background of wireless communication student presentations and projects wireless communication...
TRANSCRIPT
Background of Wireless Communication
Student Presentations and Projects
Wireless Communication Technology
Wireless Networking and Mobile IP
Wireless Local Area Networks
Wireless Communication : LAB 3
Introduction to NS2 ProgrammingIntroduction to NS2 Programming
Outline NS overview NS structure and basics Steps to create a typical NS script Summary: Generic Script Structure Vis Tools Useful pointers NS by Example (http://nile.wpi.edu/NS/) Where is documentation and Tutorials:
http://www.isi.edu/nsnam/ns/ns-documentation.html http://www.isi.edu/nsnam/ns/tutorial/
What is NS Discrete event simulator targeted for
networking research Discrete event simulation:
representing a system by a collection of states and a set of events that describe state changes.
Discrete-Event/Continuous-Time An event in NS
a packet ID that is unique for a packet with scheduled time and the pointer to an network object that handles the packet
What can ns simulate?
Topology: wired, wireless Queue Scheduling Algorithms: RED, DropTail, … Transport Protocols: TCP (all flavors), UDP, … Routing: Static and dynamic routing, MPLS, … Application: FTP, HTTP, Telnet, Traffic
generators, … Multicast Various error models for link failures Open source
NS Structure
NS is written in oTcl and C++; Efficiency and simplicity
oTcl is an extension to oTcl (object Tcl): Have to deal with objects
NS uses C++ for per-packet action e.g. scheduler, TCP implementation
oTcl for control Topology Network objects
User interface-Interactive Mode
adeel@laptop#> ./ns#> set ns [new Simulator]_o4#> $ns at 1 "puts \"Hello World!\""1#> $ns at 1.5 "exit"2#> $ns runHello World!
User interface-Batch Mode
simple.tcl set ns [new Simulator] $ns at 1 "puts \"Hello World!\""
$ns at 1.5 "exit"$ns run
adeel@laptop#> ns simple.tclHello World!
Basic Tcl proc test{ } { set a 43 set b 27 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
Basic oTcl Class vehicle vehicle instproc characterize{} { $self instvar NumberOfWheels_ puts "$NumberOfWheels_ -wheel vehicle is a vehicle“ } Class car -superclass vehicle car instproc characterize{} {
$self instvar NumberOfWheels_ puts "$NumberOfWheels_ -wheel vehicle is a car"
}set a [new vehicle]set b [new car]$a set NumberOfWheels_ 3$b set NumberOfWheels_ 4$a characterize$b characterize
Tcl/oTcl Common Problem
Generally useless debugging information:
no object(_o24 cmd line 1)
invoked from within“_o24 cmd drop-target { }”
invoked from within“catch “$self cmd $args” ret”
(procedure “_o24” line 2)
Fortunately, you do NOT need to be a Tcl expert for using NS
Structure of a typical ns script Creating event scheduler Opening trace files Creating topology Creating the transport layer
“connection” Creating application to generate
traffic Start and stop the traffic flows
Structure of a typical ns script Creating event scheduler Opening trace files Creating topology Creating the transport layer
“connection” Creating application to generate
traffic Start and stop the traffic flows
Create Event Scheduler
Create scheduler set ns [new Simulator]
Schedule event $ns at <time> <event>
<event> is any legitimate ns/tcl commands
Start scheduler $ns run
Structure of a typical ns script Creating event scheduler Opening trace files Creating topology Creating the transport layer
“connection” Creating application to generate
traffic Start and stop the traffic flows
Open trace files Ex.1
Trace packets on all links set fp [open test.out w] $ns trace-all $fp trace format:<event> <time> <from> <to> <pkt_type> <size> <flag><flow_id><src>
<dst><seq_no> <ack_seq_no>
r 1 0 2 tcp 1000 - - - - - - - - - - - - - - - - - 0 0.0 3.1 29 199
+ 1 0 2 tcp 1000 - - - - - - - - - - - - - - - - - 0 0.0 3.1 29 199
- 1 0 2 tcp 1000 - - - - - - - - - - - - - - - - - 0 0.0 3.1 29 199
d 1.00234 0 2 tcp 1000 - - - - - - - - - - - - 0 0.0 3.1 29 199
