Mobile Computing and Networks (4351602) - Winter 2023 Solution

Question 1(a) [03 marks]

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Differentiate between client server and peer to peer network.

Answer:

Mnemonic: “CSS-P: Client-Server = Centralized Security, P2P = Peer Power”

Question 1(b) [04 marks]

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Explain ARP Protocol with its working.

Answer:

ARP (Address Resolution Protocol) maps IP addresses to MAC addresses in local networks.

Working Process:

• Broadcast Request: Host broadcasts ARP request with target IP
• Cache Check: Receiving hosts check if IP matches theirs
• Reply Generation: Target host sends ARP reply with MAC address
• Cache Update: Requesting host updates ARP table

ARP Table Example:

IP Address      MAC Address         TTL
192.168.1.1     00:1A:2B:3C:4D:5E   300s

Mnemonic: “BCRU: Broadcast, Cache, Reply, Update”

Question 1(c) [07 marks]

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Explain OSI model with diagram.

Answer:

The OSI (Open Systems Interconnection) model has 7 layers for network communication.

graph TD
    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]

Layer Functions:

• Physical: Bit transmission over physical medium
• Data Link: Frame transmission, error detection
• Network: Routing, IP addressing
• Transport: End-to-end delivery, TCP/UDP
• Session: Connection management
• Presentation: Data encryption, compression
• Application: User interfaces, email, web

Mnemonic: “All People Seem To Need Data Processing”

Question 1(c OR) [07 marks]

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What is Congestion? Explain Congestion Control.

Answer:

Congestion occurs when network traffic exceeds available bandwidth, causing packet delays and losses.

Types of Congestion Control:

Congestion Control Techniques:

• Traffic Shaping: Regulate data transmission rate
• Admission Control: Limit new connections during congestion
• Load Shedding: Drop packets when buffers full
• Backpressure: Send congestion signals upstream

Mnemonic: “TALB: Traffic, Admission, Load, Backpressure”

Question 2(a) [03 marks]

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What is Ad-hoc Network? Explain it.

Answer:

Ad-hoc Network is a wireless network without fixed infrastructure where nodes communicate directly.

Characteristics:

• Self-organizing: Automatic network formation
• Dynamic topology: Nodes can join/leave freely
• Multi-hop routing: Messages relay through intermediate nodes
• Distributed control: No central authority

Applications:

• Emergency response, military operations, sensor networks

Mnemonic: “SDMD: Self-organizing, Dynamic, Multi-hop, Distributed”

Question 2(b) [04 marks]

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Explain Handover Management in Mobile IP.

Answer:

Handover is the process of maintaining connectivity when a mobile node moves between networks.

Handover Process:

sequenceDiagram
    participant MN as Mobile Node
    participant FA1 as Foreign Agent 1
    participant FA2 as Foreign Agent 2
    participant HA as Home Agent
    
    MN->>FA2: Agent Discovery
    FA2->>MN: Advertisement
    MN->>HA: Registration Request
    HA->>MN: Registration Reply
    HA->>FA1: Update Tunnel

Types:

• Hard Handover: Break-before-make connection
• Soft Handover: Make-before-break connection

Mnemonic: “DARU: Discovery, Advertisement, Registration, Update”

Question 2(c) [07 marks]

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Explain Three tier architecture of mobile computing with diagram.

Answer:

Three-tier architecture separates mobile applications into presentation, application logic, and data layers.

graph TB
    subgraph "Tier 1: Presentation Layer"
        A[Mobile Device]
        B[User Interface]
        C[Input/Output]
    end
    
    subgraph "Tier 2: Application Layer"
        D[Business Logic]
        E[Processing Rules]
        F[Middleware]
    end
    
    subgraph "Tier 3: Data Layer"
        G[Database Server]
        H[Data Storage]
        I[Data Management]
    end
    
    A --> D
    D --> G

Layer Functions:

• Presentation: User interface, mobile apps
• Application: Business logic, middleware services
• Data: Database management, storage systems

Benefits:

• Scalability: Independent layer scaling
• Maintainability: Separate concerns
• Flexibility: Technology independence

Mnemonic: “PAD: Presentation, Application, Data”

Question 2(a OR) [03 marks]

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Explain Need of Wireless Network.

