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ACE User Guide 5 Predicting Application Performance

Application Characterization Environment/Release 10.0 ACE-5-1

5 Predicting Application Performance

ACE leverages OPNETs predictive modeling technology to help you determinehow variations in your application and network will affect your applicationsperformance. ACE includes four separate predictive features:

QuickPredictThis feature allows you to quickly determine how networkvariations will affect your applications performance. This allows you toanswer questions such as, How will my application be affected if I double theavailable bandwidth between two tiers? See QuickPredict on page ACE-5-3for more information.

QuickRecodeThis feature allows you to quickly determine how variationsin your application will affect its overall performance. You do this by manuallyediting your application task to create a hypothetical application andcomparing its performance to the original. This allows you to study questionssuch as, How will my application be affected if my database could transmita record in 30 messages, rather than the current 300? See QuickRecode on

page ACE-5-13 for more information.

ACE discrete-event simulationsYou can create network scenarios basedon ACE tasks. You can then take full advantage of OPNET event-basedsimulation engine and model library to test your application in a wide varietyof network scenarios. For example, you can create a virtual deployment ofan FTP application to test the effects of multiple downloads on theapplications overall response time. See ACE Discrete-Event Simulations onpage ACE-5-15 for more information.

ACE traffic flowsGiven an existing network, you can import end-to-endtraffic directly from ACE. You can also scale the ACE traffic to model the

effects of multiple iterations on a single node or multiple nodes. ACE trafficflows are especially useful when you want to study the effects of massivedeployments, in which a discrete-event simulation of hundreds or thousandsof transactions would require too much time or memory. See ACE TrafficFlows on page ACE-5-23 for more information.


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ACE-5-2 Application Characterization Environment/Release 10.0

Important Notes

This section includes notes about the different predictive features in ACE.

Real-World Applications vs. QuickPredict and Discrete-Event Simulations

QuickPredict and discrete-event simulations start with a pure model of an

applications behavior, without regard to the underlying network. The ACEprediction engine filters out network effects that the agent observed when itcaptured the application. For this reason, your ACE prediction results (such asapplication response times) might differ from those observed in your real-worldnetwork. To directly compare your observed application behavior againstQuickPredict or discrete-event simulations, you must make sure that yournetwork settings in ACE (such as packet loss, TCP window size, etc.) accuratelyreflect conditions in your network.

QuickPredict produces typical response times, while there might be no suchthing as a typical response time in your network. If your network is

experiencing packet loss, multiple runs of a transaction over TCP can producea significant range of response times. This happens because TCP is highlysensitive to the type of packets that are being lost. A lost ACK(acknowledgement) packet does not typically affect response time, but a lostSYN (connection open) packet can delay the response time by 3 seconds ormore.

QuickPredict vs. Discrete-Event Simulations

You can do predictive analyses of an application using both QuickPredict anddiscrete-event simulations. Here are the primary distinctions between thesemethods:

As its name implies, QuickPredict provides instant or near-instant results. Adiscrete-event simulation might take several minutes or more to produceresults (depending on the complexity of your scenario).

Because it uses analytical simulation, QuickPredict produces less accurateresults than a discrete-event simulation.

QuickPredict can predict the effects of five factors (bandwidth, latency, linkutilization, packet loss, and TCP window size) on each tier-pair connection inan ACE task. This is a small subset of the what-if scenarios you can testusing discrete-event simulation.

QuickPredict uses a different definition of packet loss from that used inOPNETs simulation kernel. In QuickPredict, the packet-drop rate indicatesthe tail-drop point at which all further packets in a particular message floware dropped (for example, due to an overflowed buffer).


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Traffic Flows vs. Discrete-Event Simulations

You can simulate an applications performance using both traffic flows importedfrom ACE and discrete-event simulations (as described in ACE Discrete-EventSimulations on page ACE-5-15). ACE traffic flows can speed up discrete-eventsimulations.

ACE flows are often preferable when modeling large application deployments,because discrete-event simulations might require large amounts of time andcomputer memory. For example, suppose you want to virtually deploy an ERPapplication on dozens or hundreds of remote clients. A discrete-eventsimulation for such a scenario could generate an extremely high number ofsimulation events and require several hours to complete.

QuickPredict

QuickPredict enables you to quickly determine how varying bandwidths,

latencies, and other network parameters will affect application performance.You create what-if scenarios by varying the characteristics of one or morenetwork paths. QuickPredict shows the results using a standard OPNETanalysis panel (x-y graph).

Using QuickPredict

The following diagram shows the basic QuickPredict Control window, which youopen by choosing AppDoctor > QuickPredict. The basic idea of QuickPredict isthat you vary the parameters for a particular network path; then you click UpdateGraph to see how these variations affect the application response time (y axison the resulting graph).

Figure 5-1 QuickPredict ControlBasic Dialog Box

The X Axis radio buttons determine which of the available parameters(Bandwidth or Latency) will form the x axis in the resulting graph. You can thenmodify the non-x-axis parameter using the edit field or the slider.

1. Choose path

to modify

2. Choose x-axis

parameter and

range

3. Vary other

parameters for the

selected path

4. View results


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Viewing Results

The QuickPredict results graph shows how the network parameter you specifiedwill affect your applications response time (y axis). Changes to the non-x-axisparameter value made with the slider are reflected in the graph immediately;click Update Graph to view the effects of other changes.