Open trace files Ex.2#Open the Trace file set tf [open out.tr w] $ns trace-all $tf
Create Topology
Create nodes set n0 [$ns node] set n1 [$ns node]
Create links and queues $ns <link-type> $n0de1 $node2 <bandwidth> <delay>
<queue-type>
<queue-type>: DropTail, RED, WFQ, SFQ, … <link-type>: duplex-link, simplex-link $ns duplex-link $n0 $n1 1Mb 10ms
DropTail
Create Flow: UDP
UDPCreate agents
- set udp [new Agent/UDP] - set null [new Agent/NULL]Attach to the nodes
- $ns attach-agent $n0 $udp- $ns attach-agent $n1 $null
Establish the “connection”- $ns connect $udp $null
Create Connection: TCP
TCPCreate agents
- set tcp [new Agent/TCP] - set tcpsink [new Agent/TCPSink]Attach to the nodes
- $ns attach-agent $n0 $tcp- $ns attach-agent $n1 $tcpsink
Establish the “connection”- $ns connect $tcp $tcpsink
Create Application
On Top of UDP: CBR set cbr0 [new Application/Traffic/CBR] $cbr0 attach-agent $udp
On Top of TCP: FTP set ftp [new Application/FTP] $ftp attach-agent $tcp
Start & Stop the traffic
Schedule to start the traffic $ns at 0.0 “$cbr0 start”
Schedule to stop the traffic $ns at 5.0 “$cbr0 stop” $ns at 5.0 “finish”proc finish { } {
global ns fp$ns flush-trace; close $fp
exec …. &}
Summary: Generic Script Structure
set ns [new Simulator]set ns [new Simulator] # [Turn on tracing]# [Turn on tracing] # Create topology# Create topology # Setup packet loss, link dynamics# Setup packet loss, link dynamics # Create routing agents# Create routing agents # Create: # Create: # - multicast groups# - multicast groups # - protocol agents# - protocol agents # - application and/or setup traffic sources# - application and/or setup traffic sources # Post-processing procs# Post-processing procs # Start simulation# Start simulation
Example 1 - TCP
Simple scenario with TCP and UDP connections
n0TCP
n4UDP
n1 n2
n5UDPrecvr
n3TCPSink
1.5Mb10ms
5Mb2ms
5Mb 2ms
TCP : Step 1
Scheduler & tracing#Create schedulerSet ns [new Simulator]
#Turn on tracingset f [open out.tr w]$ns trace-all $fSet nf [open out.nam w]$ns namtrace-all $nf
TCP : Step 2
Create topology#create nodesset n0 [$ns node]set n1 [$ns node]set n2 [$ns node]set n3 [$ns node]
TCP : Step 3
#create links$ns duplex-link $n0 $n1 5Mb 2ms DropTail$ns duplex-link $n1 $n2 1.5Mb 10ms
DropTail$ns duplex-link $n2 $n3 5Mb 2ms DropTail$ns queue-limit $n1 $n2 25$ns queue-limit $n2 $n1 25
TCP : Step 4
Create TCP agents set tcp [new Agent/TCP]set sink [new Agent/TCPSink]$ns attach-agent $n0 $tcp$ns attach-agent $n3 $sink$ns connect $tcp $sink
TCP : Step 5
Attach traffic
set ftp [new Application/FTP]$ftp attach-agent $tcp
#start application traffic$ns at 1.1 “$ftp start”
TCP : Step 6
End of simulation wrapper (as usual)$ns at 2.0 “finish”Proc finish {} {
global ns f nfclose $fclose $nfputs “Running nam…”exec nam out.nam &exit 0
}$ns run
Example 2
Example 2
#Create a simulator object set ns [new Simulator]
#Define different colors for data flows (for NAM) $ns color 1 Blue $ns color 2 Red
#Open the NAM trace file set nf [open out.nam w] $ns namtrace-all $nf
Example 2
#Define a 'finish' procedure proc finish {} { global ns nf $ns flush-trace #Close the NAM trace file close $nf #Execute NAM on the trace file exec nam out.nam & exit 0 }
Example 2
#Create four nodes set n0 [$ns node] set n1 [$ns node] set n2 [$ns node] set n3 [$ns node]
#Create links between the nodes $ns duplex-link $n0 $n2 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
Example 2
#Give node 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
#Monitor the queue for link (n2-n3). (for NAM) $ns duplex-link-op $n2 $n3 queuePos 0.5
#Setup a TCP connection set tcp [new Agent/TCP] $tcp set class_ 2 $ns attach-agent $n0 $tcp set sink [new Agent/TCPSink] $ns attach-agent $n3 $sink $ns connect $tcp $sink $tcp set fid_ 1
Example 2
#Setup a FTP over TCP connection set ftp [new Application/FTP] $ftp attach-agent $tcp $ftp set type_ FTP
#Setup a UDP connection set udp [new Agent/UDP] $ns attach-agent $n1 $udp set null [new Agent/Null] $ns attach-agent $n3 $null $ns connect $udp $null $udp set fid_ 2
