Computer Networking (4343202) - Summer 2024 Solution

Question 1(a) [3 marks]

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Explain packet switching network.

Answer: Packet switching is a network communication method where data is divided into small packets before transmission.

Diagram:

graph LR
    A[Source] --> B[Packets Created]
    B --> C[Packet 1]
    B --> D[Packet 2]
    B --> E[Packet 3]
    C --> F[Router]
    D --> F
    E --> F
    F --> G[Different paths]
    G --> H[Destination]

• Independent routing: Each packet travels independently through network
• Flexible paths: Packets can take different routes to reach destination
• Efficiency: Better utilization of network bandwidth

Mnemonic: “DIVE” - Data Into Various Elements

Question 1(b) [4 marks]

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Write functional description of any four layers of OSI reference model.

Answer: The OSI model divides network communication into seven distinct layers, each with specific functions.

• Application layer: Interface between network and applications
• Presentation layer: Data formatting and encryption
• Session layer: Dialog control and synchronization
• Transport layer: End-to-end connection and reliability

Mnemonic: “All People Seem To Need Data Processing”

Question 1(c) [7 marks]

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Explain Network topologies and with diagram.

Answer: Network topology refers to the physical or logical arrangement of devices in a network.

Diagram:

• Bus topology: All devices connected to single cable
• Star topology: All devices connected to central hub/switch
• Ring topology: Devices connected in closed loop
• Mesh topology: Each device connected to every other device
• Tree topology: Hierarchical star networks connected via bus

Mnemonic: “BSRMT” - “Better Solutions Require Multiple Topologies”

Question 1(c) OR [7 marks]

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Draw the diagram of TCP/IP protocol suite and explain the functions of Application Layer, Transport Layer and Network Layer in detail.

Answer: The TCP/IP protocol suite organizes network communication into four functional layers.

Diagram:

• Application Layer: User interface to network, application-specific protocols
• Transport Layer: Reliable data transmission, error recovery, flow control
• Network Layer: Routing packets between networks, IP addressing

Mnemonic: “ATN works” - Application, Transport, Network works together

Question 2(a) [3 marks]

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Compare connection-oriented protocol and connection less protocol.

Answer: Connection-oriented and connectionless protocols differ in how they handle data transmission.

Mnemonic: “REACH” - Reliability Exists in All Connection Handshakes

Question 2(b) [4 marks]

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Explain Fast Ethernet & Gigabit Ethernet.

Answer: Fast Ethernet and Gigabit Ethernet are higher-speed versions of the original Ethernet standard.

• Fast Ethernet: 10x faster than original 10Base-T Ethernet
• Gigabit Ethernet: 10x faster than Fast Ethernet, backward compatible
• Cabling: Uses higher quality cabling to achieve greater speeds
• Applications: High-bandwidth network backbones, server connections

Mnemonic: “Fast Gets Going” - 100 to 1000 Mbps progression

Question 2(c) [7 marks]

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Differentiate between Router, Hub and Switch.

Answer: Routers, hubs, and switches are network devices with different capabilities and functions.

Diagram:

Mnemonic: “RHS order” - “Router Has Smarts, Hub Shares Signal, Switch Sends Specifically”

Question 2(a) OR [3 marks]

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Define E-mail system and list application of E-Mail.

Answer: An email system is a network service that allows exchange of digital messages between users.

Applications of Email:

• Business communication
• Personal messaging
• File sharing
• Marketing and newsletters
• Notifications and alerts

Mnemonic: “BCPFN” - “Business Communication, Personal, Files, Newsletters”

Question 2(b) OR [4 marks]

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Differentiate between IPv4 and IPv6.

Answer: IPv4 and IPv6 are Internet Protocol versions with significant differences.

• IPv4: Traditional addressing with limited space
• IPv6: Next-generation addressing with massive capacity
• Transition: Dual-stack, tunneling and translation mechanisms

Mnemonic: “4 SMALL, 6 HUGE” - IPv4 Small address space, IPv6 Huge address space

Question 2(c) OR [7 marks]

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Discuss on Firewall with concept, principles, limitations, trusted system, Kerberos- concept in network security.

Answer: Firewalls are critical network security systems that monitor and control incoming and outgoing traffic.

Principles of Firewall:

• Default deny: Block everything unless explicitly allowed
• Defense in depth: Multiple security layers
• Least privilege: Minimal necessary access

Limitations:

• Cannot protect against authorized users
• Limited against encrypted malicious traffic
• Performance impact on network

Trusted Systems:

• Systems meeting specific security requirements
• Formal security policy enforcement
• Access control and authentication mechanisms

Kerberos Concept:

• Authentication protocol using trusted third party
• Ticket-based access control system
• Mutual authentication between client and server
• Time-sensitive tickets prevent replay attacks

Mnemonic: “FLASK” - “Firewalls Lock Access, Secure with Kerberos”

Question 3(a) [3 marks]

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Describe Sub-layers of Data link Layers.

