Ch-1 Network Operating System

Table of Contents

Q 1. What is computer Network ? What are its advantages?

A computer network is a collection of interconnected devices, such as computers, servers, printers, routers, and switches, that can communicate with each other and share resources. These networks can be small, like those found in homes or offices, or large, like those spanning across cities or even continents.

Advantages:

Resource Sharing: Users can share devices like printers, scanners, and data stored on servers.
Communication: Facilitates communication through email, instant messaging, and video conferencing.
Cost Efficiency: Sharing resources reduces the need for duplicate equipment, saving costs.
Centralized Data Management: Centralized servers make it easier to manage and secure data.
Flexibility: Users can access resources and information from anywhere within the network.
Improved Collaboration: Allows multiple users to work on the same document or project simultaneously.
Increased Productivity: Access to shared resources and faster communication tools can boost productivity.

Q 2. What are the components of the computer network?

A computer network is build up from several components. These components together make it possible to transfer data from one device to another and make smooth communication between two different devices. Basic components of a computer network are :

Servers: Specialized computers that provide services or resources to other computers on the network, such as file storage, email, or web hosting.
Clients : Clients are computer that request and receive service from the servers to access and use the network resources.
Hub: A hub is a hardware device that divides the network connection among multiple devices. When a computer requests information from the network, it sends the request to the hub via a cable.The hub then broadcasts the request to all devices on the network. However, hubs consume more bandwidth and limit communication efficiency. Nowadays, hubs are obsolete and replaced by more advanced components like switches and routers.
Routers: Devices that forward data packets between different networks. They determine the best path for data to travel and enable communication between devices on different networks.
Switches: Devices that connect multiple devices within a local network. They forward data packets to the intended recipient within the same network.
Network Interface Cards (NICs): Hardware components installed in computers and other devices to enable them to connect to a network. There are two types of NICs:
Wired NIC: Integrated into the motherboard, it uses cables and connectors for data transfer.
Wireless NIC: Contains an antenna for wireless network connections (e.g., laptops have wireless NICs). NICs provide the physical interface for connecting to network cables or wireless signals.
Transmission Medium: Includes cables (e.g., Ethernet, fiber optic) used for data transmission.

Q 3. Explain the working of TCP/IP?

The Transmission Control Protocol/Internet Protocol (TCP/IP) is a suite of networking protocols used to facilitate communication and data exchange over the Internet and other computer networks. It provides a set of rules and conventions that govern how data is transmitted, routed, and received between devices.

TCP/IP model divides the data into a 4-layer procedure, where the data first go into this layer in one order and again in reverse order to get organized in the same way at the receiver’s end.

Layers of TCP/IP Model

Application Layer
Transport Layer(TCP/UDP)
Network/Internet Layer(IP)
Data Link Layer

Data Link Layer− The protocol in this layer works in the link between different devices in the network. It includes Protocol for Ethernet and Address Resolution Protocol.
Network Layer − It consists of IP and Internet Control Message Protocol (ICMP). IP takes care of the destination and host addresses and makes sure the connection is maintained. ICMP reports errors in case the connection is not proper.
Transport Layer − The transfer of data is done in this layer. It is responsible for maintaining the communication between the sender and receiver. TCP or UDP (User Datagram Protocol) is used for this purpose.
Application Layer − It consists of HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), POP3 (Post Office Protocol 3), SMTP (Simple Mail Transfer Protocol), and SNMP (Simple Network Management Protocol). It is called the application layer because it consists of application data.

Q 4. What do you mean by IP Addressing? Discuss classful addressing scheme?

IP Addressing: An IP address (Internet Protocol address) is a numerical label assigned to each device connected to a computer network. It serves as a unique identifier for devices within a network, allowing them to communicate with each other. IP addresses play a critical role in routing data packets across the internet and local networks.

IP Address Classes

The IPv4 address is divided into two parts:

Network ID
Host ID

The class of IP address is used to determine the bits used for network ID and host ID and the number of total networks and hosts possible in that particular class. Each ISP or network administrator assigns an IP address to each device that is connected to its network.

