Question 1(a) [3 marks]

List the different Network Topologies and discuss any one in detail.

Answer:

Topology	Description
Star	All devices connected to central hub/switch
Ring	Devices connected in circular fashion
Bus	All devices connected to single cable
Mesh	Every device connected to every other device
Tree	Hierarchical structure with root node
Hybrid	Combination of two or more topologies

Star Topology Details:

Central Hub: All nodes connect to one central device
Point-to-Point: Each connection is dedicated between node and hub
Easy Management: Simple to install and troubleshoot

Mnemonic: "STAR = Single Terminal All Reach"

Question 1(b) [4 marks]

Explain how point-to-point and broadcast transmission technologies are used in modern communication systems with examples of real-world applications and discuss their advantages and limitations.

Answer:

Technology	Point-to-Point	Broadcast
Connection	Direct link between two devices	One-to-many communication
Example	Telephone, VPN tunnels	Radio, TV, WiFi
Data Flow	Bidirectional	Unidirectional/Multidirectional

Point-to-Point Applications:

Dedicated Lines: Leased lines between offices
Satellite Links: Ground station to satellite communication
Cable Modems: Home to ISP connection

Broadcast Applications:

WiFi Networks: Router broadcasts to multiple devices
Television: One transmitter to many receivers

Mnemonic: "P2P = Private Path, Broadcast = Big Audience"

Question 1(c) [7 marks]

Describe OSI model with function of all layers.

Answer:

Layer	Name	Function
7	Application	User interface, network services
6	Presentation	Data encryption, compression, formatting
5	Session	Establishes, manages, terminates sessions
4	Transport	Reliable data transfer, error correction
3	Network	Routing, logical addressing (IP)
2	Data Link	Frame formatting, error detection
1	Physical	Bit transmission, electrical signals

graph LR
    A[Application Layer 7] --> B[Presentation Layer 6]
    B --> C[Session Layer 5]
    C --> D[Transport Layer 4]
    D --> E[Network Layer 3]
    E --> F[Data Link Layer 2]
    F --> G[Physical Layer 1]

Key Functions:

Upper Layers (5-7): Handle application-related services
Lower Layers (1-4): Handle data transmission and routing
Encapsulation: Each layer adds its own header

Mnemonic: "All People Seem To Need Data Processing"

Question 1(c OR) [7 marks]

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

Answer:

Layer	Name	Function	Protocols
4	Application	User services, applications	HTTP, FTP, SMTP, DNS
3	Transport	End-to-end communication	TCP, UDP
2	Internet	Routing, logical addressing	IP, ICMP, ARP
1	Network Access	Physical transmission	Ethernet, WiFi

graph LR
    A[Application Layer] --> B[Transport Layer]
    B --> C[Internet Layer]
    C --> D[Network Access Layer]

Layer Functions:

Application: Provides network services to applications
Transport: Ensures reliable or unreliable delivery
Internet: Routes packets across networks using IP addresses
Network Access: Handles physical transmission media

Mnemonic: "Applications Transport Internet Networks"

Question 2(a) [3 marks]

Describe Function of firewall in network security.

Answer:

Firewall Functions:

Packet Filtering: Controls incoming and outgoing network traffic
Access Control: Blocks unauthorized access attempts
Traffic Monitoring: Logs and analyzes network activity

Types:

Hardware Firewall: Physical device protecting entire network
Software Firewall: Program installed on individual computers
Stateful Inspection: Tracks connection states and contexts

Mnemonic: "Firewall = Filter, Access, Monitor"

Question 2(b) [4 marks]

Compare FDDI (Fiber Distributed Data Interface) and CDDI (Copper Distributed Data Interface) in terms of their key characteristics, advantages, and applications.

Answer:

Feature	FDDI	CDDI
Medium	Optical fiber	Twisted pair copper
Speed	100 Mbps	100 Mbps
Distance	Up to 200 km	Up to 100 meters
Cost	Higher	Lower
Security	Higher (difficult to tap)	Lower (easier to tap)
Installation	Complex	Simple

FDDI Advantages:

Long Distance: Supports campus-wide networks
High Security: Immune to electromagnetic interference
Reliability: Better error detection and recovery

CDDI Advantages:

Cost Effective: Uses existing copper infrastructure
Easy Installation: Standard twisted pair cabling
Compatibility: Works with existing network equipment

Mnemonic: "FDDI = Fiber Distance, CDDI = Copper Cost"

Question 2(c) [7 marks]

Explain and distinguish Ethernet, Fast Ethernet, Gigabit Ethernet.

