lab 3

Lab 3: Evaluating Application Performance across a WAN

Objective

In this lab, we have a small LAN with 20 users for a startup company named

Deltasoft Technologies. We investigate the application performance for this

company over a T1 line. We will also plan the network by adding a redundant

link between the LAN and the ISP.

Overview

Deltasoft Technologies’ LAN consists of 20 user PCs sharing three printers

and a local file and email server. The users run different online applications

including E-mail, web browsing, video streaming, and FTP. Users also run

locally served applications like intranet E-mail, print, and database access.

Our goal is to study the response time for two critical tasks: FTP downloads

and Web Page downloads. We’ll also analyze the link utilization between the

LAN and the ISP.

After an initial assessment, we’ll split the LAN into two smaller switched

segments and add an extra T1 link between the LAN and the ISP to double

the available capacity. Load balancing will ensure that both T1 links are

equally utilized.

Then we’ll study the effect of failing one of the devices and see the advantage

of having the redundant link.

Lab Instructions

Step 1: Open Lab 1

1. Start IT Guru.

2. Select File

3. Scroll down to the project named Small_Company_LAN_over_WAN,

select it and click OK.

Open…

OPNET IT Guru Lab 3, Page 1

Deltasoft Technologies’ network is laid out as mentioned in the overview.

The company also has a shared local E-mail and File Server. As an exercise,

add a server from the Object Palette and configure it for E-mail and File

Sharing applications. This will give you an example of how objects are

deployed to modify a network model.

OPNET IT Guru Lab 3,

Step 2: Add a local Server

1. Open the Object Palette.

2. There are a lot of different objects, which represent network components.

From the pull-down menu at the top, you can select a group of

components by vendor or protocol.

3. Select ethernet from the pull-down menu.

4. Select ethernet_server form the palette and click on the workspace to

deploy the server. Right-click in the workspace to stop deploying more

servers.

5. To add a link connecting the server and the switch, select the 10BaseT

link from the Object Palette.

6. Click on the 10BT_Switch and then on the server you just added. Right-

click in the workspace to stop deploying more links.

7. Close the Object Palette.


Step 3: Configure the local server for Email and File Sharing

Configure the new server to support E-mail and File Sharing Applications.

These applications are already defined in the Applications Object.

1. Right-click on the new server and select Edit Attributes.

2. Set the name attribute to Email & File Server.

3. Click in the Value column for Application: Supported Services where it

says None and select Edit…

4. Configure the 2 Applications as follows:

• Set the number of Rows to 2.

• Click in the Name column for first row and select Email (Heavy).

• Click in the second row and select Database.


5. Click OK twice.

6. Save the project: Click File

Save.

Step 4: Configure and Run the Simulation

Now that the local E-mail and File Sharing server has been configured,

evaluate the network performance for a busy hour of the day.

1. Click on the configure/run simulation toolbar button.

2. Make sure the Simulation Duration is set to 1 hour.

3. Click Run. Monitor the progress bar as the simulation proceeds. It will take

about 2 minutes for the simulation to finish.

4. When the simulation completes, Click Close.

Step 5: View Results

View the various statistics such as Web Application Response Time, FTP

Download Response Time and the WAN link utilization.

1. Right-click on the WAN link and select View Results to view the utilization

results for this link.


2. Expand point-to-point and select utilization

interested in the download link utilization.

since we are only

3. Select Show. This is the graph for utilization, which will be discussed later,

so do not close the graph window.

4. Click Close in the View Results window.

5. Right-click in an empty space in the workspace and select View Results

to view the global Web Application and FTP Download Response Time.

6. Choose Global Statistics

7. Click Show.

8. With the same statistic (HTTP Response Time) selected, change the filter

on the right-hand bottom corner to average and click on Add.

9. Click on the graph you just created to put the average curve on the same

panel.

10. Repeat the same procedure to view Ftp Download Response Time

(sec). Unselect the previous statistic before selecting the new one.

Note: To toggle the graphs on and off, use the hide or show all graphs

button.

HTTP

Page Response Time (seconds).


Your results should be similar to the graphs above.

• Download link utilization averages 92%.

• Web Application Response Time is close to 1.3 seconds.

• FTP Download Response Time is close to 2.5 seconds.

• With such high download link utilization; this does not give much available

bandwidth for potential user applications.

Now, we will perform two experiments. We’ll first add a redundant T1 link to

double the capacity. Load balancing is used to ensure traffic is evenly

distributed between the two links. Then, we’ll fail one of the devices to see the

advantage of adding the new link.


