Transcript Network Simulator ns-2

Network Simulator ns-2
Agenda
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Introduction
Interface
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Simulator
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Tcl and OTcl
TclCL
Wired network
Wireless network
Program Assignment
2
Introduction
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NS-2: network simulator version 2
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Discrete event simulator
Packet level simulation
Features
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Open source
Scheduling, routing and congestion control
Wired networks: P2P links, LAN
Wireless networks: terrestrial (ad-hoc, cellular;
GPRS, UMTS, WLAN, Bluetooth), satellite
Emulation and trace
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NS-2: Paradigm
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Object-oriented programming
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Protocol layering
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Large scale simulation
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Modularity and extensibility
Maintenance and reusability
Split-language programming
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Scripting language (Tcl)
System programming language (C)
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NS-2: Split Languages
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Tcl scripts (Tcl/OTcl)
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C codes (C/C++)
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Interpreted (interactive)
Setup and configuration
Compiled (efficient)
Algorithms and protocols
TclCL (OTcl/C++)
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Link Tcl/OTcl scripts and C/C++ codes
Provide a layer of C++ glue over OTcl
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NS-2: Split Objects
OTcl/C++ split objects
Pure C++
objects
Pure OTcl
objects
OTcl
TclCL linkage
C++
NS-2
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NS-2: A Tcl Script Example
#!/home/hsieh/ns-allinone-2.27/bin/ns
set
set
$ns
for
ns [new Simulator]
nf [open out.tr w]
trace-all $nf
{set i 0} {$i<2} {incr i} {
set n($i) [$ns node]
;# create the nodes
}
$ns duplex-link $n(0) $n(1) 1Mb 10ms DropTail
# Create a UDP agent
set udp(src) [new Agent/UDP]
$udp(src) set packetSize_ 500
$ns attach-agent $n(0) $udp(src)
proc finish {} {
global ns nf
$ns flush-trace; close $nf
}
$ns at 5.0 "finish"
$ns run
/home>ns abc.tcl
/home>abc.tcl
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NS-2: A C++ Code Example
static class UdpAgentClass : public TclClass {
public:
UdpAgentClass() : TclClass("Agent/UDP") {}
TclObject* create(int, const char*const*) {
return (new UdpAgent());
}
} class_udp_agent;
UdpAgent::UdpAgent() : Agent(PT_UDP), seqno_(-1)
{
bind("packetSize_", &size_);
}
void UdpAgent::sendmsg(int nbytes, AppData* data, const char* flags)
{
Packet *p;
p = allocpkt();
hdr_cmn::access(p)->size() = size_;
hdr_rtp::access(p)->seqno() = ++seqno_;
p->setdata(data);
target_->recv(p);
}
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TclCL: Class TclObject
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Base class in NS-2 for split objects
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Usage
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Mirrored in both C++ (TclObject) and OTcl
(SplitObject)
Instantiation, bind and command
Example
set tcp [new Agent/TCP]
$tcp set window_ 30
$tcp advanceby 5000
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Class TclObject: Hierarchy
SplitObject OTcl class
hierarchy
C++ class
hierarchy
TclObject
Connector
Agent
Agent
Agent/TCP
TcpAgent
_o123
Agent/TCP
OTcl object
*tcp
Agent/TCP
C++ object
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Class TclObject: Binding
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Bi-directional variable bindings
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Link C++ member variables (compiled) to OTcl
instance variables (interpreted)
Initialization through the closest OTcl class
variable
Agent/TCP set window_ 50
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Do all initialization of bound variables in
~ns/tcl/lib/ns-default.tcl
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Otherwise a warning will be issued when the
shadow compiled object is created
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Class TclObject: Binding
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C++
TcpAgent::TcpAgent() {
bind(“window_”, &wnd_);
… …
}
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bind(), bind_time(), bind_bool(), bind_bw()
OTcl
Agent/TCP set window_ 50
set tcp [new Agent/TCP]
$tcp set window_ 100
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Class TclObject: Command
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Invoke C++ compiled functions through OTcl
interpreted methods
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Hook point
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A way of implementing OTcl methods in C++
Tcl method unknown{}
OTcl method cmd{}
Send all arguments after cmd{} call to
TclObject::command()
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Use Tcl::resultf() in C++ to pass back
results
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Class TclObject: Command
$tcp send
no such
SplitObject::unknown{}
procedure
OTcl space
$tcp cmd send
C++ space
TcpAgent::command()
Yes
process and return
match
“send”?
No
Invoke parent:
return Agent::command()
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Class TclObject: Command
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OTcl
set tcp [new Agent/TCP]
$tcp advance 100
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C++
int TcpAgent::command(int argc,
const char*const* argv) {
if (argc == 3) {
if (strcmp(argv[1], “advance”) == 0) {
int newseq = atoi(argv[2]);
……
return TCL_OK;
}
}
return (Agent::command(argc, argv);
}
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TclCL: Summary
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Class TclObject
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Class TclClass
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Unified interpreted (OTcl) and compiled (C++)
class hierarchies
Seamless access (procedure call and variable
access) between OTcl and C++
Mechanism that makes TclObject work
Class Tcl
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Primitives to access OTcl interpreter
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NS-2: Directory Structure
ns-allinone (ftp://ftp.isi.edu/nsnam/ns-allinone-2.30.tar.gz)
Tcl8
TK8
OTcl
TclCL
...
tcl
ex
examples
test
validation tests
ns-2
lib
nam-1
...
C++ code
mcast
...
OTcl code
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Network Simulator ns-2
Part II: Wired Network
Class Hierarchy
TclObject
recv()
Scheduler
NsObject
Node
Connector
Queue
Delay Agent
