IGNOU BCA MCS-22 Operating System Concepts and Networking Management Solved Question Paper (December 2023)

Q1. (a) Write the Linux/Unix commands for: (2×5=10 marks)

(i) List all hidden files in a directory.
(ii) List all process currently running on the system.
(iii) Set permission to a file, say "sample.txt" so that the file can be read by owner only.
(iv) Print last 10 lines of a file.
(v) Show all user, currently logged on.

Answer:

Linux/Unix commands are essential tools for system administration and file management. Each command serves specific purposes in the operating system environment.

(i) List all hidden files in a directory:

ls -la

(ii) List all process currently running on the system:

ps -ef

(iii) Set permission to a file "sample.txt" so that it can be read by owner only:

chmod 400 sample.txt

(iv) Print last 10 lines of a file:

tail filename

(v) Show all users currently logged on:

who

Q1. (b) Why do we need a firewall? Explain the working of firewall in detail. Also, explain the limitations of using firewall. (2+5+3 marks)

Answer:

Why do we need a firewall?
Firewalls are essential security components that protect networks and systems from unauthorized access, cyber attacks, and malicious activities. They act as a barrier between trusted internal networks and untrusted external networks like the Internet.

Working of Firewall in Detail:

Packet Filtering:
→ Examines each data packet's header information
→ Checks source and destination IP addresses, port numbers, and protocols
→ Compares packet attributes against predefined security rules
→ Allows or blocks packets based on configured policies

Stateful Inspection:
→ Maintains connection state information in memory
→ Tracks TCP connection states and UDP sessions
→ Ensures responses match legitimate outbound requests
→ Provides better security than simple packet filtering

Application Layer Filtering:
→ Analyzes application-specific data content
→ Understands protocols like HTTP, FTP, SMTP
→ Can filter based on URLs, email content, or file types
→ Provides deep packet inspection capabilities

Limitations of Using Firewall:

→ Internal Threats: Cannot protect against threats from inside the network
→ Application Vulnerabilities: Cannot prevent attacks on application layer flaws
→ Performance Impact: May slow down network traffic due to inspection overhead
→ Configuration Complexity: Requires expertise to configure and maintain properly
→ Encrypted Traffic: Limited ability to inspect encrypted communications
→ Single Point of Failure: If firewall fails, network security is compromised

Q1. (c) Differentiate between FAT32 and FAT16 file systems. Explain the features of NTFS in context of Windows 2000 OS. (3+7 marks)

Answer:

Difference between FAT32 and FAT16:

FAT16:
→ Maximum partition size: 2GB
→ Maximum file size: 2GB
→ Uses 16-bit file allocation table entries
→ Cluster size ranges from 2KB to 32KB
→ Less efficient for large drives due to large cluster sizes

FAT32:
→ Maximum partition size: 2TB
→ Maximum file size: 4GB
→ Uses 32-bit file allocation table entries
→ Smaller cluster sizes, more efficient storage
→ Better performance and reduced disk space wastage

Features of NTFS in Windows 2000:

Security Features:
→ Access Control Lists (ACLs) for fine-grained permissions
→ File and folder level security settings
→ Encryption support using Encrypting File System (EFS)
→ User quotas to control disk usage per user

Reliability Features:
→ Journaling file system with transaction logging
→ Automatic error checking and bad sector remapping
→ Shadow copy service for file versioning
→ Self-healing capabilities for minor file system corruption

Performance Features:
→ Support for large files (up to 16TB) and volumes (up to 256TB)
→ File compression to save disk space
→ Sparse files support for efficient storage
→ Defragmentation capabilities for optimized performance

Advanced Features:
→ Hard links and symbolic links support
→ Alternate data streams for additional file metadata
→ Volume mounting and junction points
→ Unicode filename support for international characters

Q1. (d) What is X-Windows? Explain the major components of Unix-based GUI's in X-Windows. (2+8 marks)

Answer:

What is X-Windows?
X-Windows (also known as X11 or X Window System) is a network-transparent windowing system that provides the basic framework for building graphical user interfaces in Unix-like operating systems. It separates the display server from client applications, allowing distributed computing across networks.

