Mobile Computing and Networks (4351602) - Winter 2024 Solution

Question 1(a) [3 marks]

#

List out types of congestion control and explain any one

Answer:

Open-Loop Congestion Control Explanation:

• Prevention approach: Takes action before congestion occurs
• Traffic shaping: Controls data rate at sender
• Admission control: Limits new connections during high traffic
• Load shedding: Drops packets when buffer full

Mnemonic: “Open Prevents Traffic Admission Load”

Question 1(b) [4 marks]

#

Explain Address Resolution Protocol briefly

Answer:

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

Working Process:

• ARP Request: Broadcast message asking “Who has IP X?”
• ARP Reply: Target device responds with its MAC address
• ARP Cache: Stores IP-MAC mappings for future use
• Dynamic mapping: Updates entries automatically

Table: ARP Message Types

Mnemonic: “ARP Requests Broadcast, Replies Cache Dynamic”

Question 1(c) [7 marks]

#

Explain TCP/IP model with all layers and functionalities of each layer

Answer:

TCP/IP Model is a four-layer network protocol stack for internet communication.

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

Layer Functions:

• Application Layer: Provides network services to applications
• Transport Layer: Ensures reliable data delivery with error control
• Internet Layer: Routes packets across networks using IP addressing
• Network Access Layer: Handles physical data transmission

Mnemonic: “All Transport Internet Network”

Question 1(c OR) [7 marks]

#

Explain OSI model with each layer functionality

Answer:

OSI Model is a seven-layer reference model 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 Functionalities:

Mnemonic: “Physical Data Network Transport Session Presentation Application”

Question 2(a) [3 marks]

#

Explain subnetting in short

Answer:

Subnetting divides a large network into smaller sub-networks for better management.

Key Concepts:

• Subnet mask: Defines network and host portions
• Network efficiency: Reduces broadcast traffic
• Address conservation: Better IP utilization
• Security: Isolates network segments

Example: Network: 192.168.1.0/24 → Subnets: 192.168.1.0/26, 192.168.1.64/26

Mnemonic: “Subnet Network Efficiency Address Security”

Question 2(b) [4 marks]

#

Explain stop and wait ARQ protocol of data link layer with example

Answer:

Stop and Wait ARQ is a flow control protocol ensuring reliable data transmission.

Working Process:

• Send frame: Transmitter sends one frame
• Wait for ACK: Sender waits for acknowledgment
• Timeout: Retransmits if no ACK received
• Next frame: Sends next frame after ACK

Example: File transfer where each packet waits for confirmation before sending next.

Mnemonic: “Send Wait Timeout Next”

Question 2(c) [7 marks]

#

Draw diagram of IPv4 datagram Header and explain it

Answer:

IPv4 Header contains control information for packet routing and delivery.

Field Explanations:

Mnemonic: “Version IHL Service Total TTL Protocol Source Destination”

Question 2(a OR) [3 marks]

#

What is HTTPS? List important key features of HTTPS

Answer:

HTTPS (HTTP Secure) is encrypted HTTP using SSL/TLS for secure web communication.

Key Features:

• Encryption: Data encrypted in transit
• Authentication: Verifies server identity
• Data integrity: Prevents data tampering
• Trust: SSL certificates provide validation

Security Benefits:

• Protects sensitive information
• Prevents man-in-the-middle attacks
• Search engine ranking boost

Mnemonic: “HTTPS Encrypts Authentication Data Trust”

Question 2(b OR) [4 marks]

#

Give Answer of any two:

Answer:

1) How many bits HOST ID use by class B and C?

• Class B: 16 bits for Host ID (65,534 hosts)
• Class C: 8 bits for Host ID (254 hosts)

2) What is IP range for Class A and D?

• Class A: 1.0.0.0 to 126.255.255.255
• Class D: 224.0.0.0 to 239.255.255.255 (Multicast)

Mnemonic: “B=16, C=8, A=1-126, D=224-239”

Question 2(c OR) [7 marks]

#

Explain classful IPv4 addresses scheme

Answer:

Classful IPv4 Addressing divides IP address space into five classes based on first octets.

Address Classes:

pie title IPv4 Address Classes
    "Class A (50%)" : 50
    "Class B (25%)" : 25
    "Class C (12.5%)" : 12.5
    "Class D (6.25%)" : 6.25
    "Class E (6.25%)" : 6.25

Characteristics:

• Class A: 16.7 million hosts per network
• Class B: 65,534 hosts per network
• Class C: 254 hosts per network
• Limitations: Address wastage, inflexible allocation

Mnemonic: “A-Large, B-Medium, C-Small, D-Multicast, E-Experimental”

Question 3(a) [3 marks]

#

List out types of applications uses mobile computing

Answer:

Mobile Computing Applications:

• Location-based services: GPS navigation, location sharing
• Mobile payments: Digital wallets, UPI transactions
• Social networking: Facebook, Instagram, Twitter

Mnemonic: “Communication Navigation E-commerce Entertainment Business Healthcare”

Question 3(b) [4 marks]

#

Explain use of Gateways and list types of Gateways

Answer:

Gateway connects networks with different protocols and architectures.