DropTail RED
TCP
Reno
target_
Classifier
Trace
Enq Deq Drop
SACK
Vegas
Process
Application
FTP
AddrClassifier
PortClassifier
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Simulation Elements
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Create the event scheduler (simulator)
[Setup tracing]
Create network topology
[Setup routing]
[Insert error modules/network dynamics]
Create connection (transport)
Create traffic (application)
Start the scheduler
Post-process data
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Event Scheduler
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Create event scheduler
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Schedule events (OTcl)
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OTcl: $ns at <time> <TCL_command>
C++: Scheduler::schedule(h,e, delay)
Obtain simulation time
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set ns [new Simulator]
OTcl: $ns now
C++: Scheduler::clock()
Start scheduler
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$ns run
The last line of your OTcl script
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Trace
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Trace packets on all links
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$ns trace-all [open nstr.out w]
<event>
+
r
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<pkt> <size> -- <fid> <src> <dst> <seq> <uid>
cbr
210 ------- 0
0.0
3.1
0
0
cbr
210 ------- 0
0.0
3.1
0
0
cbr
210 ------- 0
0.0
3.1
0
0
$ns namtrace-all [open namtr.out w]
Turn on tracing on specific links
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<t> <from> <to>
1
0
2
1
0
2
1.00234 0
2
$ns trace-queue $n0 $n1
$ns namtrace-queue $n0 $n1
Output trace to /dev/null if not desired
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Network Topology
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Nodes
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set n0 [$ns node]
set n1 [$ns node]
Links and queues
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$ns duplex-link $n0 $n1 \
<bandwidth> <delay> <queue>
queue: DropTail, RED, CBQ, FQ, …
Link delay = f (bandwidth, delay)
= packet transmission time + propagation delay
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Network Topology: Node
n0
n1
Port
Classifier
dmux_
Addr
Classifier
Node entry
classifier_
dmux_
entry_
Node entry
entry_
classifier_
Unicast Node
multiclassifier_
Multicast
Classifier
Multicast Node
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Network Topology: Link
n0
n1
duplex link
head_
enqT_
tracing
queue_
drophead_
deqT_
drpT_
link_
ttl_
n1
entry_
simplex link
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Routing
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Unicast routing
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Default static routing
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$ns rtproto <type> <nodes>
type: Static (default), Session, DV, LS, Manual
nodes: default entire topology
Dijkstra’s all-pairs shortest path first algorithm
Route calculation is done before simulation starts
Link cost
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$ns cost $n0 $n1 <cost>
default link cost = 1
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Routing
n0
n1
Port
Classifier
Addr
Classifier
Node entry
entry_
0
1
dmux_
classifier_
head_
enqT_
queue_
drophead_
deqT_
link_
ttl_
n1
entry_
drpT_
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Routing
n0
n1
Port
Classifier
Port
Classifier
Addr
Classifier
Addr
Classifier
entry_
0
1
dmux_
Link n0-n1
classifier_
entry_
1
0
dmux_
classifier_
Link n1-n0
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Transport: TCP
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TCP
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set
set
$ns
$ns
$ns
Use
tcp [new Agent/TCP]
tcpsink [new Agent/TCPSink]
attach-agent $n0 $tcp
attach-agent $n1 $tcpsink
connect $tcp $tcpsink
create-connection{}
Customization
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$agent set fid <fid>
$agent set packetSize_ <size>
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Transport
n0
n1
Port
Classifier
Addr
Classifier
entry_
0
1
0
Port
Classifier
dst_= 1.0
Agent/TCP
agents_
dmux_
Link n0-n1
classifier_
entry_
Addr
Classifier
0
1
0
dmux_
dst_= 0.0
Agent/TCPSink
agents_
classifier_
Link n1-n0
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Application
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FTP
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CBR
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set ftp [new Application/FTP]
$ftp attach-agent $tcp
$tcp attach-app FTP
set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 1000
$cbr set rate_ 16000
Start traffic generation
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$ns at <time> “$app start”
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Application
n0
n1
Application/FTP
Port
Classifier
entry_
Addr
Classifier
0
0
1
dmux_
Port
Classifier
dst_=1.0
Agent/TCP
agents_
Link n0-n1
classifier_
entry_
Addr
Classifier
0
1
0
dmux_
dst_=0.0
Agent/TCPSink
agents_
classifier_
Link n1-n0
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Packet
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Packets are events
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Packets contain header section and data
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Header section is a cascade of all in-use headers
Each packet contains a common header
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Can be scheduled to “arrive”
packet size (used to compute transmission time)
packet type
timestamp, uid, …
All in-use headers are included when
simulation starts
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Change packet size to reflect header cascading
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Packet Header
cmn header
header
data
ip header
tcp header
rtp header
Example: Get the pointer to
the common header:
p->access(hdr_cmn::offset_)
trace header
ts_
ptype_
uid_
size_
iface_
...
or, HDR_CMN(p)
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Packet Flow
n0
n1
Port
Classifier
Addr
Classifier
entry_
0
1
0
Application/FTP
Port
Classifier
dst_=1.0
Addr
Classifier
Agent/TCP
Link n0-n1
entry_
0
dst_=0.0
Agent/TCPSink
1
0
Link n1-n0
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Recap
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NsObject: generic receive method recv()
for packet reception
Connector: one neighbor target_
Node: collection of classifiers and agents
Link: encapsulation of queue and delay
Classifier: packet demultiplexer (routing)
Agent: protocol endpoint or implementation
of routing protocol
Application: traffic generation
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Network Simulator ns-2
Part III: Wireless Network
Wireless Network
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Wireless network
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Nodes can move
