Data Communication and Computer Networks
Table of Contents
- OSI Model (All 7 Layers)
- TCP/IP Model
- Transmission Media
- Multiplexing Techniques
- Switching Techniques
- Error Detection and Correction
- Flow Control
- Congestion Control
- Routing Algorithms
- IP Addressing (IPv4/IPv6)
- NAT, DHCP, DNS
- Application Layer Protocols
- Network Devices
- SDN Basics
- Quality of Service (QoS)
OSI Model (All 7 Layers)
The OSI (Open Systems Interconnection) model is a 7-layer reference framework defined by ISO (ISO 7498) that standardizes network communication.
Layer 7 — Application Layer
- Purpose: Interface between user applications and network services.
- Key Protocols: HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, SNMP, Telnet, SSH
- Functions: File transfer, email, web browsing, virtual terminal access
- PDU (Protocol Data Unit): Data/Message
- Key Concept: Does NOT refer to the application itself, but the services the application uses
Layer 6 — Presentation Layer
- Purpose: Data translation, encryption, and compression
- Functions:
- Data Translation: Converts between different data formats (e.g., EBCDIC ↔ ASCII)
- Encryption/Decryption: SSL/TLS begin here
- Compression: Reduces data size for transmission
- Examples: JPEG, MPEG, MIDI, GIF, SSL (partially)
Layer 5 — Session Layer
- Purpose: Establishes, manages, and terminates sessions (connections) between applications
- Functions: Dialog control (half-duplex/full-duplex), synchronization (checkpoints), and session recovery
- Examples: NetBIOS, RPC, PPTP, SCP
Layer 4 — Transport Layer
- Purpose: End-to-end data transfer, reliability, flow control
- Key Protocols: TCP (reliable, connection-oriented), UDP (unreliable, connectionless)
- Functions: Segmentation, reassembly, error recovery, flow control
- PDU: Segment (TCP) / Datagram (UDP)
- Port Numbers: Identifies specific processes (e.g., HTTP=80, HTTPS=443, FTP=21)
Layer 3 — Network Layer
- Purpose: Logical addressing, routing, path determination
- Key Protocols: IP (IPv4/IPv6), ICMP, ARP, RARP, IGMP, OSPF, RIP, BGP
- Functions: IP addressing, packet forwarding, routing, fragmentation
- PDU: Packet
- Devices: Router, Layer 3 switch
Layer 2 — Data Link Layer
- Purpose: Node-to-node data transfer, framing, MAC addressing, error detection
- Two Sublayers:
- LLC (Logical Link Control): Flow control, error checking
- MAC (Media Access Control): Physical addressing, medium access methods (CSMA/CD, CSMA/CA)
- Key Protocols: Ethernet (IEEE 802.3), Wi-Fi (IEEE 802.11), PPP, HDLC, Frame Relay
- PDU: Frame
- Devices: Switch, Bridge, NIC
Layer 1 — Physical Layer
- Purpose: Transmission of raw bit stream over physical medium
- Functions: Bit rate, physical topology (star, bus, ring, mesh), transmission mode (simplex, half-duplex, full-duplex), signal encoding
- Devices: Hub, Repeater, Modem, Cables
- PDU: Bits
OSI Layer Quick Reference Table
| Layer | Name | PDU | Key Function | Example Protocols |
|---|---|---|---|---|
| 7 | Application | Data | User interface | HTTP, FTP, SMTP |
| 6 | Presentation | Data | Translation/Encryption | SSL, JPEG, ASCII |
| 5 | Session | Data | Session management | NetBIOS, RPC |
| 4 | Transport | Segment | Reliability, flow ctrl | TCP, UDP |
| 3 | Network | Packet | Routing, addressing | IP, ICMP, OSPF |
| 2 | Data Link | Frame | MAC, error detection | Ethernet, PPP |
| 1 | Physical | Bits | Bit transmission | RS-232, DSL |
TCP/IP Model
The TCP/IP model is the practical, implementation-focused model used on the internet. It has 4 layers.
| TCP/IP Layer | OSI Equivalent | Key Protocols |
|---|---|---|
| Application | Layers 5, 6, 7 | HTTP, FTP, SMTP, DNS, SNMP |
| Transport | Layer 4 | TCP, UDP, SCTP |
| Internet | Layer 3 | IPv4, IPv6, ICMP, ARP, IGMP |
| Network Access (Link) | Layers 1, 2 | Ethernet, Wi-Fi, PPP, DSL |
TCP vs UDP Comparison
| Feature | TCP | UDP |
|---|---|---|
| Connection | Connection-oriented | Connectionless |
| Reliability | Guaranteed delivery | Best-effort (no guarantee) |
| Ordering | Ordered delivery | No ordering guarantee |
| Speed | Slower (overhead) | Faster (minimal overhead) |
| Header Size | 20-60 bytes | 8 bytes |
| Flow Control | Yes (sliding window) | No |
| Congestion Control | Yes | No |
| Use Cases | Web, email, file transfer | Streaming, gaming, VoIP, DNS |
TCP Three-Way Handshake
- SYN: Client → Server (synchronize sequence)
- SYN-ACK: Server → Client (acknowledge + synchronize)
- ACK: Client → Server (acknowledge connection)
TCP Connection Termination (Four-Way)
- FIN from sender → ACK from receiver
- FIN from receiver → ACK from sender
Transmission Media
Guided (Wired) Media
| Media | Bandwidth | Distance | Interference | Cost |
|---|---|---|---|---|
| Twisted Pair (Cat 5/6/7) | Up to 10 Gbps | 100m | Moderate | Low |
| Coaxial Cable | Up to 100 Mbps | 500m | Low | Medium |
| Fiber Optic (Single-mode) | Up to 100+ Gbps | 100+ km | None | High |
| Fiber Optic (Multi-mode) | Up to 10 Gbps | 2 km | None | Medium-High |
Fiber Optic Advantages
- Extremely high bandwidth
- Immune to electromagnetic interference (EMI)
- Very low attenuation (signal loss)
- Secure (very difficult to tap)
- Lightweight and thin
Unguided (Wireless) Media
| Type | Frequency | Range | Use Case |
|---|---|---|---|
| Radio Waves | 3 KHz – 1 GHz | Omnidirectional | AM/FM, TV |
| Microwaves | 1 GHz – 300 GHz | Directional | Satellite, cellular |
| Infrared | 300 GHz – 400 THz | Line-of-sight | Remote controls |
Key Terms
- Bandwidth: Maximum data rate of a channel (bps)
- Attenuation: Signal loss over distance
- Noise: Unwanted signal interference
- Shannon's Capacity: C = B × log₂(1 + SNR) where B = bandwidth, SNR = signal-to-noise ratio
- Nyquist Bit Rate: C = 2B × log₂(L) where L = number of signal levels
Multiplexing Techniques
Multiplexing allows multiple signals to share a single communication channel.
