HyunJun Choi Aug 27, 2004 OPNET Simulator HyunJun Choi Aug 27, 2004 Informational Communication University

HyunJun Choi Aug 27, 2004

OPNET Simulator

HyunJun ChoiAug 27, 2004

Informational Communication University


Contents

• Modeling Overview• Process domain• Node domain• Project domain


What is OPNET?

• A powerful network simulation tool– comprehensive development environment for modeling of

communication networks and distributed systems– Accuracy and easy-of-use for network planner

• System requirements– Visual studio 6.0

• References– www.opnet.com– www.simus.net


Modeling Overview


Backgrounds

• Object orientation– OPNET Consists of objects, each with configurable sets of attribute– Objects Belong to classes

• Specialized in communication networks and information systems

• Graphical specification

• Flexibility to develop detailed custom models– OPNET provides a flexible, high-level programming language with

extensive support

• Automatic generation of simulations– Automatically compiled with C programming language


Typical Applications of OPNET

• Standards-based LAN and WAN performance modeling

• Internetworking planning

• Research and development in communications architectures and protocols

• Distributed sensor and control networks

• Mobil packet radio networks

• Satellite networks


OPNET simulator Architecture

Initial Specification

Analysis

Data Collection andSimulation

Re-Specification

Simulation Project Cycle


Specification Editors

• Project Editor– Specify network topology and configure nodes and links

• Node Editor– Create models of nodes by specifying internal structure and

capabilities– Combine modules

• Process Editor– Develop models of decision-making processes representing

protocols, algorithms, resource managers, operation systems, etc.

• Link Editor– Create, edit, and view link models

• Packet Format Editor– Specify packet format, defining the order, data type, and size of

fields contained within the packet

• ICI Editor– Create, edit, and view interface control information formats


Specification Editors (cont’d)

• PDF Editor– Create, edit, and view PDF

• Probe Editor– Identify sources of statistics and animation that are to be collected

during a simulation– Done before execution

• Simulation Tool– Design and run sequences of simulations, each potentially

configured with different inputs and/or outputs

• Analysis Tool– Plot and process numerical data generated by simulations


Graphical Editors for networks, node, and process models


Modeling domains

Domain Editor Modeling Focus

Network Project

Network topology described in terms of subnetworks, nodes, links, and geographical context.

Node Node

Node internal architecture described in terms of functional elements and data flow between them.

Process Process

Behavior of process (protocols, algorithms, applications), specified using finite state machines and extended high-level languages


Network domain example


Node domain example


Process domain example


Simulation Output Data Types

• Output vectors– Most common results type– Consist of dependent and independent variables, pairs of real

values

• Output Scalars– Individual values

• Ex) Averages, Probabilities, peak value, etc.– Ex) Throughput vs. Offered Load


OPNET model hierarchy


Process domain


Process Model Example

• Sink Process


Interrupt-Driven Execution

• Process are driven by events– Internally or externally interrupted


Process Hierarchy

• Root process – Child process– Call KP Op_pro_create()


Interrupt Steering Example


Local Process Resources

• Input and Output Streams– Packet streams are objects in Node Editor and used to connect modules toge

ther– Packet streams connect source with destination modules which are called ou

tput and input streams

• Input stream to receiver process– op_intrpt_stream(), op_pk_get(), op_strm_pksize(),and etc.

• Output stream from sender process– Op_pk_send(), op_pk_send_delayed(), op_pk_send_forced(),and ect.


Graphical expression of Streams


Graphical expression of Streams (Cont’d)

Recall this picture!


State Transition diagram

• Proto-C models consist of two basic components– States and Transitions

• A process has two executives– Enter executive and Exit executive

• Forced and Unforced States– Forced State (Green)

• Proceeds without any event

– Unforced State (Red)• Pauses between enter and exit executives• Waits for interrupt to break

Blocked

Blocked

Enter

Enter

Exit

Exit

< Execution Flow Thorough Unforced States>


Execution Flow through Combination of Unforced and Forced States

Invocation starts at top of exit executives of unforced states

Invocation starts at bottom of Enter executives of unforced states


State Transition diagram (Cont’d)


Initial state & transitions

• Initial state– Must be designed in each process model– Occur only once

• Transitions– Movement of a process from state to state and conditions under

which such changes may take places

(condition)/Executive


Transition Examples


Transition Examples (Cont’d)


Macro Definitions within Process Model Header Block


Variables

• State variable– Used to represent the information accumulated and retained by a

process– Require a memory allocation of corresponding size that will last as

long as the process exists

• Temporary variable– Used to store information that doesn’t require persistency– Doesn’t require additional memory

• Global variable– Used to provide a means for multiple processes in different

modules


Attributes

• Specify Characteristics of a process – Ex) time out duration, window size, max number of retransmission,

etc.


Attributes usage example


Node Domain


Node modeler example

• Ethernet Lan


Typical Node Models

• Work station– Generate and receive transfers of files or sparse packets and

manage several concurrent network connections

• Packet switch– Supports large numbers of incoming and outgoing data links and

performs packet routing at high speeds

• Satellite terminal– Generates and receives packets according to a CA protocol

• Remote data sensor– Acts as a simple source of packets, usually transmitting them in

bursts


Module definition

• Processor modules– Primary general-purpose building blocks of node models– Can be specified by process model attribute– Used to perform general processing of data packets

• Queue modules– Provide superset of the functionality of processor modules– Are related to memories


Module definition (Cont’d)

• Transmitter modules– Serve as the outbound interface between packet streams in side a

node and communication links outside node


Module definition (Cont’d)

• Receiver modules– Serve as the inbound interface between communication links

outside a node and packet streams inside the node


Connection definition

• Packet streams– Support the flow of data packets between modules– Three methods for transferring a packet and notifying arrivals

• Scheduled arrival– Is scheduled of the destination module– Occurs after all other events

• Forced arrival– Occurs immediately

• Quiet arrival– No stream interrupt occurs at all


Connection definition (Cont’d)

• Statistic wire– Unlike packet streams, it convey individual values– Individual values are used as an interface where the source module

and can share certain values with destination module – Each module within a node has a set of local input and output

statistics


Connection definition (Cont’d)

• Logical Associations– Do not actually carry data between modules– Do not exit during simulation, but used purely as specification

devices– Used to interpret structure


OSI/OPNET layering analogy


Network Domain


Project modeler example

• Office network


Network domain

• Define the overall scope of a system to be simulated• Size and scope of the networks modeled can range simple to

complex


Network objects

• Subnetworks– Provide a powerful mechanism to manipulate complex networks

structures and to break down the system’s complexity through abstractions

– Have Fixed, mobile, satellite types


Network objects (Cont’d)

• Communication nodes– Exits within a subnetwork and represents a network device with a

wide range of possible capabilities– Determined by node models– Have fixed, mobile, and satellite types


Network objects (Cont’d)

• Communication links– Allow communication of information between nodes in the form of

structured message called packets– Simplex, duplex point to point, bus and taps


Modeling node and subnetwork movement

• Trajectories– Vector based

• Direction and velocity

– segment based• Time and three dimension (x, y and altitude)


Simulation time-packet switching-

Documents

HyunJun Choi Aug 27, 2004 OPNET Simulator HyunJun Choi Aug 27, 2004 Informational Communication University