]]

Multicast: Step 4• Sender 0

# Transport agent for the traffic source# Transport agent for the traffic sourceset set udp0udp0 [new Agent/UDP][new Agent/UDP]$ns attach$ns attach--agent $agent $n1n1 $$udp0udp0$$udp0udp0 set set dst_addrdst_addr_ $_ $group1group1$$udp0udp0 set set dst_portdst_port_ 0_ 0

# Constant Bit Rate source #0 # Constant Bit Rate source #0 set set cbr0cbr0 [new Application/Traffic/CBR][new Application/Traffic/CBR]$$cbr0cbr0 attachattach--agent $agent $udp0udp0# Start at time 1.0 second# Start at time 1.0 second$ns at 1.0 "$$ns at 1.0 "$cbr0cbr0 start"start"

Multicast: Step 5• Sender 1

# Transport agent for the traffic source# Transport agent for the traffic sourceset set udp1udp1 [new Agent/UDP][new Agent/UDP]$ns attach$ns attach--agent $agent $n3n3 $$udp1udp1$$udp1udp1 set set dst_addrdst_addr_ $_ $group2group2$$udp1udp1 set set dst_portdst_port_ 0_ 0

# Constant Bit Rate source #0 # Constant Bit Rate source #0 set set cbr1cbr1 [new Application/Traffic/CBR][new Application/Traffic/CBR]$$cbr1cbr1 attachattach--agent $agent $udp1udp1# Start at time 1.1 second# Start at time 1.1 second$ns at 1.1 "$$ns at 1.1 "$cbr1cbr1 start"start"

Multicast: Step 6

• Receiver with dynamic membership

# Can also be Agent/Null# Can also be Agent/Null

set set rcvrrcvr [new Agent/[new Agent/LossMonitorLossMonitor]]

# Assign it to node $n2# Assign it to node $n2

$ns at $ns at 1.21.2 "$n2 join"$n2 join--group $group $rcvrrcvr $$group2group2""$ns at $ns at 1.251.25 "$n2 leave"$n2 leave--group $group $rcvrrcvr $$group2group2""$ns at $ns at 1.31.3 "$n2 join"$n2 join--group $group $rcvrrcvr $$group2group2""$ns at $ns at 1.351.35 "$n2 join"$n2 join--group $group $rcvrrcvr $$group1group1""

Multicast: Step 7

• End-of-simulation wrapper (as usual)

$ns at 2.0 "finish"$ns at 2.0 "finish"proc finish {} {proc finish {} {

global ns global ns fdfdclose $close $fdfd$ns flush$ns flush--tracetraceputs "running puts "running namnam..."..."exec exec namnam mcast.nammcast.nam &&exit 0exit 0

}}$ns run$ns run

Example: Web traffic

1

2

0

8 3

56

49

7

10 11

1.5Mb, 40ms

10Mb, 20ms

Multiple levels of feedback effects in Web traffic

TCP

HTTP

userclient server

request

response

request

response

timeuserclick

userclick

userclickend of page

user think timepage transmission

> 10sec

1~10sec

< 1sec

2008/10/7

3-level Web Model

•User sessionUser arrivalNumber of page per user

•PagePage arrivalNumber of objects per page

•ObjectObject arrivalObject size

Web

object

user

Page

Web traffic: Step 1

• Scheduler and tracing# Create scheduler# Create schedulerset ns [new Simulator]set ns [new Simulator]

# instantiate web traffic class# instantiate web traffic classset pool set pool [new [new PagePool/WebTrafPagePool/WebTraf]]

# Turn on Tracing# Turn on Tracingset set fdfd [new [new ““web.namweb.nam”” w]w]$ns $ns namtracenamtrace--all $all $fdfd

Web traffic: Step 2

• Topology# Create nodes# Create nodesfor {set i 0} {$i < 12} {for {set i 0} {$i < 12} {incrincr i} {i} {

set n($i) [$ns node]set n($i) [$ns node]}}$ns set $ns set srcsrc_ [list 2 3 4 5 6]_ [list 2 3 4 5 6]$ns set $ns set dstdst_ [list 7 8 9 10 11]_ [list 7 8 9 10 11]

# Create links# Create links$ns duplex$ns duplex--link $n(0) $n(1) 1.5Mb 40ms link $n(0) $n(1) 1.5Mb 40ms DropTailDropTail$ns duplex$ns duplex--link $n(0) $n(2) 10Mb 20ms link $n(0) $n(2) 10Mb 20ms DropTailDropTail$ns duplex$ns duplex--link $n(0) $n(3) 10Mb 20ms link $n(0) $n(3) 10Mb 20ms DropTailDropTail

