Question 1(a) [3 marks]

List Various network Topologies of computer network and explain any one.

Answer:

Table: Network Topologies

Topology	Description
Star	Central hub connects all devices
Ring	Devices connected in circular chain
Bus	Single cable backbone connection
Mesh	Every device connects to every other
Tree	Hierarchical branching structure
Hybrid	Combination of multiple topologies

Star Topology Explanation:

Central Hub: All devices connect to one central point
Easy Installation: Simple to add/remove devices
Single Point Failure: Hub failure affects entire network

Mnemonic: "SRBMTH - Star Ring Bus Mesh Tree Hybrid"

Question 1(b) [4 marks]

Compare LAN, WAN and MAN.

Answer:

Comparison Table:

Parameter	LAN	MAN	WAN
Coverage	Building/Campus	City/Metropolitan	Country/Global
Speed	Very High (1-100 Gbps)	High (10-100 Mbps)	Medium (1-100 Mbps)
Cost	Low	Medium	High
Ownership	Private	Public/Private	Public

Key Points:

LAN: Local Area Network for small areas
MAN: Metropolitan Area Network for cities
WAN: Wide Area Network for large distances

Mnemonic: "LMW - Local Metropolitan Wide"

Question 1(c) [7 marks]

Draw the layered architecture of OSI reference model and write at least two services provided by each layer of the model.

Answer:

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]

Services by Each Layer:

Layer	Services
Application (7)	Email services, File transfer
Presentation (6)	Data encryption, Data compression
Session (5)	Session establishment, Session termination
Transport (4)	Flow control, Error correction
Network (3)	Routing, Path determination
Data Link (2)	Frame synchronization, Error detection
Physical (1)	Bit transmission, Signal conversion

Mnemonic: "All People Seem To Need Data Processing"

Question 1(c OR) [7 marks]

Explain Each layer of TCP/IP Model with its protocol.

Answer:

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

TCP/IP Model Layers:

Layer	Protocols	Function
Application	HTTP, FTP, SMTP, DNS	User applications
Transport	TCP, UDP	End-to-end delivery
Internet	IP, ICMP, ARP	Routing packets
Network Access	Ethernet, Wi-Fi	Physical transmission

Key Features:

Simplified Model: Only 4 layers vs OSI's 7
Protocol Suite: Complete networking solution
Internet Standard: Basis of modern internet

Mnemonic: "ATIN - Application Transport Internet Network"

Question 2(a) [3 marks]

Explain functions of following network devices: Repeater, Hub

Answer:

Device Functions:

Device	Function	Layer
Repeater	Signal amplification, Range extension	Physical (1)
Hub	Signal broadcasting, Collision domain sharing	Physical (1)

Details:

Repeater: Regenerates weak signals over long distances
Hub: Connects multiple devices in star topology
Shared Medium: Both create single collision domain

Mnemonic: "RH - Repeat Hub signals"

Question 2(b) [4 marks]

Explain the following term 1) FDDI 2) ARP, RARP

Answer:

FDDI (Fiber Distributed Data Interface):

Technology: 100 Mbps fiber optic network
Topology: Dual ring for fault tolerance
Application: Backbone networks, high reliability

ARP (Address Resolution Protocol):

Function: Maps IP address to MAC address
Process: Broadcasts request, receives reply

RARP (Reverse ARP):

Function: Maps MAC address to IP address
Usage: Diskless workstations, boot process

Mnemonic: "FAR - FDDI ARP RARP"

Question 2(c) [7 marks]

Explain the Function of firewall in network security with principles and Kerberos-concept.

Answer:

Firewall Functions:

graph TD
    A[Internet] --> B[Firewall] --> C[Internal Network]
    B --> D[Block Threats]
    B --> E[Allow Traffic]
    B --> F[Log Activity]

Firewall Principles:

Packet Filtering: Examines packet headers
Stateful Inspection: Tracks connection states
Application Gateway: Deep packet inspection

Kerberos Concept:

Authentication Service: Secure user verification
Ticket System: Time-limited access tokens
Three-party Protocol: Client, Server, Key Distribution Center

Security Benefits:

Access Control: Prevents unauthorized access
Network Protection: Shields internal resources

Mnemonic: "FPK - Firewall Protects with Kerberos"

Question 2(a OR) [3 marks]

Explain functions of following network devices: Switch, Router

Answer:

Device Functions:

Device	Function	Layer
Switch	MAC address learning, Frame forwarding	Data Link (2)
Router	IP routing, Path selection	Network (3)

Details:

Switch: Creates separate collision domains per port
Router: Connects different networks, makes routing decisions
Intelligence: Switch learns MAC, Router maintains routing table

Mnemonic: "SR - Switch Routes intelligently"

Question 2(b OR) [4 marks]

Explain the following term 1) CDDI 2) DHCP and BOOTP

Answer:

CDDI (Copper Distributed Data Interface):

Technology: FDDI over copper cables
Speed: 100 Mbps over twisted pair
Cost: Cheaper alternative to fiber FDDI

DHCP (Dynamic Host Configuration Protocol):

Function: Automatic IP address assignment
Process: Discover, Offer, Request, Acknowledge
Benefits: Centralized IP management

BOOTP (Bootstrap Protocol):

Function: Network bootstrap for diskless clients
Static: Fixed IP address assignment
Predecessor: Earlier version of DHCP

Mnemonic: "CDB - CDDI DHCP BOOTP"

Question 2(c OR) [7 marks]

Explain Software define network(SDN) with its Architecture, Application, Advantage and limitation.

Answer:

graph TD
    A[SDN Controller] --> B[OpenFlow Protocol]
    B --> C[Network Switches]
    A --> D[Network Applications]
    D --> E[Traffic Engineering]
    D --> F[Security Policies]

SDN Architecture:

Control Plane: Centralized network intelligence
Data Plane: Packet forwarding devices
Application Plane: Network applications and services

Applications:

Cloud Computing: Dynamic resource allocation
Network Virtualization: Multiple virtual networks
Traffic Engineering: Optimized path selection

Advantages:

Centralized Control: Simplified network management
Programmability: Custom network behaviors
Flexibility: Rapid service deployment

Limitations:

Single Point Failure: Controller dependency
Scalability: Performance bottlenecks
Security: New attack vectors

Mnemonic: "SCAP - Software Control Application Programmable"

Question 3(a) [3 marks]

Find the class of following IP address. 1) 01111000 00001111 10101010 11000000 2) 11101000 01010101 11111111 11000011

Answer:

IP Address Classification:

Binary Address	Decimal	First Octet	Class
01111000...	120.15.170.192	120 (64-127)	Class A
11101000...	232.85.255.195	232 (224-239)	Class D

Class Ranges:

Class A: 1-126 (0xxxxxxx)
Class B: 128-191 (10xxxxxx)
Class C: 192-223 (110xxxxx)
Class D: 224-239 (1110xxxx)

Results:

First IP: Class A (Unicast)
Second IP: Class D (Multicast)

Mnemonic: "ABCD - A(1-126) B(128-191) C(192-223) D(224-239)"

Question 3(b) [4 marks]

Differentiate IPv4 and IPv6.

Answer:

IPv4 vs IPv6 Comparison:

Feature	IPv4	IPv6
Address Length	32 bits	128 bits
Address Format	Dotted decimal	Hexadecimal
Address Space	4.3 billion	340 undecillion
Header Size	Variable (20-60 bytes)	Fixed (40 bytes)
Security	Optional (IPSec)	Built-in (IPSec)
Configuration	Manual/DHCP	Auto-configuration

Key Differences:

Addressing: IPv6 provides vastly more addresses
Security: IPv6 has mandatory security features
Performance: IPv6 has simplified header structure

Mnemonic: "IPv4 to IPv6 = More addresses, Better security"

Question 3(c) [7 marks]

Explain Static and Dynamic Routing Algorithms.

Answer:

Static Routing:

graph LR
    A[Administrator] --> B[Manual Route Entry]
    B --> C[Routing Table]
    C --> D[Fixed Paths]

Dynamic Routing:

graph LR
    A[Routing Protocol] --> B[Route Discovery]
    B --> C[Automatic Updates]
    C --> D[Adaptive Paths]

Comparison Table:

Aspect	Static Routing	Dynamic Routing
Configuration	Manual setup	Automatic discovery
Adaptability	No adaptation	Adapts to changes
Resource Usage	Low CPU/Memory	Higher CPU/Memory
Scalability	Poor for large networks	Good for large networks
Protocols	None required	RIP, OSPF, BGP

Applications:

Static: Small networks, specific paths
Dynamic: Large networks, fault tolerance

Mnemonic: "SD - Static=Simple, Dynamic=Automatic"

Question 3(a OR) [3 marks]

Explain CIDR. How does it differ from traditional IP address allocation methods?