Answer:

Type	Speed	Standard	Cable Type	Distance
Ethernet	10 Mbps	802.3	Coax/UTP	100m
Fast Ethernet	100 Mbps	802.3u	UTP Cat5	100m
Gigabit Ethernet	1000 Mbps	802.3z/ab	Cat5e/6, Fiber	100m/5km

graph LR
    A[Ethernet 10 Mbps] --> B[Fast Ethernet 100 Mbps]
    B --> C[Gigabit Ethernet 1000 Mbps]

Key Differences:

Speed Evolution: 10x increase at each generation
Media Support: From coax to twisted pair to fiber
Applications: LAN backbone, server connections, desktop
Backward Compatibility: Newer standards support older devices

Standards:

10Base-T: 10 Mbps over twisted pair
100Base-TX: 100 Mbps over Category 5 UTP
1000Base-T: 1 Gbps over Category 5e/6 UTP

Mnemonic: "Every Fast Gigabit = 10, 100, 1000"

Question 2(a OR) [3 marks]

Explain its role and function of router within a network infrastructure.

Answer:

Router Functions:

Packet Forwarding: Routes data packets between different networks
Path Determination: Selects best route using routing tables
Network Isolation: Separates broadcast domains

Key Roles:

Inter-network Communication: Connects LANs to WANs
Traffic Management: Controls data flow between networks
Protocol Translation: Converts between different network protocols

Mnemonic: "Router = Route, Isolate, Connect"

Question 2(b OR) [4 marks]

Explain the structure of FDDI (Fiber Distributed Data Interface) and give its advantages.

Answer:

FDDI Structure:

    Node A -------- Node B
      |               |
      |               |
    Node D -------- Node C
    
    Primary Ring: Clockwise
    Secondary Ring: Counter-clockwise

Components:

Dual Ring: Primary and secondary rings for redundancy
Token Passing: Uses token for media access control
Concentrators: Connect multiple stations to ring

Advantages:

High Reliability: Dual ring provides fault tolerance
Fast Speed: 100 Mbps data transmission rate
Long Distance: Supports up to 200 km ring circumference
Self-Healing: Automatic reconfiguration when link fails

Mnemonic: "FDDI = Fast, Dual, Distance, Immune"

Question 2(c OR) [7 marks]

Explain roll of network Devices. Describe in brief about all the devices.

Answer:

Device	Layer	Function
Repeater	Physical	Regenerates signals, extends distance
Hub	Physical	Connects multiple devices, shared bandwidth
Bridge	Data Link	Connects LANs, reduces collisions
Switch	Data Link	Intelligent hub, dedicated bandwidth
Router	Network	Connects different networks, routing
Gateway	All Layers	Protocol conversion, network interconnection

graph TD
    A[Physical Layer] --> B[Repeater, Hub]
    C[Data Link Layer] --> D[Bridge, Switch]
    E[Network Layer] --> F[Router]
    G[All Layers] --> H[Gateway]

Device Functions:

Repeater: Amplifies and regenerates signals
Hub: Simple connection point for multiple devices
Bridge: Intelligent forwarding based on MAC addresses
Switch: High-performance bridge with multiple ports
Router: Intelligent path selection between networks
Gateway: Complete protocol stack conversion

Mnemonic: "Repeat, Hub, Bridge, Switch, Route, Gateway"

Question 3(a) [3 marks]

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

Answer:

Data Link Layer Protocols:

HDLC (High-Level Data Link Control)
PPP (Point-to-Point Protocol)
Ethernet (IEEE 802.3)

HDLC Protocol Details:

Frame Structure: Flag, Address, Control, Data, FCS, Flag
Error Detection: Frame Check Sequence (FCS)
Flow Control: Sliding window mechanism

HDLC Frame Format:

+------+------+------+------+------+------+
| Flag |Addr  |Ctrl  | Data | FCS  | Flag |
| 8bit |8bit  |8bit  |      |16bit | 8bit |
+------+------+------+------+------+------+

Mnemonic: "HDLC = High Data Link Control"

Question 3(b) [4 marks]

Explain error control and flow control at data link layer

Answer:

Control Type	Purpose	Methods
Error Control	Detect and correct transmission errors	CRC, Checksum, Parity
Flow Control	Manage data transmission rate	Stop-and-Wait, Sliding Window

Error Control Methods:

Detection: CRC, Checksum identify errors
Correction: ARQ (Automatic Repeat Request)
Prevention: Forward Error Correction (FEC)

Flow Control Methods:

Stop-and-Wait: Send one frame, wait for ACK
Sliding Window: Send multiple frames before ACK
Buffer Management: Prevent receiver overflow

Mnemonic: "Error = Detect, Flow = Control"

Question 3(c) [7 marks]

Compare IPv6 and IPv4.

Answer:

Feature	IPv4	IPv6
Address Length	32 bits	128 bits
Address Space	4.3 billion	340 undecillion
Header Size	20-60 bytes (variable)	40 bytes (fixed)
Notation	Decimal (192.168.1.1)	Hexadecimal (2001:db8::1)
Fragmentation	Router and host	Host only
Security	Optional (IPSec)	Built-in (IPSec)
Configuration	Manual/DHCP	Auto-configuration

IPv4 Example: 192.168.1.100 IPv6 Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

Key Differences:

Address Exhaustion: IPv4 addresses nearly exhausted
Header Efficiency: IPv6 simplified header structure
Security: IPv6 has built-in security features
Quality of Service: Better QoS support in IPv6

Mnemonic: "IPv6 = Infinite, Integrated, Improved"

Question 3(a OR) [3 marks]

Explain the differences between guided and unguided transmission media used in computer networks

Answer:

Media Type	Guided	Unguided
Definition	Physical path exists	No physical path
Examples	Twisted pair, Coax, Fiber	Radio, Microwave, Satellite
Direction	Point-to-point	Broadcast

Guided Media:

Twisted Pair: Telephone lines, LANs
Coaxial Cable: Cable TV, older networks
Fiber Optic: High-speed, long-distance

Unguided Media:

Radio Waves: WiFi, Bluetooth
Microwaves: Point-to-point links
Infrared: Short-range communication

Mnemonic: "Guided = Ground, Unguided = Air"

Question 3(b OR) [4 marks]

Describe circuit switching and packet switching.

Answer:

Feature	Circuit Switching	Packet Switching
Connection	Dedicated path established	No dedicated path
Resource Allocation	Fixed bandwidth	Shared resources
Example	Traditional telephone	Internet
Delay	Constant	Variable

Circuit Switching:

Setup Phase: Establishes dedicated connection
Data Transfer: Continuous transmission
Teardown: Releases connection resources

Packet Switching:

Store-and-Forward: Packets stored at intermediate nodes
Dynamic Routing: Each packet routed independently
Resource Sharing: Bandwidth shared among users

Mnemonic: "Circuit = Continuous, Packet = Pieces"

Question 3(c OR) [7 marks]

Explain IPv4 OR IPv6 in detail.

Answer (IPv4):

IPv4 Address Structure:

32-bit Address: Divided into 4 octets
Dotted Decimal: 192.168.1.1 format
Network + Host: Address split into network and host portions

Class	Range	Network Bits	Host Bits	Use
A	1-126	8	24	Large networks
B	128-191	16	16	Medium networks
C	192-223	24	8	Small networks

Special Addresses:

Loopback: 127.0.0.1 (local host)
Private: 192.168.x.x, 10.x.x.x, 172.16-31.x.x
Broadcast: 255.255.255.255

Subnetting:

Subnet Mask: Identifies network portion
CIDR: Classless Inter-Domain Routing
Variable Length: Different subnet sizes

IPv4 Header:

0               16              32
+---------------+---------------+
|Version| IHL   |Type of Service|
+---------------+---------------+
|     Total Length              |
+---------------+---------------+
|Identification |Flags|Fragment |
+---------------+---------------+
| TTL  |Protocol|Header Checksum|
+---------------+---------------+
|     Source Address            |
+---------------+---------------+
|   Destination Address         |
+---------------+---------------+

Mnemonic: "IPv4 = 4 octets, 32 bits, Classes A-C"

Question 4(a) [3 marks]

Give full name of ARP and RARP and describe them.