Web traffic: Step 3

• Set up client and server nodes

$$pool pool setset--numnum--clientclient [[llengthllength [$ns set [$ns set srcsrc_]]_]]$pool $pool setset--numnum--serverserver [[llengthllength [$ns set [$ns set dstdst_]]_]]

set i 0set i 0foreachforeach s [$ns set s [$ns set srcsrc_] {_] {

$pool $pool setset--clientclient $i $n($s)$i $n($s)incrincr ii

}}set i 0set i 0foreachforeach s [$ns set s [$ns set dstdst_] {_] {

$pool $pool setset--serverserver $i $n($s)$i $n($s)incrincr i i

}}

Web traffic: Step 4• Specify the distributions for page arrival,

page size, object arrival, object sizeset set interPageinterPage [new [new RandomVariableRandomVariable/Exponential] /Exponential] $$interPageinterPage set set avgavg_ 1_ 1set set pageSizepageSize [new [new RandomVariableRandomVariable/Constant]/Constant]$$pageSizepageSize set set valval_ 1_ 1set set interObjinterObj [new [new RandomVariableRandomVariable/Exponential]/Exponential]$$interObjinterObj set set avgavg_ 0.01_ 0.01set set objSizeobjSize [new [new RandomVariable/ParetoIIRandomVariable/ParetoII]]$$objSizeobjSize set set avgavg_ 10_ 10$$objSizeobjSize set shape_ 1.2set shape_ 1.2

Web traffic: Step 5• Schedule web sessions

# Let# Let’’s schedule two sessionss schedule two sessions$pool set$pool set--numnum--session 2session 2# Let# Let’’s have 10 pages per sessions have 10 pages per sessionset set numPagenumPage 1010

# session 1 starts at time 0.1s# session 1 starts at time 0.1s$pool $pool createcreate--sessionsession 0 $0 $numPagenumPage 0.1 $0.1 $interPageinterPage $$pageSizepageSize$$interObjinterObj $$objSizeobjSize

# session 2 starts at time 1.2s # session 2 starts at time 1.2s $pool create$pool create--session 1 $session 1 $numPagenumPage 1.2 $1.2 $interPageinterPage $$pageSizepageSize$$interObjinterObj $$objSizeobjSize

Web traffic: Step 6

• End-of-simulation wrapper (as usual)

$ns at 10.0 "finish"$ns at 10.0 "finish"proc finish {} {proc finish {} {

global ns global ns fdfdclose $close $fdfd$ns flush$ns flush--tracetraceputs "running puts "running namnam..."..."exec exec namnam web.namweb.nam &&exit 0exit 0

}}$ns run$ns run

Question?


• What is ns-2• Fundamentals• writing ns-2 codes• Wireless support• Traces support and visualization• Emulation• Related work

Writing ns-2 codes

• Extending ns• In OTcl• In C++

• Debugging

ns Directory Structure

TK8.3 OTcl tclclTcl8.3 ns-2 nam-1

tcl

ex test lib

...

...

examples validation tests

C++ code

OTcl code

ns-allinone

mcast

ensure new changes do not

break the old codes

Extending ns in OTcl

• If you don’t want to compile• source your changes in your simulation

scripts• Otherwise

• Modifying code; recompile• Adding new files

• Change Makefile (NS_TCL_LIB), tcl/lib/ns-lib.tcl• Recompile

Add Your Changes into ns

TK8.3 OTcl tclclTcl8.3 ns-2 nam-1

tcl

ex test lib

...

...

examples validation tests

C++ code

OTcl code

ns-allinone

mcastmysrc

msg.tcl

Add Your Change into ns• tcl/lib/ns-lib.tclClass SimulatorClass Simulator……source ../source ../mysrc/msg.tclmysrc/msg.tcl

• MakefileNS_TCL_LIB = NS_TCL_LIB = \\tcl/mysrc/msg.tcltcl/mysrc/msg.tcl \\……

• Or: change Makefile.in, make make distcleandistclean, then ./configure ./configure ----enableenable--debug ,debug ,

make depend make depend andand makemake

Writing ns-2 codes

• Extending ns• In OTcl• In C++

• New components

Extending ns in C++

• Modifying code• make depend• Recompile

• Adding code in new files• Change Makefile• make depend• recompile

Creating New Components

• Guidelines• Two styles

• New agent based on existing packet headers• Add new packet header

Guidelines

• Decide position in class hierarchy• I.e., which class to derive from?

