1. Why does a process need to have a port number for Internet communication?

2. Compare the client-server with P2P architecture. What are the pros/cons of each architecture?

3. Let the following figure be the schematic view of a communication network between two end-systems A and B.

Assume that the nodal processing delay is negligible. Also, assume that the link between A and the router is 10,000 meters long and the link between B and the router is 20,000 meters long. If the propagation speed in both links is 200,000,000 m/sec, answer the following questions:

a. (10 points) What is the total propagation delay for a packet sent from A to B? (Hint: propagation delay of a link is directly proportional to its length and reversely proportional to its propagation speed).

b. Calculate the total transmission delay of a 50MB file sent from A to B (Hint: 1MB is 223 bits and 1Mb/sec is 106bits/sec)

c. Is the queuing delay of sending a file from A to B equal to the queuing delay of sending the same file from B to A? Explain your answer.

d. What is the end-to-end network throughput when a 10MB file is transferred from A to B?

e.What is the end-to-end network throughput when a 100KB file is transferred from B to A? Assume that the router's buffer is large enough to avoid any data loss possibilities. Also, assume that the file is divided into 50 2KB chunks by B before being transferred to A and the router forwards a data chunk to A when it completely receives it from B.

f. Assume that B sends a 2GB (234 bits) file to A after chunking it to 2KB packets. What should be the minimum router buffer size if we want to avoid any data loss for this file transfer?

R110Mb/s R220Mb/s Router