Computer Networks & Data Communication (4361101) - Winter 2024 Solution

Question 1(a) [3 marks]

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Explain star topology in detail.

Answer: Star topology connects all devices to a central hub or switch. Each device has dedicated point-to-point connection with central device.

Diagram:

Key Features:

• Central Hub: All connections pass through central device
• Dedicated Links: Each node has separate connection
• Easy Management: Simple to add/remove devices

Mnemonic: “Star Shines Central” - All devices connect to central point

Question 1(b) [4 marks]

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Explain client-server network.

Answer: Client-server is network architecture where clients request services from centralized servers. Server provides resources and services to multiple clients.

Table: Client vs Server

Key Components:

• Client: Requests data/services from server
• Server: Provides centralized resources and processing
• Network: Medium for communication between client-server

Mnemonic: “Client Calls, Server Serves”

Question 1(c) [7 marks]

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Write a functional description of all layer of TCP/IP model.

Answer: TCP/IP model has four layers providing end-to-end communication over networks.

Table: TCP/IP Model Layers

Layer Functions:

• Application Layer: Provides network services to user applications
• Transport Layer: Ensures reliable data delivery between processes
• Internet Layer: Routes packets across multiple networks using IP
• Network Access Layer: Handles physical transmission of data

Mnemonic: “All Transport Internet Networks” (ATIN)

Question 1(c OR) [7 marks]

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Explain the functions of Data Link Layer & Network Layer of OSI reference model.

Answer: Data Link and Network layers provide reliable transmission and routing capabilities in OSI model.

Table: Layer Comparison

Data Link Layer Functions:

• Framing: Organizes bits into frames
• Error Control: Detects and corrects transmission errors
• Flow Control: Manages data transmission rate

Network Layer Functions:

• Routing: Determines best path for packets
• Logical Addressing: Uses IP addresses for identification
• Packet Forwarding: Routes packets between networks

Mnemonic: “Data Links Locally, Network Routes Globally”

Question 2(a) [3 marks]

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Compare repeater and hub.

Answer: Both devices amplify signals but operate differently in network architecture.

Table: Repeater vs Hub

Key Differences:

• Port Count: Repeater has 2 ports, hub has multiple
• Usage: Repeater extends distance, hub connects multiple devices

Mnemonic: “Repeater Extends, Hub Connects”

Question 2(b) [4 marks]

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Explain wireless LAN.

Answer: Wireless LAN uses radio waves for network communication without physical cables.

Diagram:

Key Components:

• Access Point: Central wireless communication device
• Wireless Clients: Devices with WiFi capability
• Radio Frequencies: 2.4GHz and 5GHz bands commonly used

Advantages:

• Mobility: Users can move freely within coverage area
• Easy Installation: No physical cable installation required

Mnemonic: “Wireless Waves Connect”

Question 2(c) [7 marks]

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Explain FDDI & CDDI.

Answer: FDDI and CDDI are ring-based network technologies providing high-speed data transmission.

Table: FDDI vs CDDI Comparison

FDDI Features:

• Dual Ring: Primary and secondary rings for fault tolerance
• Token Passing: Deterministic access method
• Self-Healing: Automatic recovery from failures

CDDI Features:

• Copper Medium: Uses unshielded twisted pair cables
• Same Protocol: Identical to FDDI except transmission medium
• Cost Effective: Lower implementation cost than FDDI

Ring Structure:

Mnemonic: “FDDI Fiber Fast, CDDI Copper Cheap”

Question 2(a OR) [3 marks]

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How does a firewall protect data.

Answer: Firewall acts as security barrier between trusted internal network and untrusted external networks.

Protection Methods:

• Packet Filtering: Examines packet headers for security rules
• Access Control: Blocks unauthorized access attempts
• Traffic Monitoring: Monitors all incoming and outgoing traffic

Mnemonic: “Firewall Filters Foes”

Question 2(b OR) [4 marks]

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Explain the structure of FDDI and give its advantages.

Answer: FDDI uses dual counter-rotating rings for high-speed, fault-tolerant networking.

Structure Components:

• Primary Ring: Main data transmission path
• Secondary Ring: Backup path for fault recovery
• Dual Attachment Stations: Connect to both rings
• Single Attachment Stations: Connect to one ring only

Advantages:

• High Speed: 100 Mbps transmission rate
• Fault Tolerance: Automatic recovery using secondary ring
• Long Distance: Supports up to 200 km networks

Mnemonic: “FDDI Dual Rings Deliver Reliability”

Question 2(c OR) [7 marks]

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Explain and distinguish Ethernet, Fast Ethernet, Gigabit Ethernet.

Answer: Evolution of Ethernet standards providing increasing bandwidth and improved performance.