• Create new packet header (if necessary)• Create C++ class, fill in methods• Define OTcl linkage (if any)• Write OTcl code (if any)• Build (and debug)

New Agent, Old Header

• Exercise: TCP jump start• Wide-open transmission window at the

beginning• From cwndcwnd_ += 1_ += 1 To cwndcwnd_ = MAXWIN__ = MAXWIN_

TCP Jump Start – Step 1

TclObject

NsObject

Connector Classifier

Delay AddrClassifierAgent McastClasifierQueue Trace

DropTail RED TCP Enq Deq Drop

Reno SACK JS

Handler

Packet Format

header

dataip header

tcp header

rtp header

trace header

cmn header

...

ts_

ptype_

uid_

size_

iface_

New Packet Header

• Create new header structure• Create static class for OTcl linkage (packet.h)• Enable tracing support of new header(trace.cc)• Enable new header in OTcl (tcl/lib/ns-packet.tcl)• This does not apply when you add a new field

into an existing header!

How Packet Header WorksPacket

next_

hdrlen_

bits_ size determinedat compile time

size determinedat compile time

size determinedat compile time

……

hdr_cmn

hdr_ip

hdr_tcp

size determinedat simulatorstartup time

(PacketHeaderManager)

PacketHeader/Common

PacketHeader/IP

PacketHeader/TCP

Agent/Message – Step 1

TclObject

NsObject

Connector Classifier

Delay AddrClassifierAgent McastClasifierQueue Trace

DropTail RED TCP Enq Deq Drop

Reno SACK

Message

Writing ns-2 codes

• Extending ns• In OTcl• In C++• Debugging: OTcl/C++, memory• Pitfalls

Debugging C++ in ns

• C++/OTcl debugging

• Memory debugging• purify• dmalloc

C++/OTcl Debugging

• Usual technique• Break inside command()• Cannot examine states inside OTcl!

• Solution• Execute tcl-debug inside gdb

C++/OTcl Debugging

((gdbgdb) ) call call Tcl::instance().eval(Tcl::instance().eval(““debugdebug 11””))15: 15: lappendlappend auto_path $auto_path $dbg_librarydbg_librarydbg15.3> wdbg15.3> w*0: application*0: application15: 15: lappendlappend auto_path $auto_path $dbg_librarydbg_library

dbg15.4> Simulator info instancesdbg15.4> Simulator info instances_o1_o1dbg15.5> _o1 nowdbg15.5> _o1 now00dbg15.6> # and other fun stuffdbg15.6> # and other fun stuffdbg15.7> dbg15.7> cc((gdbgdb) where) where#0 0x102218 in write()#0 0x102218 in write()............

Memory Debugging in ns

• Purify• Set PURIFY macro in ns Makefile• Usually, put -colloctor=<ld_path>

• Gray Watson’s dmalloc library• http://www.dmalloc.com• make distclean• ./configure --with-dmalloc=<dmalloc_path>• Analyze results: dmalloc_summarize

dmalloc: Usage

• Turn on dmalloc• alias dmalloc ’eval ‘\dmalloc –C \!*`’• dmalloc -l log low

• dmalloc_summarize ns < logfile• ns must be in current directory• Itemize how much memory is allocated in

each function

Pitfalls

• Scalability vs flexibility• Or, how to write scalable simulation?

• Memory conservation tips• Memory leaks

Scalability vs Flexibility

• It’s tempting to write all-OTcl simulation• Benefit: quick prototyping• Cost: memory + runtime

• Solution• Control the granularity of your split object by

migrating methods from OTcl to C++

THE Merit of OTcl

Program size, complexity

C/C++ OTcl

• Smoothly adjust the granularity of scripting to balance extensibility and performance

• With complete compatibility with existing simulation scripts

high low

split objects

Object Granularity Tips

• Functionality• Per-packet processing C++• Hooks, frequently changing code OTcl

• Data management• Complex/large data structure C++• One-time configuration variables OTcl

Memory usage

Simulator 268KBUnicast node 2KBMulticast node 6KBDuplex link 9KBPacket 2KB

Memory Conservation Tips

• Remove unused packet headers• Avoid tracetrace--allall

• Use arrays for a sequence of variables• Instead of n$in$i, say n($i)n($i)