You can add another result to the active graph by clicking Add Curve(s) beforechanging a parameter value; this allows you to directly compare the effects ofdifferent parameter settings in the same graph. (Note that a graph can showmultiple results only if they share the same x-axis; if you specify a new x-axisparameter, QuickPredict shows the result in a separate graph.)

Figure 5-2 Sample QuickPredict Results

Publishing Results

You can publish QuickPredict results in an ACE web report ( File > GenerateACE Web Report) or a Microsoft Word report (File > Generate MS Word Report(.rtf)) . These reports include all open graphs and the parameter settings foreach network path.

To export your results to a spreadsheet program like Excel, right-click in a graphand choose Export Graph Data To Spreadsheet.

Default results graph with curve for one

latency value

Added Curve results in graph with curves for two

latency values


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Control Panels: Basic, Advanced, Table, and Bar Chart

QuickPredict provides four different control panels you can use to specifyparameters:

Basic control panelWhen you start QuickPredict (by choosing AppDoctor> QuickPredict), the Basic control panel appears. It is useful for studying the

effect of bandwidth and latency variations over a single network path (seeBasic Control Panel on page ACE-5-6 for more information).

Advanced control panelYou can open this window by clicking Advancedin the Basic or Table View control panel. This control is similar to the Basiccontrol panel, but with the following additional capabilities:

Allows you to modify all possible parameters (bandwidth, latency, linkutilization, packet loss, and TCP window size) on a specific network path.

Provides control over the number of data points calculated.

This control panel is useful for more detailed what-if scenarios over a singleconnection (see Advanced Control Panel on page ACE-5-7 for more

information).

Table View control panelYou can open this window by clicking TableView in the Basic or Advanced control panel. This control panel allows youto view and modify all parameter settings for all network paths in theapplication task. It is useful for what-if scenarios that involve variations onmultiple network paths (see Table View Control Panel on page ACE-5-9 formore information).

Bar control panelTo open this window, choose AppDoctor > QuickPredictBar Chart in the ACE Treeview or the Data Exchange Chart. This windowdivides the total predicted response time into components of processing time

and delay. You can also compare multiple scenarios directly, and createtemplates of your QuickPredict settings (see QuickPredict Bar Chart Panelon page ACE-5-11 for more information).

Keep in mind that all network paths in your application task have the same setof parameters. These three control panels differ primarily in the number ofparameters and paths they show.


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Basic Control Panel

To open the Basic control panel, choose AppDoctor > QuickPredict. This controlallows you to specify bandwidth and latency variations on a single network pathat a time.

Figure 5-3 QuickPredict ControlBasic Control Panel

The following table describes, in alphabetical order, the controls available in theBasic control panel.

Table 5-1 QuickPredict ControlBasic Controls (Part 1 of 2)

Control Description

Add Curve(s) Retains the current curve in the active graph and addsa new result curve that will reflect future changes to thesettings.

NOTE: If you specified a different parameter for thex-axis, QuickPredict shows the results in a differentgraph.

Advanced Switches to the Advanced control panel.Choose Network Path toModify

Selects the network path whose performance you wantto study.

Choose Values Specifies a value for the remaining non-x-axisparameter.

NOTE: If you enter a new value in the edit field, youmust click Update Graph to show the result of thischange. If you use the slider, the result graph updatesautomatically.

NOTE: You can change the minimum/maximum rangefor a parameter slider by clicking in the range fieldsbeneath the slider.

Close Exits QuickPredict.

Compare Imports another ACE task into QuickPredict to comparewith the current task.

NOTE: Use this feature only with tasks that are directlycomparablethat is, for tasks that record variations onthe same application and were captured over the samenetwork tiers.


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Advanced Control Panel

To open the Advanced control panel, click the Advanced button in the Basicor Table View QuickPredict Control window. This control panel allows you tomodify all available parameters on a single network path at a time.

Figure 5-4 QuickPredict ControlAdvanced Control Panel

Min

Max

Sets the minimum or maximum range of the x-axisparameter.

Table View Switches to the Table View control panel.

Update Graph Updates the active graph to reflect the currentparameter settings.

X Axis Specifies which parameter (Bandwidth or Latency) touse for the x axis of the result graph. (The y axis isalways application response time.)

End of Table 5-1

Table 5-1 QuickPredict ControlBasic Controls (Part 2 of 2)

Control Description


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The following table describes, in alphabetical order, the controls in theAdvanced control panel.

Table 5-2 QuickPredict ControlAdvanced Controls

Control Description

Add Curve(s) Retains the current curve in the active graph and adds

a new result curve that will reflect future changes to thesettings.


Choose Network Path toModify

Selects the network path whose performance you wantto study.



NOTE: Use this feature only with tasks that are directlycomparablethat is, for tasks that record variations on

the same application and were captured over the samenetwork tiers.

Min

Max


Number of Data Points Specifies the number of data points that QuickPredictgenerates for the results curve.

Parameters Specifies values for the remaining non-x-axisparameters. (Controls for the current x-axis parameterare disabled.)

NOTE: If you enter a new value in the edit field, youmust click Update Graph to show the result of this

change. If you use the slider, the result graph updatesautomatically.

