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Goals Understanding NS-2 Hands-on Experience with NS2
Ns-2 by Example Write your own scripts
Extending NS2 Implementing new functionality
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Schedule Presentation (60 min) Group Assignments (10 min) Practices (1 Hr) Q & A session (~15 min)
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Talk Overview What is ns-2? (the evolution) Architecture Basic Tcl/Otcl commands Elements of an ns-2 simulation Example Online Resources &
Documentation
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What is ns?
A discrete event, packet-level simulator Targeted at networking research Supports the simulation of
intserv/diffserv, Multicast, Transport, Applications, Wireless (fixed, mobile, satellite)
REAL variant (1989)DARPA (LBL, Xerox PARC, UCB, and USC/ISI) (1995)
Ns-3 Project (Ongoing)
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Status ns-2
100K lines of C++ 70K lines of OTcl 50K+ lines of test suite, examples, docs
Platforms Most UNIX and UNIX-like systems (FreeBSD,
Linux, Sun Solaris) Window 95/98/NT with Cygwin (Emulation only for FreeBSD for now)
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Remember! A simulator model of a real-world
system is necessarily a simplification. For example, in simulating TCP No SYN/FIN Equal size segments No variable window advertisement
Bugs: “Users of ns are responsible for verifying for themselves that their simulations are not invalidated by bugs”.
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Architecture: Object-Oriented C++ for “data”
Per packet action OTcl for control
Periodic or triggered action Modularity (+), re-usability(+),
scalability(+) Speed(-), memory(-)
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OTcl and C++: The Duality
C++ OTcl
Pure C++objects
Pure OTclobjects
C++/OTcl split objects
ns
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Script in interactive modelinux21% ns
% set ns [new Simulator]
_o3
% $ns at 1 “puts \“Hello World!\””
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% $ns at 1.5 “exit”
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% $ns run
Hello World!
linux21%
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A script in batch mode
#simple.tclset ns [new Simulator]
$ns at 1 “puts \“Hello World!\””
$ns at 1.5 “exit”
$ns run
linux21% ns simple.tcl
Hello World!
linux21%
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Basic Tclset a 43set b 27proc test { a b } {
set c [expr $a + $b]set d [expr [expr $a - $b] * $c]for {set k 0} {$k < 10} {incr k} {
if {$k < 5} { puts “k < 5, pow = [expr pow($d, $k)]” } else { puts “k >= 5, mod = [expr $d % $k]” } }}test 43 27
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Basic OTclClass MomMom instproc greet {} {
$self instvar age_puts “$age_ years old mom: How are you doing?”
}
Class Kid -superclass MomKid instproc greet {} {
$self instvar age_puts “$age_ years old kid: What’s up, dude?”
}
set mom [new Mom]
$mom set age_ 45
set kid [new Kid]
$kid set age_ 15
$mom greet
$kid greet
SIMULATE WIRED NETWORK
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Elements of ns-2 Simulation Create the event scheduler [Turn on tracing] Create network Setup routing Insert errors Create transport connection Create traffic Transmit application-level data
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Creating Event Scheduler Create event scheduler
set ns [new Simulator] Schedule events
$ns at <time> <event> <event>: any legitimate ns/tcl
commands Start scheduler
$ns run
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Tracing
Trace packets on all links $ns trace-all [open test.out w]