Answer:

CIDR (Classless Inter-Domain Routing):

Concept: Variable length subnet masking
Notation: IP address/prefix length (e.g., 192.168.1.0/24)
Flexibility: Subnets of any size

Traditional vs CIDR:

Method	Allocation	Efficiency
Traditional	Fixed class boundaries	Wasteful (Class B = 65,536 IPs)
CIDR	Variable subnet sizes	Efficient allocation

Benefits:

Address Conservation: Reduces IP address waste
Route Aggregation: Summarizes multiple routes

Mnemonic: "CIDR = Classless Intelligent Address Routing"

Question 3(b OR) [4 marks]

Describe DSL technology with its types, advantages and limitations.

Answer:

DSL (Digital Subscriber Line):

Technology: High-speed internet over telephone lines
Frequency: Uses higher frequencies than voice

DSL Types:

Type	Speed	Application
ADSL	Asymmetric (faster download)	Home users
SDSL	Symmetric (equal up/down)	Business
VDSL	Very high speed	Short distances

Advantages:

Always-on Connection: No dial-up required
Existing Infrastructure: Uses phone lines
Cost-effective: Affordable high-speed access

Limitations:

Distance Dependent: Speed decreases with distance
Line Quality: Requires good copper lines
Availability: Not available everywhere

Mnemonic: "DSL = Digital Speed Limited by distance"

Question 3(c OR) [7 marks]

Explain error control and flow control at data link layer in detail.

Answer:

Error Control:

graph LR
    A[Data Transmission] --> B[Error Detection]
    B --> C{Error Found?}
    C -->|Yes| D[Request Retransmission]
    C -->|No| E[Accept Data]
    D --> A

Error Control Methods:

Method	Technique	Application
Parity Check	Single bit error detection	Simple systems
Checksum	Mathematical sum verification	TCP/UDP
CRC	Polynomial division	Ethernet, Wi-Fi
ARQ	Automatic Repeat Request	Reliable protocols

Flow Control:

graph LR
    A[Sender] --> B[Buffer Check]
    B --> C{Buffer Full?}
    C -->|No| D[Send Data]
    C -->|Yes| E[Wait]
    E --> B

Flow Control Techniques:

Stop-and-Wait: Send one frame, wait for ACK
Sliding Window: Multiple frames in transit
Buffer Management: Prevents overflow

Implementation:

Hardware Level: Buffer status signals
Software Level: Protocol acknowledgments

Mnemonic: "EF - Error detection, Flow regulation"

Question 4(a) [3 marks]

Explain video over IP.

Answer:

Video over IP (VoIP):

Technology: Transmits video signals over IP networks
Digitization: Converts analog video to digital packets
Real-time: Requires low latency transmission

Components:

Encoder: Compresses video data
Network: IP infrastructure for transport
Decoder: Decompresses at destination

Applications:

Video Conferencing: Business communications
Streaming: Entertainment services
Surveillance: Security systems

Requirements:

Bandwidth: High data rate needs
QoS: Quality of Service guarantees

Mnemonic: "VIP = Video Internet Protocol"

Question 4(b) [4 marks]

Explain Electronic-Mail with its protocol.

Answer:

Email System Components:

graph LR
    A[User Agent] --> B[SMTP Server]
    B --> C[Internet]
    C --> D[POP3/IMAP Server]
    D --> E[Recipient]

Email Protocols:

Protocol	Function	Port
SMTP	Send/relay messages	25, 587
POP3	Download messages	110
IMAP	Server-based access	143

Protocol Details:

SMTP: Simple Mail Transfer Protocol for sending
POP3: Downloads mail to local device
IMAP: Keeps mail on server, multi-device access

Message Flow:

Composition: User creates message
Submission: SMTP sends to server
Delivery: Server forwards to recipient
Retrieval: POP3/IMAP downloads message

Mnemonic: "SPI - SMTP sends, POP3/IMAP receives"

Question 4(c) [7 marks]

Explain Role of DNS- Domain Name System Describe the process of DNS resolution.

Answer:

DNS Role:

Name Resolution: Converts domain names to IP addresses
Hierarchical System: Distributed database structure
Internet Navigation: Makes web browsing user-friendly

DNS Resolution Process:

sequenceDiagram
    participant C as Client
    participant L as Local DNS
    participant R as Root Server
    participant T as TLD Server
    participant A as Authoritative Server
    
    C->>L: Query www.example.com
    L->>R: Query root
    R->>L: Refer to .com TLD
    L->>T: Query .com TLD
    T->>L: Refer to example.com
    L->>A: Query example.com
    A->>L: Return IP address
    L->>C: Return IP address

Resolution Steps:

Local Cache Check: Check local DNS cache
Recursive Query: Contact local DNS server
Root Server: Get TLD server reference
TLD Server: Get authoritative server reference
Authoritative Server: Get final IP address
Response Return: IP address returned to client

DNS Record Types:

A Record: Maps name to IPv4 address
AAAA Record: Maps name to IPv6 address
CNAME: Canonical name alias
MX: Mail exchange server

Benefits:

User Friendly: Remember names, not numbers
Load Distribution: Multiple IP addresses
Service Location: Find specific services

Mnemonic: "DNS = Directory Name Service"

Question 4(a OR) [3 marks]

Explain WWW, HTML.