• Avoid OTcl temporary variables• temp=A; B=temp

• Use dynamic binding•• delay_bind()delay_bind() instead of bind()bind()• See object.{h,cc}

• Use different routing strategies• Computing routing tables dominate the simulation setup time

• Run on FreeBSD• use less memory for malloc()

Memory Leaks

• Purify or dmalloc, but be careful about split objects:•• for {set i 0} {$i < 500} {for {set i 0} {$i < 500} {incrincr i} {i} {

•• set a [new set a [new RandomVariableRandomVariable/Constant]/Constant]

•• }}

• It leaks memory, but can’t be detected!• Solution

• Explicitly delete EVERY split object that was new-ed

Final Word

• My extended ns dumps OTcl scripts!• Find the last 10-20 lines of the dump• Is the error related to “_o*** cmd …” ?

• Check your command()• Otherwise, check the otcl script pointed by the

error message

Questions?

Outline

• An introduction to ns-2• What is ns-2• Fundamentals• Writing ns-2 codes• Traces support and visualization• Wireless support• Emulation• Related work

ns nam Interface

• Color• Node manipulation• Link manipulation• Topology layout• Protocol state• Misc

nam Interface: Color

• Color mapping$ns color 40 red$ns color 40 red

$ns color 41 blue$ns color 41 blue

$ns color 42 chocolate$ns color 42 chocolate

• Color ↔ flow id association$tcp0 set fid_ 40$tcp0 set fid_ 40 ;# red packets;# red packets

$tcp1 set fid_ 41$tcp1 set fid_ 41 ;# blue packets;# blue packets

nam Interface: Nodes• Color

$node color red$node color red

• Shape (can’t be changed after sim starts)$node shape box$node shape box ;# circle, box, hexagon;# circle, box, hexagon

• Marks (concentric “shapes”)$ns at 1.0 $ns at 1.0 ““$n0 add$n0 add--mark m0 blue boxmark m0 blue box””$ns at 2.0 $ns at 2.0 ““$n0 delete$n0 delete--mark m0mark m0””

• Label (single string)$ns at 1.1 $ns at 1.1 ““$n0 label $n0 label \\””web cache 0web cache 0\\””””$node label$node label--at upat up$node label$node label--color bluecolor blue

nam Interfaces: Links

• Color$ns duplex$ns duplex--linklink--op $n0 $n1 color "green"op $n0 $n1 color "green"

• Label$ns duplex$ns duplex--linklink--op $n0 $n1 label "op $n0 $n1 label "abcedabced““$ns duplex$ns duplex--linklink--op $n1 $n2 labelop $n1 $n2 label--color bluecolor blue$ns duplex$ns duplex--linklink--op $n1 $n2 labelop $n1 $n2 label--at downat down

• Queue position$ns duplex-link-op queuePos right

• Dynamics (automatically handled)$ns $ns rtmodelrtmodel Deterministic {2.0 0.9 0.1} $n0 $n1Deterministic {2.0 0.9 0.1} $n0 $n1

• Asymmetric links not allowed

nam Interface: Topology Layout

• “Manual” layout: specify everything$ns duplex$ns duplex--linklink--op $n(0) $n(1) orient rightop $n(0) $n(1) orient right

$ns duplex$ns duplex--linklink--op $n(1) $n(2) orient rightop $n(1) $n(2) orient right

$ns duplex$ns duplex--linklink--op $n(2) $n(3) orient rightop $n(2) $n(3) orient right

$ns duplex$ns duplex--linklink--op $n(3) $n(4) orient 60degop $n(3) $n(4) orient 60deg

• If anything missing automatic layout

nam Interface: Misc

• Packet color$ns color $n blue$ns color $n blue$agent set fid_ $n$agent set fid_ $n

• Annotation• Add textual explanation to your simulation$ns at 3.5 "$ns trace$ns at 3.5 "$ns trace--annotate annotate \\““packet droppacket drop\\""““

• Control playback $ns at 0.0 "$ns set$ns at 0.0 "$ns set--animationanimation--rate 0.1ms"rate 0.1ms"

The nam user interface

Summary of nam

• Turn on nam tracing in your Tcl script• As easy as turning on normal tracing

•$ns namtrace $file

• Specify color/shape/label of node/link• $ns duplex-link-op $node1 $node2 orient left

• Execute nam• exec nam $filename

A live demoNam.exe

namgraph

• Display a graph showing when packets are received/dropped.