<event> <time> <from> <to> <pkt> <size> -- <fid> <src> <dst> <seq> <attr><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- 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0- 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0
Trace packets on all links in nam format $ns namtrace-all [open test.nam w]
Must appear immediately after creating scheduler
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Tracing Turn on tracing on specific links
$ns trace-queue $n0 $n1 $ns namtrace-queue $n0 $n1
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Creating Network Nodes
set n0 [$ns node] set n1 [$ns node]
Links and queuing $ns duplex-link $n0 $n1
<bandwidth> <delay> <queue_type>
<queue_type>: DropTail, RED, CBQ, FQ, SFQ, DRR
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Creating Network: LAN 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
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Inserting Packet Errors Creating Error Module
set loss_module [new ErrorModel] $loss_module set rate_ 0.01 $loss_module unit pkt $loss_module ranvar [new
RandomVariable/Uniform] $loss_module drop-target [new
Agent/Null] Inserting Error Module
$ns lossmodel $loss_module $n0 $n1
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Network Dynamics Link failures
Hooks in routing module to reflect routing changes
Four models$ns rtmodel-at <time> up|down $n0 $n1$ns rtmodel-at <time> up|down $n0 $n1$ns rtmodel Trace <config_file> $n0 $n1$ns rtmodel Trace <config_file> $n0 $n1$ns rtmodel Exponential {<params>} $n0 $n1$ns rtmodel Exponential {<params>} $n0 $n1$ns rtmodel Deterministic {<params>} $n0 $n1$ns rtmodel Deterministic {<params>} $n0 $n1
Parameter list[<start>] <up_interval> <down_interval> [<finish>][<start>] <up_interval> <down_interval> [<finish>]
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Setup Routing Unicast
$ns rtproto <type> <type>: Static, Session, DV, cost, multi-
path Multicast
$ns multicast (right after [new Simulator]) or set ns [new Simulator –multicast on]
$ns mrtproto <type> <type>: CtrMcast, DM, ST, BST
(centralized,dense mode, shared tree
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Creating Connection: UDP UDP
set udp [new Agent/UDP] set null [new Agent/Null] $ns attach-agent $n0 $udp $ns attach-agent $n1 $null $ns connect $udp $null
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Creating Traffic: On Top of UDP CBR
set src [new Application/Traffic/CBR] Exponential or Pareto on-off
set src [new Application/Traffic/Exponential]
set src [new Application/Traffic/Pareto]
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Creating Connection: TCP TCP
set tcp [new Agent/TCP] set tcpsink [new Agent/TCPSink] $ns attach-agent $n0 $tcp $ns attach-agent $n1 $tcpsink $ns connect $tcp $tcpsink
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Creating Traffic: On Top of TCP FTP
set ftp [new Application/FTP] $ftp attach-agent $tcp
Telnet set telnet [new Application/Telnet] $telnet attach-agent $tcp
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Creating Traffic: Trace Driven Trace driven
set tfile [new Tracefile] $tfile filename <file> set src [new Application/Traffic/Trace] $src attach-tracefile $tfile
<file>: Binary format (native!) inter-packet time (msec) and packet size
(byte)
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Application-Level Simulation Features
Build on top of existing transport protocol
Transmit user data, e.g., HTTP header Two different solutions
TCP: Application/TcpApp UDP: Agent/Message
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Script Structure for Wired Scenario
# parameters and options# parameters and options
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:
# - 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
SIMULATE WIRELESS NETWORK
