opnet tutorial

Obtain a written specification of the system you will be modeling
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Understanding your goals
What general questions do you want the simulation to answer? Sample questions:
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Choosing aspects to be modeled
From those general questions, formulate specific research objectives, such as:

What is the throughput at a specific receiver? What is the effect of changing a link‟s transmission rate? What offered traffic load causes the system to become unstable?
You will be able to choose the proper input Input may refer to a predefined aspect of the model (such as connectivity) or may be more parametric (such as traffic generation rate) To study effects on a system, keep most inputs constant and vary one or two over a range


Collect more or different statistics? Change the level of granularity? Model different aspects of your system?
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Result statistically useful?
Is the model operating in steady state?
start
Understanding the system Understanding your goals for the study Choosing aspects to be modeled Defining input and output
no Choosing input range and running simulations Result sufficiently detailed
Example

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System results accurate?
Output should be “sanity-checked” for accuracy and robustness

Does all output make sense? Can it be justified? Does the model behave a appropriately?
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OPNET features
Hierarchical network models Subnetwork nesting Object-oriented modeling Node and protocols Clear and simple modeling paradigm Finite state machine modeling Integrated debugger Geographical and mobility modeling Total openness API, source code Integrated analysis tools Animation Import data from text file and popular tools



How much will replacing our Ethernet LAN with an FDDI hub increase throughput? How much does a customized protocol improve efficiency in my cellular network? How much will adding 100 users lengthen response time?
Keep most variables constant except for one or two that you vary over a range Usually possible to analytically estimate upper and lower bounds for the range Then, choose input values that span this range After running initial simulations you may decide to


Understand the features your simulation tool offers Understand how those features can best describe your system
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Choosing a range of input and running simulation
One technique: predict output first, then compare predicated to actual output
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Results sufficiently detailed?
As needed, either widen the input range to get “the bigger picture” or narrow it to focus on a specific region Should you:
Run simulations for a longer period until outputs are stable Model that never reaches steady state indicates unstable system Look at various statistical measures to ensure model is in steady state
OPNET application areas OPNET‟s purpose Flow diagram : a simulation study OPNET overview OPNET features OPNET modeling architecture OPNET directory structure OPNET editors


Extend the range Focus on a narrow range to obtain finer detail First range chosen was 1 - 10 Mb/s with step 1 Mb/s Second range chosen was 7.0 - 8.0 Mb/s with step 0.2 Mb/s
These objectives determine the granularity required in the model
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Defining the data input and output
Choosing input is a critical step If you:

Understand the system Understand your goals Have defined the specific aspects to be modeled Have you clarified the questions to be addressed
The use of OPNET (Lab 1,2)


M/M/1 queue Packet Switching Events and Event list concept Kernel Procedures
Troubleshooting
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More study of OPNET


Introduction to OPNET
System result accurate
no
Specifying the system model
yes
no
Result statistically end useful?
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Understanding the proposed system
You must the understand the proposed system to model it accurately. Model cannot be more accurate than your understanding. Recommendation
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OPNET application areas
Analyzing performance and behavior of communications networks Developing protocols and algorithms, or modifying existing ones Evaluating distributed system architectures

Expect initial transient behavior, converging to steady state. Look for rising means, increasing queue lengths, or other output that is still varying. This might mean that the model is not in steady state.
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OPNET‟s purpose
Input : you describe the model graphically and develop input parameter sets(data rates, traffic load, etc) OPNET will simulates scenarios from your input Output can be :
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OPNET overview
You will learn about OPNET‟s architecture You will again a broad understanding of the tools OPNET offers for building a model, running a simulation, and analyzing output


graphs tables numerical values animations
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Specifying the system model
A general simulation tool can represent your system in many different ways. To use it effectively:
OPNET Tutorial
Lecturer: Tae-Hyong Kim (B201-4) thkim@cespc1.kumoh.ac.kr
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Contents
Introduction to OPNET Model library of OPNET

Model naming convention Creating new devices


Graphs displaying different analyses of one or more parameter sets Animation displaying simulations interactively and dynamically
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Flow diagram : a simulation study
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Defining the data input and output
Determine which output (throughput, ETE delay, etc.) you need and the best presentation method Output may be presented in many forms such as