Data Communications and Networking Solution Manual by Behrouz Forouzan (4th Edition)

Data Communications and Networking Solution Manual by Behrouz Forouzan (4th Edition) CHAPTER 1 1 Introduction Solutions to Odd-Numbered Review Questions and Exercises Review Questions 1. The five components of a data communication system are the sender , receiver , transmission medium , message , and protocol . 3. The three criteria are performance , reliability , and security . 5. Line configurations (or types of connections) are point -to-point and multipoint . 7. In half-duplex transmission , only one entity can send at a time; in a full-duplex transmission , both entities can send at the same time. 9. The number of cables for each type of network is: a. Mesh : n (n – 1) / 2 b. Star: n c. Ring : n – 1 d. Bus: one backbone and n drop lines 11. An internet is an interconnection of networks. The Internet is the name of a spe - cific worldwide network 13. Standards are needed to create and maintain an open and competitive market for manufacturers, to coordinate protocol rules, and thus guarantee compatibility o f data communication technologies. Exercises 15. With 16 bits, we can represent up to 216 different colors. 17. a. Mesh topology : If one connection fails, the other connections will still be work - ing. b. Star topology : The other devices will still be able to send data through the hub; there will be no access to the device which has the failed connection to the hub. c. Bus Topology : All transmission stops if the failure is in the bus. If the drop-line fails, only the corresponding device cannot operate. 2 d. Ring Topology : The failed connection may disable the whole network unless it is a dual ring or there is a by -pass mechanism. 19. Theoretically, in a ring topology , unplugging one station, interrupts the ring. How - ever, most ring networks use a mechanism that bypasses the station; the ring can continue its operation. 21. See Figure 1.1 Figure 1.1 Solution to Exercise 21 Hub Station Station Station Station Repeater Repeat er Station Station Station Station Repeat er Station 23. a. E-mail is not an interactive application. Even if it is delivered immediately, it may stay in the mail -box of the receiver for a while. It is not sensitive to delay. b. We normally do not expect a file to be copied immediately. It is not very sensi - tive to de lay. c. Surfing the Internet is the an application very sensitive to delay. We except to get access to the site we are searching. 25. The telephone network was originally designed for voice communication; the Internet was originally designed for data communic ation. The two networks are similar in the fact that both are made of interconnections of small networks. The telephone network, as we will see in future chapters, is mostly a circuit -switched network; the Internet is mostly a packet -switched network. CHAPTER 2 1 Network Models Solutions to Odd-Numbered Review Questions and Exercises Review Questions 1. The Internet model, as discussed in this chapter, include physical , data link , net- work , transport , and application layers. 3. The application layer supports the user. 5. Peer -to-peer processes are processes on two or more devices communicating at a same layer 7. Headers and trailers are control data added at the beginning and the end of each data unit at each layer of the sender and removed at the corresponding layers of the receiver. They provide source and destination addresses, synchronization points, information for error detection, etc. 9. The data link layer is responsible for a. framing data bits b. providing the physical addresses of the sender/receiver c. data rate control d. detection and correction of damaged and lost frames 11. The transport layer oversees the process -to-process delivery of the entire message. It is responsible for a. dividing the message into manageable segments b. reassembling it at the destination c. flow and error control 13. The application layer services include file transfer , remote access , shared data - base management , and mail services . Exercises 15. The International Standards Organization , or the International Organization of Standards , (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network com - munications is the Open Systems Interconnection (OSI) model.