Stage: Phase 1

EXPERIMENT NO 01: ANALYSIS OF TCP CONGESTION CONTROL MECHANISM AND OSPF ROUTING PROTOCOL USING OPNET SIMULATOR.

Release date: April 8, 2015

Submitted By:

Name: Nusrat Jahan Sadia Islam Shachi

Roll: IT -12013 IT-12030

Year: 3rd Semester: 2nd

Objectives:

Get familiar with simulation tool-OPNET. To study the behaviour and implementation of slow start and congestion

avoidance algorithms. To simulate the OSPF routing scheme in an IP network. To know the effect of dividing the network into various areas.

Therefore the analysis covers the new features introduced by TCP and OSPF.

Task 1:

Overview:

Previous versions of Transport Control Protocol (TCP) start a connection with the sender injecting multiple segments into the network, up to the window size advertised by the receiver. This is fine when the hosts are placed on the same LAN. But if there are routers and slower links between the sender and the receiver different problems can arise. Some intermediate router must queue the packets and it is possible for the router to run out of space in the queue. The algorithm to avoid this is called slow start. Beginning transmission into a network with unknown conditions requires TCP to slowly probe the network to determine the available capacity, in order to avoid congesting the network with an inappropriately large burst of data. Slow start adds another window to the sender's TCP, i.e., the congestion window, called cwnd. Although congestion avoidance and slow start are independent algorithms with different objectives, in practice they are implemented together.

When congestion occurs TCP must slow down its transmission rate of packets into the network, and then invokes slow start to get things going again.

Creating Network:

1. Create a new project. (File New).2. Name the project acronym TCP and the scenario NoDrop. Here, acronym must be

substituted with the student's own acronym!3. Create an empty scenario with Europe as a map and no technologies included.4. Open the internet toolbox object palette if it's not already open and add an

Application Configure object to the workspace. Rename this object to Applications.5. Edit the Application Definitions of the object and set the Application name to FTP

Application. Choose the FTP application and set the following values (Application Definitions Row 0 Description FTP).

6. Add a Profile Configure object to the workspace and rename it to Profiles.7. Edit the Profile Configuration of this object by adding a new profile and naming it FTP

Profile.8. Applications should be named FTP Application. Set Start Time Offset to constant (5)

and Duration to End of Profile. Set Repeatability to Once at Start Time.

After the configuration of the application and profile objects, we will now create the network for analysing the behaviour of the TCP protocol. Place a subnet over Paris in the workspace and name the subnet Paris.

Enter now the Paris subnet.

9. Place an ethernet server in the workspace and rename it to Server Paris. Place an ether-

net4 slip8 gtwy router in the workspace next to the server and rename it to Router Connect the server and the router with a 100BaseT cable 10. Open the server's attributes and add FTP Application as a Supported Service in the

Application list item. Set the Server Address to Server Paris.10. Expand TCP Parameters and disable both Fast Retransmit and Fast Recovery.

Save your changes and exit the Paris subnet. Now place a subnet over Stockholm and set its name to Sthlm. Enter now the Stockholm subnet. 12. Place an ethernet wkstn in the workspace. Rename it to Client Sthlm. Furthermore, place an ethernet4 slip8 gtwy router in the workspace next to the client and rename it to

Router Sthlm. Connect the client and the router with a 100BaseT cable. 13. Edit the attributes of the client such that it uses the FTP Profile created earlier and set the client Address attributes to Client Sthlm. 14. Set the symbolic name of Application: Destination Preferences to FTP Server and set The actual Name to the name of the server in Paris.

Save your changes and exit the Stockholm subnet. We will model now the networks between Paris and Stockholm as an Internet Protocol (IP) cloud. Place an ip32 cloud on the workspace. 15. Connect the router in the Paris subnet to the Europa Internet IP Cloud with a PPP DS3 cable. 16. Connect the router in the Sthlm subnet to the Europa Internet IP Cloud with a PPP DS3 Cable.

Before running the congestion avoidance simulation you will need to select the statistics that we want to analyze later. Thus, for the server in Paris you will need to select the Congestion Windows Size (bytes) statistic (Node Statistics TCP Connection Congestion Windows Size (bytes)). 17. Right click on the Congestion Window Size (bytes) and select Change Collection mode. Check the advance checkbox in the pop-up dialog.

Run the simulation 10 minutes. Visualize now the results of the simulation. 18. View the results by choosing: Object statistics Choose From Maps Network Paris

Server Paris TCP Connection Congestion Window Size (bytes).

Task2 :

Overview:

The Open Shortest Path First (OSPF) protocol is an Interior Gateway Protocol (IGP) used for routing in IP networks. It is a link state protocol employing Dijkstra’s algorithm to calculate

the least cost path. The algorithm calculates the shortest path to each destination based on the cumulative cost required to reach that destination. The cumulative cost is a function of the cost of the various interfaces needed to be traversed in order to reach that destination. The cost (or the metric) of an interface in OSPF is an indication of the overhead required to send packets across that interface. The cost of an interface is calculated based on the bandwidth.

Creating a Network:

1. Create a new project (File New).

2. Name the project acronym OSPF and the scenario to NoAreas. Here, acronym must be substituted with the student's own acronym.

