Notes for 9th Class
Chapter 5: Computer Networks
Write short answers to the following questions.
i. Describe any three difficulties a company may face in running a business without having a computer network.
Ans:
- Difficult to share office equipment
- Communication and collaboration are difficult without a computer network
- Difficult to protect data
ii. What is meant by data transmission?
Ans: Data Transmission
Data Transmission is the process of sending data from one device to another. It consists of the sender, receiver and the medium which carries the Information. There are three modes of data transmission which are simplex, Half-duplex and Full duplex.
iii. Differentiate between Half-duplex and Full-duplex transmission modes.
Ans: Half-Duplex Transmission Mode
A Half-duplex mode can send and receive data/information in both directions but not simultaneously. During data transmission, one end is the sender and the other is the receiver.
Examples
Half-duplex transmission is used in ATM machines for withdrawal of cash, money transfer and paying bills, etc.
Full-duplex Transmission Mode
A Full-duplex mode is used to transmit data/information in both directions simultaneously.
A Full-duplex mode can transmit more data/information at a higher rate.
Examples of Full-duplex modes are communication between computers in a network and communication over a telephone line.
iv. Define network architecture.
Ans: Network Architecture
Network architecture refers to layout of network that consists of computers, communication devices, software, wired or wireless transmission of data and connectivity between components.
A computer network can be as small as two computers linked together by a single cable whereas large networks connect thousands of computers and other devices.
v. Differentiate between a server and a client computer.
Ans: Server Computer
A Server is a main computer in a network which is used to manage the network and facilitate other computers. Server shares its resources, such as hard disk, printers and Internet connection etc.
Client Computer
Clients are computers in a network that access services made available by a server.
In a client/server network, each computer on the network acts as either a server or a client. Servers are not used as client computers and client computers are not used as servers.
vi. Compare LAN and WAN.
Ans: Local Area Network (LAN)
| Local Area Network (LAN) | Wide Area Network (WAN) |
| 1. It is a network that covers a limited area, usually ranging from a small office to a campus of nearby buildings. | 1. Wide Area Network spans a large area, connecting several locations an organization across cities, countries and continents. |
| 2. LAN is restricted to a limited geographical area. | 2. Wide Area Network WAN spans large geographical area. |
| 3. Data transmission speed is fast. | 3. Data transmission speed is slow. |
| 4. Data communication problems rarely occur. | 4. Data communication problems often occur |
| 5. Transmission medium is owned by the user organization | 5. Transmission medium is leased lines or public systems such as telephone lines or satellite links. |
vii. Why the star topology is more reliable than bus or ring topologies?
Ans: Due to the following reasons star topology is more reliable than bus or ring topology
- Provides fast communication between computers.
- Easy to connect new devices to the network.
- Easy to detect and fix faults.
- Failure of one computer does not stop the functioning of the entire network.
viii. Mention any three problems which may occur if the peer-to-peer network is used for a large number of users in an organization.
Ans: Problems of Peer-to-Peer Networks
i) Large peer-to-peer networks become difficult to manage.
ii) It does not provide centralized security.
iii) No single person is assigned to administer the resources of the network.
ix. What is ISDN?
Ans: ISDN
ISDN stands for Integrated Services Digital Network. It offers a maximum speed of 128Kbps. This speed is faster than Dial-up but slower than DSL. ISDN can transmit both voice and data at the same time over one cable. Users need ISDN digital telephone service from a telephone company. They also need a faster modem than a Dial-up modem. ISDN service is being replaced by faster DSL service.
x. What is CDMA technology?
Ans: CDMA Technology
CDMA stands for Code Division Multiple Access. It is a wireless cellular communication technology. CDMA services include short messaging, voice, data and video transmission. It can provide a speed of several Mbps for video transmission.
Write long answers to the following questions.
i. What are the advantages of using networks?
Ans: Advantages of using networks
The following are some common uses of networks.
Hardware Sharing
A network allows sharing of computer hardware such as hard disks and printers. A hard disk can be attached to a server to share it with other network users. A single hard disk can provide storage space to many users.
Software Sharing
Application software can be installed on a server and shared over the network. There is no need to install it on all the computers in a network.
File Sharing
A user of a network can easily share files with other users over the network. A user can place a file in a shared location on one computer and make it available to other users.
Users can access view and modify information stored on another computer in the network.
Internet Sharing
A single high-speed Internet connection can be shared with all the users over a network. There is no need to provide a separate Internet connection to every user on the network.
ii. Describe Client/Server and Peer-to-peer networks.
Ans: Client/Server Network
A server is the main computer in a network. It manages network resources and helps other computers. Clients are computers that use services from the server. In a client/server network, each computer is either a server or a client. Servers do not act as clients, and clients do not act as servers. The server shares its resources, like hard disks, printers, and Internet connection, with the client computers.
