building realistic application models for discrete event simulation for opnet

CONFIDENTIAL RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc.

2007 OPNET Technologies, Inc.

Building Realistic Application Models for Discrete Event Simulation

R&D Solutions for Commercial and Defense Networks

Session 1586

CONFIDENTIAL RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc.

2010 OPNET Technologies, Inc.

2

1586 Building Realistic Application Models for Discrete Event Simulation

CONFIDENTIAL RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc. 2010 OPNET Technologies, Inc.

What Can You Expect from This Session?

Application ModelingModeling methodologiesTransaction Whiteboard in Real Application Simulation Module

Prediction studies and model validation

PrerequisitesFamiliarity with OPNET Modeler

3



Agenda

Application modeling methodologiesCreating application model in Transaction WhiteboardLab 1Application modeling basicsIntroduction to scripting in Transaction WhiteboardLab 2Sophisticated application logicApplication model analysis Lab 3How do I Review

4



Application Modeling Can Answer Questions

How will my application perform on my network?Setting response time expectations for new applications, baselines for existing applications

How will changes to existing applications affect my network?Will the existing network infrastructure support the changes?

How will changes to my network affect my existing applications?How will server consolidations and link upgrades affect response times?

5



Application Modeling Options

Standard applicationsMore information available in session 1418 (OPNK08)

Custom applications Multi-tier applicationsTasks and Phases

Application DemandsSimilar to IP flowsModel simple request response transactions

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Application Modeling Options (cont.)

Real Application Simulation ModuleTransaction Whiteboard Capture and import real world traffic Model real applications from capture data

Transaction WhiteboardUse an existing trace fileBuild from scratch (greenfield design)Model complex applications

New

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Using Transaction Whiteboard in Application Modeling

What is Transaction Whiteboard?Environment for creating application definitions for planning / prediction

When should you use Transaction Whiteboard?Modeling new applications

From scratch (greenfield design)Using sophisticated application logicFrom real world application capturesIn a service-oriented architecture (SOA) environment using Web Service Definition Language (WSDL) files

Modifying an existing application captured with ACE Analyst Real Application Simulation Module

Edit/modify existing traceChain applications

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Real Application Modeling Methodology

Predict/ValidateQuickPredict

AppDoctor/Application Delay TrackingDiscrete Event Simulation (DES)

Understand the applications behaviorPerform captures (existing application)Get specifications (new application)

Create/refine the application modelImport application (existing)Build from scratch (new)Create from WSDL file(s) (new)

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Agenda

Application modeling methodologiesCreating application model in Transaction WhiteboardLab 1Application modeling basicsIntroduction to scripting in Transaction WhiteboardLab 2Sophisticated application logicApplication model analysisLab 3How do I Review

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Creating Application Models from Packet Captures

Capturing real world application traffic using ACE Live or OPNET Application Capture agents

TransactionWhiteboard

Real Application Simulation

ModuleCapture Agent

New

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What Happens When You Open a Web Page in a Browser?

HTTP GET (rfc1945.html)HTTP responseRequest / response for each image on the page

Client

Web Server

HTTP GET(100 bytes)

Response(2000 bytes)

Tier Processing Delay(0.05 seconds)

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HTTP ExampleIn Transaction Whiteboard

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HTTP ExampleWhat Did We Really Do?

What are you defining?TiersMessagesDependencies

Created a logical definition of an applicationIndependent of any particular networkSequence of message sends glued together by dependenciesDeployment to DES maps logical tiers to physical nodes

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Data Exchange Chart

Primary editing spaceGraphical representation of

TiersMessagesDependencies

Timeline

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Message Editor

Tabular interface for editing message propertiesOnly selected messages appear

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What Types of Delays Does a Message See as it Crosses a Network?

Bandwidth delayTime it takes to stream all bits onto the linkThis number varies with message sizeCan be calculated from message size and link bandwidth

Latency delayTime it takes for signal (1 bit) to travel across network

Distance / speed of lightThis is a constant number for all messages

Protocol delay Protocol effects such as TCP slow start

Congestion delayQueuing on devicesCan vary from message to messageUnknown prior to running the application, can vary for each run

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5 seconds

30 seconds

Latency Delay

Bandwidth Delay

Network Delays (Example)

Example: Sending a 30,000-bit packetBandwidth = 1,000 bpsLatency = 5 seconds

Client

Server

T = 0

30,000 bits

10 20 30 40 50

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Slope

Convenience when creating the application modelBandwidth and latency delays only

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QuickPredict

Deploy application model on a virtual network

Answer what-if questionsCompare several virtual network conditions simultaneously

Refine the application model

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Review

Application ModelingWhy?How?

