Chapter # 04 Class IX
Data Communication and Computer Networks
Q#1: List the properties of a good communication system. Explain any one.
Ans:
1. Delivery
2. Accuracy
3. Timelines
4. Jitter
Accuracy: The system must deliver the data accurately. Data that has been altered during transmission and left uncorrected is not useful.
2. Accuracy
3. Timelines
4. Jitter
Accuracy: The system must deliver the data accurately. Data that has been altered during transmission and left uncorrected is not useful.
Q#2: Why OSI model is broken up in layers?
Ans: The OSI model is conceptual. It is broken up into layers so a person can visualize network communications and steps a computer takes when it encapsulates data from the application to the medium.
Q#3: Explain the purpose of Standard Organization.
Ans: Standard Organization develops, coordinates, revises, amends and reissues technical standards. These standards are intended to address the requirements of a group of concerned devices. There are several organizations working on standardization of computing equipment. IEEE, IETF, ITU and ANSI are the examples of widely reputed standard organizations.
Q#4: Give one example of LAN, WAN and MAN.
Ans:
Q#5: How can we measure bit rate and baud rate? Give an example of each.
Ans:
• Bit Rate: Bit rate can be measured with transmission of number of bits per second. For example bit rate is 10kbps means 10,000 bits are transferred within one second.
• Baud Rate: Baud rate can be measured with the number of signal units per second. For example baud rate is 9600 means 9600 signal level changes are happening within a second.
Q#6: List the seven layers of OSI model.
Ans: The Open System Interconnection Model (OSI) is a conceptual model developed by ISO. This
model divides a communication system into seven abstraction layers.
1. Physical layer
2. Data layer
3. Network layer
4. Transport layer
5. Session layer
6. Presentation layer
7. Application layer
1. Physical layer
2. Data layer
3. Network layer
4. Transport layer
5. Session layer
6. Presentation layer
7. Application layer
Q#7: Explain components of communication using single example.
Ans: A Communication system has following five components.
1. Message:
It is the information or data to be communicated or transmit.
2. Sender:
It is the device that generates and sends a message. It can be a computer, telephone handset,
etc.
3. Receiver:
Any particular digital electronic device which has capability to receive data in form of
message.
4. Medium:
It is the channel or path through which the message is carried from sender to the receiver.
5. Protocol:
Protocols are the rules and procedures on which computers exchange data on network.
Q#8: Write the function of following network devices. Amplifiers, Routers, Switch, Hub. \
Ans:
• Switch:
A switch or network switch is a networking device that connects computers and other devices
like printers, scanners and cameras on a network.
• Router:
A Router is a device that connects two or more networks. Routers are a combination of
hardware and software. The main function of a router is to determine the optimal data path
and transfer the information through that path.
• Amplifiers:
Amplifiers are used to overcome attenuation and make signal stronger again. It is measured in
decibels.
• Hub:
A hub is a physical layer networking device which is used to connect multiple devices in a
network. They are generally used to connect computers in a LAN.
Q#9: List one merit and one demerit of each topology.
Ans: Following are the merits and demerits of fundamental topologies.
Ans:
Topology:
The physical layout in which computer are connected or the arrangement of computer in a
network is called topology.
Types of Topology:
1. Bus Topology:
In bus topology computers and other devices are connected with a single cable. The
central cable is the backbone of the network and every device communicates with the other
device through this bus.
2. Ring Topology:
In ring topology, computers are connected in a ring or circle shape. The signal travels
around the loop in one direction and passes through each computer. The recipient of the
message receives the message while another computer acts like a repeater to send it to the
next computer.
3. Star Topology:
In star topology, all the computers are connected to a central device called hub or
switch. To communicate with any computer, the sender must send information to the hub.
Then the hub transmits that information to the destination.
Q#11: List the causes of signal impairments. Explain them.
Ans: There are three causes of signal impairments:
1. Attenuation
2. Distortion
3. Noise
• Noise:
Unwanted signal that mixes up with the original signal during the transmission of data is called
noise. It can be induced noise, crosstalk noise, thermal noise and impulse noise which may
damage the signal.
• Attenuation:
Attenuation means loss of energy. A signal loses its energy due to the resistance of medium
while it is transmitted. Amplifiers are used to overcome it. It is measured in decibel.
• Distortion:
Distortion means change in the shape of the signal. A composite signal has several frequencies.
Each having different speed in the medium and may reach at different time at destination. This
is called Distortion.
Q#12: What is the difference between radio wave and microwave?
Ans: Following are the some major difference between radio wave and microwave.
Radio Waves and Microwaves
Ans:
Analog and Digital Signal
Q#14: What is the difference between Bit rate and Baud rate?
Ans:
Bit Rate and Baud Rate
Q#15: What is the difference between Physical Address and Logical Address? (2022)
Ans:
Q#17: What do you mean by computer network? Write the names of different networks. (2023)
Ans: A computer network is a system that connects two or more computers to share information
electronically. Computers can connect using physical wires, such as fiber optics, or wirelessly.
Names of different networks are:
Physical Address and Logical Address
Q#16: Differentiate between LAN, MAN, and WAN?
Ans:
LAN, MAN and WAN
1. Local Area Network (LAN)
2. Wide Area Network (WAN)
3. Metropolitan Area Network (MAN)
Q#18: What is meant by transmission medium. Define guided and unguided media. (2023)
Ans: A transmission medium is a system or substance that transmits signals for telecommunication. It
can be a physical connection or interface between the transmitter and the receiver.
With guided transmission media, the waves are guided along a physical path; examples of guided
media include phone lines, twisted pair cables, coaxial cables, and optical fibers. Unguided
transmission media are methods that allow the transmission of data without the use of physical
means to define the path it takes.
Q#19: What do you mean by communication? Define any three components of communication
system. (2023)
Ans: Communication is the exchange of data and information between computers over a
communication channel. It allows computers to share resources, collaborate on tasks, and access
information stored on other devices.
Three Basic components of communication system are:
Transmitter:
A transmitter is an electrical device used in telecommunications to generate radio waves so that data
may be sent or sent using an antenna.
Communication channel:
A communication channel refers to either a physical transmission medium, such as a wire, or a logical
link over a multiplexed media, such as a radio channel.
Receiver:
The receiver processes the received signal, which is picked up from the broadcast signal at the channel
output, to recreate the original message signal in a recognizable form for delivery.
Q#20: What are the different types of topologies? Explain each. (2022)
Ans: Topology:
The physical layout in which computer are connected or the arrangement of computer in a
network is called topology.
Types of Topology:
1. Bus Topology:
In bus topology computers and other devices are connected with a single cable. The
central cable is the backbone of the network and every device communicates with the other
device through this bus.
2. Ring Topology:
In ring topology, computers are connected in a ring or circle shape. The signal travels
around the loop in one direction and passes through each computer. The recipient of the
message receives the message while another computer acts like a repeater to send it to the
next computer.
3. Star Topology:
In star topology, all the computers are connected to a central device called hub or
switch. To communicate with any computer, the sender must send information to the hub.
Then the hub transmits that information to the destination.
Q#21: Define components used in communication system. (2021)
Ans: A Communication system has following five components.
1. Message:
It is the information or data to be communicated or transmit.
2. Sender:
It is the device that generates and sends a message. It can be a computer, telephone handset,
etc.
3. Receiver:
Any particular digital electronic device which has capability to receive data in form of
message.
4. Medium:
It is the channel or path through which the message is carried from sender to the receiver.
5. Protocol:
Protocols are the rules and procedures on which computers exchange data on network.
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