Unit 6: Introduction to Computer Networks — Short Questions

A computer network is a system of linked devices and computers that may exchange data and operate together. Networks can range from small, Local Area Network (LANs, Local Area Networks) to large area network, WANs, including the Internet.

Following are the primary components:

• Nodes
• Links
• Switches
• Routers

Devices that are connected to the network, such as computers, smartphones, and printers. Nodes play an important role in many areas of computer science, including data structures, computer networks, neural networks, and blockchain systems.

Devices that connect multiple nodes within a network to forward data. In computer networks, switches serve as central devices that receive data packets from linked devices and intelligently transfer them to their intended destination, improving network efficiency and minimizing traffic congestion.

The primary objective of computer network is to enable resource sharing, data communication and collaboration:

• Resource Sharing
• Data Communication
• Connectivity and Collaboration

A protocol is a formal agreement between two parties. A network protocol is a formal arrangement between two computers to send and receive information.

Transmission Media is the channel or path through which the data or information is transferred from one place to another in a computer network. Some examples of transmission media are coaxial cable, fiber optic cable, microwaves, etc.

A router is a networking device that interconnects networks or allows devices to connect to it. It directs data packets between different network. Think of it as a traffic director on the internet, making sure that data gets from one place to another efficiently.

SIM 'stands for Subscriber Identity Module. It is a small card inserted into a mobile device that contains unique information to identify and authenticate the subscriber on a mobile network.

An access point works by receiving data from the wired network and transmitting it wirelessly to your devices. It also receives data from your wireless devices and sends it to the wired network.

Topology of a network is a geometric representation of the relationship among the interconnected devices.
Types: Four types of network topologies are:

• Bus topology
• Ring topology
• Star topology
• Mesh topology

Network communication modes describe how data is transmitted between devices. There are three primary modes: Simplex, Half-Duplex, and Full-Duplex.

The Open Systems Interconnection (OSI) Model is a framework used to understand how different networking protocols interact. It has 7 layers, each with a specific function.

Here is the list of 7 layers of OSI model:

• Physical Layer
• Data Link Layer
• Network Layer
• Transport Layer
• Session Layer
• Presentation Layer
• Application Layer

IP stands for Internet Protocol. It is a method of identifying each computer on the internet. All IP addresses are unique. Each device gets its own unique IP address when its gets connected to the Internet.

Firewalls are security systems that monitor and control incoming and outgoing network traffic based on predetermined security rules. Firewalls act as barriers between trusted internal networks and untrusted external networks, like a security checkpoint.

Encryption transforms data into a secure format that can only be read or understood by authorized parties with the correct decryption key. Decryption is the process of converting the encrypted data back to its original form.

Malware Malicious software such as viruses, worms, and ransomware that can damage or steal data.
Phishing: Attempts to trick users into revealing sensitive information through deceptive emails or websites.

A PAN is a small network used for communication between personal devices, such as smartphones, tablets, and laptops, within a short range. Example: Bluetooth connections between a smartphone and a wireless headset form a PAN.

A CAN is a network that connects multiple LANs within a limited geographical area, such as a university campus or a business park.

The network that connects various departments and buildings within a university is a CAN.

Networks are connected together to make a larger network which is called network of networks or internet.

A computer sends a message on the bus. The computer to whom the message is sent receives it while others ignore it. At each end of bus a device called terminator is attached so that the signals do not bounce back on the bus causing errors.

In bus topology all of the devices of the network are connected to a common transmission medium which has exactly two end points called terminator.

A bus topology connects all devices of the network through a single common cable having exactly two end points. This cable is called backbone of the topology.

A ring can be unidirectional or bidirectional
Unidirectional: In a unidirectional ring topology, data is sent either clockwise or anti clockwise.
Bidirectional: In a bidirectional ring topology, data can travel in any direction. Upon receiving data, a computer may pass data to its next neighbor.

Advantages
1. Star topology is more reliable and support large numbers of computers than bus topology.
2. It is easy to detect and fix errors than bus topology.
Disadvantages
1. Lengthy cable is required as compared to bus topology.
2. Star topology is expensive as compared to bus topology.

In ring topology, a failure of connection between two computers may down the whole network.

Data communication refers to exchange of messages between sending and receiving devices through some communication medium. Following are the main components of data communication.

• Sender
• Receiver
• Message
• Protocol
• Transmission Medium

Sender Sender is a device that initiates the communication process. It sends messages consisting of text, numbers, picture etc. It is also called transmitter.
Receiver: Receiver is a device that receives a message. It is also called sink. The receiver can be computer, printer or another device.

Message is the data or information to be communicated. It may consist of text, number, pictures, sound, video or any combination of these.
Packet: In networking, a packet is a small unit of data that is transferred across a network. It includes Payload (Actual Content) and Control Information (Address of sender and receiver).

The Transport Layer ensures that data is transferred from one process rerunning on source end system to a process souring on destination end system. It manages data flow control and error checking.

Error detection and correction, as well as node-to-node data transport, are handled by the Data Link Layer. It ensures error-free data transmission from the physical layer.
Physical Layer: Physical layer is about the physical medium used in communication, like cabling etc.

IPv4 address is a 32 bit numbers that uniquely identifies a network interface on a machine. When the Internet Protocol was originally designed, the standard was known as Internet Protocol Version 4 (IPv4). IPv4 is divided in four groups separated by '.'
Example: IPv4 address is like: 172.16.254.1

IPv6 address is a 128 bits numbers that uniquely identifies a network interface on a machine. In IPv6, there are 8 groups separated by ':'