• Enabling namgraph• Run the namfilter script on your nam trace file:

exec tclsh /path/to/namfilter.tcl out.nam

namgraph

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 currently available

The nam editor

Topology generator

• Inet• GT-ITM• TIERS• BRITE

Summary

http://www.isi.edu/nsnam/ns/ns-topogen.html

Packages Graphs Edge Method

NTG n-level probabilistic

RTG Flat random Waxman

GT-ITM Flat random, n-level, Transit-stub various

TIERS 3-level spanning tree


• What is ns-2• Fundamentals• Writing ns-2 codes• Traces support and visualization• Wireless support• Emulation• Related work

Wireless support in ns-2

• Introduction• Wireless basics• Wireless internals

• Ad hoc routing• Mobile IP• Satellite networking• Directed diffusion

Contributions to wireless in ns• Original wireless model in ns contributed

by CMU’s Monarch group• Other major contributions from UCB, Sun

microsystems, univ of cincinnati, ISI etc• Other contributed models (not integrated)

in wireless ns includes Blueware, BlueHoc, Mobiwan, GPRS, CIMS etc

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

Wireless Examplefor ad hoc routing

• Scenario• 3 mobile nodes• moving within 670mX670m flat topology• using DSDV ad hoc routing protocol• Random Waypoint mobility model• TCP and CBR traffic

• ns-2/tcl/ex/wireless-demo-csci694.tcl

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


# 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)

• An omniscient observer• 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 Godset god [create-god 3]$ns at 900.00 “$god set-dist 2 3 1”


# 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 Generator

setdestsetdest --n <num_of_nodes> n <num_of_nodes> --p p pausetimepausetime --s s <<maxspeedmaxspeed> > --t <t <simtimesimtime> > --x <x <maxxmaxx> > --y y <<maxymaxy>>

Source: nsns--2/indep2/indep--utils/cmuutils/cmu--scenscen--gen/setdest/gen/setdest/

• 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/TCP trafficns ns cbrgen.tclcbrgen.tcl [[--type type cbr|tcpcbr|tcp] [] [--nnnn nodes] [nodes] [--seed seed seed] [seed] [--mc connections] [mc connections] [--rate rate]rate rate]

•• CBR trafficCBR trafficns ns cbrgen.tclcbrgen.tcl ––type type cbrcbr ––nnnn 20 20 ––seed 1 seed 1 ––mc 8 mc 8 --rate 4rate 4

• TCP trafficns ns cbrgen.tclcbrgen.tcl ––type type tcptcp --nnnn 15 15 --seed 0 seed 0 ––mc 6mc 6

• Source: nsns--2/indep2/indep--utils/cmuutils/cmu--scenscen--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"…….


# Define node movement model source <movement-scenario-files>

# Define traffic modelsource <traffic-scenario-files>


# Define node initial position in namfor {set i 0} {$i < 3 } { incr i} {

$ns initial_node_position $node($i) 20}

# 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

Energy Extension

• Node is energy-aware• Define node by adding new options:$ns_ node-config \

–energyModel EnergyModel-initialEnergy 100.0-txPower 0.6-rxPower 0.2

nam Visualization

• Use nam to visualize:• Mobile node position• Mobile node moving direction and speed• Energy consumption at nodes (color keyed)

nam Visualization

• Replace$ns $ns namtracenamtrace--all $all $fdfd

with$ns $ns namtracenamtrace--allall--wireless $wireless $fdfd

At the end of simulation, do$ns $ns namnam--endend--wireless [$ns now]wireless [$ns now]

Wireless support in ns-2

• Introduction• Wireless basics• Wireless internals

• Ad hoc routing• Mobile IP• Satellite networking• Directed diffusion

Wireless Internals

• Mobilenode• Basic node that has address and port de-

muxes, routing agent etc• Stack of network components consisting of LL,

MAC, NetIF radio-model etc• Wireless channel

Portrait of A Mobile Node

Node

ARP

Propagation and antenna models

MobileNode

LL

MAC

PHY

LL

CHANNEL

LL

MAC

PHY

Classifier: Forwarding

Agent: Protocol Entity

Node Entry

LL: Link layer object

IFQ: Interface queue

MAC: Mac object

PHY: Net interface

protocolagent

routingagent

addrclassifier

portclassifier

255

IFQIFQ

defaulttarget_

Radio propagation/antenna models

Prop/ant

Mobile Node : Components

• Classifiers• defaulttarget_ points to routing agent object• 255 is the port id assigned for rtagent_