No explicit “links” used to connect nodes
Wireless network extension
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Mobile node
Wireless channel and propagation model
Packet headers
Topology and movement
Routing and forwarding
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Class Hierarchy
TclObject
NsObject
Node
Channel
Propagation
Connector
MobileNode
WirelessChannel
TwoRayGround
BiConnector
uptarget_
downtarget_
Phy
MAC
WirelessPhy
802.11
Delay
LL
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Mobile Node: Portrait
Node
port
classifier
Classifier: Forwarding
protocol
agent
Node Entry
255
addr
classifier
defaulttarget_
LL
routing
agent
ARP
IFQ
MAC
PHY
MobileNode
Propagation
and antenna
models
Agent: Protocol entity
LL
LL: Link layer object
IFQ
IFQ: Interface queue
MAC
MAC: MAC object
PHY
PHY: Network interface
CHANNEL
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Example: Ad Hoc Network
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Scenario
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3 mobile nodes
Move within a 670m*670m flat topology
DSR ad hoc routing protocol
Random waypoint mobility model
UDP and CBR traffic
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An Example – Step 1
# Create simulator
set ns [new Simulator]
# Create a topology in a 670m x 670m area
set topo [new Topography]
$topo load_flatgrid 670 670
# ns trace and nam trace
$ns trace-all [open ns.tr w]
$ns namtrace-all-wireless [open ns.nam w] 670 670
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An Example – Step 2
# Create God
set god [create-god 3]
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God: General Operations Director
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Keep the number of nodes in the network
Called by 802.11 MAC to keep a sequence number
cache of all nodes
Store an array of the smallest number of hops
required to reach one node to another
Used for setdest operation
$ns at 100.00 “$god set-dist 2 3 1”
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An Example – Step 3
# Define how to create a mobile node
$ns node-config \
-adhocRouting DSR \
-llType LL \
-macType Mac/802_11 \
-ifqLen 50 \
-ifqType Queue/DropTail/PriQueue \
-phyType Phy/WirelessPhy \
-antType Antenna/OmniAntenna \
-propType Propagation/TwoRayGround \
-channel [new Channel/WirelessChannel] \
-topoInstance $topo
-agentTrace ON \
-routerTrace OFF \
-macTrace OFF \
-movementTrace OFF
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Energy Parameters
$ns node-config \
–energyModel
-initialEnergy
-txPower
-rxPower
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Node is energy-aware
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EnergyModel \
100.0 \
0.6 \
0.2
Node status: on / off / sleep
Pt_ and Pt_consume_
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An Example – Step 4
# Create mobile nodes
for {set i 0} {$i<3} {incr i} {
set node($i) [$ns node]
# disable random motion for static network
$node($i) random-motion 0
}
# Define movement model (if applicable)
source movement-scenario-files
# Define traffic model (if applicable)
source traffic-scenario-files
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Scenario: Movement
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Mobile movement generator
~ns/indep-utils/cmu-scen-gen/setdest/setdest
setdest -n <numNodes>
-p <pauseTime> -s <maxSpeed>
-t <simTime> -x <maxX> -y <maxY>
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Random movement
$node random-motion 1
$node start
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Change POSITION_UPDATE_INTERVAL and
MAX_SPEED internally
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A Movement File
$node_(0) set X_ 83.4
$node_(0) set Y_ 239.4
$node_(0) set Z_ 0.0
$node_(1) set X_ 257.1
$node_(1) set Y_ 345.4
$node_(1) set Z_ 0.0
$node_(2) set X_ 591.3
$node_(2) set Y_ 199.4
$node_(2) set Z_ 0.0
$ns_ at 33.0 "$node_(0) setdest 89.7 283.5 19.2“
$ns_ at 51.0 "$node_(1) setdest 221.8 80.9 14.9"
$ns_ at 50.0 "$node_(2) setdest 369.5 170.5 3.4"
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Scenario: Traffic
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Traffic pattern generator
CBR (UDP) or FTP (TCP) traffic
 ~ns/indep-utils/cmu-scen-gen/cbrgen.tcl
ns cbrgen.tcl [-type cbr|tcp]
[-nn nodes] [-seed seed]
[-mc connections] [-rate rate]
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Specify in the OTcl script
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Same as the wired network scenario
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A Traffic Scenario
set udp_(0) [new
$ns_ attach-agent
set null_(0) [new
$ns_ attach-agent
Agent/UDP]
$node_(0) $udp_(0)
Agent/Null]
$node_(2) $null_(0)
set cbr_(0) [new Application/Traffic/CBR]
$cbr_(0) set packetSize_ 1000
$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)
$ns_ at 20.0 "$cbr_(0) start"
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An Example – Step 5
# Define node initial position in nam
for {set i 0} {$i < 3} {incr i} {
$ns initial_node_position $node($i) 20
}
# Tell ns/nam the simulation stop time
$ns at 100.0 “$ns nam-end-wireless 100.0”
$ns at 100.0 “$ns halt”
# Start your simulation
$ns run
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Summary
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NS-2 is an open source, discrete event, and
packet level network simulator
NS-2 is written in C++ with OTcl interpreter
as a front end
TclCL provides linkage for class hierarchy,
object instantiation, variable binding and
command dispatching
NS-2 provides abundant implementations of
protocols used in wired and wireless networks
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Random Variable
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Test the following script
Change pareto to exponential distribution.
53
M/M/1 Queueing System
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Arrival: Poisson arrival with rate 
Service: Packet size is exponential distribution
(average tx duration is )
 = /
Average number of packet in the queue is /(1- ).
Compare the theoretical value and simulation results.
54
Many TCP
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Many TCP (Agent/TCP/Newreno) sessions
sharing a bottleneck link and single
destination (D)
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Draw queue size of node BN every 0.1s.
Draw throughput of each TCP sessions every 0.1s.
TCP
TCP
S
S
1Mbps
1Mbps
BN
1Mbps
D
1Mbps
TCP
S
55
TCP over DSDV
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3 node ad-hoc simulation
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Channel: wireless channel
Propagation: Tworayground
Mac: 802.11
Queue: priority queue
Routing protocol: DSDV
Topology: 400mx500m
Position of nodes: n0(5,5), n1(490,285), n2(150,240)
TCP sender at n0 and receiver at n2
Draw TCP window size
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NS2 Installation Guidelines