Classful Addressing

The 32-bit IP address is divided into five sub-classes. These are given below:

Class A: IP addresses belonging to class A ranges from 0.0.0.0 – 127.255.255.255. The network ID is 8 bits long. The host ID is 24 bits long. Class A addresses are assigned to the networks that contain a large number of hosts. The higher-order bit of the first octet in class A is always set to 0. The remaining 7 bits in the first octet are used to determine network ID. The 24 bits of host ID are used to determine the host in any network.
Class B : IP addresses belonging to class B ranges from 128.0.0.0 – 191.255.255.255. IP address belonging to class B is assigned to networks that range from medium-sized to large-sized networks. The network ID is 16 bits long. The host ID is 16 bits long. The higher-order bits of the first octet of IP addresses of class B are always set to 10. The remaining 14 bits are used to determine the network ID. The 16 bits of host ID are used to determine the host in any network.
Class C : IP addresses belonging to class C range from 192.0.0.0 – 223.255.255.255.IP addresses belonging to class C are assigned to small organizations or individual networks. The network ID is 24 bits long. The host ID is 8 bits long. The higher-order bits of the first octet of IP addresses of class C is always set to 110. The remaining 21 bits are used to determine the network ID. The 8 bits of host ID are used to determine the host in any network.
Class D: IP addresses belonging to class D range from 224.0.0.0 – 239.255.255.255.IP address belonging to class D is reserved for multi-casting. The higher-order bits of the first octet of IP addresses belonging to class D is always set to 1110. The remaining bits are for the address that interested hosts recognize.
Class E : IP addresses of class E range from 240.0.0.0 – 255.255.255.254. IP addresses belonging to class E are reserved for experimental and research purposes. The higher-order bits of the first octet of class E are always set to 1111.

Q 5. What is network routing ? Explain its types.

Routing is the process by which data packets are forwarded from their source to their destination across a network. It involves selecting the optimal path for data transmission based on various factors.

Types of Routing

Static Routing: In static routing, network administrators manually configure routing tables on routers to define the paths that data packets should take.Static routes are typically used in small networks with relatively stable topology and predictable traffic patterns. While simple and easy to configure, static routing does not adapt to changes in network conditions and may not be suitable for large or dynamic networks.
Dynamic Routing: Dynamic routing protocols automate the process of updating routing tables by exchanging routing information between routers. These protocols use algorithms to calculate the best path for data packets based on factors such as hop count, link cost, and network congestion. Examples of dynamic routing protocols include Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Border Gateway Protocol (BGP).

Dynamic routing is more flexible and scalable than static routing, making it well-suited for large and dynamic networks where topology changes frequently.

Q 6. What is NOS ? write down its advantages?

NOS stands for Network Operating System. It is a specialized operating system that provides networking capabilities and services to devices connected to a computer network. NOS enables devices such as computers, servers, printers, and network devices to communicate, share resources, and access network services. Examples of NOS: Microsoft Windows Server, UNIX/Linux, Artisoft’s LANtastic, Banyan’s VINES. Here are some advantages of using a NOS:

Network Management: It allows network administrators to monitor network performance, troubleshoot issues, and enforce security policies.
Resource Sharing: NOS facilitates resource sharing among devices on the network. Users can share files, printers, scanners, and other peripherals, reducing the need for duplicate equipment and improving resource utilization.
Centralized Authentication and Access Control: NOS typically includes authentication mechanisms such as usernames, passwords, and access control lists (ACLs) to control access to network resources.
Data Backup and Recovery: Administrators can schedule regular backups of network data and restore files or systems in the event of data loss or system failure.
Security Features: NOSs incorporate various security features to protect network resources from unauthorized access, data breaches, and malicious attacks.
Remote Access and Mobility: NOSs support remote access technologies such as VPN (Virtual Private Network) and remote desktop services, allowing users to securely connect to the network from remote locations.

Q 7. What is linux ? What are its features?

Linux is a free and open-source Unix-like operating system kernel first developed by Linus Torvalds in 1991. It is the foundation of many popular operating systems, known as Linux distributions or simply “distros,” such as Ubuntu, Debian, Fedora, and CentOS. Linux is widely used in both personal and enterprise computing environments due to its stability, security, and flexibility.