3. Select an empty scenario.4. Select Office and set both the x span and y span to 200. Do not include any

technologies.

Review the values and click OK. Open the object palette and change the palette to routers. (See Figure 17)

5. Place 10 slip8 gtwy's in the workspace.6. Change the object palette to internet toolbox.7. Connect all the routers using PPP DS3 links and rename the nodes.8. Assign OSPF as the routing protocol for your network. You should select the All

interfaces.9. Auto-assign IP addresses for your network.10. Configure the cost of different interfaces.

Now is time to configure the traffic demands between several routers in your network. (Traffic CreateTraffic Flows IP Unicast)

11. What is the Create a traffic demand between router B and router D with traffic originating from router B.

12. Create a traffic demand between router C and router H with traffic originating from router C.

The paths of the traffic demands should be now visible. To hide the traffic demands select View Demand Objects Hide All. Save the project.

Configure OPNET to run the simulation for 30 minutes for each scenario. Display the simulation results for each scenario (Protocols IP Demands Display Routes for Configured Demands).

Conclusion:

With the help of this lab, we have learnt how data packet is transferred in any network system. From the second task of OSPF, we have accomplished the work of passing of data packet through any path in the minimum cost.

Stage: Phase 2

EXPERIMENT NO 01:SIMULATION OF NETWORK USING BUS AND STAR TOPOLOGY.

Release date: April 8, 2015

Submitted By:

Name: Nusrat Jahan Sadia Islam Shachi

Roll: IT -12013 IT-12030

Year: 3rd Semester: 2nd

Objectives:

Get familiar with simulation tool-OPNET.

To simulate a network using a simple star and bus topology. To know the comparison between bus and star topology.

Task 1:

Overview:

Networks are being upgraded or deployed from scuff all over the world. The area of network planning is thus fetching all the more noteworthy. Networks have grown swiftly over the past few decades, with confront of connecting the relevant networks together, so that the

users can share the network’s wealth. Topology refers to the way in which the network of computers is connected. Each topology is suited to specific tasks and has its own advantages and disadvantages. The choice of topology is dependent upon type and number of equipment being used, planned applications and rate of data transfers, required response times and finally the cost. There are FOUR major challenging topologies BUS, RING, STAR,

and FDDI. Most networking software supports all topologies. In bus topology, a common cable connects all the nodes and provides for the backbone of a network essentially. In star topology, each node is connected to a central hub.

Creating network using Bus topology:

1. Start Riverbed Modeler Academic Edition ⇒ Choose New from the File menu.2. Select Project ⇒ Click OK ⇒ Name the project <your initials>_Ethernet, and the

scenario Coax_2 ⇒ Make sure that the Use Startup Wizard is checked ⇒ Click OK.

3. In the Startup Wizard: Initial Topology dialog box, make sure that Create Empty. Scenario is selected ⇒ Click Next ⇒ Choose Office from the Network Scale list ⇒ Click Next ⇒ Assign 200 to X Span and keep Y Span as 100 ⇒ Click Next twice ⇒ Click Finish.

4. Close the Object Tree dialog box.5. Select Topology Rapid Configuration. From the drop-down menu choose bus and click

OK.6. Click the Select Models button in the Rapid Configuration dialog box. From the Model

List drop-down menu choose ethcoax and click OK.7. In the Rapid Configuration dialog box, set the following eight values and click OK.

To choose the statistics to be collected during the simulation.

8. Right-click anywhere in the project workspace and select Choose Individual Statistics DES from the pop-up menu.

9. In the Choose Results dialog box, choose the following 2 statistics:

A. Traffic Received (in packets/Sec) by the traffic sinks across all nodes.

B. Traffic Sent (in packets/sec) by the traffic sources across all nodes

.

Here we need to configure the duration of the simulation:1. Click on the Configure / Run Simulation button.2. Set the duration to be 2.0 minutes.

Task 2:

Creating network using Star topology:

1. Start Riverbed Modeler Academic Edition ⇒ Choose New from the File menu.2. Select Project ⇒ Click OK ⇒ Name the project <your initials>_Ethernet, and the

scenario Coax_2 ⇒ Make sure that the Use Startup Wizard is checked ⇒ Click OK.3. In the Rapid Configuration dialog box, set the following six values: Center Node Mod=

ethernet16_hub, Periphery Node Model = Ethernet station, Link Model = 10BaseT, Number =16, Y=50, and Radius = 42 Click OK.

The 10BaseT link represents an Ethernet connection operating at 10Mbps

To choose the statistics to be collected during the simulation:

10. Right-click anywhere in the project workspace and select Choose Individual Statistics DES from the pop-up menu.

11. In the Choose Results dialog box, choose the following 3 statistics:A. Ethernet Delay – this represents the end-to-end delay of all packets received by all the station.

B. Traffic Received (in packets/Sec) by the traffic sinks across all nodes.

C. Traffic Sent (in packets/sec) by the traffic sources across all nodes

Here we need to configure the duration of the simulation:

1. Click on the Configure / Run Simulation button.2. Set the duration to be 2.0 minutes.

Conclusion:

As we have learnt how to create networks using different topology, we can use the idea to create improved and better network system. This lab also provides us clear concept about the comparison of the topologies.