Downloading

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NS2 is available from http://www.isi.edu/nsnam/ns/ns-build.html
Download the ns-allinone package, ns-allinone-2.30.tar.gz
Installing NS2


Go to directory of downloaded ns-allinone.tar.gz
Unpack the file using:
tar -xzvf ns-allinone-2.30.tar.gz

Go to the ns-allinone directory:
cd ns-allinone-2.30
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Install it with the command
./install

How to run ns2

Type
./ns [filename].tcl
57
NS2 Useful Links

Network Simulator NS-2

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
NS-2 Homepage (http://www.isi.edu/nsnam/ns/)
NS-2 Manual (http://www.isi.edu/nsnam/ns/nsdocumentation.html)
Getting started with NS-2


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
Marc Greis's tutorial
(http://www.isi.edu/nsnam/ns/tutorial/index.html)
NS by example (http://nile.wpi.edu/NS/)
NS2 for beginners
(http://www-sop.inria.fr/maestro/personnel/Eitan.Altman/COURS-NS/n3.pdf)
OTcl (ftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/tutorial.html)
58
References

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The ns Manual, January 2002
IEC ns workshop slides, June 2000
First ns workshop slides, September 1997
Wetherall and Lindblad, “Extending Tcl for
Dynamic Object-Oriented Programming,”
Proceedings of the Tcl/Tk Workshop, 1995
Welch, “Practical Programming in Tcl and Tk”,
Prentice-Hall, 1995
Ousterhout, “Tcl and the Tk Toolkit,” AddisonWesley, 1994
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