Table: Ethernet Comparison

Key Differences:

• Bandwidth: Each generation increases speed by factor of 10
• Media Support: Newer standards support more cable types
• Backward Compatibility: Higher standards support lower speeds

Applications:

• Ethernet: Legacy systems, basic connectivity
• Fast Ethernet: Desktop connections, small networks
• Gigabit Ethernet: Server connections, backbone networks

Mnemonic: “Ethernet Evolves: 10-100-1000”

Question 3(a) [3 marks]

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Explain types of DSL.

Answer: DSL provides high-speed internet over existing telephone lines using different frequency bands.

Table: DSL Types

Characteristics:

• ADSL: Different upload/download speeds for home users
• SDSL: Same speed both directions for business use

Mnemonic: “DSL: Asymmetric, Symmetric, Very-fast”

Question 3(b) [4 marks]

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Explain ARP & RARP.

Answer: ARP and RARP provide address resolution between IP and MAC addresses.

Table: ARP vs RARP

ARP Process:

• Request: Broadcast “Who has IP address X?”
• Reply: Target responds with MAC address
• Caching: Stores mapping in ARP table

RARP Process:

• Request: “What is my IP address?”
• Server Response: RARP server provides IP address

Mnemonic: “ARP: Address Resolution Protocol, RARP: Reverse ARP”

Question 3(c) [7 marks]

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Describe circuit switching and packet switching.

Answer: Two fundamental approaches for establishing communication paths in networks.

Table: Circuit vs Packet Switching

Circuit Switching:

• Path Establishment: Dedicated circuit created before communication
• Resource Reservation: Bandwidth reserved for entire session
• Guaranteed Service: Consistent performance throughout connection

Packet Switching:

• Store and Forward: Packets stored temporarily at intermediate nodes
• Dynamic Routing: Each packet can take different path
• Resource Sharing: Network resources shared among multiple connections

Diagram: Packet Switching

Mnemonic: “Circuit Commits, Packet Partitions”

Question 3(a OR) [3 marks]

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Describe DHCP & BOOTP protocol.

Answer: Both protocols automatically assign IP addresses to network devices.

Table: DHCP vs BOOTP

Functions:

• DHCP: Dynamic address assignment with lease management
• BOOTP: Bootstrap protocol for diskless workstations

Mnemonic: “DHCP Dynamic, BOOTP Bootstrap”

Question 3(b OR) [4 marks]

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Explain IPv4 & IPv6 in detail.

Answer: Internet Protocol versions providing addressing and routing capabilities.

Table: IPv4 vs IPv6

IPv4 Features:

• Address Format: 192.168.1.1 (4 octets)
• Classes: A, B, C, D, E address classes
• NAT Required: Address shortage requires NAT

IPv6 Features:

• Address Format: 2001:db8::1 (8 groups of 4 hex digits)
• No NAT Needed: Abundant address space
• Built-in Security: IPSec support mandatory

Mnemonic: “IPv4 Four Octets, IPv6 Six-teen Bytes”

Question 3(c OR) [7 marks]

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Draw and explain constructional details of twisted pair cable, coaxial cable, and fiber optic cable with label.

Answer: Three main types of guided transmission media with different construction and characteristics.

Twisted Pair Cable:

Coaxial Cable:

Fiber Optic Cable:

Construction Details:

• Twisted Pair: Copper wires twisted to reduce interference
• Coaxial: Central conductor surrounded by dielectric and shield
• Fiber Optic: Glass core with cladding for total internal reflection

Characteristics:

• Twisted Pair: Low cost, easy installation, limited bandwidth
• Coaxial: Better shielding, higher bandwidth than twisted pair
• Fiber Optic: Highest bandwidth, immune to electromagnetic interference

Mnemonic: “Twisted Copper, Coax Shielded, Fiber Light”

Question 4(a) [3 marks]

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Name any three data link layer protocol and explain any one in detail.

Answer: Common data link layer protocols: HDLC, PPP, Ethernet.

HDLC (High-Level Data Link Control):

• Frame Structure: Flag, Address, Control, Data, FCS, Flag
• Error Control: Uses sequence numbers and acknowledgments
• Flow Control: Sliding window protocol for efficient transmission

Key Features:

• Bit-oriented: Works with bit streams rather than characters
• Full-duplex: Simultaneous bidirectional communication

Mnemonic: “HDLC Handles Data Link Control”

Question 4(b) [4 marks]

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Explain TCP and UDP protocol.

Answer: Transport layer protocols providing different levels of service reliability.

Table: TCP vs UDP

TCP Features:

• Connection Setup: Three-way handshake establishes connection
• Error Recovery: Retransmits lost packets automatically
• Flow Control: Prevents sender from overwhelming receiver

UDP Features:

• No Connection: Sends data without establishing connection
• Best Effort: No guarantee of delivery or order
• Low Overhead: Minimal header for fast transmission

Mnemonic: “TCP Trustworthy, UDP Unreliable but Quick”

Question 4(c) [7 marks]

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Describe VoIP with example.