Major Components of Unix-based GUIs in X-Windows:

X Server:
→ Core component that manages display hardware and input devices
→ Handles keyboard, mouse, and monitor interactions
→ Provides low-level graphics operations and window management
→ Runs on the machine with the physical display

X Client Applications:
→ Programs that use X protocol to display graphical interfaces
→ Can run on remote machines and display locally
→ Communicate with X server through X11 protocol
→ Include applications like text editors, web browsers, and games

Window Manager:
→ Controls window placement, movement, and resizing
→ Manages window decorations like title bars and borders
→ Handles window focus and stacking order
→ Popular examples: fvwm, twm, KWin, Metacity

Desktop Environment:
→ Provides complete desktop experience with integrated applications
→ Includes file managers, panels, and system utilities
→ Offers consistent look and feel across applications
→ Examples: GNOME, KDE, XFCE, MATE

Widget Toolkits:
→ Libraries providing graphical user interface components
→ Include buttons, menus, text boxes, and other UI elements
→ Popular toolkits: GTK+, Qt, Motif, Tk
→ Enable developers to create consistent user interfaces

Display Manager:
→ Provides login screen and session management
→ Starts X server and manages user authentication
→ Handles multiple user sessions and remote connections
→ Examples: XDM, GDM, KDM, LightDM

Q2. (a) What do you mean by Packet Switching? Explain the Datagram and Virtual Circuit approach of packet switching. (6 marks)

Answer:

Packet switching is a digital networking communications method that groups data transmitted over a network into packets. Each packet contains source and destination address information and is routed independently through the network. This method allows efficient use of network resources and provides fault tolerance.

Datagram Approach (Connectionless):

Characteristics:
→ Each packet is treated independently
→ No connection establishment required before data transmission
→ Packets may take different routes to reach destination
→ No guaranteed delivery order of packets

Advantages:
→ Fast and efficient for short communications
→ No connection setup overhead
→ Network resilience - if one route fails, packets find alternate paths
→ Better network utilization

Virtual Circuit Approach (Connection-oriented):

Characteristics:
→ Establishes a logical connection before data transmission
→ All packets follow the same predetermined path
→ Maintains connection state information at intermediate nodes
→ Guarantees packet delivery order

Advantages:
→ Reliable data delivery with error checking
→ Better quality of service control
→ Efficient for long communications
→ Reduced packet header overhead after connection establishment

Q2. (b) Explain POP3 and IMAP Protocols. (4 marks)

Answer:

POP3 (Post Office Protocol version 3):

Functionality:
→ Downloads emails from server to client device
→ Typically deletes emails from server after download
→ Works in offline mode once emails are downloaded
→ Simple and lightweight protocol

Characteristics:
→ One-way synchronization from server to client
→ Limited server-side storage management
→ Best suited for single device access
→ Uses port 110 (non-secure) or 995 (secure)

IMAP (Internet Message Access Protocol):

Functionality:
→ Keeps emails stored on the server
→ Allows multiple devices to access same mailbox
→ Supports server-side searching and filtering
→ Enables selective downloading of email parts

Characteristics:
→ Two-way synchronization between server and clients
→ Server-side folder organization and management
→ Better for multiple device environments
→ Uses port 143 (non-secure) or 993 (secure)
→ More complex but feature-rich protocol

Q2. (c) What are Guided and Unguided Media? Explain optical fibre. List the advantages and disadvantages of unguided media. (5+5 marks)

Answer:

Guided Media:
Guided media are physical transmission paths that direct electromagnetic signals along a specific route. Examples include twisted pair cables, coaxial cables, and optical fibers. These media provide a dedicated communication channel between devices.

Unguided Media:
Unguided media transmit electromagnetic signals through air, space, or water without physical conductors. Also known as wireless media, they include radio waves, microwaves, infrared, and satellite communications.

