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Network SimulationChapter 2: OPNET– A Tool for Discrete Event Simulation (DES)

Prof. Dr. Jürgen Jasperneite

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Lecture Objectives

• Learn how OPNET can be used for– Application troubleshooting– Network planning and design– Operational validation

• Understand and be able to explain the value of OPNET• Get a hands-on learning experience and learn various

OPNET features

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OPNET

• OPtimised Network Engineering Tools– OPNET for short– http://www.opnet.com/

• General-purpose tool for discrete event simulations• Object-oriented design• The simulator can be used for:

– traffic modeling of telecommunication networks– protocol modeling– modeling queueing networks– modeling multiprocessors and other distributed hardware systems– validating hardware architectures– evaluating performance aspects of complex software systems– . . . modeling any other system where the discrete event approach

is suitable.

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Where is OPNETin the world of simulation tools?

• There are a lot of network simulation tools available:– Non-commercial:

• SMURPH www.cs.ualberta.ca/~pawel/SMURPH/smurph.html

• NS www.isi.edu/nsnam/ns/

• NetSim++• OMNET++ www.omnetpp.org• .....

– Commercial:• COMNET III• OPNET www.opnet.com -> state of the art• ...

– Here we use the academic version IT Guru !2:O

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The Virtual Network Environment (VNE)

Virtual Network EnvironmentReplicates the behavior of your entire network,

including its routers, switches, servers, protocols,and individual applications

Traffic,Topology, andConfigurations Planning

Improve price /performance

Operational Validation

Reduce costly mistakes

Troubleshooting

Identify problems faster

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Examples of Problems Solved

• IT Guru can be used to– Identify problems

• Increasing traffic loads by 20% causes unacceptable FTPresponse times

• If the Chicago router fails, the Seattle router becomesoverloaded

• The link between Seattle and Portland averages 10% utilization

– Pinpoint causes• The FTP server is not fast enough• More traffic than expected is being routed through Seattle

– Test solutions• Where is the best location for a new server?• Which router configuration will give the best performance?

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Discrete Event Simulation Workflow

• Create/import topology/configuration• Create traffic• Choose statistics• Run simulation• View results• Duplicate or create new scenario• Publish results

Iterate

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DES Example: Technology Migration

• Problem: Voice-over-IP applicationschoppy

• Cause: Voice packetdelay variation

• Potential solution:Understand theeffect of adding IPQoS

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DES Example: Protocol Behavior

• Problem: Large file transferstoo slow

• Upgrading from T1 (1.544Mbps) to T3 (44.7 Mbps) linksis costly, and moreimportantly, does not help

• Cause: TCP is throttlingthroughput

• Solution: Modify TCP windowsize

• Cost: $0

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• Capture traffic• Import packet trace file(s)• Visualize application behavior• Diagnose problems• Explore potential solutions• Document application analysis• Import into IT Guru for analysis

ACE Workflow

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ACE: Application Characterization Environment

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Summary

• IT Guru can predicts performance of infrastructure byaiding in– Application analysis– Application deployments– Capacity planning– Technology migration– Understanding protocol behavior– Identifying network configuration errors– Failure analysis– Device change management2:

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Workflow (not limited to IT Guru)

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IT Guru Workflow

• Projects and Scenarios– Startup Wizard

• Building Topologies– Creating Topologies– Network Object– Model Libraries– LAN and Cloud Objects– Object Attributes– Model Architecture– Subnets

• Creating Traffic• Choosing Statistics• Viewing Results2:

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Project Editor and Topologies

• Project Editor– Networks are modeled and created in this editor– The first step is to specify project and scenario names and select

how to create the topology

• Topology can be created or imported from– Empty Scenario - built manually– ACE traffic file– Device Configuration files– Circuit Switched Text files– ATM Text files– XML

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Capacity Planning Project

Baseline Scenario

Scenario WithUpgraded Links

Baseline ScenarioWith Doubled Traffic

Projects and Scenarios

• A scenario is a snapshot of the entire networkconfiguration, topology,and traffic

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IT Guru Workflow

• Projects and Scenarios– Startup Wizard

• Building Topologies– Creating Topologies– Network Object– Model Libraries– LAN and Cloud Objects– Object Attributes– Model Architecture– Subnets

• Creating Traffic• Choosing Statistics• Viewing Results2:

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What Is a Topology?