Answer: Voice over Internet Protocol transmits voice communications over IP networks instead of traditional telephone systems.

VoIP Components:

• IP Phone: Hardware device for VoIP calls
• Softphone: Software application for computer-based calls
• Gateway: Connects VoIP to traditional phone networks
• PBX: Private branch exchange for business phone systems

VoIP Process:

1. Voice Capture: Microphone converts voice to analog signal
2. Digitization: ADC converts analog to digital samples
3. Compression: Codec compresses audio data
4. Packetization: Voice data divided into IP packets
5. Transmission: Packets sent over IP network
6. Reconstruction: Receiving end reassembles and plays audio

Example Applications:

• Skype: Consumer VoIP service for personal calls
• WhatsApp Calling: Mobile VoIP application
• Business PBX: Corporate phone systems using VoIP

Advantages:

• Cost Effective: Lower long-distance call costs
• Feature Rich: Video calling, conferencing, call forwarding
• Scalability: Easy to add new users

Disadvantages:

• Internet Dependency: Requires stable internet connection
• Quality Issues: May suffer from network congestion
• Power Dependency: Requires electricity unlike traditional phones

Mnemonic: “VoIP: Voice over Internet Protocol”

Question 4(a OR) [3 marks]

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Explain DNS (Domain Name System).

Answer: DNS translates human-readable domain names into IP addresses for network communication.

DNS Components:

• Domain Names: Hierarchical naming system (www.example.com)
• Name Servers: Computers that store DNS records
• Resolvers: Client software that queries DNS servers

DNS Process:

1. User enters domain name in browser
2. Local resolver queries DNS server
3. DNS server returns corresponding IP address

Mnemonic: “DNS: Domain Name to IP Address”

Question 4(b OR) [4 marks]

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Write a short note on DSL.

Answer: Digital Subscriber Line provides high-speed internet access over existing telephone infrastructure.

DSL Technology:

• Frequency Division: Uses higher frequencies than voice calls
• Simultaneous Use: Internet and phone can work together
• Distance Limitation: Performance decreases with distance from exchange

DSL Types:

• ADSL: Asymmetric speeds for residential users
• SDSL: Symmetric speeds for business applications
• VDSL: Very high speeds over short distances

Advantages:

• Existing Infrastructure: Uses existing telephone lines
• Always On: Continuous internet connection
• Cost Effective: Lower cost than dedicated lines

Mnemonic: “DSL: Digital Subscriber Line over Phone Lines”

Question 4(c OR) [7 marks]

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Explain forum and blogs with example.

Answer: Online platforms for information sharing and community interaction.

Table: Forum vs Blog

Forum Characteristics:

• Discussion Threads: Topics organized by subject
• User Participation: Multiple users contribute to discussions
• Categories: Topics organized into different sections
• Moderation: Community rules and moderators maintain order

Blog Characteristics:

• Personal Publishing: Individual or organization publishes content
• Chronological Order: Posts displayed by date
• Comments: Readers can respond to blog posts
• RSS Feeds: Readers can subscribe to updates

Examples:

• Technical Forums: Stack Overflow for programming questions
• Community Forums: Reddit for diverse topics
• Personal Blogs: Individual websites sharing experiences
• Corporate Blogs: Company blogs for marketing and updates

Benefits:

• Knowledge Sharing: Users share expertise and experiences
• Community Building: Brings together people with common interests
• Problem Solving: Forums help users find solutions
• Content Creation: Blogs provide platform for publishing

Mnemonic: “Forums Foster Discussion, Blogs Broadcast Information”

Question 5(a) [3 marks]

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Define the terms “encryption”.

Answer: Encryption converts plaintext data into ciphertext to protect information from unauthorized access.

Encryption Process:

• Plaintext: Original readable data
• Algorithm: Mathematical process for transformation
• Key: Secret parameter used in encryption algorithm
• Ciphertext: Encrypted unreadable data

Purpose:

• Confidentiality: Prevents unauthorized data access
• Data Protection: Secures sensitive information during transmission

Mnemonic: “Encryption: Plain to Cipher with Key”

Question 5(b) [4 marks]

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Explain any two of following: (1) WWW (2) FTP (3) SMTP

Answer:

WWW (World Wide Web):

• Hypertext System: Documents linked through hyperlinks
• HTTP Protocol: HyperText Transfer Protocol for web communication
• Web Browser: Client software for accessing web pages
• Web Server: Hosts websites and serves web pages

FTP (File Transfer Protocol):

• File Transfer: Protocol for transferring files between computers
• Client-Server: FTP client connects to FTP server
• Two Modes: Active and passive modes for data transfer
• Authentication: Username and password for access control

Features:

• WWW: Graphical interface, multimedia support, hyperlinks
• FTP: Large file transfer, directory navigation, resume capability

Mnemonic: “WWW: Web World Wide, FTP: File Transfer Protocol”

Question 5(c) [7 marks]

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Difference between symmetric and asymmetric encryption algorithms

Answer: Two fundamental approaches to cryptographic key management with different characteristics.