Uses of Gateways:

• Protocol conversion: Translates between different protocols
• Network bridging: Connects dissimilar networks
• Security: Firewall and access control
• Data filtering: Manages traffic flow

Types of Gateways:

Mnemonic: “Gateways Convert Bridge Secure Filter”

Question 3(c) [7 marks]

#

Draw and explain architecture of mobile computing

Answer:

Mobile Computing Architecture consists of three main components working together.

graph TD
    A[Mobile Device] <--> B[Communication Network]
    B <--> C[Fixed Infrastructure]
    
    A1[Hardware] --> A
    A2[OS & Apps] --> A
    A3[Data] --> A
    
    B1[Wireless Network] --> B
    B2[Protocols] --> B
    B3[Base Stations] --> B
    
    C1[Servers] --> C
    C2[Databases] --> C
    C3[Internet] --> C

Architecture Components:

Key Features:

• Mobility: Users can move while maintaining connectivity
• Wireless communication: Radio waves for data transmission
• Distributed computing: Processing across multiple devices
• Location independence: Access services from anywhere

Challenges:

• Limited bandwidth: Wireless networks have capacity constraints
• Battery life: Mobile devices have power limitations
• Security: Wireless transmission vulnerable to attacks

Mnemonic: “Mobile Communication Fixed - Mobility Wireless Distributed Location”

Question 3(a OR) [3 marks]

#

List security standards in mobile computing

Answer:

Mobile Computing Security Standards:

• Authentication protocols: Verify user identity
• Encryption standards: Protect data confidentiality
• Access control: Manage resource permissions

Mnemonic: “WPA SSL IPSec EAP 802.11i FIPS”

Question 3(b OR) [4 marks]

#

Explain key functions of communication gateway

Answer:

Communication Gateway manages data exchange between different network systems.

Key Functions:

Detailed Functions:

• Message routing: Determines optimal path for data
• Error handling: Manages transmission errors and recovery
• Traffic management: Controls data flow and congestion
• Authentication: Verifies sender and receiver identity

Benefits:

• Enables interoperability between different systems
• Centralizes network management
• Provides security checkpoint

Mnemonic: “Protocol Data Routing Security - Message Error Traffic Authentication”

Question 3(c OR) [7 marks]

#

Explain use of middleware and list types of middleware

Answer:

Middleware provides software layer between applications and operating system for distributed computing.

Uses of Middleware:

• Connectivity: Links distributed applications
• Interoperability: Enables different systems to work together
• Abstraction: Hides complexity of underlying systems
• Scalability: Supports system growth and expansion

graph TD
    A[Applications] --> B[Middleware Layer]
    B --> C[Operating System]
    B --> D[Network Services]
    B --> E[Database Services]

Types of Middleware:

Benefits:

• Reduced complexity: Simplifies application development
• Reusability: Common services for multiple applications
• Maintainability: Centralized management of services
• Platform independence: Works across different systems

Mnemonic: “Message RPC Object Database Transaction Web”

Question 4(a) [3 marks]

#

Explain working phases of Mobile IP

Answer:

Mobile IP Working Phases enable seamless mobility for mobile devices across networks.

Three Main Phases:

Phase Details:

• Agent Discovery: Mobile node detects available agents through advertisements
• Registration: Mobile node registers current location with home agent
• Tunneling: Home agent encapsulates and forwards packets to foreign agent

Mnemonic: “Agent Registration Tunneling”

Question 4(b) [4 marks]

#

Explain Handover management in Mobile IP

Answer:

Handover Management maintains connectivity when mobile node moves between networks.

Handover Process:

• Movement detection: Identifies change in network attachment
• New agent discovery: Finds new foreign agent
• Registration update: Updates location with home agent
• Data forwarding: Redirects traffic to new location

Types of Handover:

Challenges:

• Packet loss: During handover transition
• Delay: Registration and tunneling setup time
• Resource management: Efficient use of network resources

Mnemonic: “Movement Discovery Registration Forwarding”

Question 4(c) [7 marks]

#

Explain Registration and Tunneling in Mobile IP

Answer:

Registration and Tunneling are core mechanisms enabling Mobile IP functionality.

