TNK092: Network Simulation/Nätverkssimulering

Network Simulation---ns2

Lecture 2

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An Example with all we’ve seen so far.

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#Open the NAMtrace fileset nf [open out.nam w]$ns namtrace-all $nf

#Open the Trace fileset tf [open out.tr w]$ns trace-all $tf

#Create links between the nodes$ns duplex-link $n0 $n2 2Mb 10ms DropTail$ns duplex-link $n1 $n2 2Mb 10ms DropTail$ns duplex-link $n2 $n3 1.7Mb 20ms DropTail

#Give links position (for NAM)$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

set ns [new Simulator]#Define different colors#for data flows (for NAM)$ns color 1 Blue$ns color 2 Red

#Define a 'finish' procedureproc finish {} { global ns nf tf $ns flush-trace #Close the NAM trace file close $nf #Close the Trace file close $tf #Execute NAM on the trace file exec nam out.nam & exit 0}

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

#Set Queue Size of link (n2-n3) to 10$ns queue-limit $n2 $n3 10

#Monitor the queue for link (n2-n3). (for NAM)$ns duplex-link-op $n2 $n3 queuePos 0.5

n3n2

n0

n1

An Example with all we’ve seen so far..

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#Open the NAMtrace fileset nf [open out.nam w]$ns namtrace-all $nf

#Open the Trace fileset tf [open out.tr w]$ns trace-all $tf

#Create links between the nodes$ns duplex-link $n0 $n2 2Mb 10ms DropTail$ns duplex-link $n1 $n2 2Mb 10ms DropTail$ns duplex-link $n2 $n3 1.7Mb 20ms DropTail

#Give links position (for NAM)$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

set ns [new Simulator]#Define different colors#for data flows (for NAM)$ns color 1 Blue$ns color 2 Red

#Define a 'finish' procedureproc finish {} { global ns nf tf $ns flush-trace #Close the NAM trace file close $nf #Close the Trace file close $tf #Execute NAM on the trace file exec nam out.nam & exit 0}

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

#Set Queue Size of link (n2-n3) to 10$ns queue-limit $n2 $n3 10

#Monitor the queue for link (n2-n3). (for NAM)$ns duplex-link-op $n2 $n3 queuePos 0.5

#Setup a TCP connectionset tcp [new Agent/TCP]$ns attach-agent $n0 $tcpset sink [new Agent/TCPSink]$ns attach-agent $n3 $sink$ns connect $tcp $sink$tcp set fid_ 1

#Setup an FTP over TCP connectionset ftp [new Application/FTP]$ftp attach-agent $tcp$ftp set type_ FTP

#Setup a UDP connectionset udp [new Agent/UDP]$ns attach-agent $n1 $udpset null [new Agent/Null]$ns attach-agent $n3 $null$ns connect $udp $null$udp set fid_ 2

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ftp

cbr

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tcp

sink

#Setup a CBR over UDP connectionset cbr [new Application/Traffic/CBR]$cbr attach-agent $udp$cbr set type_ CBR$cbr set packet_size_ 1000$cbr set rate_ 1mb$cbr set random_ false

#Schedule events for the CBR and FTP agents$ns at 0.1 "$cbr start"$ns at 1.0 "$ftp start"$ns at 4.0 "$ftp stop"$ns at 4.5 "$cbr stop"

#Detach tcp and sink agents (not so necessary)$ns at 4.5 "$ns detach-agent $n0 $tcp ; in the SAME line $ns detach-agent $n3 $sink"

#Call the finish procedure after 5#seconds of simulation time$ns at 5.0 "finish”

#Print CBR packet size and intervalputs "CBR packet size = [$cbr set packet_size_]"puts "CBR interval = [$cbr set interval_]"

#Run the simulation$ns run

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ftp

cbr

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To create agents or traffic sources, a user should know the class names these objects (Agent/TCP, Agnet/TCPSink, Application/FTP and so on).

Remember to look at look at the …/tcl/libs/ns-default.tcl file.

This file contains the default configurable parameter value settings for available network objects.

Hint: a good indicator of what kind of network objects are available in NS and what are their configurable parameters.

An Example with all we’ve seen so far... epimyth

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n0

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ftp

cbr

upd null

tcp

sink

0 0.1 1.0 4.0 4.5 sec

ftp

cbr

Tracing

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Besides the NAM trace ns2 can provide an ASCII trace file.

At every link a packet is

Trace Enabled Simple NS Simulation Script

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About Awk

AWK is a tool that allows “simple” data manipulation on trace files.