Application Modeling basics in Transaction WhiteboardTiersMessagesDependenciesData Exchange ChartMessage EditorSimple Network EstimationQuickPredict

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Agenda


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Lab 1: Overview

GoalTo determine the expected response time for downloading a large file

Unable to perform a packet capture

StepsRepresent the application model in Transaction WhiteboardUse QuickPredict to estimate the response time

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Lab 1: Review

Modeled the file download in Transaction WhiteboardUsed QuickPredict to understand the expected response timeDidnt need an ACE file to perform this study

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Agenda


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Connections

Why is it important to model connections?

Applications use connections in specific waysFTP

Control connectionData connection

HTTPSingle connection (HTTP 1.0)Multiple connections (HTTP 1.1)

In Transaction WhiteboardEvery message belongs to a connection

Source / destination ports are assigned at run time

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TCP Connections

How are connections handled during simulation?Opening connections

A TCP three-way handshake occurs in simulation the first time a connection is used

Closing connectionsBy default, connections are closed when the task is complete

You can explicitly close a connection using the Transaction Whiteboard scripting APIs

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UDP Connections

UDP connections are fundamentally different than TCP connectionsUDP does not provide reliable delivery of messages

Modeling challengeHow does the application know when a packet is lost?What should happen if a packet is lost?

How should this application behave? Is message 4 sent? When?

1 2 3 4

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Drop Response

Ignore packet dropThe application resumes after a timer expires

Parameters: timeout, continue flag

Acknowledgement basedACKs are sent to indicate that a packet was receivedPackets are retransmitted if an ACK is not received within a timeout periodParameters: timeout, ACK size, max number of retransmissions, continue flag

Negative acknowledgement basedNACKs are sent to indicate that a packet was not receivedPacket is retransmitted if an NACK is receivedParameters: timeout, NACK size, max number of retransmissions, continue flag

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Drop Response Configuration

Per Connection:

Per Message:

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Distributions

Introduce variabilityMessage sizeTier processing timeUser think time

Distribution typesExponentialUniformNormalPareto

Note: QuickPredict uses the mean value of the distribution

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Modeling Repeated Request / Response Patterns

How would you model the following chatty application1400 turns between web_server db_server

Each request is 50 bytesEach request is sent 0.002 seconds after receiving a responseEach response is 200 bytesEach response is sent 0.013 seconds after receiving a request

OptionsDraw ~1400 messagesCopy and paste ~1400 timesUse message groups

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Message Groups

Quickly define a request/response patternConverted to individual messages prior to simulation

Defining a message group

Total application turnsTotal application bytes Total application bytes Total processing at source tierTotal processing at destination tier

Colors represent the message size in each direction

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How is a Message Group Converted to Messages?

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Creating and Modifying Messages

Rapid message entry

Multi-level undo/redo

Tag

Multi-message editing mode

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Multi-Message Editing

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Agenda


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Modifying the Sequence of Actions Dynamically

What have we really defined in an application model?Sequence of message send actions glued together by dependenciesStatic definition of an applicationSequence of steps are always executed in the same order

But applications are complexApplication behavior isnt always known in advanceSequence of steps vary with each simulation runNetwork conditions can affect application behavior

Logic scripts can be used to model dynamic applications

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Logic Scripts

Python codeModify or add to the sequence of actions

Other opportunities to write Python codeHeader BlockInitialization BlockFunction Block

Logic scripts are interpreted during simulation

QuickPredictDiscrete event simulation (DES)

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Example: Home-Grown Calendar Application

Consider the following home-grown calendar applicationUsers can request to view by

Day (10K)Week (100K)Month (500K)

Same application, the only difference is the size of the response

Modeling optionsCreate three Transaction Whiteboard filesImport one of the ACE files into Transaction Whiteboard and thenparameterize the response size

We will take this approach

40



Adding Parameters to an Application

Why?Change the applications behavior in the project editorModel reuseSave time

What can be parameterized?Message sizeWait timeAnything

MethodologyDeclare the parameterWrite logic scriptGive the parameter a value during deployment

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Declare the Parameter

Scripting / Declare ParametersNameTypeDefault valueDescription

Value can be changed in the project editor

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Write Logic Script

Insert a logic scriptRight-click on dependencyAdd Logic Script

Write code that uses the parameter

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Give the Parameter a Value During Deployment

Application deployment in DES Task Definition objectTask SpecificationEdit ACE Parameters

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Review: Adding Parameters to an Application

Why?Change the applications behavior in the project editorModel reuseSave time

Anything can be parameterized

MethodologyDeclare the parameterWrite logic scriptGive the parameter a value during deployment

45



Agenda


46



Lab 2: Introduction

OverviewStudy a web page which erroneously sends a large image fileGiven a capture for above page being downloaded by client

ObjectiveUse Transaction Whiteboard to model the corrected size of big imageUsing QuickPredict compare the download time for dial-up and broadband users.