• Organized set of network objects• Defines

– Node location– Connectivity– Configuration

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Creating a Topology

• Topologies can be built manually or imported• To build manually:

– Choose appropriate node and link objects– Position nodes and links– Set node and link attributes

• To import:– Use third-party software to gather topology information– Import into IT Guru– Fine-tune and verify the model– Create Model Assistant file to streamline future imports

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3 Subnet Types

Subnets

• Organizes network components• Represents actual network physical constructs• No behavioral aspects• Stationary, mobile or satellite

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Choosing Network Objects

• Object Palettes– A catalog of different network devices

• Utility objects– Simplify the setup and configuration of network model

• Standard models– Generic network devices

• Vendor models– Vender specific network devices

• LAN objects– A network object that represents a LAN entity

• Cloud objects– Represents a cluster of routers or ISP

• Attributes– Device inputs that control its behavior

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Network Domain: Network Objects

Generic Devices

• Network models consist of nodes, links and subnets• Nodes represent network devices and groups of devices

– Servers, workstations, routers, etc.– LAN nodes, IP clouds, etc.

• Links represent point-to-point and bus links• Icons assist the user in quickly locating the correct nodes and links• Vendor models are distinguished by a specific color and logo for each

company

Vendor Devices

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Subnets

• Contain segments of the network• Add hierarchy to model• Provide geographical and logical organization• Not related to IP subnets

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Device Models

• The Standard Model Library comprises the majority ofobjects

– Routers– Switches– Hubs– Workstations– Servers– Firewalls– Load Balancers– Printers

• Models represent both hardware and software – fullprotocol stacks are modeled

Graphical conventions for network objects

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Cloud Models

• Cloud models represent backbone networks• Helpful for modeling packet transmission through an external network

or ISP• Clouds have attributes such as Latency and Packet Loss Ratio• ATM and Frame Relay clouds support PVCs through the network

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Object Attributes

Object attributes control device behavior.All objects have attributes.

Right-click

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Model Architecture

• Within each IT Guru model is a fullprotocol stack

• Each protocol is modeled individuallyto simulate exactly the protocol’sspecified behavior

• All models are thoroughly tested forhigh fidelity

• Demo:– Explore Model Architecture with OPNET

Modeler

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Node Domain

• Basic building blocks (modules) include processors,queues, and transceivers

– Processors are fully programmable via their process model– Queues also buffer and manage data packets– Transceivers are node interfaces

• Interfaces between modules– Packet streams– Statistic wires

Receiver Transmitters

Processor

Queues

Stat WirePacket Stream

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Process Domain

• Process model components– State transition diagrams– Blocks of C code– OPNET Kernel Procedures (KPs)– State variables– Temporary variables

• A process is an instance of a process model• Processes can dynamically create child processes• Processes can respond to interrupts

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Background Maps

Map backgrounds addgeographical context and makemodels easy to interpret

TIFF, MIFF (MapInfo), andGEOTIFF image maps canbe imported, as shownbelow

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IT Guru Workflow

• Projects and Scenarios– Startup Wizard

• Building Topologies– Creating Topologies– Network Object– Model Libraries– LAN and Cloud Objects– Object Attributes– Model Architecture– Subnets

• Creating Traffic• Choosing Statistics• Viewing Results2:

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Common Networked Applications

• To represent a person using e-mail and downloading files:– Edit Application Config node to support email and FTP– Define the level of use or use a predefined level– Define a user in the Profile Config node that uses the email and FTP

applications you just configured– Set the client to support the user profile you just created– Set the server to support the email and FTP applications

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Common Networked Applications

• Includes various networkapplications with pre-defined load levels

• View and edit these settingsby selecting a predefinedload and then selecting“Edit…”