Sample AWK code:

BEGIN {sum+=$2; array[N]=$2} END { for(i=1;i<=N;i++) { sumsq+=((array[i]-(sum/N))^2); } print sqrt(sumsq/N)}_______________________________________________________________________________________________________________________

To run use:awk -f Average.awk out.tr

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End to end delay (measure-delay.awk)

BEGIN {#initial the highest packet id highest_packet_id = 0;}{ event = $1; time = $2; from = $3; to = $4; type = $5; pktsize = $6; flow_id = $8; src = $9; dst = $10; seq_no = $11; packet_id = $12;

if ( packet_id > highest_packet_id ) highest_packet_id = packet_id;

if ( start_time[packet_id] == 0 ) start_time[packet_id] = time;

if ( flow_id == 2 && action != "d" ) { if ( event == "r" ) { end_time[packet_id] = time; } } else { end_time[packet_id] = -1; }}

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awk -f measure-delay.awk out.tr > cbr-delay

END { for (packet_id=0; packet_id<=highest_packet_id; packet_id++ ) { start = start_time[packet_id]; end = end_time[packet_id]; packet_duration = end - start;

if ( start < end ) printf("%f %f\n", start, packet_duration); }}

Remember . . .

Plotting with gnuplotGnuplot(http://www.gnuplot.info/;http://www.gnuplot.info/documentation.html)

#plotdelay.plotset term png medium #000000set output "cbr-delay.png"set ylabel "End-to-End delay(sec)"set xlabel "Start transmission time(sec)" set xrang [0:5]set xtics 0, 0.5, 5set yrang [0:0.1]set ytics 0, 0.01, 0.1set title "CBR end-to-end delay"plot "cbr-delay" title "CBR" with linespoints lt -1 pt 8

gnuplot>load ’plotdelay.plot’

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xgraph

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xgraph cbr-delay

Jitter (awk codes)#cbr-jitter.awkBEGIN {old_time=0;old_seq_no=0;i=0;}{ action = $1; time = $2; node_1 = $3; node_2 = $4; type = $5; flow_id = $8; node_1_address = $9; node_2_address = $10; seq_no = $11; packet_id = $12;

if(node_1==2 && node_2==3 && type=="cbr" && action=="r")

{ dif=seq_no-old_seq_no; if(dif==0) dif=1; jitter[i]=(time-old_time)/dif; seq[i]=seq_no; i=i+1; old_seq_no=seq_no; old_time=time; }}

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awk –f cbr-jitter.awk out.tr > cbr-jitter

END {for (j=1; j <i ;j++)printf("%d\t%f\n",seq[j],jitter[j]);}

Jitter (...more awk codes)#cbr-jitter2.awkBEGIN {highest_packet_id = 0;}{ action = $1; time = $2; node_1 = $3; node_2 = $4; type = $5; flow_id = $8; node_1_address = $9; node_2_address = $10; seq_no = $11; packet_id = $12; if ( packet_id > highest_packet_id )

{ highest_packet_id = packet_id; } if ( start_time[packet_id] == 0 ) { pkt_seqno[packet_id] = seq_no; start_time[packet_id] = time; } if ( flow_id == 2 && action != "d" )

{ if ( action == "r" ) { end_time[packet_id] = time; } } else { end_time[packet_id] = -1;}}

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END { last_seqno = 0; last_delay = 0; seqno_diff = 0; for ( packet_id = 0; packet_id <= highest_packet_id; packet_id++ ) { start = start_time[packet_id]; end =end_time[packet_id]; packet_duration = end - start; if ( start < end ) { seqno_diff = pkt_seqno[packet_id]- last_seqno; delay_diff = packet_duration - last_delay; if (seqno_diff == 0) { jitter =0; } else { jitter = delay_diff/seqno_diff; } printf("%f %f\n", start, jitter); last_seqno = pkt_seqno[packet_id]; last_delay = packet_duration; } }}

$awk –f cbr-jitter2.awk out.tr > cbr-jitter

Packet loss (awk codes)# cbr-loss.awkBEGIN {fsDrops = 0;numFs = 0;}{action = $1;time = $2;node_1 = $3;node_2 = $4;src = $5;flow_id = $8;node_1_address = $9;node_2_address = $10;seq_no = $11;packet_id = $12;if (node_1==1 && node_2==2 && action == "+")numFs++;if (flow_id==2 && action == "d")fsDrops++;}END {printf("number of packets sent:%d lost:%d\n", numFs,fsDrops);}

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Throughput (awk codes)BEGIN { init=0; i=0;}{action = $1;time = $2;from = $3;to = $4;type = $5;pktsize = $6;flow_id = $8;src = $9;dst = $10;seq_no = $11;packet_id = $12;

