計(jì)算機(jī)網(wǎng)絡(luò)自頂向下方法(原書(shū)第6版)第1-3章習(xí)題及答案

1、Homework Problems and QuestionsChapter 1 Review QuestionsSECTION 1.1R1. What is the difference between a host and an end system? List several differenttypes of end systems. Is a Web server an end system?R2. The word prot

2、ocol is often used to describe diplomatic relations. How doesWikipedia describe diplomatic protocol?R3. Why are standards important for protocols?SECTION 1.2R4. List six access technologies. Classify each one as home acc

3、ess, enterpriseaccess, or wide-area wireless access.R5. Is HFC transmission rate dedicated or shared among users? Are collisionspossible in a downstream HFC channel? Why or why not?R6. List the available residential acce

4、ss technologies in your city. For each typeof access, provide the advertised downstream rate, upstream rate, and monthly price.R7. What is the transmission rate of Ethernet LANs? R8. What are some of the physical media t

5、hat Ethernet can run over?R9. Dial-up modems, HFC, DSL and FTTH are all used for residential access.For each of these access technologies, provide a range of transmission rates and comment on whether the transmission rat

6、e is shared or dedicated.R10. Describe the most popular wireless Internet access technologies today. Com-pare and contrast them.SECTION 1.3R11. Suppose there is exactly one packet switch between a sending host and arecei

7、ving host. The transmission rates between the sending host and the switch and between the switch and the receiving host are R1 and R2, respec- tively. Assuming that the switch uses store-and-forward packet switching, wha

8、t is the total end-to-end delay to send a packet of length L? (Ignore queuing, propagation delay, and processing delay.)R12. What advantage does a circuit-switched network have over a packet-switchednetwork? What advanta

9、ges does TDM have over FDM in a circuit-switched network?R13. Suppose users share a 2 Mbps link. Also suppose each user transmits continu-ously at 1 Mbps when transmitting, but each user transmits only 20 percent of the

10、time. (See the discussion of statistical multiplexing in Section 1.3.)68 CHAPTER 1 ? COMPUTER NETWORKS AND THE INTERNETone of these packets arrives to a packet switch, what information in the packet does the switch use t

11、o determine the link onto which the packet is forwarded? Why is packet switching in the Internet analogous to driving from one city to another and asking directions along the way?R21. Visit the Queuing and Loss applet at

12、 the companion Web site. What is themaximum emission rate and the minimum transmission rate? With those rates, what is the traffic intensity? Run the applet with these rates and deter- mine how long it takes for packet l

13、oss to occur. Then repeat the experiment a second time and determine again how long it takes for packet loss to occur. Are the values different? Why or why not?SECTION 1.5R22. List five tasks that a layer can perform. Is

14、 it possible that one (or more) ofthese tasks could be performed by two (or more) layers?R23. What are the five layers in the Internet protocol stack? What are the principalresponsibilities of each of these layers?R24. W

15、hat is an application-layer message? A transport-layer segment? A network-layer datagram? A link-layer frame?R25. Which layers in the Internet protocol stack does a router process? Whichlayers does a link-layer switch pr

16、ocess? Which layers does a host process?SECTION 1.6R26. What is the difference between a virus and a worm?R27. Describe how a botnet can be created, and how it can be used for a DDoSattack.R28. Suppose Alice and Bob are

17、sending packets to each other over a computernetwork. Suppose Trudy positions herself in the network so that she can capture all the packets sent by Alice and send whatever she wants to Bob; she can also capture all the

18、packets sent by Bob and send whatever she wants to Alice. List some of the malicious things Trudy can do from this position.ProblemsP1. Design and describe an application-level protocol to be used between anautomatic tel

19、ler machine and a bank’s centralized computer. Your protocol should allow a user’s card and password to be verified, the account balance (which is maintained at the centralized computer) to be queried, and an account wit