NOTE: You can change the minimum/maximum rangefor a parameter slider by clicking in the range fieldsbeneath the slider.

Table View Switches to the Table View control panel.


X Axis Specifies which one of the five parameters to use forthe x axis of the result graph. (The y axis is alwaysapplication response time.)

End of Table 5-2


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Table View Control Panel

To open the Table View control panel, click the Table View button in the Basicor Advanced QuickPredict Control window. This control panel allows you tomodify all available parameters on all network paths in the task.

Figure 5-5 QuickPredict ControlTable View Control Panel

The following table describes, in alphabetical order, the controls in the TableView control panel.

Table 5-3 QuickPredict ControlTable View Controls (Part 1 of 2)

Control Description

Add Curve(s) Retains the current curve in the active graph and addsa new result curve that will reflect future changes to thesettings.


Advanced Switches to the Advanced control panel.



NOTE: Use this feature only with tasks that are directly

comparablethat is, for tasks that record variations onthe same application and were captured over the samenetwork tiers.

Min

Max


Number of Data Points Specifies the number of data points that QuickPredictgenerates for the results curve.

Red text

and range

indicate

current

x-axis

parameter.

Left-click a

parameter

cell to set

its value.


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QuickPredict Bar Chart

The QuickPredict Bar Chart window is similar to the QuickPredict Table view,but has these additional features:

In addition to predicting application response time in a scenario, this Chartbreaks down the total application response time into separate componentsof application processing time and network delay (propagation, transmissionand protocol/congestion delay).

In this window, you can save and load templates of your network settings.This makes it easy to reuse your network conditions and compare resultswith new condition settings.

Parameter Table Shows all parameters of all network paths (tier pairs).The parameter used for the x axis is shown in red withits range of values.

NOTE: If you enter a new value for a parameter, you

must click Update Graph to show the result of thischange.

Set X-Axis Uses the selected parameter for the x axis of the resultsgraph. (To select a parameter, right-click on it.)

NOTE: You can also specify a parameter for the x axisby left-clicking it and choosing Put on x axis from thepop-up menu.


End of Table 5-3

Table 5-3 QuickPredict ControlTable View Controls (Part 2 of 2)

Control Description


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QuickPredict Bar Chart Panel

To open the QuickPredict Bar Chart, choose AppDoctor > QuickPredict BarChart in either the ACE Treeview window or the Data Exchange Chart. As in theTable view, you can modify all available parameters on all network paths in thetask.

Figure 5-6 QuickPredict ControlBar Chart Control Panel

Left-click a parameter

cell to set its value, then

click Update Results

To put a parameter on the

slider, left-click in the cell

and choose Put on Slider


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The following table describes, in alphabetical order, the controls in the TableView control panel.

Table 5-4 QuickPredict ControlBar Chart View Controls

Option/Field Description

Add Scenario Add a new scenario to the QuickPredict results. In this case, a scenario

means a new set of network parameters for the same application.

Compare Imports another ACE task into QuickPredict to compare with the current

task.

NOTE: Use this feature only with tasks that are directly

comparablethat is, for tasks that record variations on the same

application and were captured over the same network tiers.

Graph Options Label categories larger than X percentUse this option to label

components that account for X percent or more of the total delay time.

Show SLAIf you specify an SLA (in seconds), the SLA threshold

appears as a vertical line in the bar graph. This makes it easy to see if

the application violates an SLA in a specific scenario.

Load Template Load a scenario from a template file

Parameter Slider You can use this slider to see immediately how changes in a single

parameter affect the total application response time as well as the

relative amounts of network vs. application delay.

To put a parameter in this slider, click in the parameter cell and choose

Put on slider from the pull-down menu.

To specify a range for the slider, enter minimum and maximum values in

the fields below the slider. You can also set the slider using the Value

field above the slider.

Save Template Save the current settings for all scenarios to a template file

Tabular Results

Bar Charts

View the QuickPredict results in in a table

View the QuickPredict results in bar charts

Update Results Update the bar charts and the tabular results to reflect the current

parameter settings.

NOTE: You must click this button after you change a parameter setting

in the table.

End of Table 5-4


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QuickRecode

QuickRecode enables you to manually edit parts of an ACE task; you can thenpredict the behavior of your hypothetical application using either QuickPredictor event-based simulation. Using this approach, you can determine the effectsof specific changes in an application without changing the actual code.

Note the following considerations:

When you run QuickPredict on an edited application, ACE calculates andshows results for both the original and the edited application.

When you import an edited application into OPNET (Topology > ImportTopology > From ACE in the Project Editor), your discrete-event simulationresults will reflect your edited (not the original) ACE task. For this reason, werecommend that you always save an edited ACE task under a new name soyou can retain the original information.

Procedure 5-1 Editing an ACE Task Using QuickRecode

1 Open your ACE task and switch to the Data Exchange Chart; then make sure thatthe chart is set to the application view (Application Chart Only in the pull-downmenu above the chart).

2 Select a group of messages to edit.

The following limitations apply when selecting groups for a QuickRecodeoperation:

All messages must be within the same tier pair.

All messages in the group must be consecutive (that is, there are no interveningmessages).

If a selected message has a dependency to a message on a different tier pair,this message must be either the first or last message in the selected group.