StepsImport capture file into Real Application Simulation ModuleCreate a Transaction Whiteboard file from packet captureParameterize the size of the big image in the web pageUse QuickPredict to determine the download time

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Lab 2: Review

Summary:Created application model by capturing real world traffic using Real Application Simulation ModuleParameterized the size of the big image transaction

Declared the parameterWrote logic script that used the parameter

Determined the response time for HTTP transaction

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Agenda


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What Can You Do in a Logic Script?

BasicAccess parametersModify unsent messages

SizeCPU timeUser time

Collect custom statistics

For more informationTransaction Whiteboard Scripting API section of the ACE Analyst User Guide

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What Can You Do in a Logic Script? (cont.)

AdvancedCreate messages on the flySchedule interrupts (timeout, message received)Loop (for loop, goto)Invoke a child taskDynamic tier mapping (ie: custom load balancing)Trigger server and mainframe jobs in a discrete event simulation

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Supported Classes and Methods

To obtain information about an executing taskCreate or modify actionsManage child tasks

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Example: Modeling a Chatty Database Application

Modeling the performance of a customer tracking database

You have a capture of the applicationSimple query results in many repeated SQL requests

Number of customers is expected to triple in 2012

So will the number of requests!

How does the response time vary if we change the number of SQL requests?

Will the application scale?

ACE Trace

53



Chatty Database Application (Approach #1)

Dynamically repeat a portion of the application definition (goto)

Tag first and last messages of patternDeclare a parameter for the number of times we want to loopWhen the last message is received, goto the first message

Increment our loop countOnly loop back if the loop count is less than our parameter

def last_message_received (self):num_rows = self.get_parameter ('num_rows')if (self.loop_count < num_rows):

self.loop_count = self.loop_count + 1first_message = self.get_message ('first_message')self.goto_action (first_message)

last_message = self.get_message ('last_message')self.register_receipt_callback (last_message, self.last_message_received, ())

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Chatty Database Application (Approach #2)

Dynamically create the pattern of messages Nest the pattern within a for loop

Declare a parameter for the number of times we want to loop

Messages do not appear in the Data Exchange Chart num_requests = self.get_parameter ('num_rows')

message = Nonefor i in num_requests:

message = self.create_message (21, 'Oracle_Client', 'Oracle_Server' message)message = self.create_message (16, 'Oracle_Server', 'Oracle_Client' message)message.cpu_time = .000752message = self.create_message (111, 'Oracle_Client', 'Oracle_Server' message)message.cpu_time = .000737message = self.create_message (56, 'Oracle_Server', 'Oracle_Client' message)message.cpu_time = .001170message = self.create_message (258, 'Oracle_Client', 'Oracle_Server' message)message.cpu_time = .001109message = self.create_message (124, 'Oracle_Server', 'Oracle_Client' message)message.cpu_time = .001591message = self.create_message (17, 'Oracle_Client', 'Oracle_Server' message)message.cpu_time = .000719message = self.create_message (11, 'Oracle_Server', 'Oracle_Client' message)message.cpu_time = .000764message = self.create_message (17, 'Oracle_Client', 'Oracle_Server' message)message.cpu_time = .0001176message = self.create_message (11, 'Oracle_Server', 'Oracle_Client' message)message.cpu_time = .0000930

size sender receiver parent action

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Chatty Database Application (Review)

Accessed a parameter

Scheduled a message received interruptLooped using goto

Created messages on the flyLooped a for loop

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Example: Adding a Front-End to an Existing Database Application

Extend analysis of customer tracking database to study deployment over a WAN

New front-endBack-end exists as a separate file

Modeling goalsNetwork impactResponse time

How should we model this application?

Front-end application model

Back-end application model

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Stitching in Child Task

Invoke the existing fileChild is stitched into the parent fileParent can pass parameters down to the child

action task name is blocking parameters

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Combining Two Transactions

+

What would the composite application look like?client

app_server

db_server

app_server

59



Blocking vs. No-Blocking Mode

Blocking:

Non-blocking:

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Invoking Child Task: Declare Child Tasks

Declare the child taskRequired stepMap tier names

Actual tier name doesnt need to exist in the parent task

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Three-Tier SQL Application (Review)

Example of application chainingAllows one task file to invoke anotherReusability of existing filesBlocking vs. non-blocking

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Agenda


63



Custom Statistics

Modeling studies are not limited to response time analysisAnalyze response time of sub-components of an applicationTrack the number of times a particular event happens

Logic scripts allow user to define custom statistics

Statistic are selectable and can be collected in discrete event simulation (DES) see Lab 3

64



Application Delay Tracking

AppDoctor for discrete event simulation (DES)

Tells the story of a packetAnalyze components of delayIdentify problems quickly

Answers the following questionsDid my application spend more time processing at the application layer or in the network layer?What intermediate nodes or links were the largest bottlenecks?Where were application packets dropped?What are my slowest applications?