Optical Fibre:

Structure:
→ Core: Inner glass or plastic cylinder that carries light signals
→ Cladding: Surrounding layer with lower refractive index for total internal reflection
→ Buffer coating: Protective layer preventing physical damage
→ Outer jacket: Additional protection against environmental factors

Working Principle:
→ Uses light pulses to transmit data
→ Total internal reflection keeps light within the core
→ LED or laser diodes generate light signals
→ Photodetectors convert light back to electrical signals

Types:
→ Single-mode fiber: Small core, long-distance transmission
→ Multi-mode fiber: Larger core, shorter distances

Advantages of Unguided Media:

→ Mobility: Allows device movement during communication
→ Easy Installation: No physical cables required
→ Cost-effective: Reduced infrastructure costs for wide area coverage
→ Flexibility: Easy to reconfigure and expand networks
→ Accessibility: Can reach remote and difficult terrain areas

Disadvantages of Unguided Media:

→ Security Concerns: Signals can be intercepted more easily
→ Interference: Susceptible to electromagnetic interference and weather conditions
→ Limited Bandwidth: Generally lower data rates compared to optical fiber
→ Signal Attenuation: Signal strength decreases over distance
→ Licensing Requirements: May need regulatory approval for frequency use

Q3. (a) Define Topology in context of Computer Network. List the advantages of Computer Network. (6 marks)

Answer:

Network Topology:
Network topology refers to the physical or logical arrangement of network devices and the connections between them. It defines how devices are interconnected and how data flows through the network. Topology determines the network's performance, reliability, and scalability characteristics.

Types include: Bus, Star, Ring, Mesh, Tree, and Hybrid topologies.

Advantages of Computer Network:

→ Resource Sharing: Share hardware, software, and data resources among multiple users efficiently
→ Communication: Enable email, instant messaging, video conferencing, and file transfer
→ Cost Reduction: Eliminate duplicate resources and reduce overall system costs
→ Centralized Management: Easier administration, backup, and security management
→ Data Security: Centralized data storage with proper access controls and backup systems
→ Scalability: Easy to add new devices and expand network capacity
→ Reliability: Redundancy and fault tolerance through multiple paths and backup systems
→ Performance: Load distribution and parallel processing capabilities
→ Flexibility: Support for various applications and protocols
→ Remote Access: Access resources from anywhere with proper connectivity

Q3. (b) Explain the working of Ring Topology. (4 marks)

Answer:

Ring topology is a network configuration where devices are connected in a circular fashion, forming a closed loop. Each device is connected to exactly two other devices, creating a ring-like structure where data travels in one direction around the ring.

Working of Ring Topology:

Data Transmission:
→ Data travels in a unidirectional manner around the ring
→ Each device acts as a repeater, regenerating and forwarding signals
→ Messages pass through each intermediate device until reaching destination
→ Token passing protocol often used for media access control

Token Passing Mechanism:
→ Special token frame circulates around the ring
→ Only the device holding the token can transmit data
→ After transmission, device releases token to next device
→ Ensures collision-free data transmission

Advantages:
→ No collision detection required
→ Equal access opportunity for all devices
→ Predictable network performance

Disadvantages:
→ Single point of failure - if one device fails, entire network stops
→ Difficult to troubleshoot and add new devices
→ Data must pass through multiple devices, causing delays

Q3. (c) Explain the process of Apache Server setting in Linux in detail. (10 marks)

Answer:

Apache HTTP Server is the most widely used web server software. Setting up Apache in Linux involves installation, configuration, and optimization for web hosting services.

Step 1: Installation

Ubuntu/Debian:

sudo apt update
sudo apt install apache2

CentOS/RHEL:

sudo yum install httpd
# or for newer versions
sudo dnf install httpd

Step 2: Service Management

# Start Apache service
sudo systemctl start apache2  # Ubuntu/Debian
sudo systemctl start httpd    # CentOS/RHEL

# Enable auto-start on boot
sudo systemctl enable apache2
sudo systemctl enable httpd

# Check service status
sudo systemctl status apache2

Step 3: Configuration Files

Main Configuration File:
→ Ubuntu/Debian: /etc/apache2/apache2.conf
→ CentOS/RHEL: /etc/httpd/conf/httpd.conf