Answer:

Wireless Networks provide connectivity without physical cables.

Needs:

• Mobility: Users can move freely while connected
• Flexibility: Easy network expansion and reconfiguration
• Cost-effective: Reduced cabling infrastructure costs
• Accessibility: Internet access in remote areas

Applications:

• Mobile communications, WiFi hotspots, IoT devices

Mnemonic: “MFCA: Mobility, Flexibility, Cost, Accessibility”

Question 2(b OR) [04 marks]

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Explain Registration, tunneling and encapsulation in mobile ip.

Answer:

Mobile IP Components:

Process Flow:

Original Packet → Encapsulation → Tunnel → Decapsulation → Destination

Registration Steps:

• Mobile node discovers foreign agent
• Sends registration request to home agent
• Home agent updates location binding

Mnemonic: “RTE: Registration, Tunneling, Encapsulation”

Question 2(c OR) [07 marks]

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What is Middleware? Write down examples of middleware and explain any one of them in detail.

Answer:

Middleware is software that connects different applications and services in distributed systems.

Examples of Middleware:

• Message-Oriented Middleware (MOM)
• Remote Procedure Call (RPC)
• Object Request Broker (ORB)
• Database Middleware
• Web Services

Message-Oriented Middleware (MOM) - Detailed:

Architecture:

graph LR
    A[Sender Application] --> B[Message Queue]
    B --> C[MOM Layer]
    C --> D[Message Queue]
    D --> E[Receiver Application]

Features:

• Asynchronous Communication: Non-blocking message exchange
• Reliability: Message persistence and delivery guarantees
• Scalability: Handle multiple concurrent connections
• Platform Independence: Cross-platform communication

Benefits:

• Loose coupling between applications
• Improved system reliability
• Better fault tolerance

Mnemonic: “ARSP: Asynchronous, Reliable, Scalable, Platform-independent”

Question 3(a) [03 marks]

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Give Full form for ‘www’. Explain it.

Answer:

WWW = World Wide Web

Explanation:

• Global Information System: Interconnected web of documents
• HTTP Protocol: Uses HyperText Transfer Protocol
• URL Addressing: Unique resource locators
• Hyperlinks: Navigate between web pages

Components:

• Web servers, browsers, HTML documents, URLs

Mnemonic: “GHUH: Global, HTTP, URL, Hyperlinks”

Question 3(b) [04 marks]

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Explain applications of Mobile Computing.

Answer:

Mobile Computing Applications:

Key Features:

• Location-based services: GPS navigation, local search
• Mobile payments: Digital wallets, contactless transactions
• IoT integration: Smart home, wearable devices

Mnemonic: “BHEE: Business, Healthcare, Education, Entertainment”

Question 3(c) [07 marks]

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Explain working of DHCP with the help of diagram and explain its advantages.

Answer:

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to network devices.

DHCP Process (DORA):

sequenceDiagram
    participant C as Client
    participant S as DHCP Server
    
    C->>S: 1. DHCP Discover (Broadcast)
    S->>C: 2. DHCP Offer (IP + Config)
    C->>S: 3. DHCP Request (Accept Offer)
    S->>C: 4. DHCP Acknowledge (Confirm)

Configuration Information Provided:

• IP address and subnet mask
• Default gateway address
• DNS server addresses
• Lease duration

Advantages:

• Automatic Configuration: No manual IP assignment
• Centralized Management: Single point of control
• Efficient IP Usage: Dynamic allocation prevents waste
• Reduced Errors: Eliminates manual configuration mistakes
• Easy Maintenance: Simple network changes

DHCP Message Types:

• DISCOVER, OFFER, REQUEST, ACK, NAK, RELEASE, RENEW

Mnemonic: “DORA: Discover, Offer, Request, Acknowledge”

Question 3(a OR) [03 marks]

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Write down: Importance of HTTPS.

Answer:

HTTPS (HyperText Transfer Protocol Secure) provides secure web communication.

