Laboratory 4 - Introduction to Network Simulation

Objectives

1. Get the OpNet network simulator up and running
2. Learn how OpNet works
3. Run a simple simulation of a small network

Preparation

The OpNet Network Simulator (the IT Guru Academic edition, which is available for free from OpNet.com) is a tool that you can use to simulate a large variety of network configurations; it allows you to gather various performance measurements and analyze them. We'll be using OpNet in the lab for a few weeks, simulating some different types of networks.

To get started, you will get OpNet up and running on one of the lab PCs, then you will run the tutorial that is supplied with it. The software should already be installed, but in order to get it running, you will need to obtain a license key from OpNet. These keys are free, but they require that you register with OpNet (this is a pretty small price to pay in order to run their software for free). Before you come to lab, you'll need to register with OpNet and get a license key. Visit the OpNet User Registration page, which can also be found from the IT Guru Academic Edition page. Register, and make sure you put in your valid email address. Once you successfully complete the registration process, you will receive an email at the specified email address that includes the user name you selected and a password. You must bring this user name and password to the lab with you.

In addition to bringing the user name and password to the lab with you, for your pre-lab, you should forward the registration email you received from OpNet to Anthony. Failure to do so gets 0 points for the pre-lab and verbal and/or physical abuse when you get to the lab and aren't ready to get started.

In Lab Activities

First off, boot your machine up in Windows (I know, Windows is evil, but that's the way life goes...). Once you are logged into Windows, you should find the OpNet application installed. You need to run the application and get it licensed. (The instructions below are also available on the OpNet web site, along with some pictures, in case this isn't clear.)

1. Open Firefox and go to the License Activation page for OpNet. You will be prompted to enter the username and password from your registration email.
2. Start the OpNet application.
3. If the program displays the Restricted Use Agreement, click on the I Agree button (read it first if you want to know what you are signing).
4. Click on License Management.
5. Click on Next.
6. It should display a page with a "License Request Code" at the bottom; click on the Copy to Clipboard button beside it.
7. It will start up Internet Explorer - if you are prompted for a username and password, enter the ones from the registration email (it shouldn't do this). Unfortunately, something weird is going on, and it will probably give you a "Page not Found" error.
8. That's why you started Firefox - it can open the page. Switch to Firefox and paste the clipboard into the box for the License Request Code, then click Submit.
9. The next page should display an "Approval Code". Copy this to the clipboard.
10. Switch back to the OpNet application and click on Next.
11. It should display a page where you enter the Approval Code; click the Paste from Clipboard button to copy in the Approval Code.
12. Click on Next.
13. Click on Close.
14. Exit the application and restart it. The application should now be licensed and ready to run.

1. Open the Preferences page from the Edit menu.
2. Enter "license" into the Find box; it should show you a list of the license-related settings.
3. Make sure that license_server is set to localhost.
4. Set license_server_standalone to TRUE.
5. Go back to the Find box and enter "mod".
6. Check the mod_dirs setting. This is a list of the directories where OpNet will look for models to use in simulations; it's similar to the PATH in Linux. The first directory in the list is where your models will be saved; it may be set to Z:\op_models. You can keep this directory, or change it to something like Z:\CS440\OpNet; if you want to organize the files on your Windows share a little more. Whatever you choose, use Windows Explorer to create that directory.
7. Click OK.

Now everything should be ready to work up a simulation. From the Help menu, select Tutorial, and read the Introduction lesson. Once you're done, you can simulate a simple network. From the Help menu, select Tutorial, and run the Small Internetworks tutorial.

For the tutorial, you are to collect some Discrete Event Simulation (DES) statistics for the original scenario (first_floor) and the second scenario (expansion). These include the following:

• The Ethernet load (in bits/sec) on the server (node_31)
• The Ethernet delay (in sec) network-wide

In addition to these statistics from the tutorial, also gather the following statistics:

• The Bit Error Rate (BER) for the link between the server (node_31) and the first-floor switch (node_30) - this is under low-level point-to-point statistics
• The throughput (in bits/sec) and utilization in each direction on the server-switch link - these are under point-to-point statistics (this will be four separate statistics)

You should use the "Compare Results" tool on all of these statistics, as well as the two from the tutorial. You should also generate the time-averaged server load comparison graph that is shown in the tutorial - you can do this in the "Compare Results" window that is displaying the server load graph, by changing the drop-box list that says "as is" to "time-average". You should also generate a time-averaged comparison graph for the throughput of the link in each direction.

If you and want to capture a graph for inclusion in your lab report, go to "View Results" or "Compare Results", select the statistic you want, make sure what you expect is in the preview window, and click Show. This should pop up a windows containing the graph. You can use the right-click menu to change things about the graph, like adding axis labels. When you have it the way you want it, pressing <ALT>-Print Screen will copy the window to the clipboard. You can then paste it into a Word document. When you are done with the window and close it, you'll have to choose whether to "Hide" or "Delete" the panel - I usually just delete it.

Bonus: If you have the time and the inclination, try adding another expansion scenario that has 30 nodes on the second floor instead of 15. See how this affects the network load and delay. You don't need to compare BER, throughput, and utilization statistics, just the load and delay. To set up this simulation, select Scenarios ... Switch to Scenario ... first_floor. This should get you back to the original scenario. Then do Duplicate Scenario and set up a new expansion with the additional nodes in the second floor star.

Make sure that you are comfortable with running OpNet and setting up a simulation; we will be doing a few more labs using it.

Lab Report

Your lab report should include the following information:

• A description of the network you simulated, including a description of each scenario. Include the goals of the simulation; what is it that you were trying to analyze?
• A brief description of the statistics you captured for each scenario and the parameters you used when running the simulation. (For example, what was the duration of the simulation?)
• A description of the results of the simulation for each scenario. Include captures of the graphs generated when you compared each of the statistics between the two different scenarios (there should be seven different graphs). Also include the time-averaged graph comparing the load between the two scenarios.
• An analysis of the results - were the changes in the network performance for the second scenario what you expected? Did the network appear to still be usable after the expansion?
• If you got a chance to do the third scenario, also include the results for it and an analysis of those results as a separate section.
• A conclusion - what did you learn? What problems did you encounter? Do you have any suggested extensions or improvements for the lab?

This is a more involved write-up than the ones you had to do for the first three labs. I'm not expecting a book, but make sure you do a reasonable job. The report should be fairly complete; someone shouldn't need to open the tutorial to figure out what it was you were simulating. It should be well formatted, so it's easy to find the information.

Make sure that you are following Anthony's submission guidelines - it's enough joy and happiness slogging through 45 or so lab reports, without having to play mind-reader and decipher what each of them is. Failure to pay attention to the posted requirements for the labs and assignments will start to result in significant loss of points for the assignment.

The lab write-up is due by the end of the day Wednesday (i.e. 11:59 PM) for the Tuesday lab section and by the end of the day Friday for the Thursday lab section.