3 Right-click on the selected group and choose QuickRecode Selected Items from

the pop-up menu.

The QuickRecode Selected Items dialog box appears.


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Figure 5-7 QuickRecode Dialog Box

Use this dialog box to modify the behavior of your real-world application (numberof turns, amount of application data, and processing delay associated with each

tier). For example, you might specify a double-payload level by doubling theamount of application data transmitted by each tier.

4 Specify the characteristics for your hypothetical application, then click OK toclose the dialog box and accept your changes.

A red band appears around the group in the Data Exchange Chart and the group

itself changes color to indicate that it has been edited.

Figure 5-8 Packet Group Edited Using QuickRecode

5 Edit other groups, if desired, by repeating steps 25.

6 Save your edited task under a new name (File > Save As). You can now evaluate

the effects of your edited application using either QuickPredict or by running adiscrete-event simulation.

End of Procedure 5-1

edited group


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ACE Discrete-Event Simulations

You can import ACE data into a new or existing network. You can then useOPNETs discrete-event simulation engine and model library to predict anapplications performance in a wide variety of scenarios.

Once you have made a satisfactory ACE task, you might want to include it inprojects and run discrete-event simulations to test the applications behavior invarious conditions. You can:

Add one or more ACE tasks to an existing scenario. See Adding an ACETask to an Existing Scenario on page ACE-5-19.

Importing an ACE task into a new scenario. See Importing an ACE Task intoa New Project or Scenario on page ACE-5-15.

Importing an ACE Task into a New Project or Scenario

You can quickly create a network scenario based on one or more ACE tasks.When you import the ACE model, the Model Wizard does the following:

A network topology is created. You can control certain aspects of thetopology during the import process (as described in Procedure 5-2 Importingan ACE Model on page ACE-5-15) and can always reconfigure the topologyafter it is created. You will see the nodes and links that represent yourtopology in the workspace.

An application is created. You can control certain aspects of the applicationduring the import process (as described in Procedure 5-2 Importing an ACEModel on page ACE-5-15) and can always reconfigure the application afterit is created. When the ACE import is complete, you will see the task,

application, and profile definition objects in the workspace.

Statistics are chosen for collection. OPNET considers the topology and typeof application, then chooses certain statistics for collection. You can alwaysadjust the statistics chosen after import.

Procedure 5-2 Importing an ACE Model

1 If necessary, create a project or scenario.

If the Startup Wizard appears, choose Import from ACE in the Initial Topology

window and click Next.

If the Startup Wizard does not appear, choose Topology > Import Topology >From ACE in the Project Editor.

The Configure ACE Application dialog box appears.


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Figure 5-9 Completed Configure ACE Application Dialog Box

2 Complete the Application Details section of the dialog box. This section includesthe following components:

NameAn application can be composed of a single task or multiple tasks. If the

application is a single task, you can use the task name. If the application ismultiple tasks, choose a descriptive name that is not the name of a single task.

After your network is created, you will see this name as the Name attribute in the(Applications Definitions) table.

Repeat ApplicationThe number of times the application will repeat, per hour,per user. The value entered becomes the value of the Inter-repetition Time(seconds) attribute. To show the attribute, select Edit Attributes from the Profile

Definition object, then select Profile Configuration > Applications > Repeatability.The attribute is the length of time that elapses between repetitions of the

application, so if (for example) you specified that the application repeat just onceper hour, the value shown will be 3,600 seconds.

Using the following limitThis sets an limit on the number of times theapplication repeats. Infinite means that there is no limit. The value entered

becomes the value of the Number of Repetitions attribute. To show the attribute,select Edit Attributes from the Profile Definition object, then select Profile

Configuration > Applications > Repeatability.

3 Complete the Contained Tasks section of the dialog box as follows:

3.1 Click on the Add Task button.

A row is added to the Contained Tasks table.


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3.2 Click on Specify in the ACE Trace File column.

A pop-up box appears, listing all trace files included in any of the mod_dirsdirectories.

3.3 Select the file that represents the first task in your application.

3.4 Click on the Add Task button again to add further tasks to your application.

The pop-up box now contains a shorter, filtered list of files. Only those files

that are possible tasks in your application are listed. OPNET determineswhich tasks are possible by determining the first talker (the tier that sent

the first application message in the trace) of the first task, then presentsonly those trace files that have the same first talker.

3.5 Use the Delete Task button as needed to adjust the tasks in your application.

4 Click Next.

The Create ACE Topology dialog box appears.

Figure 5-10 Completed Create ACE Topology Dialog Box

5 Complete the LAN Details section of the dialog box. This section includes the

following components:

Number of ClientsSpecify the number of clients running the application. If two

or more clients are specified, they are represented by a LAN model and thenumber of clients you specify becomes the value for the Number of Workstations

attribute.

Packet AnalyzerIf you have only one client, you might wish to include a packet

analyzer. If you specify that an analyzer be included, you will not see it as aseparate node, but one will be integrated with the switch in the local network and

the attribute Packet Analyzer Configuration will be included on that switch.

Client LocationSpecify the client location in relation to the application servers.

If the client is remote, complete the WAN Details section.


