Network Simulator 2. Telematica I (CdL Ing. INF) Ing. Giuseppe Piro.

Transcription

1 Network Simulator 2 Telematica I (CdL Ing. INF) Ing. Giuseppe Piro g.piro@poliba.it 1

2 NS-2 Goals NS-2 is a Network Simulator - version 2 Can setup network topologies Generate packet traffic similar to Internet and measure various parameters - Modeling Network Components -Traffic models and applications Web, FTP, telnet, audio, sensor nets Transport protocols: TCP (Reno, SACK, etc), UDP, multicast Routing and queueing: static routing, multicast, ad-hoc routing Queueing disciplines: drop-tail, RED, FQ Link layer: wired, wireless, satellite - Post simulations analysis tracing, plotting, visualization, error models, etc - Support networking research and education Protocol design, traffic studies, etc Protocol comparison Modify or create your own modules 2

3 NS2 is a Discrete Time Event Simulator Model world as events Simulation is a list of events Process: take next one, run it, until done NS-2 Functionality t=1 A enqueues pkt on LAN t=1.0 A sends pkt to NIC A s NIC starts carrier sense Node A t=1.005 A s NIC concludes cs, starts tx t=1.006 B s NIC begins reciving pkt t=1.01 B s NIC concludes pkt t=1.01 B s NIC passes pkt to application Ethernet link Node B 3

4 NS-2 Functionality Event List: is a list of events that must be processed by Event Scheduler. 4

5 NS-2 Software Structure -Object-oriented structure -Objects implemented in C++ and OTcl -C++ (object-oriented general purpose programming language) -for the core of NS simulator -per packet processing -fast to run, detailed, complete control -OTCL (object-oriented extensions of Tool Command Language, scripting language) -for control -simulation setup, configuration -fast to write and change 5

6 NS-2 Software Structure NAM : Network Animator Nam is a Tcl/TK based animation tool for viewing network simulation traces and real world packet traces 6

7 -Create OTCL script for your network model -nodes, links, traffic sources, sinks, Working on NS-2 by Steps -Parameterize simulation objects -Links: queue sizes, link speeds, -Transport Protocols: TCP flavor and parameters,... -Collect statistics -dump everything to trace, post process it -gather stats during simulation within OTCL script -modify Ns source code -Run NS multiple times -confidence intervals 7

8 Working on NS-2 by Steps Results 8

9 Working on NS-2 by Steps 9

10 Network Model A Network Model is realized interconnecting different components denominated ns objects The objects ns2 is built beginning from a hierarchical structure of classes C++ All the objects are derivable from the class NSObject that is the base for all the classes 10

11 Network Model Each network component is an C++ object and it can be created by OTcl scripting set Net_Component [new Net_Component_Type] set CBR [new Application/Traffic/CBR] It is possible to set network component parameters by OTcl scriptig $Net_Component set param_ value $CBR set packetsize_

12 Create NS Simulation Create event scheduler Create nodes and links Create connections Create traffic sources/sinks Enable tracing 12

13 Create NS Simulation simulator object Simulator is the most important ns object and it must be created at the beginning of OTcl scripting set ns [new Simulator] This class provides to: -Simulation configuration -Event scheduler -Network topology configuration Standard classes of network model are Node, Link, Agent, Monitor, Trace, etc. 13

14 Node object represents a single network device. It implements IP protocol functionalities (address, routing). Unicast vs Multicast node. One node object creator: N node objects creator: Create NS Simulation node and links (1) set node [$ns node] for { set i 0 } { $i < $N } { incr i } { } set node$i [$ns node] 14

15 Create NS Simulation node and links (2) Link object connect together two nodes. Simplex vs Duplex link. $ns duplex-link $node1 $node2 <bandwidth> <delay> <queue_type> <delay> determines propagation delay; <queue_type> determines queueing policy (DropTail, RED, CBQ, FQ) set n1 [$ns node] set n2 [$ns node] $ns duplex-link $n1 $n2 1.7Mb 20ms DropTail 15

16 Create NS Simulation connections Agent object represents a Transport Protocol (TCP, UDP, etc). Each flow has a Source Agent and a Destination Agent. set src [new Agent/UDP] set dst [new Agent/NULL] Agent object must be attach to nodes and, then, connect to each other $ns attach-agent $n1 $src $ns attach-agent $n2 $dst $ns connect $src $dst 16