Step 6: Switch to Next Scenario

Switch To Scenario

• Select Scenarios

Small_Company_LAN_With_Two_Switches_Over_WAN.

The company network is divided into two smaller segments each connected

to a switch. The LAN is connected to the Internet with two T1 lines. EIGRP is

used to perform load balancing on the two links.

Step 7: Configure and Run the Simulation

Rerun the simulation for a busy hour of the day to see if the load is balanced

across the two links as intended.

Refer to previous steps for setting the duration and running the simulation.

Step 8: Compare Results

Compare the link utilizations, Web Application and FTP Download Response

Times. We expect that the additional link to the ISP should reduce the

application response times. The two links should also split the link utilizations.


1. Right-click on the lower WAN link and select Compare Results.

2. Expand point-to-point under Company_LAN.WAN LINK 1[0] and select

utilization .

3. Click Show.

4. Click Close in the View Results window.

5. Right-click on the upper WAN link and select View Results.

6. Expand point-to-point and select utilization .

7. Click Show and select Close in the View Results window. Since this link

was not present in the previous scenario, we only see a graph for the

current scenario.

8. Now compare the Response Times. Right-click in an empty space in the

workspace and select Compare Results.

9. Choose Global Statistics

10. From the right-hand bottom corner pull-down menus, select average and

click Show.

Ftp

Download Response Time (sec).


11. Repeat the same steps above to select Page Response Time (seconds)

under Global Statistics / HTTP. Deselect the previous statistics before

selecting the new one.

•

As expected, the link utilization for the lower link reduced from 92% to

55% and the new link utilization is close to408%. Thus, load balancing has

been done.

Web Application Response Time went down from about 1.1 seconds to

0.45 seconds.

FTP Download Response Time went down from 1.25 seconds to 0.6

seconds.

This is a significant improvement in both, link utilizations and response

times.

•

•

•


The advantage of using an additional T1 line can be seen by failing one of the

routers or links. We’ll fail one router and compare the utilizations and

application response times.

Step 9: Switch to Next Scenario

• Select Scenarios

Switch To Scenario

Small_Company_LAN_Failed_One_Router_Over_WAN.

Step 10: Fail one Device

We will fail one of the routers connecting the LAN to the ISP.

•

Right-click on any one of the routers and select Fail This Node. A red X

appears on the router.

Step 11:Configure and run the simulation

Rerun the simulation for a busy hour to evaluate the network performance.

•

Refer to previous steps for setting the duration and running the simulation.

Step 12: Compare Results

Compare the results of utilizations and Response Times for all 3 scenarios.

This will give a clear picture of the effect of having an additional T1 link.


1. Select Results

2. To compare the lower link utilization statistics, choose Object Statistics

Company_LAN

WAN LINK 1 [0]

utilization .

Compare Results…

3. Click Show.

4. To compare the link utilization for the upper T1 link, unselect the previous

statistics, then choose Object Statistics

Company_LAN

WAN

LINK 2 [0]

utilization

and click Show.


5. To compare the response times, choose Global Statistics

Download Response Time (sec).

6. Select average from the pull-down menus on the bottom right corner.

Ftp

7. Click Show.


8. Repeat the same procedure for comparing HTTP Page Response Time.


Conclusion

•

These results show that the additional T1 link has a significant

improvement in link utilizations as well as the application response times.

•

Also, if one of the link or router fails, all the users can still access the

Internet at the cost of higher utilization and response times.


Advanced Scenario

•

Advanced Scenario 1. Create duplicate scenario of

Small_Company_LAN_With_One_Switch_Over_WAN and change the

data rate of the WAN link to get an average web response time of 0.5

seconds. Then duplicate the scenario

Small_Company_LAN_With_Two_Switches_Over_WAN and set the data

rate for both the WAN links to the value you used in the previous scenario.

Observe the web response time with this data rate.

•

Advanced Scenario 2. There is continuous streaming between the music

server and several users defined by a traffic demand object. You can view

this object by selecting View

Demand Objects

Show All. Try

changing the traffic volume for these demands.

Hint: Edit the Traffic (packets/sec) and Traffic (bits/sec) attributes of the

demand object. Observe its effect on the Web Application and FTP

Download Response Times.

•

Advanced Scenario 3. Duplicate the last scenario. Recover the failed

router and then fail one of the WAN links. Check to see if the results

change.


lab 3

Documents