Solutions to Odd-Numbered Review Questions and Exercises
Solution Manual for Data Communications and
Networking by Behrouz Forouzan
CHAPTER 1
Introduction
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 specific
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 of
data communication technologies.
Exercises
15. With 16 bits, we can represent up to 216 different colors.
17.
1
,2
a. Mesh topology: If one connection fails, the other connections will still be
working.
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.
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. However, 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 Repeater
Station Station Station Station
Repeater
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 sensitive to delay.
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 communication. 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
, Solutions to Odd-Numbered Review Questions and Exercises
Network Models
Review Questions
1. The Internet model, as discussed in this chapter, include physical, data link,
network, 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
database 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
communications is the Open Systems Interconnection (OSI) model.
17.
a. Reliable process-to-process delivery: transport layer
b. Route selection: network layer
1
, 2
c. Defining frames: data link layer
d. Providing user services: application layer
e. Transmission of bits across the medium: physical layer 19.
a. Format and code conversion services: presentation layer
b. Establishing, managing, and terminating sessions: session layer
c. Ensuring reliable transmission of data: data link and transport layers
d. Log-in and log-out procedures: session layer
e. Providing independence from different data representation: presentation layer
21. See Figure 2.1.
Figure 2.1 Solution to Exercise 21
23. Before using the destination address in an intermediate or the destination node, the packet goes through
error checking that may help the node find the corruption (with a high probability) and discard the
packet. Normally the upper layer protocol will inform the source to resend the packet.
25. The errors between the nodes can be detected by the data link layer control, but the error at the node
(between input port and output port) of the node cannot be detected by the data link layer.
CHAPTER 3
Data and Signals
Review Questions
1. Frequency and period are the inverse of each other. T = 1/ f and f = 1/T.
Solution Manual for Data Communications and
Networking by Behrouz Forouzan
CHAPTER 1
Introduction
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 specific
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 of
data communication technologies.
Exercises
15. With 16 bits, we can represent up to 216 different colors.
17.
1
,2
a. Mesh topology: If one connection fails, the other connections will still be
working.
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.
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. However, 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 Repeater
Station Station Station Station
Repeater
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 sensitive to delay.
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 communication. 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
, Solutions to Odd-Numbered Review Questions and Exercises
Network Models
Review Questions
1. The Internet model, as discussed in this chapter, include physical, data link,
network, 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
database 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
communications is the Open Systems Interconnection (OSI) model.
17.
a. Reliable process-to-process delivery: transport layer
b. Route selection: network layer
1
, 2
c. Defining frames: data link layer
d. Providing user services: application layer
e. Transmission of bits across the medium: physical layer 19.
a. Format and code conversion services: presentation layer
b. Establishing, managing, and terminating sessions: session layer
c. Ensuring reliable transmission of data: data link and transport layers
d. Log-in and log-out procedures: session layer
e. Providing independence from different data representation: presentation layer
21. See Figure 2.1.
Figure 2.1 Solution to Exercise 21
23. Before using the destination address in an intermediate or the destination node, the packet goes through
error checking that may help the node find the corruption (with a high probability) and discard the
packet. Normally the upper layer protocol will inform the source to resend the packet.
25. The errors between the nodes can be detected by the data link layer control, but the error at the node
(between input port and output port) of the node cannot be detected by the data link layer.
CHAPTER 3
Data and Signals
Review Questions
1. Frequency and period are the inverse of each other. T = 1/ f and f = 1/T.