Off, PCM Quality Speech, PCM Quality and SilenceSuppressed, Low Quality Speech, Low Quality andSilence Suppressed, IP Telephony, IP Telephony andSilence Suppressed, GSM Quality Speech, GSMQuality and Silence Suppressed, Edit

Voice

Off, Low Resolution Video, High Resolution Video,VCR Quality Video, Edit

Video Conferencing

Off, Low Load, Medium Load, High Load, EditRemote Login

Off, Text File, B/W Images, Color Prints, EditPrint

Off, Light Browsing, Heavy Browsing, Searching,Image Browsing, Edit

HTTP

Off, Low Load, Medium Load, High Load, EditFTP

Off, Low Load, Medium Load, High Load, EditEmail

Off, Low Load, Medium Load, High Load, EditDatabase

Off, EditCustom

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IT Guru Workflow

• Projects and Scenarios– Startup Wizard

• Building Topologies– Creating Topologies– Network Object– Model Libraries– LAN and Cloud Objects– Object Attributes– Model Architecture– Subnets

• Creating Traffic• Choosing Statistics• Viewing Results2:

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Choosing Statistics

• Before running a simulation, choose statistics that will helpanswer your questions about the network

• Also choose statistics that will validate your network modeland ensure its accuracy

• After running the simulation, view graphs for thosestatistics you chose

• Four types of statistics are available- Global Statistics- Node Statistics- Link Statistics

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Choosing Statistics – Global Statistics

• Represents values for all nodes in the network• Use global statistics to look at overall performance of

applications or protocols• Example: End-to-End Delay for all HTTP web page

downloads• To collect global statistics

– DES / Choose Individual Statistics /Global Statistics

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Choosing Statistics – Node Statistics

• Information specific to each individual node• Examples: End-to-End Delay for all HTTP web page

downloads from a particular workstation or server CPUutilization for each server

• Collect node statistics on allrelevant nodes at once oron individual nodes

• To collect a statistic on all nodes,use:

– DES / Choose Individual Statistics /Node Statistics

• For a specific node: Right-clickon the node, ChooseIndividual Statistics

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Choosing Statistics – Link Statistics

• Similar to Node Statistics• Statistics of point-to-point or

bus links such as throughput,utilization, packet loss ratio,and queuing delay

• To collect a statistic on all links:DES / Choose IndividualStatistics / Link Statistics

• To collect a statistic on aspecific link: Right-click the link,Choose Individual Statistics

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Configuring and Running Simulations

Number of values to becollected for each statistic

Values PerStatistic

Random numbergeneration seed

Seed

Execute the simulation forthis scenario

Run

Duration of simulation, insimulated time

Duration

DescriptionName

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IT Guru Workflow

• Projects and Scenarios– Startup Wizard

• Building Topologies– Creating Topologies– Network Object– Model Libraries– LAN and Cloud Objects– Object Attributes– Model Architecture– Subnets

• Creating Traffic• Choosing Statistics• Viewing Results2:

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Plotting Results

• Sometimes it might be useful to view multiple results at once• Multiple graphs can be displayed within the same graph panel in a

stacked or overlaid format

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Applying Filters to Results

• Variety of mathematical filters can be applied to results data• “As Is” filter is the default and represents the raw data (as if there is

no filter)• “Average” filter is

commonly used to plot therunning sample mean of theraw results data

• You can view filtered tracesin a new graph panel, or addtraces to existing graphpanels

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Comparing Results Between Scenarios

• Comparing Results automatically selects and presents thecorresponding results from all other scenarios

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Summary IT Guru

Virtual NetworkEnvironment

Traffic,Topology, andConfiguration

Application Trace

DES: Simulates precise protocol effects for capacity planning, tuning protocolbehavior, response time engineering, technology migration, QoS, etc.

ACE: Application performance troubleshooting: visualize performance,diagnose problems, explore solutions

MVI, VNES, GUI

Sniffer, OPNET Application Capture Agent, etc.

Graphs, web reports,charts, for all time-varying networkperformance metrics(e.g., app response time,queue depths,convergence time,protocol behavior, etc.)

DES

Application Visualization,Diagnosis, Analysis,Protocol Decodes

ACE