• Routing agent• May be ad hoc routing protocol like AODV,

DSDV or directed diffusion

Mobile Node: Components

• Link Layer• Same as LAN, but with a separate ARP module• Sends queries to ARP

• ARP• Resolves IP address to hardware (MAC) address• Broadcasts ARP query

• Interface queue• Gives priority to routing protocol packets• Has packet filtering capacity

Mobile Node: Components

• MAC• 802.11

• IEEE RTS/CTS/DATA/ACK for unicast• Sends DATA directly for broadcast

• SMAC (for sensor network)• Network interface (PHY)

• Used by mobilenode to access channel• Stamps outgoing pkts with meta-data• Interface with radio/antenna models

Mobile Node: Components• Radio Propagation Model

• Friss-space model – attenuation at near distance (1/r2)

• Two-ray ground reflection model for far distance (1/r4)

• Shadowing model -probabilistic

• Antenna• Omni-directional, unity-gain

Wireless Channel

• Duplicate packets to all mobile nodes attached to the channel except the sender

• It is the receiver’s responsibility to decide if it will accept the packet• Collision is handled at individual receiver• O(N2) messages grid keeper, reference-

copying etc

Grid-keeper: An Optimization

Mobile Node: Misc.

• Energy consumption model for sensor networks

• Visualization of node movement, reachability, and energy

• Validation test suites

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

Ad Hoc Routing

• Four routing protocols currently supported:• DSDV

• Contributed by CMU• DSR

• Contributed by CMU• AODV

• Recently updated version from univ. of cincinnati;• TORA

• Contributed by CMU• Examples under tcl/test/test-suite-wireless- { lan-newnode.tcl, lan-aodv.tcl, lan-tora.tcl }

A Brief on MobileIP Support

• Developed by Sun• Require a different Node structure than MobileNode• Originally implemented for wired nodes

• Wired-cmu-wireless extension• Originally CMU wireless model only supports ad-hoc

and wireless LAN• Base-stations, support hier-rtg

• Standard MobileIP• Home Agent, Foreign Agent, MobileHosts

• Example•• Under Under tcl/test/testtcl/test/test--suitesuite--wirelesswireless--lanlan--newnode.tclnewnode.tcl (tests: DSDV(tests: DSDV--wiredwired--cumcum--wireless and wireless and DSDVDSDV--wirelesswireless--mipmip))

A Brief on Satellite Networking

• Developed by Tom Henderson (UCB)• Supported models

• Geostationary satellites: bent-pipe and processing-payload

• Low-Earth-Orbit satellites• Example: tcltcl/ex/sat/ex/sat--*.*.tcltcl and and tcl/test/testtcl/test/test--suitesuite--satellite.tclsatellite.tcl

Simulate sensor network with ns-2

• Currently support• Routing

• Direct diffusion• MAC

• SMAC


• What is ns-2• Fundamentals• Writing ns-2 codes• Traces support and visualization• Wireless support• Emulation• Related work

What is Emulation ?

• Ability to introduce the simulator into a live network

• Application:• Allows testing real-world implementations• Allows testing simulated protocols

• Requirements: • Scheduler support • Packet capture and generation capabilities

Emulation in ns-2

Read packets Write packets

ns

Network

Scheduler

• ns operates in virtual time using event-driven simulation

• Real-time scheduler • Does not advance the virtual clock to next

event• Dispatches event at real-time

Emulation Objects

• Interface between ns and network traffic

• Network Objects• Access to live network via• BPF and raw sockets

• Tap Objects• Conversion between ns

and• network packet formats

Capture: BPF

ns

Inject: Raw socket

network to ns

ns to network

Modes of Operation

• Packet conversion leads to two modes of operation

• Opaque Mode• Network packet fields are not interpreted

• Protocol Mode• Network packet is interpreted

• TTL values reflect hop count in simulator• Network packet fields are generated

• Ping responder, TCP application

Opaque Mode

• Network packet is passed unmodified through simulator

Network Packet

SourceDestination

Size

Data

Ns packet contains a pointer to the network packet

SourceDestination

Size

Extern

Read packets Write packets

ns

Network

Protocol Mode

• Network packet fields are generated by the simulator

DataThe ns packet

header is mapped onto the network packet header and visa

versa .