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Application Delay Tracking (cont.)

Selective enable on a per profile basis on client workstations

Interactive tree with drill down capabilities

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Packet Analyzer and AppDoctor

Capture in DES environment (creates .csv file)Import the CSV trace (into Real Application Simulation Module)Analyze the delay components that contribute to the total response time of the application

Real ApplicationSimulation

Module

Packet Analyzer AppDoctor

67



Agenda


68



Lab 3

GoalTo find out how much of the total response time is due to the big image for broadband users

StepsWrite logic scripts to define custom statisticsImport the model into DESRun simulation and analyze results

69



Defining and Deploying Application

Task DefinitionApplication DefinitionProfile DefinitionSupported Profiles, Supported ServicesDestination Preferences, ACE Tier ConfigurationApplication deployment wizardMore info in Session 1418 (OPNETWORK 08)

70



Lab 3: Review

Comparison: Original Vs Corrected

Parameters give you the flexibility to re-use whiteboard file in multiple scenariosCustom statistics provides greater control in how you study your application

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Agenda


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How Do I Model Custom Load Balancing?

Deploying an application in the Project EditorIssue: you may not know which physical node to map a given logical tier to when the application begins

What happens if you try to go to www.google.com from Chile?

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How Do I Model Custom Load Balancing? (cont.)

What happens if you try to go to www.google.com from Chile?Automatically redirected to www.google.cl

HTTP global load balancingThree-tier application

Similar to DNS

Client doesnt pick its server until mid-way through the transaction

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Declare and set the attribute in the Project Editor

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Use a logic script to determine the physical deployment for the logical tier web_server

client_node = self.get_tier_node ('client')client_location = client_node.get_attr ('Location', 'USA')

server_nodes = self.get_nodes_compatible_with_tier ('web_server')

for i in range (server_nodes):server = server_nodes [i]server_location = server.get_attr ('Location', 'Unknown')if (client_location == server_location):

self.set_tier_node ('web_server', server)break

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How Do I Create Flows From My Transaction Whiteboard Files?

Deployed ACE traffic can be converted into IP traffic flowsToggle to convert ACE traffic to IP traffic flowsThe IP traffic flow will replace the ACE discrete trafficCan be converted back to ACE traffic (discrete). This removes the IP traffic flows that were converted earlier.

77



How Do I Add Back-End Traffic?

Four-tier applicationOnly able to capture traffic from the first three tiersDelay due to interaction with fourth tier is attributed as tier processing on the third tier

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How Do I Add Back-End Traffic? (cont.)

Import into WhiteboardInsert TierInsert Message GroupChange the parent dependency of the response from app server to web serverChange the processing time of the response

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Agenda


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What Have We Learned?

Approaches for modeling real world applications

Real Application ModelingBasic conceptsAdvanced conceptsTransaction WhiteboardLogic scripts

Parameterize a portion of an application modelComplex application logic

LoopingApplication chainingDynamic message creation

81



Whats New in 16.0

Real Application Simulation ModuleExtends Modeler with new application design and analysis featuresProvides a complete end-to-end solution for real world application modelingAdds ability to capture real trafficAppDoctor

New

82



Documentation References

Product documentationHelp / Product Documentation (F1)

Transaction Whiteboard TutorialsACE Analyst User Guide

OPNET Support Centerhttp://www.opnet.com/supportContributed modelsFAQs

1379: What are some tips for getting started with the ACE Whiteboard?

Sample Transaction Whiteboard FilesSys / examples /ACE Analyst / examples /_*

TAs will be available following the session

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Related OPNETWORK Sessions

OPNET Application Modeling courses1418: Modeling Applications using the "Standard Application" Models (from OPNETWORK 2008)1402: Planning Application Deployments with ACE Analyst1396: Introduction to Python Programming Language

Other related sessions1443: Customizing Analysis and Visualization in ACE Analyst 1404: Troubleshooting and Predicting the Impact of TCP on Application Performance with ACE1701: ACE Analyst User Feedback Forum 1433: Troubleshooting and Predicting the Performance of Web Services (SOAP, XML-RPC, REST) with ACE (from OPNETWORK 2008)

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Take-Away Points

Real Application Simulation Module capabilities

What is Transaction Whiteboard?Environment for creating application definitions for planning, simulation and analysis

What can I do with Transaction Whiteboard?Create an application from scratch (greenfield design)Modify an application captured with Real Application Simulation ModuleModel sophisticated application logic

AppDoctorProvides insight into various delays which contribute to application response time

building realistic application models for discrete event simulation for opnet

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