Importance:

• Data Encryption: Protects data in transit using SSL/TLS
• Authentication: Verifies server identity with certificates
• Data Integrity: Prevents data tampering during transmission
• Trust Building: Increases user confidence in websites

Security Benefits:

• Protection against eavesdropping and man-in-the-middle attacks

Mnemonic: “EADT: Encryption, Authentication, Integrity, Trust”

Question 3(b OR) [04 marks]

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What is Bearer Network? Explain in Detail.

Answer:

Bearer Network is the underlying network infrastructure that carries data traffic between endpoints.

Types of Bearer Networks:

Functions:

• Data Transport: Carry user data and signaling
• Quality of Service: Manage bandwidth and latency
• Routing: Direct traffic between networks
• Network Management: Monitor and control traffic

Examples:

• PSTN, Internet backbone, 4G/5G cellular networks

Mnemonic: “DQRN: Data transport, QoS, Routing, Network management”

Question 3(c OR) [07 marks]

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List out types of TCP and explain any one in detail.

Answer:

Types of TCP:

• Standard TCP (TCP Tahoe)
• TCP Reno
• TCP New Reno
• TCP Vegas
• TCP SACK (Selective Acknowledgment)
• TCP Cubic

TCP Reno - Detailed Explanation:

Features:

• Fast Retransmit: Retransmit lost packets quickly
• Fast Recovery: Avoid slow start after fast retransmit
• Congestion Avoidance: Linear increase in congestion window
• Duplicate ACK Detection: Identify packet loss

Congestion Control Algorithm:

graph TD
    A[Slow Start] --> B{3 Duplicate ACKs?}
    B -->|Yes| C[Fast Retransmit]
    C --> D[Fast Recovery]
    D --> E[Congestion Avoidance]
    B -->|No| F[Timeout?]
    F -->|Yes| A
    F -->|No| E

Advantages:

• Better Performance: Faster recovery from packet loss
• Efficiency: Maintains higher throughput
• Fairness: Equitable bandwidth sharing

Window Management:

• Exponential growth in slow start
• Linear growth in congestion avoidance

Mnemonic: “FFCE: Fast retransmit, Fast recovery, Congestion avoidance, Efficiency”

Question 4(a) [03 marks]

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Define WLAN. List out types of WLAN.

Answer:

WLAN (Wireless Local Area Network) provides wireless connectivity within a limited area.

Types of WLAN:

• Infrastructure Mode: Uses access points for connectivity
• Ad-hoc Mode: Direct device-to-device communication
• Mesh Networks: Multi-hop wireless connectivity
• Hybrid Networks: Combination of infrastructure and ad-hoc

Standards:

• IEEE 802.11a/b/g/n/ac/ax (WiFi 6)

Mnemonic: “IAMH: Infrastructure, Ad-hoc, Mesh, Hybrid”

Question 4(b) [04 marks]

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What is Routing? Explain types of Routing.

Answer:

Routing is the process of selecting paths for data packets across networks.

Types of Routing:

Dynamic Routing Advantages:

• Automatic adaptation to network changes
• Load balancing across multiple paths
• Fault tolerance with alternate routes

Mnemonic: “SDDL: Static, Dynamic, Default, Link-state”

Question 4(c) [07 marks]

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Explain architecture of WLAN.

Answer:

WLAN Architecture Components:

graph TB
    subgraph "Basic Service Set (BSS)"
        A[Access Point] 
        B[Station 1]
        C[Station 2]
        D[Station 3]
    end
    
    subgraph "Extended Service Set (ESS)"
        E[AP1] --> F[Distribution System]
        G[AP2] --> F
        H[AP3] --> F
    end
    
    A --> B
    A --> C  
    A --> D
    F --> I[Wired Network/Internet]

Architecture Elements:

• Station (STA): Wireless client devices
• Access Point (AP): Central wireless hub
• Basic Service Set (BSS): Single AP coverage area
• Extended Service Set (ESS): Multiple interconnected APs
• Distribution System (DS): Backend network connecting APs

WLAN Topologies:

• Infrastructure Mode: Centralized through AP
• Ad-hoc Mode: Direct peer-to-peer communication
• Mesh Topology: Multi-hop wireless connections

Services Provided:

• Association: Device connection to AP
• Authentication: Security verification
• Data Delivery: Packet transmission
• Roaming: Seamless movement between APs

Frequency Bands:

• 2.4 GHz (802.11b/g/n)
• 5 GHz (802.11a/n/ac/ax)

Mnemonic: “SABED: Station, Access Point, BSS, ESS, Distribution System”

Question 4(a OR) [03 marks]

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Define WPAN. List out applications of WPAN.

