2012 Fall CS HW#7 True/False Multiple Choices

Transcription

1 2012 Fall CS HW#7 True/False 1. True or False? Data transfer rate is the speed with which data is moved from one place on the network to another. 2. True or False? In the client/server model, a user may only access files stored on his/her own computer True or False? A ring topology is a LAN configuration in which a central node controls all message traffic True or False? Ethernet has become the industry standard for local-area networks. 5. True or False? An Internet service provider (ISP) is a company that provides other companies or individuals with access to the Internet. 6. True or False? Both DSL and cable connections are broadband connections. 7. True or False? A repeater is a network device that duplicates a packet and sends the duplicate by an alternate route. 8. True or False? A hub has a single input and a single output. 9. True or False? The IP address of a computer is represented by four numeric values separated by periods (dots). 10. True or False? A domain name server is a computer that attempts to translate a hostname into an IP address. T, F, F, T, T, T, F, F, T, T Multiple Choices 11. In which of the following LAN configurations do all nodes share a single communication line that carries messages in both directions? A. bus topology B. ring topology C. gateway topology D. star topology E. metropolitan topology 12. Which of the following is a computer on a LAN that handles all communication between that network and others?

2 13. Which of the following is a network device that directs a packet toward its final destination? 14. Which of the following is a network device that strengthens and propagates a signal along a long communication line? 15. Which of the following is an IP program that can be used to test whether a particular network computer is active and reachable? A. ping B. telnet C. port D. TCP/IP E. SMTP Ans; A, B, D, E, A Short Answer 16. What is protocol? What is the Internet protocol stack? What is the ISO OSI reference model? A protocol is a mutually agreed upon set of rules, conventions, and agreements for the efficient and orderly exchange of information. The Internet protocol stack, such as TCP/IP internet protocol hierarchy and ISO OSI reference model, is a suite of protocols and programs that cooperatively facilitates the network communication of Internet. The Open Systems Interconnection (OSI) reference model is a seven-layer breakdown of network interaction used to facilitate communication standards. 17. Show how a modem would encode the 5-bit binary sequence onto an analog carrier by A. Modifying its amplitude (AM) B. Modifying its frequency (FM) C. Modifying its Phase (PM)

3 A: B: C Assume a change in binary signal from 1 to 0 or 0 to 1 is detected by this change of "shift" in phase.

4 18. Encoding the 5-bit binary sequence by using the following baseband encoding techniques A. Non-return-To-Zero (NRZ) B. Unipolar Return-To-Zero (Unipolar RZ) C. Manchester A: B C 19. Give the following diagram, where the number represent the time delay across a link: A. How many simple paths (those that do not repeat a node) are there from node A to G? B. What is the shortest path from node A to node G? What is the overall delay? C. If node E fails, does that change the shortest path? If so, what is the new

5 shortest path? A. The number of simple paths from node A to G is 7. ABCG ABECG ABEDCG AFG ADCG ADEBCG ADECG B. There are two shortest paths from A to G, ADECG and ABECG, both of which have a cost of 10. C. If node E fails, then both of the shortest paths fail, as do several of the other paths. The only remaining paths are ABCG, ADCG, and AFG, all of which have a cost of CSMA/CD protocol is the medium access control protocol in the TCP/IP protocol hierarchy. As a collision is detected, all involved stations stop transmitting and wait for a random amount of time that is chosen by using the binary Exponential Backoff Algorithm. Assume the consecutive collision time of a station is 3 and a clock time is 51.2 usec. What are the possible random waiting times? n:3 k:k=min(n, 10)=3 r:random chosen integer between 0 and (2^k -1)=7 Possible Random Waiting Time ={ r * 51.2 usec, r = 0,1, 7}