Registration Process:

sequenceDiagram
    participant MN as Mobile Node
    participant FA as Foreign Agent
    participant HA as Home Agent
    
    MN->>FA: Registration Request
    FA->>HA: Forward Request
    HA->>FA: Registration Reply
    FA->>MN: Forward Reply

Registration Steps:

• Request: Mobile node sends registration request to foreign agent
• Forward: Foreign agent forwards request to home agent
• Authentication: Home agent verifies mobile node identity
• Reply: Home agent sends registration reply confirming registration

Tunneling Mechanism:

Tunneling Process:

• Packet arrival: Data arrives at home agent for mobile node
• Encapsulation: Home agent wraps packet with foreign agent address
• Tunnel transmission: Packet travels through tunnel to foreign agent
• Decapsulation: Foreign agent unwraps and delivers to mobile node

Benefits:

• Transparency: Applications unaware of mobility
• Connectivity: Maintains communication during movement
• Scalability: Supports multiple mobile nodes

Security Considerations:

• Authentication: Prevents unauthorized registration
• Encryption: Protects data in tunnels

Mnemonic: “Registration Request Forward Authentication - Tunneling Encapsulation Transmission Decapsulation”

Question 4(a OR) [3 marks]

#

Explain snooping TCP

Answer:

Snooping TCP improves TCP performance over wireless networks by handling wireless link errors.

Working Mechanism:

• Base station monitoring: Observes TCP packets
• Local retransmission: Handles wireless link errors locally
• Cache management: Stores copies of transmitted packets
• Error recovery: Retransmits lost packets without involving sender

Key Features:

Mnemonic: “Snooping Monitors Local Cache Recovery”

Question 4(b OR) [4 marks]

#

Explain Packet delivery in Mobile IP

Answer:

Packet Delivery in Mobile IP ensures data reaches mobile nodes regardless of location.

Delivery Process:

graph TD
    A[Correspondent Node] --> B[Home Network]
    B --> C{Mobile Node Location?}
    C -->|Home| D[Direct Delivery]
    C -->|Away| E[Home Agent]
    E --> F[Tunnel to Foreign Agent]
    F --> G[Mobile Node]

Delivery Scenarios:

Packet Flow Steps:

• Address resolution: Determine mobile node location
• Route selection: Choose direct or tunneled delivery
• Encapsulation: Wrap packet if tunneling required
• Forwarding: Send to appropriate destination
• Decapsulation: Unwrap packet at foreign agent
• Final delivery: Deliver to mobile node

Optimization Techniques:

• Route optimization: Direct communication when possible
• Binding cache: Store location information
• Smooth handover: Minimize packet loss during movement

Mnemonic: “Address Route Encapsulation Forward Decapsulation Delivery”

Question 4(c OR) [7 marks]

#

Describe how DHCP working with diagram

Answer:

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

DHCP Working Process:

sequenceDiagram
    participant C as Client
    participant S as DHCP Server
    
    C->>S: 1. DHCP Discover (Broadcast)
    S->>C: 2. DHCP Offer
    C->>S: 3. DHCP Request
    S->>C: 4. DHCP ACK
    
    Note over C,S: Lease Time
    
    C->>S: 5. DHCP Renewal Request
    S->>C: 6. DHCP ACK

Four-Step Process:

DHCP Components:

• DHCP Server: Manages IP address pool and assignments
• DHCP Client: Requests and uses assigned configuration
• DHCP Relay: Forwards DHCP messages across subnets
• Address Pool: Range of available IP addresses

Configuration Information Provided:

• IP Address: Unique network identifier
• Subnet Mask: Network boundary definition
• Default Gateway: Route to other networks
• DNS Servers: Domain name resolution
• Lease Time: Duration of IP assignment

Benefits:

• Automatic configuration: No manual IP assignment needed
• Centralized management: Single point for network configuration
• Efficient utilization: Dynamic allocation prevents waste
• Reduced errors: Eliminates manual configuration mistakes

DHCP Message Types:

• DISCOVER: Locate available DHCP servers
• OFFER: Response with configuration offer
• REQUEST: Accept specific server offer
• ACK: Confirm configuration assignment
• NAK: Reject configuration request
• RELEASE: Return IP address to pool
• RENEW: Extend current lease

Mnemonic: “Discover Offer Request ACK - Server Client Relay Pool”

Question 5(a) [3 marks]

#

Give types of WLAN and explain any one

Answer:

WLAN Types:

Infrastructure WLAN Explanation:

• Access Point (AP): Central coordinator for all communications
• BSS (Basic Service Set): Network coverage area of single AP
• ESS (Extended Service Set): Multiple interconnected BSSs
• Distribution System: Backbone connecting multiple APs

Characteristics:

• All communication goes through access point
• Centralized network management
• Better security and performance control

Mnemonic: “Infrastructure Ad-hoc Mesh - AP BSS ESS Distribution”

Question 5(b) [4 marks]

#

Answer the following questions:

Answer:

1) List Uses of Ad hoc Network:

2) Enlist entities and terminology of mobile computing:

Entities:

• Mobile Node (MN): Moving device
• Home Agent (HA): Permanent network representative
• Foreign Agent (FA): Temporary network coordinator
• Correspondent Node (CN): Communication partner

Terminology:

• Handover: Network switching process
• Roaming: Moving between networks
• Care-of Address: Temporary IP address

Mnemonic: “Emergency Military Conference Home Vehicular - MN HA FA CN”

Question 5(c) [7 marks]

#

Explain architecture of WLAN with neat diagram

Answer:

WLAN Architecture consists of wireless stations communicating through access points.

graph TD
    subgraph "BSS 1"
        A[Laptop] --> AP1[Access Point 1]
        B[Phone] --> AP1
        C[Tablet] --> AP1
    end
    
    subgraph "BSS 2"
        D[Desktop] --> AP2[Access Point 2]
        E[Printer] --> AP2
    end
    
    AP1 --> DS[Distribution System]
    AP2 --> DS
    DS --> F[Wired Network/Internet]
    
    subgraph "Ad-hoc Network"
        G[Device A] <--> H[Device B]
        H <--> I[Device C]
    end

Architecture Components:

Types of WLAN Architecture:

1. Infrastructure Mode:

• Centralized: All traffic through access points
• Managed: Network administration and security
• Scalable: Easy to expand coverage area

2. Ad-hoc Mode (IBSS):

• Peer-to-peer: Direct device communication
• Decentralized: No central coordinator
• Temporary: Quick setup for specific needs

Key Features:

• Mobility: Users can move within coverage area
• Wireless medium: Radio waves for communication
• Shared bandwidth: Multiple users share channel capacity
• Security: WPA/WPA2/WPA3 protocols for protection

Standards and Frequencies:

• 802.11a: 5 GHz, up to 54 Mbps
• 802.11b: 2.4 GHz, up to 11 Mbps
• 802.11g: 2.4 GHz, up to 54 Mbps
• 802.11n: 2.4/5 GHz, up to 600 Mbps
• 802.11ac: 5 GHz, up to 6.93 Gbps

Mnemonic: “STA AP BSS ESS DS - Infrastructure Ad-hoc”

Question 5(a OR) [3 marks]

#

Write features of 5G

Answer:

5G Key Features:

Advanced Capabilities:

• Enhanced Mobile Broadband (eMBB): Ultra-fast data speeds
• Ultra-Reliable Low Latency (URLLC): Mission-critical applications
• Massive Machine Type Communication (mMTC): IoT connectivity

Mnemonic: “Speed Latency Connectivity Reliability Bandwidth Energy”

Question 5(b OR) [4 marks]

#

Answer the following questions:

Answer:

1) List Type of communication middleware:

2) Define the term “Home Agent” in the context of Mobile IP:

Home Agent (HA) is a router on mobile node’s home network that:

• Maintains registration: Tracks mobile node’s current location
• Tunnels packets: Forwards data to mobile node’s foreign location
• Address management: Manages mobile node’s permanent IP address
• Authentication: Verifies mobile node identity during registration

Functions:

• Acts as proxy for mobile node when away from home
• Intercepts packets destined for mobile node
• Creates tunnels to foreign agents

Mnemonic: “Message RPC Object Service Database - HA Maintains Tunnels Address Authentication”

Question 5(c OR) [7 marks]

#

Explain Bluetooth protocol stack with diagram

Answer:

Bluetooth Protocol Stack provides layered architecture for short-range wireless communication.

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

Protocol Stack Layers:

Layer Details:

Upper Layers:

• OBEX: Object Exchange Protocol for file transfers
• SDP: Service Discovery Protocol finds available services
• TCS: Telephony Control Specification for voice calls
• RFCOMM: Serial port emulation over Bluetooth

Lower Layers:

• L2CAP: Logical Link Control manages multiple connections
• HCI: Host Controller Interface standardizes communication
• LMP: Link Manager Protocol handles connection setup
• Baseband: Manages time slots and frequency hopping

Key Features:

• Frequency Hopping: 1600 hops/second across 79 channels
• Piconet: Network of up to 8 devices
• Scatternet: Multiple overlapping piconets
• Power Classes: Class 1 (100m), Class 2 (10m), Class 3 (1m)

Advantages:

• Low power consumption: Suitable for battery devices
• Automatic pairing: Easy device connection
• Interference resistance: Frequency hopping spread spectrum
• Cost effective: Low implementation cost

Applications:

• Audio streaming: Headphones, speakers
• Data transfer: File sharing between devices
• Input devices: Keyboards, mice
• IoT devices: Sensors, smart home devices

Mnemonic: “Application Middleware Transport Network Interface Management DataLink Physical”