SOLUTIONS MANUAL & MCQS
DATA COMMUNICATION AND NETWORKING
6TH EDITION
CHAPTER NO. 01: INTRODUCTION
PRACTICE SET
ANSWERS TO QUESTIONS
Q1-1. The five components of a data communication system are the sender, receiver,
transmission medium, message, and protocol.
Q1-2. The three criteria are performance, reliability, and security.
Q1-3. Advantages of a multipoint over a point-to-point configuration (type of
connection) include ease of installation and low cost.
Q1-4. Line configurations (or types of connections) are point-to-point and multi-
point.
Q1-5. We can divide line configuration in two broad categories:
a. Point-to-point: mesh, star, and ring.
b. Multi-point: bus
Q1-6. 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.
Q1-7. We give an advantage for each of four network topologies:
a. Mesh: secure
b. Bus: easy installation
c. Star: robust
d. Ring: easy fault isolation
Q1-8. 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
Q1-9. The general factors are size, distances (covered by the network), structure,
and ownership.
Q1-10. An internet is an interconnection of networks. The Internet is the name of a
specific worldwide network
Q1-11. A protocol defines what is communicated, in what way and when. This
provides accurate and timely transfer of information between different devices
on a network.
,Q1-12. We do not need a link-layer switch because the communication in this case is
automatically one-to-one. A link-layer switch is needed when we need to
change a one-to-many communication to a one-to-one.
Q1-13. Each LAN should be connected to (n − 1) LANs. This means that we have n
× (n − 1) connections. However, if each connection can be used in both
directions, we need only [n × (n − 1)]/2 connections.
Q1-14. Local telephone communication is mostly a circuit-switched network. When
the communication is established, the circuit is dedicated between the two
parties.
Q1-15. To make the communication bidirectional, each layer needs to be able to
provide two opposite tasks, one in each direction.
Q1-16. The link-layer switch is normally involved in the first two layers of the TCP/
IP protocol suite: the physical layer and the data-link layer.
Q1-17. The router is involved in three physical layers, three data-link layers, and
only one network layer.
Q1-18. The identical objects are the two messages: one sent and one received.
Q1-19.
a. At the application layer, the unit of data is a message.
b. At the network layer, the unit of data is a datagram.
, c. At the data-link layer, the unit of data is a frame.
Q1-20. A frame is a link-layer data unit. It encapsulates a data unit coming from the
network layer. In this case, the data unit is a datagram.
Q1-21. The data unit should belong to layer 4. In this case, it is a user datagram.
Q1-22. We mentioned HTTP, FTP, SMTP, SNMP, TELNET, SSH, and DNS.
Q1-23. The transport-layer packet needs to include two port numbers: source and des-
tination port numbers. The transport-layer header needs to be at least 32 bits
(four bytes) long, but we will see in Chapter 3 that the header size is normally
much longer because we need to include other pieces of information.
Q1-24.
a. At the application layer, we normally use a name to define the destination computer name and
the name of the file we need to access. An example is .
b. At the network layer, we use two logical addresses (source and destination) to define the source
and destination computers. These addresses are unique universally.
c. At the data-link layer, we use two link-layer addresses (source and destination) to define the
source and destination connections to the link.
DATA COMMUNICATION AND NETWORKING
6TH EDITION
CHAPTER NO. 01: INTRODUCTION
PRACTICE SET
ANSWERS TO QUESTIONS
Q1-1. The five components of a data communication system are the sender, receiver,
transmission medium, message, and protocol.
Q1-2. The three criteria are performance, reliability, and security.
Q1-3. Advantages of a multipoint over a point-to-point configuration (type of
connection) include ease of installation and low cost.
Q1-4. Line configurations (or types of connections) are point-to-point and multi-
point.
Q1-5. We can divide line configuration in two broad categories:
a. Point-to-point: mesh, star, and ring.
b. Multi-point: bus
Q1-6. 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.
Q1-7. We give an advantage for each of four network topologies:
a. Mesh: secure
b. Bus: easy installation
c. Star: robust
d. Ring: easy fault isolation
Q1-8. 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
Q1-9. The general factors are size, distances (covered by the network), structure,
and ownership.
Q1-10. An internet is an interconnection of networks. The Internet is the name of a
specific worldwide network
Q1-11. A protocol defines what is communicated, in what way and when. This
provides accurate and timely transfer of information between different devices
on a network.
,Q1-12. We do not need a link-layer switch because the communication in this case is
automatically one-to-one. A link-layer switch is needed when we need to
change a one-to-many communication to a one-to-one.
Q1-13. Each LAN should be connected to (n − 1) LANs. This means that we have n
× (n − 1) connections. However, if each connection can be used in both
directions, we need only [n × (n − 1)]/2 connections.
Q1-14. Local telephone communication is mostly a circuit-switched network. When
the communication is established, the circuit is dedicated between the two
parties.
Q1-15. To make the communication bidirectional, each layer needs to be able to
provide two opposite tasks, one in each direction.
Q1-16. The link-layer switch is normally involved in the first two layers of the TCP/
IP protocol suite: the physical layer and the data-link layer.
Q1-17. The router is involved in three physical layers, three data-link layers, and
only one network layer.
Q1-18. The identical objects are the two messages: one sent and one received.
Q1-19.
a. At the application layer, the unit of data is a message.
b. At the network layer, the unit of data is a datagram.
, c. At the data-link layer, the unit of data is a frame.
Q1-20. A frame is a link-layer data unit. It encapsulates a data unit coming from the
network layer. In this case, the data unit is a datagram.
Q1-21. The data unit should belong to layer 4. In this case, it is a user datagram.
Q1-22. We mentioned HTTP, FTP, SMTP, SNMP, TELNET, SSH, and DNS.
Q1-23. The transport-layer packet needs to include two port numbers: source and des-
tination port numbers. The transport-layer header needs to be at least 32 bits
(four bytes) long, but we will see in Chapter 3 that the header size is normally
much longer because we need to include other pieces of information.
Q1-24.
a. At the application layer, we normally use a name to define the destination computer name and
the name of the file we need to access. An example is .
b. At the network layer, we use two logical addresses (source and destination) to define the source
and destination computers. These addresses are unique universally.
c. At the data-link layer, we use two link-layer addresses (source and destination) to define the
source and destination connections to the link.