Peer-to-Peer Network
In a Peer-to-Peer network, all computers have the same status. Every computer is capable of playing the role of client, server or both at the same time. Each computer on the network is known as a peer. A peer on the network can share as well as access available resources on the network.
Peer-to-peer networks are suitable for a small number of users, ranging between two to ten computers. Large peer-to-peer networks become difficult to manage.
iii. Describe the types of networks based on the area covered.
Ans: Based on the geographical distance covered, computer networks are classified into Local Area Networks, Wide Area Networks and Metropolitan Area Networks.
Local Area Network (LAN)
A local area network is a commonly used network. It is a network that covers a limited area, usually ranging from a small office to a campus of nearby buildings. Examples of LAN include networks within a school, college, business and organization. Its Data transmission speed is fast and data communication problems rarely occur.
Wide Area Network (WAN)
A Wide Area Network (WAN) covers a large area. It connects several locations of an organization across cities, countries, and continents. A WAN often links two or more LANs or MANs at each location of an organization. These LANs connect to form a WAN. Examples of WANs are the networks used in banks, airlines, and national database authorities like NADRA in Pakistan. The Internet is another example of a WAN.
Its Data transmission speed is slow and data communication problems often occur.
Metropolitan Area Network (MAN)
A Metropolitan Area Network (MAN) falls between LAN and WAN. It spans an area larger than a LAN but smaller than a WAN. Examples of MAN are networks used by telecommunication companies for providing Cable TV and Internet services.
Its Data transmission speed is slower than LAN but faster than WAN. In MAN, Fibre optic cable or wireless microwave transmission is used as a communication medium.
iv. Explain the types of network topologies.
Ans: Types Network Topology.
Four types of network topologies are commonly used which are bus, ring, star and mesh.
Bus Topology
This is the simplest network topology. It has a single central cable called a bus. All devices connect to the bus along its length to communicate. A computer sends a message on the bus. The intended computer receives the message. Other computers ignore the message. Each end of the bus has a terminator device. The terminators prevent signals from bouncing back and causing errors.
Ring Topology
The ring network topology is shaped just like a ring. It is like a bus with both ends connected. All the messages travel in the same direction. Message from one node is sent to the next node. It is received by it if it is addressed to it otherwise it is ignored and passed on to the next until the destination is reached.
Star Topology
In star topology, all the nodes are connected to a central device called a switch or hub. It is one of the most commonly used network topologies. A switch can connect 4, 8, 16, 24 or 32 nodes. A switch can be connected to another switch to expand the network.
Mesh Topology
In mesh network topology, all the network nodes are connected to all the other nodes. Messages sent on a mesh network can take possible paths from source to destination. It is not commonly used since it is costly and difficult to implement.
v. Write a note on Dial-up and DSL Internet connections.
Ans: Dial-up Line
The dial-up line uses standard telephone lines for Internet connection. It requires a Dial-up modem that provides a maximum Internet connection speed of 56Kbps. The main advantage of using a Dial-up line is that it uses a complex network of telephone lines that allows data to be transmitted to almost any location in the world. It is becoming outdated due to very slow Internet connection.
DSL
DSL (Digital Subscriber Line) provides a high-speed Internet connection. It is called broadband because it uses a broad range of frequencies to transmit data. Any Internet speed of 256Kbps or higher is called broadband. A DSL modem is needed to set up a DSL Internet connection. Internet Service Providers (ISPs) offer different DSL speeds with various monthly rates.
Select the best answer for the following MCQs.
i. In which of the following transmission modes, information is transmitted in both directions but not simultaneously?
A. Simplex mode
B. Half-duplex mode
C. Full-duplex mode
D. High-speed mode
ii. In which of the following networks, every computer can act as a client, server or both at the same time?
A. Client/server network
B. Peer-to-Peer network
C. Point-to-Point network
D. Local area network
iii. Which of the following networks provides centralized security?
A. Client/server network
B. Peer-to-peer
C. Point-to-Point network
D. Local area network
iv. Computer Networks Which of the following computers share resources on a network for others to use
A. Desktop computer
B. Client
C. Server
D. Microcomputer
v. Which of the following topologies is most expensive to implement?
A. Star
B. Bus
C. Ring
D. Mesh
vi. In which of the following network topologies is, a switch required?
A. Star
B. Bus
C. Ring
D. Mesh
vii. Which of the following networks is used to provide Cable TV and Internet services?
A. Local area network
B. Wide area network
C. Metropolitan area network
D. Point-to-Point network
viii. Which of the following provides a high-speed Internet connection?
A. Dial-up connection
B. DSL connection
C. ISDN connection
D. CDMA connection
ix. Which of the following networks connects computers across cities, countries and continents?
A. Local area network
B. Wide area network
C. Metropolitan area network
D. Client/Server network
x. Which of the following network topology uses a device called a terminator?
A. Ring topology
B. Mesh topology
C. Bus topology
D. Star topology