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Introduction to NS2

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tracing, visualization, error models, etc. modify or create your own modules. 4. NS components ... fat link. thin link. performance. tracing. 27. Introduction ... – PowerPoint PPT presentation

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Title: Introduction to NS2

1
Introduction to NS-2

Tutorial overview of NS
Create basic NS simulation
Walk-through a simple example
Model specification
Execution and trace analysis

http//www-net.cs.umass.edu/honggang/ns-cs653/
2
NS-2, the network simulator

Academic project over 10 years old
freely distributed, open source
Currently maintained by ISI (Information Sciences
Institute)
DARPA NSF projects
200K LoC, 403 page manual
Large user base
mostly academics
de facto standard in networking research
Main website http//www.isi.edu/nsnam/ns

3
NS Functionality

Discrete event simulator
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, DV routing, multicast, ad-hoc
routing
queueing disciplines drop-tail, RED, FQ
Link layer
wired, wireless, satellite
Providing Infrastructure
tracing, visualization, error models, etc
modify or create your own modules

4
NS components

NS, the simulator itself (this is all well have
time for)
NAM, the Network AniMator
visualize NS (or other) output
GUI input simple Ns scenarios
pre-processing
traffic and topology generators
post-processing
simple trace analysis, often in Awk, Perl, or Tcl
Tutorial http//www.isi.edu/nsnam/ns/tutorial
NS by example http//nile.wpi.edu/NS/

5
NS Software Structure C and OTCL

Uses two languages
C for the core of NS simulator
per packet processing
fast to run, detailed, complete control
OTCL for control our focus
simulation setup, configuration
fast to write and change

6
Steps when using NS

Create OTCL script for your network model
nodes, links, traffic sources, sinks, etc.
Parameterize simulation objects
Links queue sizes, link speeds,
Transport Protocols TCP flavor and parameters
(more than 30),
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
Create a Basic NS Simulation

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

8
Create a Basic NS Simulation

Create the event scheduler
Create nodes and links
Create connections
Create traffic sources/sinks
Enable tracing

9
Step 1 Creating Event Scheduler

Create scheduler
set ns new Simulator
Schedule event
ns at lttimegt lteventgt
lteventgt any legitimate Ns/TCL commands
Start scheduler
ns run

10
Create a Basic NS Simulation

Create the event scheduler
Create nodes and links
Create connections
Create traffic sources/sinks
Enable tracing

11
Step 2 Creating Network (Nodes Links)

Nodes
set n0 ns node
set n1 ns node
Links connect together two nodes
ns duplex-link n0 n1 ltbandwidthgt ltdelaygt
ltqueue_typegt
ltdelaygt determines propagation delay
ltqueue_typegt determines queueing policy
DropTail, RED, CBQ, FQ, SFQ, DRR

12
Create a Basic NS Simulation

Create the event scheduler
Create nodes and links
Create connections
Create traffic sources/sinks
Enable tracing

13
Step 3 Create Connections

Transports
TCP, UDP, multicast, etc.
transport protocol instances attach to nodes

14
Creating Transport Channels UDP

source and sink
set u_src new Agent/UDP
set u_dst new Agent/NULL
attach them to nodes, then connect to each other
ns attach-agent n0 u_src
ns attach-agent n1 u_dst
ns connect u_src u_dst

15
Creating Transport Channels TCP

source and sink
set t_src new Agent/TCP/Newreno
set t_dst new Agent/TCPSink
Newreno flavor of TCP
attach to nodes and each other
ns attach-agent n0 t_src
ns attach-agent n1 t_dst
ns connect t_src t_dst

16
Create a Basic NS Simulation

Create the event scheduler
Create nodes and links
Create connections
Create traffic sources/sinks
Enable tracing

17
Step 4 Create Traffic Models

Traffic (applications)
Web, ftp, telnet, audio, etc.
application objects attach to transport protocol
objects
generates traffic into transport protocol

18
Creating Traffic over TCP Channels

How to create a FTP session over TCP?
create traffic model
set ftp new Application/FTP
default is infinite file size
attach to TCP channel
ftp attach-agent t_src
schedule start time
ns at lttimegt ftp start

19
Creating Traffic over UDP Channels

How to create a CBR (Constant Bit Rate) model
over UDP?
set cbr new Application/Traffic/CBR
cbr set packetSize_ 512
cbr set interval_ 0.250
cbr attach-agent u_src
ns at lttimegt cbr start

20
Create a Basic NS Simulation

Create the event scheduler
Create nodes and links
Create connections
Create traffic sources/sinks
Enable tracing

21
Tracing dump everything into a file

Trace packets on individual link
Tracefile format
lteventgt lttimegt ltfromgt lttogt ltpktgt ltsizegt--ltflowidgt
ltsrcgt ltdstgt ltseqnogt ltaseqnogt
1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
- 1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
r 1.00234 0 2 tcp 900 ------- 1 0.0 3.1 7 15

Node 0
Node 1
enqueue
time

enqueue
dequeue
r receive
d drop

nodes involved in this event
receive
dequeue
drop
22
Tracing dump everything into a file

Trace packets on individual links
Tracefile format
lteventgt lttimegt ltfromgt lttogt ltpktgt ltsizegt--ltflowidgt
ltsrcgt ltdstgt ltseqnogt ltaseqnogt
1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
- 1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
r 1.00234 0 2 tcp 900 ------- 1 0.0 3.1 7 15

packet type
packet flags
seq number
time
packet ID

enqueue
dequeue
r receive
d drop

packet length
flow ID
source dest addresses
nodes involved in this event
23
Tracing via Monitors

Queue monitor the queue to access a link
Flow monitor particular flow within queue
to specify a link, we need
set link ns link n0 n1
to create a flow monitor
set fmon ns makeflowmon Fid
ns attach-fmon link fmon
ns at lttimegt puts fmon set pdrops_

24
Introduction to NS-2

Tutorial overview of NS
Create basic NS simulation
Walk-through simple example
Model specification
Execution and trace analysis

25
Walk-through example
Node 2
Node 0
Node 1
acks
acks
full duplex
full duplex
26
Walk-through example
One CBR source
12 FTP dest
10 FTP sources
2 FTP sources
performance
2 TCP SACK W_max 32 MSS 1400
10 TCP NewReno W_max 32 MSS 1400
One UDP
12 TCP dest
tracing
Node 2
Node 0
Node 1
acks
acks
One UDP
Two UDP dest
1 Mbps full duplex 10 msec prop delay 700 packet
buffer Drop-tail policy
2 Mbps full duplex 5 msec prop delay 100 packet
buffer Drop-tail policy
One On-Off dest One CBR dest
One On-Off Source (voice)
thin link
fat link
27
Introduction to NS-2