Answer:

Full Names:

ARP: Address Resolution Protocol
RARP: Reverse Address Resolution Protocol

Protocol	Function
ARP	Maps IP address to MAC address
RARP	Maps MAC address to IP address

ARP Process:

Request: "Who has IP 192.168.1.1?"
Reply: "192.168.1.1 is at MAC 00:1A:2B:3C:4D:5E"
Cache: Stores mappings for future use

RARP Process:

Diskless Workstations: Get IP from server
Broadcast Request: Sends MAC address
Server Response: Returns assigned IP address

Mnemonic: "ARP = Address to MAC, RARP = Reverse"

Question 4(b) [4 marks]

Describe DSL technology with its advantages and limitations.

Answer:

DSL (Digital Subscriber Line):

Type	Speed	Distance
ADSL	Up to 8 Mbps	5.5 km
VDSL	Up to 52 Mbps	1.5 km
SDSL	Up to 2 Mbps	3 km

Advantages:

Existing Infrastructure: Uses telephone lines
Always-On: Continuous internet connection
Voice + Data: Simultaneous phone and internet
Cost-Effective: Affordable for home users

Limitations:

Distance Dependent: Speed decreases with distance
Upload Speed: Lower than download speed (ADSL)
Line Quality: Affected by copper wire condition
Availability: Not available in all areas

Mnemonic: "DSL = Digital Subscriber Line"

Question 4(c) [7 marks]

Role of DNS- Domain Name System.

Answer:

DNS Functions:

Name Resolution: Converts domain names to IP addresses
Hierarchical Structure: Organized in tree-like structure
Distributed Database: Information stored across multiple servers

graph LR
    A[Root Servers] --> B[Top Level Domain .com]
    A --> C[Top Level Domain .org]
    B --> D[google.com]
    B --> E[yahoo.com]
    D --> F[drive.google.com]
    D --> G[mail.google.com]

DNS Hierarchy:

Root Domain: Highest level (.)
Top-Level Domain: .com, .org, .net, .edu
Second-Level Domain: google.com, yahoo.com
Subdomain: www.google.com, mail.google.com

DNS Resolution Process:

Client Query: User types www.example.com
Local DNS: Checks local cache
Root Server: Queries root DNS server
TLD Server: Queries .com server
Authoritative Server: Gets IP address
Response: Returns IP to client

DNS Record Types:

A Record: Maps domain to IPv4 address
AAAA Record: Maps domain to IPv6 address
CNAME: Canonical name (alias)
MX: Mail exchange server
NS: Name server records

Mnemonic: "DNS = Domain Name System"

Question 4(a OR) [3 marks]

Give full name of DHCP and BOOTP. and describe them.

Answer:

Full Names:

DHCP: Dynamic Host Configuration Protocol
BOOTP: Bootstrap Protocol

Protocol	Function
DHCP	Automatically assigns IP addresses
BOOTP	Provides IP address to diskless workstations

DHCP Process:

Discover: Client broadcasts request
Offer: Server offers IP address
Request: Client requests specific IP
Acknowledge: Server confirms assignment

BOOTP Process:

Static Configuration: Pre-configured IP assignments
Diskless Boot: Workstations boot from network
Server Response: Provides IP and boot information

Mnemonic: "DHCP = Dynamic, BOOTP = Bootstrap"

Question 4(b OR) [4 marks]

Differences Between Virtual Circuits and Datagram Networks.