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Script Structure: Wireless
# parameters and options# parameters and options
set ns [new Simulator]set ns [new Simulator]
# [Turn on tracing]# [Turn on tracing]
# create # create MobileNodeMobileNode object (PHY to layer 3 object (PHY to layer 3 configured) configured)
# Create topology# Create topology
# create mobility# create mobility
# Create Layer 4 and above# Create Layer 4 and above
# - UDP/TCP agents# - UDP/TCP agents
# - application and/or setup traffic sources# - application and/or setup traffic sources
# Post-processing procedures# Post-processing procedures
# Start simulation# Start simulation
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Example: Wireless Scenario 4x4 grid
240m
4 7
8 11
13 14
2 3
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Example: Step 1
Define Parameters
set cbr_size 500set cbr_size 500set cbr_interval 0.002set cbr_interval 0.002set num_row 4set num_row 4set time_duration 100set time_duration 100
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Example: Step 2
Protocol Optionsset val(chan) Channel/WirelessChannel ;# channel set val(chan) Channel/WirelessChannel ;# channel typetypeset val(prop) Propagation/TwoRayGround ;# radio-set val(prop) Propagation/TwoRayGround ;# radio-propagation modelpropagation modelset val(netif) Phy/WirelessPhy ;# network interface set val(netif) Phy/WirelessPhy ;# network interface typetypeset val(mac) Mac/802_11 ;# MAC typeset val(mac) Mac/802_11 ;# MAC typeset val(ifq) Queue/DropTail/PriQueue ;# interface set val(ifq) Queue/DropTail/PriQueue ;# interface queue typequeue typeset val(ll) LL ;# link layer typeset val(ll) LL ;# link layer typeset val(ant) Antenna/OmniAntenna ;# antenna modelset val(ant) Antenna/OmniAntenna ;# antenna modelset val(ifqlen) 50 ;# max packet in ifqset val(ifqlen) 50 ;# max packet in ifqset val(rp) DSDV ;# routing protocolset val(rp) DSDV ;# routing protocol
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Example: Step 3 Scheduler, Trace, Topo, God
# # # Initialize ns# Initialize ns##set ns_ [new Simulator]set ns_ [new Simulator]set tracefd [open simple.tr w]set tracefd [open simple.tr w]$ns_ trace-all $tracefd$ns_ trace-all $tracefd
# set up topography object# set up topography object set topo [new Topography]set topo [new Topography] $topo load_flatgrid 1000 1000$topo load_flatgrid 1000 1000
create-god [expr $num_row * $num_row ]create-god [expr $num_row * $num_row ]
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Example: Step 4 Create Node Object with protocols
$ns_ node-config -adhocRouting $val(rp) -llType $val(ll) \$ns_ node-config -adhocRouting $val(rp) -llType $val(ll) \
-macType $val(mac) -ifqType $val(ifq) \-macType $val(mac) -ifqType $val(ifq) \
-ifqLen $val(ifqlen) -antType $val(ant) \-ifqLen $val(ifqlen) -antType $val(ant) \
-propType $val(prop) -phyType $val(netif) \-propType $val(prop) -phyType $val(netif) \
-channel $chan1 -topoInstance $topo \-channel $chan1 -topoInstance $topo \
-agentTrace ON -routerTrace OFF\-agentTrace ON -routerTrace OFF\
-macTrace ON \-macTrace ON \
-movementTrace OFF-movementTrace OFF
for {set i 0} {$i < [expr $num_row*$num_row]} {incr i} {for {set i 0} {$i < [expr $num_row*$num_row]} {incr i} {
set node_($i) [$ns_ node]set node_($i) [$ns_ node]
}}
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Example: Step 5 Create Topologyset k 0;set k 0;
while {$k < $num_row } {while {$k < $num_row } {
for {set i 0} {$i < $num_row } {incr i} {for {set i 0} {$i < $num_row } {incr i} {
set m [expr $i+$k*$num_row];set m [expr $i+$k*$num_row];
$node_($m) set X_ [expr $i*240];$node_($m) set X_ [expr $i*240];
$node_($m) set Y_ [expr $k*240+20.0];$node_($m) set Y_ [expr $k*240+20.0];
