Task 1 Suppose you wish to close a bank branch and introduce a teller machine. Your company has won the tender to develop an application-level protocol to be used between an automatic teller machine and a bankâ€™s centralized computer. There are the following requirements that must be satisfied: â€¢ Your protocol should allow a userâ€™s card and password to be verified, the account balance (which is maintained at the centralized computer) to be queried, and an account withdrawal to be made. â€¢ Your protocol entities should be able to handle the all-to-common case in which there is not enough money in the account to cover the withdrawal.
Your tasks are as follows: a) 2 marks: Specify your protocol by listing the messages exchanged and the action taken by the automatic teller machine or the bankâ€™s centralized computer on transmission and receipt of messages. b) 5 marks: Draw a figure that shows the operation of your protocol for the case of simple withdrawal with no errors, using a time diagram. c) 2 marks: Explicitly state the assumptions made by your protocol about the underlying end-to-end transport service.
Task 2 3 marks: Define, compare and contrast TCP and UDP.
Task 3 2 marks: Consider a TCP connection between Host A and Host B. Suppose that the TCP segments travelling from Host A to Host B have source port number x and destination port number y. What are the source and destination port numbers for the segments travelling from Host B to Host A.
Task 4 Suppose Host A sends two TCP segments back to back to Host B over a TCP connection. The first segment has sequence number 90; the second has sequence number 110. a) 1 mark: Describe the operation of sending TCP segments, paying attention to the use of sequence and acknowledgement numbers. b) 1 mark: How much data is in the first segment? c) 2 marks: Suppose that the first segment is lost but the second segment arrives at B. In the acknowledgement that Host B sends to Host A, what will be the acknowledgement number?
Task 5 UDP and TCP use 1's complement for their checksums to detect errors. These checksums exploit 8-bit summands (i.e., 8-bit words in computing the checksum). The receiver received three 8-bit bytes: 01010101, 01110000, 01001100. There are the following problems to be solved: a) 2 marks: What is the 1's complement of the sum of these 8-bit bytes? Show all work. b) 2 marks: Why it is that your protocol takes the 1's complement of the sum; that is, why not just use the sum? c) 2 marks: With the 1's compliment scheme, how does the receiver detect errors? d) 2 marks: Is it possible that a one-bit error will go undetected? e) 2 marks: How about a two-bit error?
Task 6 Sliding window protocols are used to provide flow control. a) 2 marks: Describe causes of network flooding and define flow control.
b) 3 marks: Draw the Finite State Machine (FSM) of a protocol that provides sliding window flow control in a reliable network. c) 3 marks: Draw a time diagram that shows the protocol behaviour in time. Assume that the window size is n.
Task 7 Congestion of a network is a serious communication problem a) 1 mark: Describe the causes of congestion in networks. b) 2 marks: Present the basic idea of TCP congestion control. c) 2 marks: Demonstrate that the TCP congestion control approach is fair.
Task 8 Network consist of functions, services and protocols, which can be further categorised through the use of the OSI reference model. a) 2 Mark: Define, compare, and contrast the concepts of a function, service, and protocol b) 2 Marks: List and briefly explain the services provided by the network layer of the Internet taking into consideration the scope of the transport layer protocol services.
Task 9 3 Marks: Do routers have IP addresses? If so, how many?
Task 10 3 Marks: Compare and contrast the LS algorithm with DV routing algorithm.
3 Marks: List and briefly characterize routing protocols used in the Internet.