Answer: The Data Link Layer in the OSI model is divided into two sublayers with distinct functions.

Diagram:

• LLC: Provides interface to network layer, error/flow control
• MAC: Handles physical addressing and media access

Mnemonic: “MAC LLCs order” - “MAC handles Lower Layer, LLC coordinates higher”

Question 3(b) [4 marks]

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Explain IP layer protocols in detail.

Answer: The IP layer contains several key protocols that work together to facilitate internetwork communication.

• IP: Core protocol for addressing and routing packets
• ICMP: Error messages and operational information
• ARP/RARP: Address translation between layers
• IGMP: Manages multicast group memberships

Mnemonic: “I PAIR-up” - IP, ICMP, ARP, RARP work as a team

Question 3(c) [7 marks]

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Describe different types of IP addressing schemes and explain various classes in classful IP addressing with example.

Answer: IP addressing schemes define how IP addresses are allocated and structured.

Classful IP Addressing:

• Class A: Large organizations, huge number of hosts
• Class B: Medium-sized organizations
• Class C: Small networks with few hosts
• Class D: Multicast groups
• Class E: Reserved for experimental use

Mnemonic: “All Businesses Care During Exams” - Classes A, B, C, D, E

Question 3(a) OR [3 marks]

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Describe Digital Subscriber Line technology.

Answer: Digital Subscriber Line (DSL) is a technology that provides digital data transmission over telephone lines.

Diagram:

• Spectrum usage: Uses higher frequencies than voice
• Always-on: Continuous connection, no dial-up
• xDSL: Family of technologies with different capabilities

Mnemonic: “SAVE Bandwidth” - SDSL, ADSL, VDSL, HDSL Bandwidth options

Question 3(b) OR [4 marks]

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Discuss Cable Modem System.

Answer: Cable modem system provides internet access through the same coaxial cable used for cable TV.

Diagram:

• Shared medium: Neighborhood shares bandwidth
• Asymmetric: Typically faster download than upload
• DOCSIS standards: Evolving specifications for speed/features

Mnemonic: “CHAMPS” - “Cable, HFC, Access, Modem, Provider, Shared”

Question 3(c) OR [7 marks]

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Describe in brief all Transmission Media.

Answer: Transmission media are the physical paths through which data travels in a network.

Diagram:

• Guided media: Physical paths confining signals
• Unguided media: Wireless transmission through air/vacuum
• Characteristics: Bandwidth, attenuation, noise immunity, cost

Mnemonic: “TRIM-CWF” - “Twisted, Radio, Infrared, Microwave, Coaxial, Wireless, Fiber”

Question 4(a) [3 marks]

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Write note on DNS.

Answer: Domain Name System (DNS) translates human-friendly domain names to IP addresses.

Diagram:

• Distributed database: Hierarchical, globally distributed
• Caching: Improves performance, reduces load
• Critical infrastructure: Essential for Internet functionality

Mnemonic: “DIRT” - “Domain names Into Routable TCP/IP”

Question 4(b) [4 marks]

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Explain File Transfer Protocol.

Answer: File Transfer Protocol (FTP) enables transfer of files between client and server over a network.

Diagram:

• Dual channel: Control channel and data channel
• Authentication: Username/password required
• Modes: ASCII (text) or Binary (raw data)
• Active vs Passive: Different connection establishment methods

Mnemonic: “CAPS” - “Control And Port Separation”

Question 4(c) [7 marks]

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Classify different Internet Services and explain in detail.

Answer: Internet services provide various functionality over the network.

Information Access Services (Web):

• HTTP/HTTPS: HyperText Transfer Protocol, foundation of web
• HTML: Document format for displaying content
• Web browsers: Client software to access and render web content
• Web servers: Hosts websites and applications

Communication Services (Email):

• SMTP: For sending email
• POP3/IMAP: For receiving email
• Components: Mail user agents, transfer agents, delivery agents

File Sharing Services:

• FTP: Traditional file transfer protocol
• P2P: Distributed file sharing without central server
• Cloud storage: Remote file storage and synchronization

Mnemonic: “CIFRRD” - “Communication, Information, File, Remote, Real-time, Domain”

Question 4(a) OR [3 marks]

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Explain Mail Protocols.

Answer: Mail protocols facilitate electronic messaging between users.

Diagram:

• SMTP: Outgoing mail delivery, push protocol
• POP3: Simple mail retrieval, downloads and deletes
• IMAP: Advanced retrieval, server-side storage, folders
• MIME: Extends email capability for non-text content

Mnemonic: “SIM-P” - “SMTP sends, IMAP manages, POP3 pulls”

Question 4(b) OR [4 marks]

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Describe VOIP in brief.

Answer: Voice over Internet Protocol (VoIP) transmits voice communications over IP networks.

Diagram:

• Packetization: Converts analog voice to digital packets
• Benefits: Cost savings, flexibility, integration with apps
• Challenges: Quality of service, latency, jitter, packet loss

Mnemonic: “PALS” - “Packets Allowing Live Speech”

Question 4(c) OR [7 marks]

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Describe TCP and UDP protocols.