$node_($m) set Z_ 0.0$node_($m) set Z_ 0.0
}}
incr k;incr k;
}; };
Example: Step 6 Create Mobility
#Move node 11 from its original place to top-right corner#Move node 11 from its original place to top-right corner
$ns_ at 60.0 "$node_(11) setdest 990.0 990.0 15.0”$ns_ at 60.0 "$node_(11) setdest 990.0 990.0 15.0”
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Example: Step 7 Set up transport layer (UDP)
for {set i 0} {$i < $num_row } {incr i} {for {set i 0} {$i < $num_row } {incr i} {
set udp_($i) [new Agent/UDP]set udp_($i) [new Agent/UDP] set null_($i) [new Agent/Null]set null_($i) [new Agent/Null] } } $ns_ attach-agent $node_(8) $udp_(0)$ns_ attach-agent $node_(8) $udp_(0) $ns_ attach-agent $node_(4) $udp_(1)$ns_ attach-agent $node_(4) $udp_(1) $ns_ attach-agent $node_(13) $udp_(2)$ns_ attach-agent $node_(13) $udp_(2) $ns_ attach-agent $node_(14) $udp_(3)$ns_ attach-agent $node_(14) $udp_(3) $ns_ attach-agent $node_(11) $null_(0)$ns_ attach-agent $node_(11) $null_(0) $ns_ attach-agent $node_(7) $null_(1)$ns_ attach-agent $node_(7) $null_(1) $ns_ attach-agent $node_(2) $null_(2)$ns_ attach-agent $node_(2) $null_(2) $ns_ attach-agent $node_(3) $null_(3)$ns_ attach-agent $node_(3) $null_(3) for {set i 0} {$i < $num_row } {incr i} {for {set i 0} {$i < $num_row } {incr i} { $ns_ connect $udp_($i) $null_($i)$ns_ connect $udp_($i) $null_($i) }}
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Example: Step 8 Define Traffic Scenariofor {set i 0} {$i < $num_row } {incr i} {
set cbr_($i) [new Application/Traffic/CBR]$cbr_($i) set packetSize_ $cbr_size$cbr_($i) set interval_ 0.5$cbr_($i) attach-agent $udp_($i)
}}
$ns_ at 11.0234 "$cbr_(0) start"$ns_ at 10.4578 "$cbr_(1) start" $ns_ at 12.7184 "$cbr_(2) start"$ns_ at 12.2456 "$cbr_(3) start"
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Example: Step 9 End-of-simulation wrapper (as
usual) # Tell nodes when the simulation ends#for {set i 0} {$i < [expr $num_row*$num_row] } {incr i} {$ns_ at [expr $time_duration +10.0] "$node_($i) reset";}$ns_ at [expr $time_duration +10.0] "finish"$ns_ at [expr $time_duration +10.01] "puts \"NS Exiting...\"; $ns_ halt"
proc finish {} {global ns_ tracefd$ns_ flush-traceclose $tracefd}
puts "Starting Simulation..."$ns_ run
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Auxiliary Tools setdest
used to generate the positions of nodes and their moving speed and moving directions.setdest -v 1 -n 50 -p 0 -M 20 -t 900 -x 1500 -y 300
cbrgen.tclns cbrgen.tcl [-type cbr|tcp] [-nn nodes] [-seed seed] [-mc connections] [-rate rate]
Use “source <filename>.tcl” to add the generated file to scipts
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Resources http://www.isi.edu/nsnam/ns http://www.winlab.rutgers.edu/~zhibinwu Tutorials:
Marc Greis’s Tutorial (http://www.isi.edu/nsnam/ns/tutorial/index.html)
Ns by example (http://nile.wpi.edu/NS/) Wireless Tutorial (
http://www.isi.edu/nsnam/ns/ns-tutorial/wireless.ppt )
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Documentation Tcl (Tool Command Language)
http://dev.scriptics.com/scripting OTcl (MIT Object Tcl)
~otcl/doc/tutorial.html (in distribution)
ns manual Included in distribution: ~ns/doc http://www.isi.edu/~salehi/ns_doc.ps.
gz
Advanced Topics Trace analysis Architecture of Mobilenode Object Extending NS-2 with new protocols
and algorithms More complex changes:
Hybrid Node A node with multiple interfaces
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Group Assignments Download simple.tcl
http://www.winlab.rutgers.edu/~zhibinwu/simple.tcl
Modifications Node-Configure changes Random topology generation 40-node
within 1000x1000 area Random Node Mobility Changeprotocol from UDP to TCP Dynamic Traffic change
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