Answer:

WWW (World Wide Web):

Definition: Information system of interlinked documents
Access: Through web browsers using HTTP
Components: Web pages, links, URLs

HTML (HyperText Markup Language):

Purpose: Standard markup language for web pages
Structure: Tags define document elements
Hyperlinks: Connect different web resources

Relationship:

WWW: The system/platform
HTML: The content format
Integration: HTML creates WWW content

Mnemonic: "WWW uses HTML for content"

Question 4(b OR) [4 marks]

Explain HTTP and FTP.

Answer:

Protocol Comparison:

Feature	HTTP	FTP
Purpose	Web page transfer	File transfer
Port	80 (HTTP), 443 (HTTPS)	21 (control), 20 (data)
Connection	Stateless	Stateful
Security	HTTPS for security	FTPS for security

HTTP (HyperText Transfer Protocol):

Function: Request-response protocol for web
Methods: GET, POST, PUT, DELETE
Stateless: Each request independent

FTP (File Transfer Protocol):

Function: Upload/download files between systems
Modes: Active and Passive
Authentication: Username/password required

Applications:

HTTP: Web browsing, API calls
FTP: File sharing, website maintenance

Mnemonic: "HF - HTTP for Hypertext, FTP for Files"

Question 4(c OR) [7 marks]

Explain TCP and UDP protocol in transport layer in relation to connection oriented and connection less network.

Answer:

Transport Layer Protocols:

graph LR
    A[Transport Layer] --> B[TCP - Connection Oriented]
    A --> C[UDP - Connectionless]
    B --> D[Reliable Delivery]
    C --> E[Fast Delivery]

Protocol Comparison:

Feature	TCP	UDP
Connection	Connection-oriented	Connectionless
Reliability	Guaranteed delivery	Best effort
Speed	Slower (overhead)	Faster (minimal overhead)
Header Size	20 bytes	8 bytes
Flow Control	Yes	No
Error Control	Yes	Limited

TCP (Transmission Control Protocol):

Three-way Handshake: SYN, SYN-ACK, ACK
Reliable: Acknowledgment and retransmission
Flow Control: Prevents buffer overflow
Applications: Web browsing, email, file transfer

UDP (User Datagram Protocol):

No Connection Setup: Direct data transmission
Lightweight: Minimal protocol overhead
No Guarantees: Fire-and-forget approach
Applications: Video streaming, DNS, gaming

Connection Models:

Connection-Oriented: Establish, transfer, terminate
Connectionless: Direct transmission without setup

Selection Criteria:

Use TCP: When reliability is critical
Use UDP: When speed is more important

Mnemonic: "TCP = Thorough, UDP = Ultra-fast"

Question 5(a) [3 marks]

Describe Hacking and its related precautions.

Answer:

Hacking Definition:

Unauthorized Access: Breaking into computer systems
Malicious Intent: Steal, modify, or destroy data
Security Breach: Exploit system vulnerabilities

Types of Hacking:

Ethical Hacking: Authorized security testing
Malicious Hacking: Criminal activities
Social Engineering: Manipulate human behavior

Precautions:

Security Measure	Implementation
Strong Passwords	Complex, unique passwords
Software Updates	Regular patches and updates
Firewalls	Network access control
Antivirus	Malware detection and removal
Backup	Regular data backups
User Training	Security awareness programs

Mnemonic: "HSPFAB - Hacking Stopped by Passwords, Firewalls, Antivirus, Backups"

Question 5(b) [4 marks]

Explain IPSec architecture.

Answer:

IPSec (Internet Protocol Security):

graph TD
    A[IPSec Architecture] --> B[Authentication Header - AH]
    A --> C[Encapsulating Security Payload - ESP]
    A --> D[Security Association - SA]
    A --> E[Internet Key Exchange - IKE]

IPSec Components:

Component	Function
AH	Authentication and integrity
ESP	Confidentiality and authentication
SA	Security parameter agreement
IKE	Key management protocol

Operating Modes:

Transport Mode: Protects payload only
Tunnel Mode: Protects entire IP packet

Security Services:

Authentication: Verify sender identity
Integrity: Ensure data unchanged
Confidentiality: Encrypt data content
Anti-replay: Prevent packet replay attacks

Mnemonic: "AISE - AH, IPSec, SA, ESP"

Question 5(c) [7 marks]

Explain network Security topologies.