Answer:

Feature	Virtual Circuits	Datagram Networks
Connection	Connection-oriented	Connectionless
Setup	Requires setup phase	No setup required
Routing	Same path for all packets	Independent routing
Order	Packets arrive in order	May arrive out of order
Reliability	More reliable	Less reliable
Overhead	Higher setup overhead	Lower per-packet overhead

Virtual Circuits:

Path Establishment: Creates virtual connection
State Information: Maintains connection state
Examples: ATM, Frame Relay

Datagram Networks:

Independent Packets: Each packet routed separately
Stateless: No connection state maintained
Examples: Internet Protocol (IP)

Mnemonic: "Virtual = Connection, Datagram = Independent"

Question 4(c OR) [7 marks]

Explain TCP and UDP protocol in transport layer

Answer:

Feature	TCP	UDP
Connection	Connection-oriented	Connectionless
Reliability	Reliable	Unreliable
Header Size	20 bytes	8 bytes
Flow Control	Yes	No
Error Control	Yes	Basic
Speed	Slower	Faster

TCP (Transmission Control Protocol):

Three-Way Handshake: SYN, SYN-ACK, ACK
Flow Control: Sliding window mechanism
Error Recovery: Retransmission of lost packets
Congestion Control: Prevents network overload

TCP Header:

0               16              32
+---------------+----------------+
|Source Port    |Destination Port|
+---------------+----------------+
|      Sequence Number           |
+---------------+----------------+
|   Acknowledgment Number        |
+---------------+----------------+
|Hdr|   |U|A|P|R|S|F|    Window  |
|Len|   |R|C|S|S|Y|I|     Size   |
+---------------+----------------+

UDP (User Datagram Protocol):

Simple Protocol: Minimal overhead
Best Effort: No guarantee of delivery
Applications: DNS, DHCP, streaming media
Real-time Communication: Voice, video applications

UDP Header:

0               16              32
+---------------+----------------+
|Source Port    |Destination Port|
+---------------+----------------+
|    Length     |   Checksum     |
+---------------+----------------+

Applications:

TCP: Web browsing, email, file transfer
UDP: Online gaming, video streaming, DNS queries

Mnemonic: "TCP = Reliable, UDP = Fast"

Question 5(a) [3 marks]

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

Answer:

WWW (World Wide Web):

HTTP Protocol: HyperText Transfer Protocol
Web Browser: Client software (Chrome, Firefox)
Web Server: Serves web pages (Apache, IIS)

FTP (File Transfer Protocol):

File Transfer: Upload and download files
Two Modes: Active and passive mode
Authentication: Username and password required

Service	Port	Function
WWW	80/443	Web page delivery
FTP	20/21	File transfer

Mnemonic: "WWW = Web, FTP = Files"

Question 5(b) [4 marks]

Difference between symmetric and asymmetric encryption algorithms.

Answer:

Feature	Symmetric	Asymmetric
Keys	Same key for encryption/decryption	Different keys (public/private)
Speed	Fast	Slow
Key Distribution	Difficult	Easy
Examples	AES, DES	RSA, ECC

Symmetric Encryption:

Single Key: Same key used by sender and receiver
Key Management: Secure key distribution required
Performance: Fast encryption/decryption
Applications: Bulk data encryption

Asymmetric Encryption:

Key Pair: Public key for encryption, private key for decryption
Key Distribution: Public key can be shared openly
Performance: Slower than symmetric
Applications: Digital signatures, key exchange

Mnemonic: "Symmetric = Same, Asymmetric = Different"

Question 5(c) [7 marks]

Define the terms "encryption" and "decryption" in the context of cryptography.

Answer:

Encryption:

Definition: Process of converting plaintext into ciphertext
Purpose: Protect data confidentiality
Input: Plaintext + Key
Output: Ciphertext

Decryption:

Definition: Process of converting ciphertext back to plaintext
Purpose: Retrieve original data
Input: Ciphertext + Key
Output: Plaintext

graph LR
    A[Plaintext] --> B[Encryption]
    B --> C[Ciphertext]
    C --> D[Decryption]
    D --> E[Plaintext]
    F[Key] --> B
    G[Key] --> D

Cryptographic Process:

Sender: Encrypts message using key
Transmission: Sends ciphertext over network
Receiver: Decrypts ciphertext using key
Recovery: Gets original plaintext message

Types of Encryption:

Stream Cipher: Encrypts one bit/byte at a time
Block Cipher: Encrypts fixed-size blocks
Hash Function: One-way encryption (no decryption)

Applications:

Data Protection: Secure file storage
Communication: Secure messaging
Authentication: Digital signatures
Privacy: Personal information protection

Security Requirements:

Confidentiality: Only authorized users can read
Integrity: Data hasn't been tampered with
Authentication: Verify sender identity
Non-repudiation: Sender cannot deny sending

Mnemonic: "Encryption = Hide, Decryption = Reveal"

Question 5(a OR) [3 marks]

Difference between IMAP and POP3

Answer:

Feature	IMAP	POP3
Storage	Server-side	Client-side
Access	Multiple devices	Single device
Offline	Limited	Full access

IMAP (Internet Message Access Protocol):

Server Storage: Messages remain on server
Multi-Device: Access from multiple devices
Synchronization: Changes sync across devices

POP3 (Post Office Protocol 3):

Download: Messages downloaded to client
Single Device: Best for one device access
Storage: Client manages message storage

Mnemonic: "IMAP = Internet Access, POP3 = Post Office"

Question 5(b OR) [4 marks]

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

Answer:

IT Act 2008 Key Features:

Cyber Crimes: Defines various cyber offenses
Data Protection: Privacy and security requirements
Digital Signatures: Legal recognition of e-signatures
Penalties: Fines and imprisonment for violations

Major Amendments:

Section 66A: Criminalized offensive messages (later struck down)
Section 69: Government power to intercept information
Section 72A: Punishment for disclosure of personal information
Section 43A: Compensation for data breach

Impact on Cyber Laws:

Legal Framework: Comprehensive cyber law structure
Business Compliance: Data protection requirements
Individual Rights: Privacy protection mechanisms
Law Enforcement: Tools for investigating cyber crimes

Mnemonic: "IT Act = Internet Technology Act"

Question 5(c OR) [7 marks]

Difference between symmetric and asymmetric encryption algorithms.

Answer:

Aspect	Symmetric Encryption	Asymmetric Encryption
Key Usage	Same key for encrypt/decrypt	Different keys (public/private)
Key Management	Difficult key distribution	Easy key distribution
Performance	Fast processing	Slow processing
Key Length	Shorter keys (128-256 bits)	Longer keys (1024-4096 bits)
Scalability	Poor (n² key pairs needed)	Good (n key pairs needed)
Examples	AES, DES, 3DES, Blowfish	RSA, ECC, DSA, ElGamal

Symmetric Encryption Details:

Algorithm Types: Stream ciphers, Block ciphers
Key Distribution Problem: Secure channel needed for key exchange
Applications: Bulk data encryption, VPNs, file encryption
Advantages: Fast, efficient for large amounts of data
Disadvantages: Key management complexity, no digital signatures

Asymmetric Encryption Details:

Public Key Infrastructure: PKI for key management
Digital Signatures: Authentication and non-repudiation
Applications: Email security, SSL/TLS, digital certificates
Advantages: Secure key exchange, digital signatures
Disadvantages: Computationally intensive, slower processing

Hybrid Approach:

Best of Both: Combines symmetric and asymmetric encryption
Key Exchange: Asymmetric for key distribution
Data Encryption: Symmetric for actual data
Example: SSL/TLS uses both methods

graph TD
    A[Encryption Methods] --> B[Symmetric]
    A --> C[Asymmetric]
    B --> D[Same Key]
    B --> E[Fast Processing]
    C --> F[Key Pair]
    C --> G[Slow Processing]

Real-world Applications:

Banking: ATM transactions use symmetric encryption
E-commerce: HTTPS uses hybrid encryption
Email: PGP uses asymmetric for key exchange
Mobile: WhatsApp uses end-to-end encryption

Security Considerations:

Key Length: Longer keys provide better security
Algorithm Strength: Choose proven algorithms
Implementation: Proper coding prevents vulnerabilities
Key Storage: Secure key management essential

Performance Comparison:

Operation	Symmetric (AES)	Asymmetric (RSA)
Encryption	~1000 MB/s	~1 MB/s
Key Generation	Fast	Slow
Memory Usage	Low	High
CPU Usage	Low	High

Future Trends:

Quantum Computing: Threat to current asymmetric algorithms
Post-Quantum Cryptography: New algorithms being developed
Elliptic Curve: More efficient asymmetric encryption
Lightweight Cryptography: For IoT devices

Mnemonic: "Symmetric = Same Speed, Asymmetric = Advanced Security"