Answer:

WPAN (Wireless Personal Area Network) connects devices within personal space (typically 10 meters).

Applications of WPAN:

• Device Synchronization: Phone to computer data transfer
• Audio Streaming: Wireless headphones, speakers
• Input Devices: Wireless keyboard, mouse
• Healthcare: Medical sensors, fitness trackers
• Smart Home: IoT device control

Technologies:

• Bluetooth, Zigbee, NFC, infrared

Mnemonic: “DSAHS: Device sync, Streaming, Audio, Healthcare, Smart home”

Question 4(b OR) [04 marks]

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Explain working of IMAP Protocol.

Answer:

IMAP (Internet Message Access Protocol) manages email on mail servers.

IMAP Working Process:

IMAP vs POP3:

• Server Storage: Messages remain on server
• Multi-device Access: Sync across devices
• Folder Management: Server-side folder structure
• Partial Download: Headers first, body on demand

IMAP Commands:

LOGIN user password
SELECT INBOX
FETCH 1 BODY[]
STORE 1 +FLAGS (\Deleted)

Mnemonic: “CAMS: Connection, Authentication, Mailbox, Storage”

Question 4(c OR) [07 marks]

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Explain Bluetooth technology with a figure of its protocol stack.

Answer:

Bluetooth is a short-range wireless communication technology for personal area networks.

Bluetooth Protocol Stack:

graph TB
    A[Applications] --> B[OBEX/SDP]
    B --> C[RFCOMM/L2CAP]
    C --> D[HCI - Host Controller Interface]
    D --> E[LMP - Link Manager Protocol]
    E --> F[Baseband/LC - Link Controller]
    F --> G[Radio Layer]

Layer Functions:

• Radio Layer: 2.4 GHz ISM band, frequency hopping
• Baseband: Timing, access control, packet formats
• LMP: Link establishment, security, power management
• L2CAP: Packet segmentation, protocol multiplexing
• RFCOMM: Serial port emulation over wireless
• SDP: Service discovery protocol
• Applications: File transfer, audio streaming, HID

Bluetooth Characteristics:

• Range: 10 meters (Class 2 devices)
• Data Rate: 1-3 Mbps (depending on version)
• Topology: Star network (piconet)
• Security: Authentication, authorization, encryption

Bluetooth Versions:

• Classic Bluetooth (BR/EDR)
• Bluetooth Low Energy (BLE/LE)
• Bluetooth 5.0+ (Enhanced range/speed)

Applications:

• Audio devices, keyboards, file transfer, IoT sensors

Mnemonic: “RBLSRA: Radio, Baseband, LMP, SDP, RFCOMM, Applications”

Question 5(a) [03 marks]

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What is 4G? List out Features of 4G.

Answer:

4G (Fourth Generation) is a mobile communication standard providing high-speed wireless internet.

Features of 4G:

• High Data Speed: Up to 100 Mbps mobile, 1 Gbps stationary
• All-IP Network: Packet-switched architecture
• Low Latency: Reduced delay for real-time applications
• Quality of Service: Guaranteed service levels
• Global Roaming: Worldwide compatibility

Technologies:

• LTE (Long Term Evolution), WiMAX

Mnemonic: “HALQG: High-speed, All-IP, Low latency, QoS, Global roaming”

Question 5(b) [04 marks]

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Explain Centralized Computing.

Answer:

Centralized Computing processes all data and applications on a central server.