Site Configuration:
→ Ubuntu/Debian: /etc/apache2/sites-available/
→ CentOS/RHEL: /etc/httpd/conf.d/

Step 4: Virtual Host Configuration

# Create virtual host file
sudo nano /etc/apache2/sites-available/example.com.conf

<VirtualHost *:80>
    ServerName example.com
    ServerAlias www.example.com
    DocumentRoot /var/www/example.com
    ErrorLog ${APACHE_LOG_DIR}/example.com_error.log
    CustomLog ${APACHE_LOG_DIR}/example.com_access.log combined
</VirtualHost>

# Enable the site
sudo a2ensite example.com.conf

# Disable default site (optional)
sudo a2dissite 000-default.conf

Step 5: Document Root Setup

# Create document root directory
sudo mkdir -p /var/www/example.com

# Set proper permissions
sudo chown -R www-data:www-data /var/www/example.com
sudo chmod -R 755 /var/www/example.com

# Create test index file
echo "<h1>Welcome to Example.com</h1>" > /var/www/example.com/index.html

Step 6: Module Management

# Enable common modules
sudo a2enmod rewrite
sudo a2enmod ssl
sudo a2enmod headers

# Disable modules
sudo a2dismod module_name

Step 7: Firewall Configuration

# Ubuntu/Debian (UFW)
sudo ufw allow 'Apache Full'

# CentOS/RHEL (firewalld)
sudo firewall-cmd --permanent --add-service=http
sudo firewall-cmd --permanent --add-service=https
sudo firewall-cmd --reload

Step 8: Testing and Reload

# Test configuration syntax
sudo apache2ctl configtest

# Reload Apache configuration
sudo systemctl reload apache2

# Access website
curl -I http://localhost
curl -I http://your-domain.com

Q4. (a) Explain the different user authentication methods. Differentiate symmetric and asymmetric cryptography. (6+4 marks)

Answer:

Different User Authentication Methods:

Password-based Authentication:
→ Most common method using username and password combinations
→ Can include complex passwords, passphrases, and password policies
→ Vulnerable to brute force attacks and password theft

Biometric Authentication:
→ Uses unique physical characteristics like fingerprints, iris scans, facial recognition
→ Highly secure and difficult to forge
→ Requires specialized hardware and can be expensive

Token-based Authentication:
→ Physical tokens like smart cards, USB keys, or mobile apps
→ Time-based one-time passwords (TOTP) and hardware security keys
→ Provides additional security layer but can be lost or stolen

Certificate-based Authentication:
→ Uses digital certificates issued by trusted Certificate Authorities
→ Public key infrastructure (PKI) for secure authentication
→ Strong security but requires complex infrastructure

Multi-factor Authentication (MFA):
→ Combines multiple authentication methods
→ Something you know (password), have (token), and are (biometric)
→ Provides highest security level but may impact user experience

Difference between Symmetric and Asymmetric Cryptography:

Symmetric Cryptography:
→ Key Usage: Same key for encryption and decryption
→ Speed: Fast processing, suitable for large data volumes
→ Key Distribution: Secure key sharing challenge
→ Examples: AES, DES, 3DES, Blowfish

Asymmetric Cryptography:
→ Key Usage: Different keys for encryption (public) and decryption (private)
→ Speed: Slower processing due to complex mathematical operations
→ Key Distribution: Public key can be freely shared
→ Examples: RSA, ECC, Diffie-Hellman

Q4. (b) Explain the Computer-Security Classification in detail. (10 marks)

Answer:

Computer security classification systems categorize information and systems based on their sensitivity levels and the potential impact of unauthorized disclosure, modification, or destruction. These classifications help organizations implement appropriate security controls and access restrictions.

