Lab 3: Evaluating Application Performance across a WAN

Transcription

1 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 server. The users run different online applications including , web browsing, video streaming, and FTP. Users also run locally served applications like intranet , 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 Open 3. Scroll down to the project named Small_Company_LAN_over_WAN, select it and click OK. OPNET IT Guru Lab 3, Page 1

2 Deltasoft Technologies network is laid out as mentioned in the overview. The company also has a shared local and File Server. As an exercise, add a server from the Object Palette and configure it for 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, Page 2

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. Rightclick in the workspace to stop deploying more links. 7. Close the Object Palette. OPNET IT Guru Lab 3, Page 3

4 Step 3: Configure the local server for and File Sharing Configure the new server to support 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 & 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 (Heavy). Click in the second row and select Database. OPNET IT Guru Lab 3, Page 4

5 5. Click OK twice. 6. Save the project: Click File Save. Step 4: Configure and Run the Simulation Now that the local 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. OPNET IT Guru Lab 3, Page 5

6 2. Expand point-to-point and select utilization since we are only interested in the download link utilization. 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 HTTP Page Response Time (seconds). 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. OPNET IT Guru Lab 3, Page 6

7 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. OPNET IT Guru Lab 3, Page 7

8 Step 6: Switch to Next Scenario Select Scenarios Switch To Scenario 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. OPNET IT Guru Lab 3, Page 8

9 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 Ftp Download Response Time (sec). 10. From the right-hand bottom corner pull-down menus, select average and click Show. OPNET IT Guru Lab 3, Page 9

10 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. OPNET IT Guru Lab 3, Page 10

11 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. OPNET IT Guru Lab 3, Page 11

12 1. Select Results Compare Results 2. To compare the lower link utilization statistics, choose Object Statistics Company_LAN WAN LINK 1 [0] utilization. 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. OPNET IT Guru Lab 3, Page 12

13 5. To compare the response times, choose Global Statistics Ftp Download Response Time (sec). 6. Select average from the pull-down menus on the bottom right corner. 7. Click Show. OPNET IT Guru Lab 3, Page 13

14 8. Repeat the same procedure for comparing HTTP Page Response Time. OPNET IT Guru Lab 3, Page 14

15 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. OPNET IT Guru Lab 3, Page 15

16 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. OPNET IT Guru Lab 3, Page 16