Table: Symmetric vs Asymmetric Encryption

Symmetric Encryption:

• Single Key: Same key used for encryption and decryption
• Speed: Fast processing due to simple algorithms
• Key Sharing Problem: Secure key distribution challenge
• Session Keys: Often used for bulk data encryption

Asymmetric Encryption:

• Key Pair: Public key for encryption, private key for decryption
• Digital Signatures: Private key signs, public key verifies
• Key Exchange: Solves key distribution problem
• Computationally Intensive: Slower than symmetric encryption

Usage Scenarios:

• Symmetric: Bulk data encryption, secure communications
• Asymmetric: Key exchange, digital signatures, authentication

Hybrid Approach:

• Best of Both: Asymmetric for key exchange, symmetric for data
• SSL/TLS: Uses both types for secure web communications

Security Considerations:

• Symmetric: Key compromise affects all communications
• Asymmetric: Private key compromise affects only one party

Mnemonic: “Symmetric Single Key, Asymmetric Key Pair”

Question 5(a OR) [3 marks]

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Write brief note on Cyber Security.

Answer: Cyber security protects digital systems, networks, and data from digital attacks and unauthorized access.

Key Components:

• Network Security: Protects network infrastructure from intrusions
• Data Protection: Safeguards sensitive information from theft
• Application Security: Secures software applications from vulnerabilities

Common Threats:

• Malware: Viruses, worms, trojans that damage systems
• Phishing: Fraudulent attempts to steal credentials

Mnemonic: “Cyber Security: Protect Digital Assets”

Question 5(b OR) [4 marks]

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Explain hacking and its precautions.

Answer: Hacking involves unauthorized access to computer systems, often with malicious intent.

Types of Hacking:

• White Hat: Ethical hacking for security testing
• Black Hat: Malicious hacking for illegal purposes
• Gray Hat: Between ethical and malicious hacking

Common Hacking Methods:

• Password Attacks: Brute force, dictionary attacks
• Social Engineering: Manipulating people to reveal information
• Malware: Viruses, trojans, ransomware
• Network Attacks: Man-in-the-middle, packet sniffing

Precautions:

• Strong Passwords: Complex, unique passwords for all accounts
• Regular Updates: Keep software and systems updated
• Firewall: Use firewall to block unauthorized access
• Antivirus: Install and update antivirus software regularly

Mnemonic: “Hacking Hurts, Precautions Protect”

Question 5(c OR) [7 marks]

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Briefly describe the Information Technology (Amendment) Act, 2008, and its impact on cyber laws in India.

Answer: The IT Amendment Act 2008 significantly strengthened India’s cyber law framework and expanded the scope of cybercrime legislation.

Key Amendments:

• Data Protection: Enhanced provisions for protecting sensitive personal data
• Cybercrime Definitions: Expanded definitions of cybercrime including identity theft
• Penalties: Increased penalties for various cyber offenses
• Cyber Terrorism: Introduced provisions to deal with cyber terrorism

Major Provisions:

• Section 43A: Data protection and compensation for negligence
• Section 66A: Punishment for offensive messages (later struck down)
• Section 66C: Identity theft punishment
• Section 66D: Cheating by personation using computer resource

Impact on Cyber Laws:

• Legal Framework: Provided comprehensive legal framework for cybercrime
• Business Compliance: Mandated data protection measures for businesses
• Law Enforcement: Empowered authorities with investigation tools
• International Cooperation: Facilitated cooperation in cybercrime investigation

Regulatory Bodies:

• CERT-In: Computer Emergency Response Team for incident response
• Cyber Cells: Specialized police units for cybercrime investigation
• Adjudicating Officers: For compensation and penalty determination

Data Protection Requirements:

• Reasonable Security: Companies must implement reasonable security practices
• Breach Notification: Mandatory reporting of data breaches
• Compensation: Victims can claim compensation for data breaches

Challenges and Criticisms:

• Implementation: Difficulty in implementation across diverse digital landscape
• Jurisdiction: Cross-border cybercrime investigation challenges
• Technology Gap: Keeping pace with rapidly evolving technology

Recent Developments:

• Digital India: Integration with Digital India initiatives
• Privacy Laws: Preparation for comprehensive data protection legislation
• Emerging Technologies: Addressing challenges from AI, IoT, blockchain

Mnemonic: “IT Act 2008: India’s Cyber Law Foundation”