17 Traffic (applications): Web, ftp, telnet, audio, CBR, etc. Create NS Simulation traffic models Application objects attach to transport protocol objects. Application objects generates traffic into transport protocol. How to create a CBR (Constant Bit Rate) model over UDP? set cbr [new Application/Traffic/CBR] $cbr set packetsize_ 512 $cbr attach-agent $u_src $ns at <time> $cbr start 17

18 Tracing: dump everything into a file. Create NS Simulation tracing 18

19 Create NS Simulation tracing Trace file format: 19

20 Basic NS Simulation Router Destination Source 20

21 Basic NS Simulation Network model for NS: 21

22 Basic NS Simulation #Create a simulator object set ns [new Simulator] #Open the NAM trace file set nf [open out.nam w] $ns namtrace-all $nf 22

23 #Create nodes and links between the nodes set n0 [$ns node] set n1 [$ns node] set n2 [$ns node] Basic NS Simulation $ns duplex-link $n0 $n1 2Mb 10ms DropTail $ns duplex-link $n1 $n2 1.7Mb 20ms DropTail #Set Queue Size of link (n2-n3) to 10 $ns queue-limit $n1 $n

24 Basic NS Simulation #Setup a UDP connection set udp [new Agent/UDP] $ns attach-agent $n0 $udp set null [new Agent/Null] $ns attach-agent $n2 $null $ns connect $udp $null #Setup a CBR over UDP connection set cbr [new Application/Traffic/CBR] $cbr attach-agent $udp $cbr set packet_size_ 1000 $cbr set rate_ 1mb 24

25 Basic NS Simulation #Define a 'finish' procedure proc finish {} { global ns nf $ns flush-trace #Close the NAM trace file close $nf #Execute NAM on the trace file exec nam out.nam & exit 0 } 25

26 Basic NS Simulation #Schedule events for the CBR $ns at 0.1 "$cbr start" $ns at 4.5 "$cbr stop" #Call the finish procedure after 5 seconds of simulation time $ns at 5.0 "finish" #Run the simulation $ns run 26

27 Basic NS Simulation 2 Source 1 Router Destination Source 2 27

28 Basic NS Simulation 2 Network model for NS: 28

29 Basic NS Simulation 2 #Create a simulator object set ns [new Simulator] #Open the NAM trace file set nf [open out.nam w] $ns namtrace-all $nf #Create nodes and links between the nodes for { set i 0 } { $i < 4 } { incr i } { set n$i [$ns node] } $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 #Set Queue Size of link (n2-n3) to 10 $ns queue-limit $n2 $n3 10 $ns duplex-link-op $n2 $n3 queuepos

30 Basic NS Simulation 2 #Setup color for data flow $ns color 0 Blue #Setup a UDP_0 connection set udp0 [new Agent/UDP] $ns attach-agent $n0 $udp0 set null0 [new Agent/Null] $ns attach-agent $n3 $null0 $ns connect $udp0 $null0 $udp0 set fid_ 0 #Setup a CBR_0 over UDP_0 connection set cbr0 [new Application/Traffic/CBR] $cbr0 attach-agent $udp0 $cbr0 set packet_size_ 1000 $cbr0 set rate_ 1mb 30

31 Basic NS Simulation 2 #Setup color for data flow $ns color 1 Red #Setup a UDP_1 connection set udp1 [new Agent/UDP] $ns attach-agent $n1 $udp1 set null1 [new Agent/Null] $ns attach-agent $n3 $null1 $ns connect $udp1 $null1 $udp1 set fid_ 1 #Setup a CBR_1 over UDP_1 connection set cbr1 [new Application/Traffic/CBR] $cbr1 attach-agent $udp1 $cbr1 set packet_size_ 1000 $cbr1 set rate_ 1mb 31

32 Basic NS Simulation 2 #Define a 'finish' procedure proc finish {} { global ns nf $ns flush-trace #Close the NAM trace file close $nf #Execute NAM on the trace file exec nam out.nam & exit 0 } 32

33 Basic NS Simulation 2 #Schedule events for the CBR $ns at 0.1 "$cbr1 start $ns at 1 "$cbr0 start $ns at 4 "$cbr0 stop" $ns at 4.5 "$cbr1 stop #Call the finish procedure after 5 seconds of simulation time $ns at 5.0 "finish" #Run the simulation $ns run 33

34 NS-2 Resource The Netwok Simulator ns-2 Home Page: The Network Simulator ns-2 Manual: The Network Simulator ns-2 Mailing List: The Network Simulator ns-2 Tutorial: TCL/TK Resource: 34