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6 If necessary, complete the WAN Details section of the dialog box. This sectionincludes the following components:

TechnologyChoose the correct protocol. If you choose the ATM or FrameRelay protocols, a PVC configuration object with the default settings is includedin the network. You might want to adjust the PVC configuration by editing the

attributes of this object.

Packet Latency (msec)The value entered becomes the Packet Latency (secs)attribute of the cloud.

Packet Loss Ratio (1-100)The value entered becomes the Packet DiscardRatio attribute of the cloud.

Access Bandwidth (Kbps)The value entered becomes the data rate of bothlinks connected to the cloud (you can adjust these values after the network is

created).

7 Click Create.

The network is created. The topology and applications reflect the specifications

gleaned from the ACE trace file and your input. Correct statistics have beenselected.

Figure 5-11 Sample Generated Network Model

8 Review the following attributes, adjusting the configuration as necessary:

Applications Definitions object: (Application Definitions) Table. Notice that theapplication name you created is shown as the Name.

Profile Definitions object: (Profile Configuration) Table. Notice that a profile calledACE () has been created. It includes the application you

imported.

Remote Router Cloud and Cloud Local Router links: data rate. Theimport process assigns the same rate to both links; you might need to adjust

these rates.

9 Review the statistics chosen for collection, adjusting as necessary.


Web Client node.

Workstation model wasused because

Number of Clients = 1.

Local network

Configuration objects that

specify application behavior

Because client was specified as Remote from

server, a remote switch, remote router, and

cloud are created


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Adding an ACE Task to an Existing Scenario

You might already have a network model to which youd like to add the trafficfrom your ACE task. In this case, you should not use the Import Topology fromACE operation because this would overwrite your existing topology. Instead,you can:

Deploy the ACE task in the existing scenario. The ACE Model Wizardautomates the standard procedure that you would use if you were tomanually configure a custom application with an ACE model file. SeeCreating an ACE Application Model in an Existing Scenario onpage ACE-5-19.

Define a custom application that uses your ACE models as tasks andconfigure this application in the network using the standard procedure forconfiguring applications and profiles. See Manually Creating an ACEApplication Model in an Existing Scenario on page ACE-5-22.

Creating an ACE Application Model in an Existing Scenario

With the ACE Model Wizard, you can quickly create a custom application modelthat uses your ACE model in an existing scenario. When you use the ModelWizard, the following occurs:

An application is created. You can control certain aspects of the applicationduring the import process (as described in Procedure 5-2 Importing an ACEModel on page ACE-5-15) and can always reconfigure the application afterit is created. Definitions for the new application are included in the task,application, and profile definition objects in the workspace.

Statistics are chosen for collection. OPNET considers the topology and type

of application, then chooses certain statistics for collection. You can alwaysadjust the statistics chosen after import.

Procedure 5-3 Adding an ACE Task Model to an Existing Scenario

1 In the Project Editor, choose Protocols > Applications > Deploy ACE Application on

Existing Network... .

The Configure ACE Application dialog box appears.


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Figure 5-12 Completed Configure ACE Application Dialog Box

2 Complete the Application Details section of the dialog box. This section includesthe following components:

NameAn application can be composed of a single task or multiple tasks. If the

application is a single task, you can use the task name. If the application ismultiple tasks, choose a descriptive name that is not the name of a single task.

After your network is created, you will see this name as the Name attribute in the(Applications Definitions) table.

Repeat ApplicationThe number of times the application will repeat, per hour,per user. The value entered becomes the value of the Inter-repetition Time(seconds) attribute. To show the attribute, select Edit Attributes from the Profile

Definition object, then select Profile Configuration > Applications > Repeatability.The attribute is the length of time that elapses between repetitions of the

application, so if (for example) you specified that the application repeat just onceper hour, the value shown will be 3,600 seconds.

Using the following limitThis sets an limit on the number of times theapplication repeats. Infinite means that there is no limit. The value entered

becomes the value of the Number of Repetitions attribute. To show the attribute,

select Edit Attributes from the Profile Definition object, then select ProfileConfiguration > Applications > Repeatability.

3 Complete the Contained Tasks section of the dialog box as follows:

3.1 Click on the Add Task button.

A row is added to the Contained Tasks table.


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3.2 Click on Specify in the ACE Trace File column.

A pop-up box appears, listing all trace files included in any of the mod_dirsdirectories.

3.3 Select the file that represents the first task in your application.

You can view the tiers in the trace file by clicking in the Tier Names column.

3.4 Click on the Add Task button again to add further tasks to your application.

The pop-up box now contains a shorter list of files that consists only of filesthat have the same first talker as the trace file you just selected. The first

talker is the tier that sent the first packet in the trace.

3.5 Use the Delete Task button as needed to adjust the tasks in your application.Note that because the files available from the pop-up box depend on the firstfile selected, you might need to delete all tasks selected to change the

available file choices.

4 Click Next.

The Deploy Tiers dialog box appears, listing all tiers contained in the trace fileschosen in the previous dialog box. This dialog box allows you to configure nodesin the network to behave as the tiers in the trace files.

5 Complete the Deploy Tiers dialog box as follows.

5.1 Click in the Select Nodes column of the tier that is the first talker. The text atthe top of the dialog box indicates which tier is the first talker.

