Subject: data communication and computer networking

plz i need this in 2 hour at least.

Answer the following short questions: [20] a. Consider a simple application-level protocol built on top of UDP that allows a client to retrieve a file from a remote server residing at a well-known address. The client first sends a request with a file name, and the server responds with a sequence of data packets containing different parts of the requested file. To ensure reliability and sequenced delivery, the client and server use a stop-and-wait protocol. Ignoring the obvious performance issue, do you see a problem with this protocol? Think carefully about the possibility of processes crashing. (5) b. Most IP datagram reassembly algorithms have a timer to avoid having a lost fragment tie-up reassembly buffers forever. Suppose that a datagram is fragmented into four fragments. The first three fragments arrive, but the last one is delayed. Eventually, the timer goes off and the three fragments in the receiver's memory are discarded. A little later, the last fragment stumbles in. What should be done with it? (5) c. Suppose Bob joins a BitTorrent torrent, but he does not want to upload any data to any other peers (so-called free riding) (5) i. Bob claims that he can receive a complete copy of the file that is shared by the swarm. Is Bob's claim possible? Why or why not? ii. Bob further claims that he can further make his "free-riding" more efficient by using a collection of multiple computers (with distinct IP addresses) in the computer lab in his department. How can he do that? d. Discuss the problems with IP fragmentation and reassembly. What alternatives will you consider