Here are some key features of Linux:

Open Source: Linux is distributed under open-source licenses, such as the GNU General Public License (GPL), which allows users to view, modify, and distribute the source code freely.
Multiuser and Multitasking: Linux supports multiple users and concurrent execution of multiple processes, allowing multiple users to access the system simultaneously and run multiple applications concurrently without interference.
Security: Linux incorporates various security features to protect against unauthorized access, malware, and other security threats. This includes user and group permissions, access control lists (ACLs), firewalls, encryption, and security-enhanced Linux policies.
Networking Capabilities: Linux includes comprehensive networking capabilities, with support for various networking protocols, services, and utilities. It can function as a router, firewall, DNS server, web server, file server, and more, making it ideal for networking and server applications.
Community Support: Linux has a vibrant and active community of developers and users who contribute to its development, provide technical support, and share knowledge through forums, mailing lists, and online communities.
File System: Provides hierarchical file system in which files and directories are arranged.

Q 8. What are the components of Linux?

Linux is composed of several key components that work together to provide a complete operating system environment. These components include:

Kernel: The kernel is the core of the Linux-based operating system. It acts as the brain, managing how the computer interacts with its hardware and resources.

There are different types of kernels, including:

Monolithic Kernel: A single large program that handles all system services.
Hybrid Kernels: Combines features of monolithic and micro kernels.
Exo Kernels: Minimizes the kernel’s role, delegating most tasks to user-level programs.
Micro Kernels: Keeps the kernel minimal, moving most services to user space.

Shell: The shell is the command-line interface through which users interact with the operating system. It interprets user commands and executes them by communicating with the kernel. Popular shells include Bourne Shell, C Shell, TC Shell ,Korn Shell, Bash Shell.
Utilities: Linux utilities are a collection of software tools and commands that users can utilize to perform tasks. These utilities include commands like ls, man, pwd, cd, and more.
Applications: Linux applications (user-level programs) run on top of the kernel. These applications perform specific tasks and allow users to run software securely and effectively.

Q 9. What is shell ? Discuss the various types of shell

A shell is a command-line interface (CLI) that allows users to interact with the operating system. It provides a way to execute commands, manage files, and control system resources.

When we open a terminal or command prompt, we’re essentially using a shell. The shell interprets our commands and communicates with the kernel to perform tasks.

Types of Shells

There are several shells available, each with its own features and capabilities.

Bourne Shell : The original Bourne shell is named after its developer “Steve Bourne”. It was the first shell used for the Unix operating system. It provides features which are sufficient for most programmer needs.
Csh (C Shell) and Tcsh (Enhanced C Shell): C shell and Tc shell are based on the C programming language syntax and provide interactive features such as command history, job control etc. Tc shell is an improved version of C shell with additional features like command-line editing, filename completion, and job control enhancements.
Ksh (Korn Shell): Ksh is a powerful shell with advanced scripting features, developed by David Korn at AT&T Bell Labs. It provides features like associative arrays, arithmetic expansion, and advanced flow control constructs.
Bash (Bourne Again Shell): Bash is the default shell for most Linux distributions and is widely used due to its versatility and extensive features.It is backward-compatible with the original Bourne Shell and incorporates many features from other shells such as Korn shell (ksh) and C shell (csh)

Q 10. What do you mean by input & output redirection in linux?

In Linux, whenever an individual runs a command, it can take input, give output, or do both. Redirection helps us redirect these input and output functionalities to the files or folders we want, and we can use special commands or characters to do so.

Different types of redirection

Output Redirection: The > symbol is used for standard output redirection.

When we use >, the output of a command is sent to a file, overwriting any existing content in that file.

Example:

echo “Hello, world!” > output.txt

This command will create or overwrite the file output.txt with the text “Hello, world!”.

Append Output Redirection:

The >> symbol appends output to an existing file without overwriting its content.

Example:

echo “Hello users” >> demo.txt

This adds the text “Hello users” to the end of the demo.txt file.

Input Redirection: The < symbol is used for standard input redirection. It allows us to read input from a file instead of the keyboard.

