Ns Tutorial

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Ns Tutorial

Alhussein A. AbouzeidElect. Eng. Dept./U. of Washington

[email protected]

Parts of this educational presentation use examples available from http://www.isi.edu/nsnam/ns/ns-documentation.html

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Tutorial Goals Using NS (the Otcl world)

Complete examples of its usage Wired Wireless

Extending NS (the C++ world) Implementing new functionality

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Schedule Day 1: Wired simulations

Fundamentals Supporting tools

Day 2: Wireless version of Day 1 Day 3: Extending ns capability

ns internals Extending ns Lab Assignments

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Overview What is ns? (the evolution) Status of the code Resources Documentation Remark!

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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)

Currently; DARPA; NSF; collaboration with researchers: ACIRI, UCB Daedelus, CMU, Sun Microsystems, NORTEL, Cisco, Me!

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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 (rocky) (Emulation only for FreeBSD for now)

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Resources http://www.isi.edu/nsnam/ns Installed on all machines in High

Throughput Lab (EE/CSE 365)add to .cshrc: setenv TCL_LIBRARY

/condor/ns-allinone-2.1b7a/tcl8.3.2 [email protected]

[email protected] “subscribe ns-users” in body Archive: http://www.isi.edu/nsnam/ns

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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

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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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Day 1 Schedule Architecture Basic Tcl/Otcl commands Elements of an 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

Example: Multicast routing nam Visualization

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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

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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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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

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G2time1.3s

G2time1.2s

G1G2

time1.35s

Example: Multicast Routing Dynamic group membership

n0 n1

n2

n3

1.5Mb, 10ms

1.5Mb, 10ms

G1time1.25s

G2

1.5Mb, 10ms

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Multicast: Step 1

Scheduler, tracing, and topology

# Create scheduler# Create scheduler

set ns [new Simulator]set ns [new Simulator]

# Turn on multicast# Turn on multicast

$ns multicast$ns multicast

# Turn on Tracing# Turn on Tracing

set fd [new “mcast.nam” w]set fd [new “mcast.nam” w]

$ns namtrace-all $fd$ns namtrace-all $fd

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Multicast: Step 2

Topology

# Create nodes# Create nodes

set n0 [$ns node]set n0 [$ns node]




# Create links# Create links

$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail



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Multicast: Step 3 Routing and group setup

# Routing protocol: let’s run distance vector# Routing protocol: let’s run distance vector

$ns mrtproto DM$ns mrtproto DM

# Allocate group addresses# Allocate group addresses

set group1 [Node allocaddr]set group1 [Node allocaddr]

set group2 [Node allocaddr]set group2 [Node allocaddr]

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Multicast: Step 4 Sender 0

# Transport agent for the traffic source# Transport agent for the traffic sourceset set udp0udp0 [new Agent/UDP] [new Agent/UDP]$ns attach-agent $$ns attach-agent $n1n1 $ $udp0udp0$$udp0udp0 set dst_addr_ $ set dst_addr_ $group1group1$$udp0udp0 set dst_port_ 0 set dst_port_ 0

# Constant Bit Rate source #0 # Constant Bit Rate source #0 set set cbr0cbr0 [new Application/Traffic/CBR] [new Application/Traffic/CBR]$$cbr0cbr0 attach-agent $ attach-agent $udp0udp0# Start at time 1.0 second# Start at time 1.0 second$ns at 1.0 "$$ns at 1.0 "$cbr0cbr0 start" start"

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Multicast: Step 5 Sender 1

# Transport agent for the traffic source# Transport agent for the traffic sourceset set udp1udp1 [new Agent/UDP] [new Agent/UDP]$ns attach-agent $$ns attach-agent $n3n3 $ $udp1udp1$$udp1udp1 set dst_addr_ $ set dst_addr_ $group2group2$$udp1udp1 set dst_port_ 0 set dst_port_ 0

# Constant Bit Rate source #0 # Constant Bit Rate source #0 set set cbr1cbr1 [new Application/Traffic/CBR] [new Application/Traffic/CBR]$$cbr1cbr1 attach-agent $ attach-agent $udp1udp1# Start at time 1.1 second# Start at time 1.1 second$ns at 1.1 "$$ns at 1.1 "$cbr1cbr1 start" start"

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Multicast: Step 6 Receiver with dynamic membership

# Can also be Agent/Null# Can also be Agent/Null

set rcvr [new Agent/LossMonitor]set rcvr [new Agent/LossMonitor]

# Assign it to node $n2# Assign it to node $n2

$ns at $ns at 1.21.2 "$n2 join-group $rcvr $ "$n2 join-group $rcvr $group2group2""

$ns at $ns at 1.251.25 "$n2 leave-group $rcvr $ "$n2 leave-group $rcvr $group2group2""



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Multicast: Step 7 End-of-simulation wrapper (as usual)

$ns at 2.0 "finish"$ns at 2.0 "finish"proc finish {} {proc finish {} {

global ns fdglobal ns fdclose $fdclose $fd$ns flush-trace$ns flush-traceputs "running nam..."puts "running nam..."exec nam out.nam &exec nam out.nam &exit 0exit 0

}}$ns run$ns run

Documents

Ns Tutorial