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if(action=="r" && from==2 && to==3 && flow_id==2) {pkt_byte_sum[i+1]=pkt_byte_sum[i]+ pktsize;if(init==0) {start_time = time;init = 1;}end_time[i] = time;i = i+1;}}END{ printf("%.2f\t%.2f\n", end_time[0], 0);for(j=1 ; j<i ; j++){th = pkt_byte_sum[j] / (end_time[j] -start_time)*8/1000;printf("%.2f\t%.2f\n", end_time[j], th);}printf("%.2f\t%.2f\n", end_time[i-1], 0);}

Packet loss (awk codes)BEGIN {fsDrops = 0;numFs = 0;}{action = $1;time = $2;from = $3;to = $4;type = $5;pktsize = $6;flow_id = $8;src = $9;dst = $10;seq_no = $11;packet_id = $12;if (from==1 && to==2 && action == "+") numFs++;

if (flow_id==2 && action == "d") fsDrops++;}END { printf("number of packets sent:%d lost:%d\n", numFs, fsDrops);}

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Some basic ns2 structuring

In …/ns-2.34/tcl/lib: ns-lib.tcl:

The actial simulator class, most of its member function definitions are here

ns-default.tcl: default values for configurable parameters for various network

components, configure the parameter in otcl which actually take effect through C++…

ns-packet.tcl: Packet header initialization & implementation, where you register your

own packet type

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Adding your own modules...

You will develop NS2 modules in one the following file types:

What you would like to do is to incorporate these files into NS2

…how?

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File type Example

C++ code myNewMod.cc

Header definitions myNewMod.h

Tcl code myNewMod.tcl

Working assumption...

Assume that we wanted to build a multimedia application that runs over a UDP connection.

Lets say that this application implements a "five rate media scaling" which can respond to network congestion to some extent by changing encoding and transmission policy pairs associated with scale parameter values

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STEP 1: Register the new application header, by modifying the files:

…/common/packet.h and …/tcl/lib/ns-packet.tcl

1. In packet.hA. Look for:

// insert new packet types hereStatic packet_t PT_NTYPE = 62; // This MUST be the LAST oneAnd insert new packet types between those 2 lines, eg:

static const packet_t PT_Multimedia = 70; B. Look for: class p_info {

In public:In static void initName() in the long list of name_ add:

name_[PT_Multimedia] = "Multimedia";

2. In ns-packet.tcl- Look for:

foreach prot {And in the list of protocols add: Multimedia

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Adding modules Step by step...

STEP 2: Add new methods to the Agent and Application classes, by modifying the files: …/common/agent.h and …/apps/app.h

1. In agent.h-look for:

class Agent : public Connector { public:

Agent(packet_t pktType);And insert new agent methods as e.g.:

virtual int supportMM() {return 0;}virtual void enableMM() {}

2. In app.h

-look for: class Application : public Process {public: Application();And in that list also insert your application methods defintions as e.g.:

virtual void recv_msg(int nbytes, const char *msg = 0){}

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Adding modules Step by step...

STEP 3: Set defaults for the new configurable parameters,

in /tcl/lib/ns-default.tcl add......Application/MmApp set rate0_ 0.3mbApplication/MmApp set rate1_ 0.6mbApplication/MmApp set rate2_ 0.9mbApplication/MmApp set rate3_ 1.2mbApplication/MmApp set rate4_ 1.5mbApplication/MmApp set pktsize_ 1000Application/MmApp set random_ false......

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Adding modules Step by step...

STEP 4: Modify the MakefileAssuming that you have all three .h, .cc and .tcl file types you must make the following modifications (if not, reduce steps accordingly).

Note: the Makefile lies in the …/ns-2.23 directory

Lets assume your files are in …/ns-2.34/myWork

You will have to modify three places in the Makefile

1. OBJ_CC2. NS_TCL_LIB3. INCLUDEAs follows:

1. Look for

OBJ_CC = \

And add:myDir/myNewMod.o \

To one line below22

Adding modules Step by step...

File type Example

C++ code myNewMod.cc

Header definitions myNewMod.h

Tcl code myNewMod.tcl

2. Look for

NS_TCL_LIB = \

And add:myDir/myfile.tcl \To one line below

3. (OPTIONAL) Look for

INCLUDES = \

And add:-I. /myWorks \To one line below

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Adding modules Step by step...File type Example

C++ code myNewMod.cc

Header definitions myNewMod.h

Tcl code myNewMod.tcl

STEP 6: Recompile the software

./make

Note: These will be key instruction steps for Lab Assignment 2

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Adding modules Step by step...