Example:

cat < input.txt

This displays the contents of the input.txt file on the terminal.

Q 11. What do you mean by vi editor ? Explain.

The vi editor (short for “visual editor”) is a screen-oriented text editor originally created for Unix-based systems. It provides a command-line interface for editing files. Vi is lightweight, efficient, and available by default on most Linux distributions. An improved version of vi is called Vim (Vi IMproved), which adds additional features and enhancements.

Modes of Operation in Vi Editor

Command Mode: When we start vi, it begins in Command Mode. In this mode:

Characters we type are interpreted as commands (not displayed on the screen).
we can navigate through a file, delete, copy, or paste text.
To enter Command Mode from any other mode, press the [Esc] key.

Insert Mode: This mode allows us to insert text into the file. To enter Insert Mode, type i. Everything we type in this mode is added to the file.
Last Line Mode (Escape Mode): Invoked by typing a colon (:) while in Command Mode. In this mode:

The cursor jumps to the last line of the screen.
we can perform tasks like saving files and executing commands.

To open a file with vi, use the command:

vi [file_name]

Examples:

Creating a new file:

vi myfile

Opening an existing file:

vi demofile

Some useful commands of vi editor are :

Q 12. What is Cyber Crime ? Explain.

Cybercrime refers to criminal activities that are carried out using computers, networks, and digital technologies. These criminal activities are often aimed at stealing sensitive information, causing harm to individuals or organizations, or disrupting the normal functioning of computer systems and networks. Cybercrime encompasses a wide range of illegal activities, and it continues to evolve as technology advances. Here are some common types of cybercrime:

Stealing Personal Information: Just like a thief might steal your wallet, cybercriminals try to steal personal information like your passwords, credit card numbers, or social security numbers. They can then use this information to pretend to be you or steal your money.
Hacking: Hacking is when someone breaks into a computer system or a website without permission. It’s like breaking into a house through a window. Hackers can steal important data, like your emails or even your school’s records, or they can cause problems by deleting or changing things.
Phishing: Imagine getting a fake email that looks like it’s from your bank, asking for your account information. That’s called phishing. Cybercriminals send emails or messages pretending to be someone you trust to trick you into giving them your personal information.
Viruses and Malware: These are like digital germs that infect your computer or smartphone. They can slow down your device, steal your information, or even damage your files. It’s like getting sick from a virus, but for your computer.
Cyberbullying: Cyberbullying happens when someone uses the internet or social media to hurt or harass others. They might send mean messages, spread rumors, or post embarrassing photos to make someone feel bad.
Identity Theft: Just like someone might steal your wallet to pretend to be you, cybercriminals can steal your identity online by using your personal information to open accounts or make purchases in your name.
Cyberstalking: This is when someone uses the internet or social media to harass or follow someone else, making them feel scared or uncomfortable. It’s like being followed by someone in real life, but it happens online.
Denial of Service (DoS) Attacks: This is when cybercriminals flood a website or computer system with so much traffic that it crashes and becomes unavailable to users. It’s like blocking the entrance to a store so no one can get in.

Q 13. Explain the term Cyber Law?

Cyber law is like rules and regulations that govern the use of computers, the internet, and other digital technologies. It’s important because it helps protect people from cybercrime and ensures that everyone behaves responsibly online.

Here are some key things that cyber law covers:

Online Safety: Cyber law includes rules to keep people safe online. For example, it might say that companies need to protect your personal information when you shop online, or that social media websites have to take down harmful content.
Privacy: Cyber law protects your privacy on the internet. It might say that websites have to ask for your permission before collecting your personal information, like your name or email address.
Cybercrime: Cyber law helps catch and punish cybercriminals who break the law online. This includes things like hacking into computer systems, stealing someone’s identity, or spreading viruses.
Intellectual Property: Cyber law protects things like music, movies, books, and software from being stolen or copied without permission. It’s like saying that you can’t take someone else’s painting and claim it as your own.
Social Media: Cyber law includes rules for using social media responsibly. For example, it might say that you can’t bully or harass people online, or that you can’t share someone else’s private information without their permission.