Send/receive packets from application

ns

TCP Agent

Network

Host A

TCPApplication

Host B

Send/receive packets from

ns

Network Packet

SourceDestination

Size

SourceDestination

Size

Applications

• Opaque Mode• Cross-traffic interaction leading to drop, delay

and re-ordering of packets • End to End application testing

• Protocol Mode• Protocol and conformance testing• Evaluate effect of DDoS attacks • Wireless networks

Example: Setup

Goal: Make a ns TCP agent interact with a TCP server

TCP server

• Disable IP forwarding• sysctl –w

net.inet.ip.forwarding=0

• Assign 10.0.0.1 and 6000 to TCP agent

• Add route to dummy IP address

• route add 10.0.0.1 192.168.1.1

• Disable IP redirects • sysctl –w net.inet.ip.redirect=0

A 192.168.1.1 B 192.168.1.2 port 8000

Switch

nse

Example Scriptset ns [new Simulator]$ns use-scheduler RealTime

set entry_node [$ns node]set tcp_node [$ns node]

$ns duplex-link $entry_node \$tcp_node 10Mb 1ms DropTail

set tcp [new Agent/TCP/FullTcp]$ns attach-agent $tcp_node $tcp

Activate ns and Change to real-time scheduler

Create topology

Create TCP Agent

TCP Agent

tcp_node entry_node

RawSocket

BPFTCPTap

TCPTap

Example Scriptset bpf [new Network/Pcap/Live] set dev [$bpf open readonly eth0]$bpf filter "src 192.168.1.2 and src port 8000 \

and dst 10.0.0.1 and dst port 6000“set capture_tap [new Agent/TCPTap]$capture_tap network $bpf$ns attach-agent $entry_node $capture_tap$ns simplex-connect $capture_tap $tcp

set rawsocket [new Network/IP] $rawsocket open writeonlyset inject_tap [new Agent/TCPTap] $inject_tap advertised-window 512$inject_tap extipaddr “192.168.1.2" $inject_tap extport 8000$inject_tap network $rawsocket$ns attach-agent $entry_node $inject_tap $ns simplex-connect $tcp $inject_tap

TCP Agent

tcp_node

entry_node

RawSocket

CaptureTap

BPF

InjectTap

Example Script$ns at 0.01 "$tcp advance 1"$ns at 20.0 “exit 0"$ns run

start nse

TCP Server(8000)

Switch

TCP Agent

BPF Raw Socket

B 192.168.1.2A 192.168.1.1

Further Information

• http://www.isi.edu/nsnam/ns/ns-emulation.html• Scripts ~ns/emulate

• Opaque Mode:• em.tcl

• Protocol Mode• thrutcp.tcl• pingdemo.tcl• tcpemu.tcl

• Kevin Fall, Network Emulation in the Vint/NS Simulator, ISCC July 1999

Ns-2 related work

• Other simulators• Researching uses ns-2• Using ns-2 for education

Other simulators

• GloMoSim• Developed by UCLA• Based on Parsec• Good support for wireless simulation

• SSFNET• Java-based (with some C++ components)• Use DML (Domain Modeling Language) for model configuration

• OPNET and QualNet• Commercial software• Good support for all layers

• PDNS (parallel/distributed ns)• Developed by Georgia Tech• Can distribute a simulation on several 8-16 workstations • Aim to support very large simulation (memory & CPU)

• JavaSim• Another Java-based simulator

Research using ns-2

• Routing• MIT Click Router• Zone routing protocol

• Wireless• Mobility generator• MIPv6• Bluetooth• 802.11 PSM• Cellular IP • Hierarchical Mobile IP • GPRS• UMTS

Research using ns-2..

• Generator• Web traffic generators• MPEG• Several topology generators

• Others• MPLS• WFQ, CSFQ• RSVP• RIO• BLUE• TCP westwood• SCTP• Multistate error model

Using ns-2 for education

• Ns-2 scripts/nam traces repository• http://www.isi.edu/nsnam/repository/index.

html• ~ns-2/tcl/ex• ~nam/ex ~nam/edu• Some ns scripts and nam animations

can be used in widely-used textbooks• http://www.isi.edu/nsnam/ns/edu/index.html

outline - ce.aut.ac.irce.aut.ac.ir/~bakhshis/ns-2/ns-2 introduction.pdf · • share code,...

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