NS-2 Network Simulator 2 Tutorial – Emanics Summer School, Zurich 3rd June, 2008

ISSNSM — International Summer School on Network and Service Management

2nd ISSNSM’s Tutorial on

Simulating Networks with Network Simulator 2 (ns-2)

(Tutorial T2)

Speaker:

Frank Eyermann

June 3, 2008

ISSNM program chaired by Burkhard Stiller, David Hausheer, University of Zürich

ISSNM laboratory organization chaired by Cristian Morariu, Peter Racz, University of Zürich

NS-2 Network Simulator 2

This tutorial/training course was supported in part by the EC IST-EMANICS Network of Excellence (#26854).

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Tutorial – Emanics Summer School, Zurich 3rd June, 2008

Introduction

– Frank.Eyermann@unibw.de

– Information Systems Laboratory – Faculty for Computer Science – Universität der Bundeswehr, Munich

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(cid:137)Frank Eyermann

Exercise 1.1: ns-2’s Hello World

– Two nodes, link in between – Sender agent: Agent/UDP – Receiver agent: Agent/Null – Connect agents – Data source: Application/Traffic/CBR – Run from 0.5 to 4.5 sec, finish at 5.0 sec 1000 Byte, Rate 1,5mbit

Application/Traffic/CBR

Agent/Null

Agent/UDP

2mb 10ms DropTail

Node

Node

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(cid:137)Create the following scenario

Exercise 1.2

Application/FTP

Agent/TCP

1 mb 10 ms DropTail

Node

Agent/TCPSink

Agent/Null

Node

Node

1000 Byte, Rate 1,5mbit

2mb 10ms DropTail

Application/Traffic/CBR

Agent/UDP

2mb 10ms DropTail

Node

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(cid:137)Extend to the following scenario

– Connect the appropriate agents – Start the FTP application at t = 0.5s – Start the CBR data source at t = 1s – Terminate both at t = 4.5 s – Visualize the bottle neck queue:

$ns duplex-link-op $n2 $n3 queuePos 0.5

Exercise 1.2

– Observe the queue and the load on the

bottleneck link

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(cid:137)Run the simulation (cid:137)Replay the simulation with nam.

Exercise 1.3

– from DropTail to RED (Random Early Detect) – What changes can you observe?

(cid:137)Change the bottleneck drop policy

– Change the RED queue parameters trying to

make it smoother

– set l [$ns link $n2 $n3] – set q [$l queue] – #$q set thresh_ ?? # default 0 – #$q set maxthresh_ ?? # default 50 – #$q set linterm_ ?? # default 0.1

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(cid:137)The FTP traffic is now very bursty.

Exercise 1.4

– $agent set fid_ number

(cid:137)Based on 1.2 (cid:137)Name each flow

– $ns color number Color

(cid:137)Color flow 1 red and flow 2 blue

(cid:137)Predefine the links’ orientation for better

down

layout – $ns duplex-link-op $n0 $n1 orient right-

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(cid:137)Restart simulation

Exercise 1.5

– Despite tuning the queue’s parameter the

queue length changes in drastically

– Color the packets – Do you see why the RED queue does not

perform as expected?

– What function needs to be implemented?

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(cid:137)Based on exercise 1.3

Exercise 2.1: Tracing

(cid:137)Based on exercise 1.4 (cid:137)Trace all events on the bottleneck link (cid:137)Create a second trace file for only the

drops

(cid:137)Open the document „NS-2 Trace

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Formats“ – What is the normal trace format?

Exercise 2.2: Monitoring

(cid:137)Based on Exercise 1.4 (cid:137)Create a monitor for the central node (cid:137)Use sampleInterval=0.1 to

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periodically write information to file (cid:137)Do not forget to trigger the monitoring

Exercise 2.3: Monitoring

(cid:137)Based on Exercise 1.4 (cid:137)Create a monitor for the central node (cid:137)Read all 0.05 sec the following values for

each time period: – Throughput – Packet drops – Average packets in queue – Average time of a packet in queue

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(cid:137)Write them to a file

Exercise 2.3: Monitoring

– You need to create a Samples object for the

average delay

– Create a procedure which retrieves the infor-

mation from the Monitor and writes them to file – The average packets in queue you get from the

respective built-in integrator

– Care for the case when no packets have been

received in one period

– Have the procedure schedule itself again at

[expr [$ns now] + 0.05]

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(cid:137)Hints:

Exercise 2.4: Monitoring

(cid:137)Based on exercise 1.2 and 1.3 (cid:137)Compare utilization of the bottleneck

respective data

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link and average time of a packet in the queue for DropTail and RED queuing discipline – Use QueueMonitors and Samples for the

Exercise 2.5: Monitoring Flows

– Use the standard output format – Look for the format at page 243 of ns_doc.pdf

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(cid:137)Based on exercise 2.2 (cid:137)Monitor the both flows separately

Exercise 3.1: Trace Post-Processing

(cid:137)Based on exercise 2.3 (cid:137)Visualize the drops and the average

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packets in the queue with xgraph and gnuplot

(cid:137)Create the following scenario (cid:137)All clients pull FTP data from

Client 1

Exercise 3.2

0.5 to 4.5 sec

Client 2

16Mbit 25ms

16Mbit 25ms

100 Mbit 8ms DropTail

56 Mbit 12 ms DropTail

16Mbit 25ms

FTP Server

16Mbit 25ms

Client 3

Client 4

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Exercise 3.2

(cid:137)Should Client 1 invest in upgrading to a

25 MBit/s or 50 MBit/s link?

(cid:137)Or better invest in a Fast-Path option

reducing the delay to 15ms?

(cid:137)Could the provider’s queuing discipline

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influence the user’s decision?

Exercise 3.3

(cid:137)Based on exercise 1.4 (cid:137)Visualize the packet jitter of the CBR

to skip dropped packets

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data – Remember

Exercise 4.1: LANs

4 FTP-Clients

FTP-Server

Router

(cid:137)Create a typical 10 MBit/s Ethernet

(cid:137)The LAN delay should be 1 ms (cid:137)The connection from the server to the

router is a WAN (2mbit/s, 10 ms)

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(cid:137)Simulate 5 sec. FTP-Transfer

Exercise 4.2

(cid:137)nam shows a quite long queue (cid:137)What is the average queuing delay of a

packet?

(cid:137)How could the delay be reduced? Think

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of exercise 1.3 – Repeat the simulation

Exercise 5.1: Routing

(cid:137)Create the following scenario, all links

1

2

8

3

7

4

6

10MBit, 8 ms, DropTail

5

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(cid:137)Send CBR data 1 -> 6, 3 -> 8, 5 -> 2, 7 -> 4 Rate = 1.5 MBit, Size = 500 Byte (cid:137)Activate session- based routing

Exercise 5.2

– Fails each 1.5 sec for 0.5 sec

(cid:137)Link node 1 to node 2

– Is down between 1.6 and 2.5 sec

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(cid:137)Node 5

Exercise 5.3: Routing

(cid:137)Based on exercise 4.1 (cid:137)Dialup backup line, if WAN connection

down

RAS-Server

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fails – Volume based, quite expensive – 1mb, 15ms – Simulate deterministic failure 2sec up, 0,5sec

Bug in ns-2.3x

nodes-list]

{

# XXX using dummy 0 for 'changes'

$node notify-mcast 0

} – “LAN” is a node (LanNode) but misses

notify-mcast

– Hack: find method notifiy-mcast of node – Create an (empty) method stub for LanNode – Run make in folder ns-2.33

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(cid:137)On activating or deactivating of a link: foreach node [[Simulator instance] all-