# Explain the graph we received in the simulation that shows the relationship between the received (throughput) and sent (load) packets.

1. Explain the graph we received in the simulation that shows the relationship between the received (throughput) and sent (load) packets. Why does the throughput drop when the load is either very low or very high?

2. Create three duplicates of the simulation scenario implemented in this lab. Name these scenarios Coax_Q2a, Coax_Q2b, and Coax_Q2c. Set the Interarrival Time attribute of the Packet Generation Arguments for all nodes in the new scenarios as follows: ❍ Coax_Q2a scenario: exponential(0.1) ❍ Coax_Q2b scenario: exponential(0.05) ❍ Coax_Q2c scenario: exponential(0.025) In all these new scenarios, open the Confi gure Simulation dialog box, and from the Object Attributes, delete the multiple-value attribute (the only attribute shown in the list). Choose the following statistic for node 0: Ethcoax · Collision Count. Make sure that the following global statistic is chosen: Global Statistics · Traffi c Sink · Traffi c Received (packet/sec). (Refer to the “Choose the Statistics” section in the lab.) Run the simulation for all three new scenarios. Get two graphs: one to compare node 0’s collision counts in these three scenarios and the other graph to compare the received traffi c from the three scenarios. Explain the graphs and comment on the results. ( Note: To compare results you need to select Compare Results from the Results menu after the simulation run is done.)

3. To study the effect of the number of stations on Ethernet segment performance, create a duplicate of the Coax_Q2c scenario, which you created in Exercise 2. Name the new scenario Coax_Q3. In the new scenario, remove the odd-numbered nodes, a total of 15 nodes (node 1, node 3, …, and node 29). Run the simulation for the new scenario. Create a graph that compares node 0’s collision counts in scenarios Coax_Q2c and Coax_Q3. Explain the graph and comment on the results.

4. In the simulation, a packet size of 1024 bytes is used. ( Note: Each Ethernet packet can contain up to 1500 bytes of data.) To study the effect of the packet size on the throughput of the created Ethernet network, create a duplicate of the Coax_Q2c scenario, which you created in Exercise 2. Name the new scenario Coax_Q4. In the new scenario, use a packet size of 512 bytes (for all nodes). For both Coax_Q2c and Coax_Q4 scenarios, choose the following global statistic: Global Statistics · Traffi c Sink · Traffi c Received (bits/sec). Rerun the simulation of Coax_Q2c and Coax_Q4 scenarios. Create the following graphs and explain them:

a. A graph that compares the throughput as packets per second in Coax_Q2c and Coax_Q4 scenarios

b. A graph that compares the throughput as bits per second in Coax_Q2c and Coax_Q4 scenarios

LAB REPORT

Prepare a report that follows the guidelines explained in the Introduction Lab. The report should include the answers to the preceding exercises as well as the graphs you generated from the simulation scenarios.