Answer: TCP and UDP are the primary transport layer protocols in the TCP/IP suite.

TCP Three-Way Handshake:

TCP Features:

• Reliability: Acknowledgments, retransmission
• Flow control: Window-based, prevents overwhelming
• Congestion control: Slow start, congestion avoidance
• Connection management: Establishment, maintenance, termination

UDP Features:

• Lightweight: Minimal headers, no connection state
• Low latency: No handshaking or acknowledgments
• No guarantees: Data may arrive out of order, duplicated, or not at all
• Broadcast/multicast: Supports one-to-many transmission

Mnemonic: “CRUFS” - “Connection, Reliability, UDP Fast, Simple”

Question 5(a) [3 marks]

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Describe Cryptography.

Answer: Cryptography is the science of secure communication techniques that protect information.

Diagram:

• Confidentiality: Protect information from unauthorized access
• Integrity: Ensure information hasn’t been altered
• Authentication: Verify identity of communicating parties

Mnemonic: “SHAPE” - “Symmetric, Hashing, Asymmetric, Protect, Encrypt”

Question 5(b) [4 marks]

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Explain Social issues and Hacking also discuss its precautions.

Answer: Social issues in cybersecurity involve human manipulation and societal impacts of cyber threats.

Hacking Types:

• White Hat: Ethical hacking, security improvement
• Black Hat: Malicious hacking, illegal activities
• Grey Hat: Mix of ethical and questionable actions

Precautions:

• Education: Regular security awareness training
• Strong Policies: Clear security procedures and policies
• Technical Controls: Firewalls, antivirus, encryption
• Regular Updates: Patching systems against vulnerabilities
• Monitoring: Activity logs, intrusion detection

Mnemonic: “STEPS” - “Social engineering, Training, Encryption, Patches, Strong passwords”

Question 5(c) [7 marks]

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Explain IP Security in detail.

Answer: IP Security (IPsec) is a protocol suite that secures communications at the IP layer.

IPsec Modes:

Diagram:

IPsec Services:

• Authentication: Verifies sender identity
• Confidentiality: Encrypts data to prevent eavesdropping
• Integrity: Ensures data hasn’t been modified
• Anti-replay: Prevents packet replay attacks

IPsec Implementation:

• VPNs: Secure remote access and site-to-site connections
• L2TP/IPsec: Combines tunneling with security
• Authentication methods: Pre-shared keys, certificates, Kerberos

Mnemonic: “ACCEPT” - “Authentication, Confidentiality, Cryptography, Encapsulation, Protocols, Tunnel”

Question 5(a) OR [3 marks]

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Define Network Security and explain its elements.

Answer: Network security is the protection of network infrastructure, data, and access against unauthorized use, malfunction, modification, or destruction.

Diagram:

• Confidentiality: Protecting information from unauthorized access
• Integrity: Ensuring information accuracy and reliability
• Availability: Maintaining systems accessible when needed

Mnemonic: “CIMA TV” - “Confidentiality, Integrity, Monitoring, Access control, Threats, Vulnerabilities”

Question 5(b) OR [4 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 updated India’s cyber laws to address emerging cybersecurity challenges.

Key Sections:

• Section 43: Penalties for unauthorized access, data theft
• Section 66: Computer-related offenses and punishments
• Section 69: Powers for interception and monitoring
• Section 72A: Protection of personal data privacy

Impact on Cyber Laws:

• Stronger enforcement: Enhanced penalties for cyber crimes
• Expanded scope: Covered new technological developments
• Corporate responsibility: Required security practices for data
• Global alignment: Harmonized with international standards

Mnemonic: “SPEC” - “Security, Privacy, Evidence, Cyber crimes”

Question 5(c) OR [7 marks]

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Explain Email security in terms of SMTP, PEM, PGP, S/MINE, spam.

Answer: Email security protects email content and accounts from unauthorized access and attacks.

SMTP Security Issues:

• Originally designed without security
• Authentication extensions (AUTH) added later
• Vulnerable to eavesdropping without encryption
• Supports STARTTLS for encrypted transmission

PGP Email Security:

S/MIME Features:

• Uses X.509 certificates for authentication
• Provides encryption and digital signatures
• Integrated into many email clients
• Requires certificate infrastructure

Spam Protection:

• Content filtering: Analyzing message content
• Sender verification: SPF, DKIM, DMARC
• Behavioral analysis: Pattern recognition
• Blacklists/whitelists: Blocking/allowing specific senders

Email Security Best Practices:

• Encryption: Ensure privacy of message content
• Authentication: Verify sender identity
• Access controls: Protect email accounts
• Filtering: Block malicious and unwanted messages
• User education: Recognize phishing attempts

Mnemonic: “SPEED” - “S/MIME, PGP, Encryption, Email security, DMARC”