Government Security Classifications:

Confidential Level:
→ Information that could cause damage to national security if disclosed
→ Requires background checks for access
→ Examples: Military operational plans, diplomatic communications
→ Access limited to individuals with specific clearance levels

Secret Level:
→ Information that could cause serious damage to national security
→ Requires more extensive background investigations
→ Examples: Intelligence reports, advanced weapon specifications
→ Stricter access controls and monitoring requirements

Top Secret Level:
→ Information that could cause exceptionally grave damage to national security
→ Requires the most thorough background investigations
→ Examples: Nuclear weapon designs, intelligence sources and methods
→ Compartmentalized access on need-to-know basis

Commercial Security Classifications:

Public Information:
→ Information intended for public consumption
→ No special protection required
→ Examples: Marketing materials, public financial reports
→ Can be freely shared without restrictions

Internal Use:
→ Information for internal business operations
→ Limited to employees and authorized personnel
→ Examples: Internal policies, employee directories
→ Requires basic access controls

Confidential/Restricted:
→ Sensitive business information requiring protection
→ Could cause competitive disadvantage if disclosed
→ Examples: Customer lists, pricing strategies, financial data
→ Requires strong access controls and encryption

Highly Confidential/Secret:
→ Critical business information with severe impact if compromised
→ Examples: Trade secrets, merger plans, research data
→ Requires highest level of protection and monitoring

Security Implementation Measures:

Physical Security:
→ Secure facilities with controlled access
→ Biometric scanners and security guards
→ Surveillance systems and alarm mechanisms

Technical Security:
→ Encryption for data protection
→ Access control systems and authentication
→ Network security and firewalls
→ Regular security audits and monitoring

Administrative Security:
→ Security policies and procedures
→ Employee training and awareness programs
→ Background checks and security clearances
→ Incident response and recovery plans

Q5. Write short notes on the following: (5×4=20 marks)

(a) Serial Processing
(b) System calls
(c) Virtual Machines
(d) Wide Area Network
(e) Virtual Private Network

Answer:

(a) Serial Processing:
Serial processing refers to the execution of instructions or tasks one after another in a sequential manner. In early computer systems, jobs were processed one at a time without any form of multiprogramming or parallel execution. The CPU remained idle during I/O operations, leading to inefficient resource utilization. Modern systems have evolved to support concurrent processing, but serial processing is still used in specific scenarios where order of execution is critical, such as critical sections in programming and certain real-time applications.

(b) System Calls:
System calls are the interface between user programs and the operating system kernel. They provide a way for applications to request services from the operating system, such as file operations, process creation, memory allocation, and network communication. System calls ensure controlled access to system resources and maintain security boundaries between user space and kernel space. Examples include open(), read(), write(), fork(), exec(), and malloc(). The system call mechanism typically involves switching from user mode to kernel mode to execute privileged operations.

(c) Virtual Machines:
Virtual machines are software-based emulations of physical computer systems that run on host hardware. They enable multiple operating systems to run simultaneously on a single physical machine, each in its own isolated environment. VMs provide benefits like resource consolidation, improved hardware utilization, disaster recovery, and testing environments. Types include system VMs (full virtualization) and process VMs (application-level virtualization). Popular VM technologies include VMware, VirtualBox, Hyper-V, and KVM. Cloud computing heavily relies on virtualization for scalable infrastructure services.

(d) Wide Area Network (WAN):
A Wide Area Network spans large geographical areas, connecting multiple local area networks (LANs) across cities, countries, or continents. WANs use various transmission media including leased lines, satellite links, microwave, and fiber optic cables. The Internet is the largest example of a WAN. WANs typically have lower data transmission speeds compared to LANs due to distance limitations and use packet switching for data transmission. Common WAN protocols include Frame Relay, ATM, MPLS, and various VPN technologies. WANs enable global connectivity and resource sharing across distributed locations.

(e) Virtual Private Network (VPN):
A Virtual Private Network creates a secure, encrypted connection over public networks, typically the Internet, allowing users to access private network resources remotely. VPNs use tunneling protocols to encapsulate and encrypt data, ensuring confidentiality and integrity. They provide benefits like secure remote access, cost-effective connectivity, and bypassing geographical restrictions. Common VPN protocols include OpenVPN, L2TP/IPSec, PPTP, and WireGuard. VPNs are essential for remote work, connecting branch offices, and protecting sensitive communications over untrusted networks. They can be implemented as site-to-site or client-to-site configurations.