Answer:

Network Security Topologies:

graph LR
    A[Internet] --> B[Firewall]
    B --> C[DMZ]
    C --> D[Web Server]
    C --> E[Mail Server]
    B --> F[Internal Network]
    F --> G[Workstations]
    F --> H[Database Server]

Security Zones:

Zone	Purpose	Security Level
Internet	External untrusted network	Lowest
DMZ	Semi-trusted public services	Medium
Internal	Private trusted network	Highest

Topology Components:

Perimeter Security: Firewalls, IDS/IPS
Network Segmentation: VLANs, subnets
Access Control: Authentication, authorization
Monitoring: Logging, SIEM systems

Security Principles:

Defense in Depth: Multiple security layers
Least Privilege: Minimum required access
Network Isolation: Separate critical systems

Implementation Strategies:

Firewall Rules: Control traffic flow
VPN Access: Secure remote connections
Network Monitoring: Detect threats
Incident Response: Handle security events

Benefits:

Risk Reduction: Minimize attack surface
Compliance: Meet regulatory requirements
Business Continuity: Protect operations

Mnemonic: "NST = Network Security Through topology design"

Question 5(a OR) [3 marks]

Explain ISO and how it contributes to information security?

Answer:

ISO (International Organization for Standardization):

Global Standards: Develops international standards
Quality Assurance: Ensures consistent practices
Best Practices: Provides framework for implementation

ISO 27001 - Information Security:

ISMS: Information Security Management System
Risk Management: Systematic approach to security
Continuous Improvement: Regular review and updates

Contributions to Information Security:

Framework: Structured approach to security
Compliance: Meet regulatory requirements
Risk Assessment: Identify and mitigate threats

Benefits:

Standardization: Common security language
Credibility: International recognition
Improvement: Ongoing security enhancement

Mnemonic: "ISO = International Security Organization"

Question 5(b OR) [4 marks]

Give Difference between symmetric and asymmetric encryption algorithms.

Answer:

Encryption Algorithm Comparison:

Feature	Symmetric	Asymmetric
Keys	Single shared key	Key pair (public/private)
Speed	Fast	Slower
Key Distribution	Difficult	Easier
Scalability	Poor (n²-1 keys)	Better
Security	Depends on key secrecy	Mathematical complexity

Symmetric Encryption:

Examples: AES, DES, 3DES
Process: Same key encrypts and decrypts
Challenge: Secure key distribution

Asymmetric Encryption:

Examples: RSA, ECC, Diffie-Hellman
Process: Public key encrypts, private key decrypts
Advantage: No key distribution problem

Hybrid Approach:

Combination: Use both types together
Method: Asymmetric for key exchange, symmetric for data

Applications:

Symmetric: Bulk data encryption
Asymmetric: Digital signatures, key exchange

Mnemonic: "SA = Symmetric Shared, Asymmetric Apart"

Question 5(c OR) [7 marks]

Explain Email security with its standards.

Answer:

Email Security Challenges:

graph TD
    A[Email Threats] --> B[Phishing]
    A --> C[Malware]
    A --> D[Spam]
    A --> E[Data Interception]
    A --> F[Identity Spoofing]

Email Security Standards:

Standard	Purpose	Function
S/MIME	Secure email content	Encryption and digital signatures
PGP	Pretty Good Privacy	End-to-end encryption
TLS	Transport security	Secure email transmission
SPF	Sender authentication	Prevent email spoofing
DKIM	Message integrity	Digital signature verification
DMARC	Policy enforcement	Email authentication policy

Security Mechanisms:

Encryption: Protect message content
Digital Signatures: Verify sender identity
Authentication: Confirm message origin
Integrity: Ensure message unchanged

Implementation Layers:

Transport Layer: TLS/SSL encryption
Message Layer: S/MIME, PGP encryption
Policy Layer: SPF, DKIM, DMARC

Best Practices:

User Education: Recognize phishing attempts
Gateway Filtering: Block malicious emails
Regular Updates: Keep security software current
Backup Systems: Protect against data loss

Benefits:

Confidentiality: Private communications
Authentication: Verified senders
Compliance: Meet regulatory requirements
Trust: Secure business communications

Mnemonic: "SPTSD = S/MIME, PGP, TLS, SPF, DKIM protect email"