Architecture:

graph TB
    A[Central Server] --> B[Terminal 1]
    A --> C[Terminal 2] 
    A --> D[Terminal 3]
    A --> E[Terminal 4]
    
    F[Processing Power]
    G[Storage]
    H[Applications]
    
    F --> A
    G --> A
    H --> A

Characteristics:

• Single Point of Control: All processing at central location
• Thin Clients: Minimal local processing capability
• Shared Resources: CPU, memory, storage centrally managed
• Network Dependent: Requires reliable network connectivity

Advantages:

• Security: Centralized data protection
• Management: Easier system administration
• Cost: Lower client-side hardware costs

Disadvantages:

• Single Point of Failure: Server downtime affects all users
• Network Bottleneck: Heavy reliance on network performance

Mnemonic: “SSNG: Single control, Shared resources, Network dependent, Greater security”

Question 5(c) [07 marks]

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What is ipv4 addressing scheme? Explain with a neat and clean diagram with its working.

Answer:

IPv4 (Internet Protocol version 4) uses 32-bit addresses for network identification.

IPv4 Address Structure:

IPv4 Address Classes:

IPv4 Packet Header:

Working Process:

• Address Assignment: Network administrator assigns IP addresses
• Routing Decision: Router examines destination IP
• Subnet Determination: Apply subnet mask to find network
• Packet Forwarding: Route to appropriate network interface

Special Addresses:

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

Limitations:

• Address Exhaustion: Only 4.3 billion addresses
• Inefficient Allocation: Class-based wastage

Mnemonic: “ABCDE: Address classes A, B, C, D multicast, E experimental”

Question 5(a OR) [03 marks]

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What is 5G? List out Features of 5G.

Answer:

5G (Fifth Generation) is the latest mobile communication standard with enhanced capabilities.

Features of 5G:

• Ultra-High Speed: Up to 10 Gbps data rates
• Ultra-Low Latency: Less than 1ms response time
• Massive Connectivity: 1 million devices per km²
• Network Slicing: Virtual dedicated networks
• Enhanced Mobile Broadband: Improved user experience

Key Technologies:

• Millimeter wave, Massive MIMO, Beamforming

Mnemonic: “UUMNE: Ultra-speed, Ultra-low latency, Massive connectivity, Network slicing, Enhanced broadband”

Question 5(b OR) [04 marks]

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Explain Distributed Computing

Answer:

Distributed Computing spreads processing across multiple interconnected computers.

Architecture:

graph TB
    subgraph "Distributed System"
        A[Node 1] <--> B[Node 2]
        B <--> C[Node 3]
        C <--> D[Node 4]
        A <--> D
    end
    
    E[Network] --> A
    E --> B
    E --> C
    E --> D

Characteristics:

• Resource Sharing: Distributed processing and storage
• Scalability: Add more nodes to increase capacity
• Fault Tolerance: System continues if some nodes fail
• Location Transparency: Users unaware of resource locations

Advantages:

• Reliability: No single point of failure
• Performance: Parallel processing capabilities
• Cost-effectiveness: Use commodity hardware

Examples:

• Cloud computing, peer-to-peer networks, grid computing

Mnemonic: “RSFL: Resource sharing, Scalability, Fault tolerance, Location transparency”

Question 5(c OR) [07 marks]

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Explain Data Link Layer Protocol.

Answer:

Data Link Layer provides reliable data transfer between adjacent network nodes.

Functions:

• Framing: Organize bits into frames
• Error Detection: Identify transmission errors
• Error Correction: Fix detected errors
• Flow Control: Manage data transmission rate
• Access Control: Coordinate shared media access

Frame Structure:

Error Detection Methods:

Flow Control Protocols:

• Stop-and-Wait: Send one frame, wait for ACK
• Sliding Window: Multiple frames in transit
• Stop-and-Wait ARQ: Add error recovery
• Go-Back-N ARQ: Retransmit from error point
• Selective Repeat: Retransmit only error frames

Access Control Methods:

• CSMA/CD: Carrier Sense Multiple Access with Collision Detection
• CSMA/CA: Collision Avoidance
• Token Passing: Controlled access using token

Protocol Examples:

• Ethernet, PPP, HDLC, LLC

Working Process:

sequenceDiagram
    participant S as Sender
    participant R as Receiver
    
    S->>R: Data Frame
    R->>S: ACK Frame
    S->>R: Next Data Frame
    Note over R: Error Detected
    R->>S: NAK Frame
    S->>R: Retransmit Frame

Mnemonic: “FECFA: Framing, Error detection, Correction, Flow control, Access control”