The Deploy Tiers dialog box appears, listing all nodes in the network thatcan be configured as ACE tiers.

Figure 5-13 Deploy Tiers Dialog Box

5.2 Deploy this tier on at least one node by indicating which nodes in the network

behave as this tier. For the first talker, these are the nodes that start theapplication. Click OK when done.

5.3 Repeat steps a) and b) for the remaining tiers in the Deploy Tiers dialog box.


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6 Click Deploy.

The ACE application is created and configured in the network according to the

specifications derived from the ACE trace file and your input. Correct statisticshave been selected.


Manually Creating an ACE Application Model in an Existing Scenario

An ACE-generated scenario includes three configuration objects that definewhen and how an ACE task is run during a discrete-event simulation. Includingan ACE task in an existing ACE scenario involves the following three steps:

1) Include the ACE model in the Task configuration object. This objectcontains information on each specific task to be run during a discrete-eventsimulation. First add another row to the Task Specification table; then clickin the ACE Filename field and choose the ACE file name from the pull-down

menu.

2) Create an application definition in the Application configuration object. Thisobject contains information about how a specific task should be run.Creating a definition is a two-step process:

a) First create a row in the Application Definitions attribute table.

b) Then create a task description for this attribute by drilling down into thenew compound attribute, like so: Description > Custom > TaskDescription. Create a row in the Task Description table, then click in theTask Name field and select the task from the pull-down menu. You caninclude multiple ACE tasks in this table, and use the Task Weight and

Task Ordering attributes to specify when and how the definedapplication runs the individual tasks.

3) Add the application to an application profile in the Profiles configurationobject. An application profile includes a set of one or more applicationdefinitions (specified by the Applications attribute) and specifies when andhow often these applications are run (specified by the Operation Mode,Start Time, Duration and Repeatability attributes). You can create a profilefor your application definition (by adding another row to the ProfileConfiguration table) or add it to an existing profile.


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ACE Traffic Flows

You can import traffic into your network from one or more ACE tasks. Thisallows you to virtually deploy applications (modeled using ACE) in differentnetwork scenarios, and still take advantage of OPNETs hybrid simulationtechnology.

How OPNET Generates Traffic Flows from ACE

For each tier pair in the imported ACE data, OPNET creates two unidirectionaltraffic flows (A-to-B and B-to-A) that reflect the traffic intensity in each direction.These traffic flows have the following characteristics:

You can specify that one or more users repeat the ACE application at aspecific rate. Therefore, the the duration of the imported traffic does notreflect the ACE task duration.

You can specify whether the traffic on the imported flows is variable oruniform. If you specify variable traffic, OPNET divides the total duration intobuckets and calculates a traffic intensity for each bucket. If you do not specifyvariable traffic, OPNET calculates a single uniform rate of traffic for each flowobject. Figure 5-14 and Figure 5-15 show how OPNET calculates thesetraffic levels in bits per second (bps).

Figure 5-14 Traffic Calculations for Variable Traffic (bps)

Figure 5-15 Traffic Calculations for Uniform Traffic (bps)

As part of the import process, you must assign every ACE tier to one or morenodes in your network. OPNET uses these assignments to determine thesource and destination nodes for the imported traffic flows.

R sum of repetitions for selected trace files=

V trace_repetitions trace_size( )( ) R=

TAR number_of_users R 3600( ) bucket_duration=

bps_for_bucket Poisson TAR( ) V( ) bucket_duration=

bps_for_flow T U R 3600=

T application bits from source to destination=

R repetitions per user per hour=

U number of users=


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Scaling ACE Traffic

You can create traffic flows that reflect multiple executions of the imported ACEtask. There are two methods for doing this. You can use either or both of thesemethods during a single import operation.

To run the same task from multiple nodes, you can assign multiple nodes to

the same ACE tier. This tier must be the initiating tier, which is the tier thatsends the first packet and initiates the transaction. For example, supposeyou import a simple client-server FTP application in which the client is theinitiating tier. You can assign this tier to two nodes, and thus model twoseparate FTP downloads. This method is described in Assigning MultipleNodes to a Tier on page ACE-5-24.

To run the same task from a single node, you can configure an initiating nodeto launch multiple executions of the imported task. The resulting flows reflectmultiple executions of the imported task. This method is described inConfigure Initiating Node Dialog Box on page ACE-5-31.

Assigning Multiple Nodes to a Tier

When you assign multiple nodes to a tier, the import engine applies the followingrules:

If the assigned tier is the initiating tier, each replicated conversationrepresents an additional execution of the ACE task. As a result, the ACEtier-pair traffic is multiplied in the network as a whole.

If the assigned tier is a non-initiating tier, the import engine balances trafficbetween all nodes that are based on the same tier. As a result, the ACEtier-pair traffic stays constantin the network as a whole.

Examples of Multiple Node Assignments

In this section, we import the same ACE task into three different networks andexamine the resulting traffic levels. The following task involves three tiers:

client(initiating tier), web_server, anddatabase_server. We use twovariables to represent the traffic levels found in the ACE task:

cli_web_trf= the average rate of traffic between clientand web_server

web_db_trf= the average rate of traffic between web_serverand db_server

Figure 5-16 A Three-Tier ACE Application

rate of traffic

between client

and web_server

= cli_web_trf

total traffic

between web_server

anddb_server=

web_db_trf

clientis theinitiating tier


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In the first example, we assign clientto two workstations. Because clientis theinitiating tier, the imported traffic models two instances of the application; as aresult, the ACE traffic is multiplied by two.