Example 2
#Setup a CBR over UDP connection set 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"
Example 2
#Detach tcp and sink agents (not really necessary)
$ns at 4.5 "$ns detach-agent $n0 $tcp ; $ns detach-agent $n3 $sink"
#Call the finish procedure after 5 seconds of simulation time
$ns at 5.0 "finish"
#Print CBR packet size and interval
puts "CBR packet size = [$cbr set packet_size_]"
puts "CBR interval = [$cbr set interval_]"
#Run the simulation
$ns run
Tracing
cat out.tr | grep " 2 3 cbr " | grep ^r | column 1 10 | awk '{dif = $2 - old2; if(dif==0) dif = 1; if(dif > 0) {printf("%d\t%f\n", $2, ($1 - old1) / dif); old1 = $1; old2 = $2}}' > jitter.txt
Viz Tools
Nam-1 (Network AniMator Version 1) Packet-level animation Well-supported by ns
Xgraph Convert trace output into xgraph
format
NAM
Ns-nam Interface
Color Node manipulation Link manipulation Topology layout Protocol state Misc
Nam Interface: Color
Color mapping$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”)$ns at 1.0 “$n0 add-mark m0 blue box”$ns at 1.0 “$n0 add-mark m0 blue box”$ns at 2.0 “$n0 delete-mark m0”$ns at 2.0 “$n0 delete-mark m0”
Label (single string)$ns at 1.1 “$n0 label \”web cache 0\””$ns at 1.1 “$n0 label \”web cache 0\””
Nam Interface: Links
Color$ns duplex-link-op $n0 $n1 color "green"$ns duplex-link-op $n0 $n1 color "green"
Label$ns duplex-link-op $n0 $n1 label "abced"$ns duplex-link-op $n0 $n1 label "abced"
Dynamics (automatically handled)$ns rtmodel Deterministic {2.0 0.9 0.1} $n0 $n1$ns rtmodel Deterministic {2.0 0.9 0.1} $n0 $n1
Asymmetric links not allowed
Nam Interface: Topo Layout “Manual” layout: specify
everything
$ns duplex-link-op $n(0) $n(1) orient right$ns duplex-link-op $n(0) $n(1) orient right
$ns duplex-link-op $n(1) $n(2) orient right-up$ns duplex-link-op $n(1) $n(2) orient right-up
$ns duplex-link-op $n(2) $n(3) orient down$ns duplex-link-op $n(2) $n(3) orient down
$ns duplex-link-op $n(3) $n(4) orient 60deg$ns duplex-link-op $n(3) $n(4) orient 60deg
If anything missing automatic layout
Nam Interface: Protocol State Monitor values of agent variables
$ns add-agent-trace $srm0 srm_agent0$ns add-agent-trace $srm0 srm_agent0
$ns monitor-agent-trace $srm0$ns monitor-agent-trace $srm0
$srm0 tracevar C1_$srm0 tracevar C1_
$srm0 tracevar C2_$srm0 tracevar C2_
# … …# … …
$ns delete-agent-trace $tcp1$ns delete-agent-trace $tcp1
Nam Interface: Misc
Annotation Add textual explanation to your sim
$ns at 3.5 "$ns trace-annotate \“packet drop\"“$ns at 3.5 "$ns trace-annotate \“packet drop\"“
Set animation rate
$ns at 0.0 "$ns set-animation-rate 0.1ms"$ns at 0.0 "$ns set-animation-rate 0.1ms"
Useful Pointers
Directory structure:/ns-2.../ contains C++ code
/ns-2.../tcl/lib/ contains oTcl source code /ns-2.../tcl/ex/ examples simulation scripts /ns-2.../tcl/test/ validation test scripts
RED Queue Monitor Example http://nile.wpi.edu/NS
Xgraph
Other Utilities in Ns
Nam editorAvailable as part of nam-1
Tcl debuggerFor source and documentation, seehttp://www.isi.edu/nsnam/ns/ns-
debugging.html Topology generator
http://www.isi.edu/nsnam/ns/ns-topogen.html Scenario generator
http://www.isi.edu/nsnam/ns/ns-scengeneration.html
Resources
Ns distribution download http://www.isi.edu/nsnam/ns/ns-build.html
Installation problems and bug-fix http://www.isi.edu/nsnam/ns/ns-
problems.html
Ns-users mailing list [email protected] See http://www.isi.edu/nsnam/ns/ns-
lists.html Archives from above URL
Resources (contd..)
Marc Greis’ tutorial http://www.isi.edu/nsnam/ns/tutorial
Ns-users archive Ns-manual
http://www.isi.edu/nsnam/ns/ns-documentation.html
Tcl (Tool Command Language) http://dev.scriptics.com/scripting Practical programming in Tcl and Tk, Brent
Welch Otcl (MIT Object Tcl)
~otcl/doc/tutorial.html (in distribution)
Resources (contd..)
NS Frequently Asked Questions: http://www.isi.edu/nsnam/ns/ns-faq.html
Lloyd Wood - introducing ns:http://www.ee.surrey.ac.uk/Personal/
L.Wood/ns/
QUESTIONS
???