Figure 5-17 Deployment Example 1 (Traffic Multiplied)

In the following example, we assign web_serverto two firewall nodes. Becausethere is only one initiating node, OPNET models a single instance of theapplication. However, the network uses two web servers to carry traffic betweenthe client and the database server. Therefore, the traffic is balanced (divided)between the replicated traffic flows.

Figure 5-18 Deployment Example 2 (Traffic Divided)

web_db_trf* 2

per node pair =

cli_web_trf

both node pairs =

cli_web_trf* 2

traffic between

clients and webserver:

traffic between web

server and databaseserver:

clients web server database server

per node pair =

cli_web_trf/ 2

both node pairs =

cli_web_trf

per node pair =

web_db _trf/ 2

both node pairs =

web_db_trf

traffic between

client and web

servers:

traffic between web

servers and database

server:

client web servers database server


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In the following example, we assign client(the initiating tier) to threeworkstations and web_server(a non-initiating tier) to two firewalls. The resultingtraffic models three instances of the application, with the overall traffic balancedbetween two web servers.

Figure 5-19 Deployment Example 3 (Traffic Multiplied / Divided)

Import Procedure

Procedure 5-4 Importing Traffic Flows from ACE

1 In the Project Editor, choose Traffic > Import Traffic Flows > From ACE.

The ACE Traffic Import: Specify Tasks dialog box appears.

2 In the Tasks table (upper left), add the ACE tasks you want to import. For

information on importing multiple tasks, see Specify ACE Tasks Dialog Box onpage ACE-5-27.

Note that when you select an ACE task, the tier names appear in the Tiers Presenttable (lower left).

3 After you specify the ACE tasks you want to import, click Next.

The ACE Traffic Import: Assign Nodes dialog box appears.

You use this dialog box to nodes (in the Project Editor window) to ACE tiers (in the

Node Assignments by Tier treeview). OPNET uses these assignments todetermine the source and destination nodes for the resulting traffic flows. (For a

detailed description of this dialog box, see Assign Nodes Dialog Box on

page ACE-5-28.)

4 For each ACE tier in the Node Assignments treeview on the left, do the followingprocedure. Repeat this procedure until every tier has at least one node assigned.

4.1 Select the tier to which you want to assign a node. To select a tier, click on it

in the Node Assignments treeview or set the Current Tier pull-down menu.

per node pair =

cli_web_trf/ 2

all node pairs =

cli_web_trf* 3

traffic betweenclients and web

servers:

per node pair =

(web_db _trf* 3) / 2

both node pairs =

web_db_trf* 3

traffic between webservers and database

server:

clients web servers database server


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4.2 Go to the Project Editor window and select the nodes that you want to assign.You can assign a tier to multiple nodes; see Assigning Multiple Nodes to a

Tier on page ACE-5-24 for more information.

4.3 Return to the Assign Nodes dialog box and click Assign Selected Nodes.

In the Node Assignments treeview, the assigned nodes appear as children

of the current tier.

If you are assigning the initiating tier, the Configure Initiating Node dialog

box appears. You can use this dialog box to specify the type of flow objectsto use, the traffic duration, and how often the node initiates instances of the

application. See Configure Initiating Node Dialog Box on page ACE-5-31for more information.

5 After you assign nodes to all tiers, review your assignments in the NodeAssignments treeview. To edit an assignment, right-click on a node in the treeview

and choose the desired option from the pop-up menu. See Treeview Pop-Up MenuOperations on page ACE-5-30 for more information.

6 You might want to export your tier/node assignments to a spreadsheet. This makes

it easy to edit and reuse your assignments when you do future imports. SeeSaving, Editing and Reusing Tier Assignments on page ACE-5-29 for moreinformation.

To save your current assignments to a spreadsheet, click Save.

7 Click Finish to import the traffic.


Specify ACE Tasks Dialog Box

Figure 5-20 Specify Tasks Dialog Box

The Specify ACE Tasks dialog box appears after you choose Traffic > ImportTraffic Flows > From ACE. You use this dialog box to specify the ACE tasks youwant to import.


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You can import multiple tasks in the same operation, subject to the followingrestrictions:

All tasks must include the same set of tier names.

All tasks must have the same initiating tier. This is the tier that sends the veryfirst packet in the task, and thus starts the application.

When you import multiple tasks, the import merges the traffic. For each tier pair,the resulting flows reflect the combined traffic levels from all imported tasks. Forexample, suppose you import two tasks that record an FTP application betweena client and a server tier. Total server-to-client traffic is 50 kilobytes in the firsttask, and 100 kilobytes in the second task. The resulting server-to-client trafficflow will specify 150 kilobytes, or the sum of the average traffic between the twotasks. (This example assumes that you do not scale the traffic as described inScaling ACE Traffic on page ACE-5-24.)

Assign Nodes Dialog Box

Figure 5-21 Assign Nodes Dialog Box

The Assign Nodes dialog box appears after you specify the ACE tasks you wantto import. You can do the following tasks in this dialog box:

Specify traffic sources and destinations (required): To do this, you selectnodes in the Project Editor window and then assign the selected nodes tospecific ACE tiers. OPNET creates traffic flows between these nodes thatreflect traffic levels between the corresponding ACE tiers.

Save tier/node assignments to a spreadsheet (optional): You might want tosave your assignments to a comma separated value (.csv) file. You can edityour assignments and quickly load them when you do future imports. SeeSaving, Editing and Reusing Tier Assignments on page ACE-5-29 for moreinformation.


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Customize initiating nodes (optional):You can customize the traffic duration,traffic levels and demand models for any nodes that you assign to theinitiating tier. See Configure Initiating Node Dialog Box on page ACE-5-31 formore information.

Saving, Editing and Reusing Tier Assignments

The Assign Nodes dialog box includes two buttons (Save and Load) that enableyou to save, edit, and reuse your node assignments. This feature can beespecially useful for imports that involve a large number of node assignments.For example, you might want to import a client-server application, and assign100 nodes to the client tier. You can assign the nodes, export the assignments

to a .csv file, edit the file using a spreadsheet program like Excel (if desired), andreuse the settings in future imports.

Table 5-5 Assign Nodes Dialog Box

Item Description

Assign Selected Nodes Assigns all selected nodes in the Project Editor to the

current tier.

Create variable traffic flow If this option is enabled, OPNET calculates variable traffic

intensities using the trace arrival rate, which is calculated

using a Poisson distribution. If this option is not enabled,

OPNET calculates a uniform traffic intensity for each flow

object. For more information, see Figure 5-14 on

page ACE-5-23 and Figure 5-15 Traffic Calculations forUniform Traffic (bps) on page ACE-5-23.

Current Tier Select a tier to assign

Deploy Tier to Selected

Nodes

Assigns the selected tier to all selected nodes in the Project

Editor

Load Loads tier/node assignments from an ASCII file (see Saving,

Editing and Reusing Tier Assignments on page ACE-5-29

for more information)

Node Assignments by Tier Treeview shows the current nodes assignments. You

cannot import traffic until all tiers have at least one node

assigned.

Save Export current tier/node assignments to an ASCII file (see

Saving, Editing and Reusing Tier Assignments onpage ACE-5-29 for more information)

End of Table 5-5


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You might find it most efficient to create assignment templates that require aminimal number of changes after you import their contents into the Assign ACETiers dialog box.

NoteYou can import assignment settings from a spreadsheet only if thespreadsheet and the Assign ACE Tiers dialog box contain the same set of tiernames.

Treeview Pop-Up Menu Operations

To edit an existing node assignment, right-click on a node in the NodeAssignments treeview, as shown in the following diagram.

Figure 5-22 Treeview Pop-Up Menu in Assign Nodes Dialog Box

Table 5-6 Assign Nodes Pop-Up Menu Operations

Item Description

Edit Deployment Opens the Configure Traffic Load dialog box; see Configure

Initiating Node Dialog Box on page ACE-5-31 for more

information (initiating node only)

Set as Default Deployment Apply configuration settings for the selected tier to all future

initiating tiers (initiating node only)

Copy Deployment Copy configuration settings of the current node (initiating

node only)

Paste Deployment Paste the copied configuration settings to the selected node

(initiating node only)

Unassign Node Unassign the selected tier from the selected node; removes

this node from the tree

End of Table 5-6


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Configure Initiating Node Dialog Box

Figure 5-23 Configure Initiating Node Dialog Box

The Configure Initiating Node dialog box appears only when the Assign Nodesdialog box is open. This box appears when you do the following actions:

Assign a node to an initiating tier. If you assign multiple nodes, this dialog boxappears multiple times (once for each assigned node)

Right-click on an assigned node and choose Edit Configuration from thepop-up menu.

You can specify the following information in this dialog box:

The type of demand model used to create the traffic flows (Demand Typepull-down menu)

The simulation interval during which the node initiates the application tasks

(Start Time and End Time fields)

How often the node initiates the application task (Number of Users andRepetitions per User per Hour fields)

NoteYou can specify this information for initiating nodes only.


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Table 5-7 lists the items in the Configure Initiating Node diallog box.

Table 5-7 Configure Initiating Node Dialog Box

Item Description

Apply to Xremaining nodes This option appears only when you assign multiple nodes to

an initiating tier. If you check this box, the current settings

are applied to the remaining nodes in the selection set.

Demand Type The demand model used to model the traffic flows for this

application

End Time The simulation time when the node no longer initiates

sessions of the ACE application.

Number of Users

Repetitions per hour per user

Traffic scaling factor. These fields determine the rate (in

repetitions per hour) at which the node initiates sessions of

the application task. This scales the traffic for all

conversation pairs that support the ACE sessions initiated

by the current tier.

Example: Suppose you import a three-tier

(clientweb_serverdb_server) application task. You set

Number of Users to 10 and Repetitions to 10. This results in100 repetitions of the application session per hour. As a

result, OPNET scales the traffic on the related conversation

pairs (clientweb_server and

web_serverdb_server) by a factor of 100.

Start Time The simulation time when the node starts to initiate sessions

of the application task.

Task The task to be repeated during the specified interval

End of Table 5-7

ace 22 predicting

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