Frequency Division Multiplexing (FDM)
- Concept: Channel bandwidth divided into frequency bands; each signal assigned a band
- Guard Bands: Small unused frequency gaps prevent interference
- Use Case: Radio/TV broadcasting, cable TV, ADSL
- Advantage: Simultaneous transmission
- Disadvantage: Wasted bandwidth due to guard bands
Time Division Multiplexing (TDM)
- Concept: Time divided into slots; each signal gets a recurring time slot
- Types:
- Synchronous TDM: Fixed slots (wasted if a source has no data)
- Statistical/Asynchronous TDM: Dynamic slot allocation (more efficient)
- Use Case: Traditional telephone networks (T1/E1 lines), SONET/SDH
- Advantage: Efficient use of bandwidth
- Disadvantage: Requires synchronization
Wavelength Division Multiplexing (WDM)
- Concept: Multiple light wavelengths (colors) transmitted over a single fiber optic cable
- Types: CWDM (Coarse WDM), DWDM (Dense WDM)
- Use Case: Long-haul fiber optic networks, internet backbone
- Advantage: Massive bandwidth multiplication
- Disadvantage: Expensive equipment
Code Division Multiplexing (CDM/CDMA)
- Concept: Each user assigned a unique code; all share same frequency simultaneously
- Use Case: 3G mobile networks, GPS
- Advantage: Secure, resistant to interference
- Disadvantage: Complex, requires power control
Switching Techniques
Circuit Switching
- Concept: Dedicated path established before communication begins
- Phases: Circuit establishment → Data transfer → Circuit teardown
- Use Case: Traditional telephone network (PSTN)
- Advantage: Guaranteed bandwidth, no delay variation
- Disadvantage: Inefficient (bandwidth wasted during idle periods)
Packet Switching
- Concept: Data broken into packets; each packet routed independently
- Two Approaches:
- Datagram: Each packet routed independently (connectionless) — like IP
- Virtual Circuit: Logical path established; all packets follow it (connection-oriented) — like MPLS
- Use Case: Internet, modern data networks
- Advantage: Efficient bandwidth utilization
- Disadvantage: Variable delay (jitter), potential congestion
Message Switching
- Concept: Store-and-forward entire messages at each node
- Use Case: Email (historically)
- Disadvantage: High latency, requires large storage at each node
Error Detection and Correction
Error Types
- Single-bit error: Only one bit altered
- Burst error: Multiple consecutive bits altered (more common)
Error Detection Methods
Parity Check
- Single Parity: Add one bit to make total 1s even (even parity) or odd (odd parity)
- Limitation: Can only detect odd number of bit errors
- Two-Dimensional Parity: Arranges data in grid; parity for rows and columns — can detect and correct single-bit errors
Checksum
- Method: Sum all data words; take 1's complement as checksum
- Receiver: Sum all words including checksum; result should be all 1s
- Use Case: IP header checksum, TCP/UDP checksum
- Limitation: Cannot detect errors where bits cancel out
Cyclic Redundancy Check (CRC)
- Concept: Binary division using a generator polynomial; remainder is CRC
- Sender: Divide data by generator polynomial → append remainder (CRC)
- Receiver: Divide received data by same polynomial → remainder 0 means no error
- Common Polynomials:
- CRC-8: x⁸ + x² + x + 1
- CRC-16: x¹⁶ + x¹⁵ + x² + 1
- CRC-32: Used in Ethernet (IEEE 802.3)
- Strength: Detects all single-bit errors, all double-bit errors, all odd-number errors, most burst errors
Error Correction Methods
Hamming Code
- Concept: Multiple parity bits inserted at power-of-2 positions
- Hamming Distance: Minimum number of bit changes to convert one valid codeword to another
- Formula: To detect d errors → need d+1 Hamming distance; to correct d errors → need 2d+1 Hamming distance
- Key Formula: 2^r ≥ m + r + 1 (where m = data bits, r = parity bits)
- Example: For 4 data bits, need 3 parity bits → (7,4) Hamming code
- Process:
- Calculate parity bits using XOR of specific bit positions
- At receiver, recalculate parity → syndrome bits indicate error position
Flow Control
Flow control ensures the sender doesn't overwhelm the receiver.
Stop-and-Wait Flow Control
- Mechanism: Sender transmits one frame, waits for ACK before sending next
- Efficiency: U = Td / (Td + 2 × Tp) where Td = transmission time, Tp = propagation time
- Very low efficiency for high-bandwidth, high-delay links
Sliding Window Protocol
- Mechanism: Sender can send multiple frames before receiving ACK
- Window Size (W): Maximum number of unacknowledged frames
- Efficiency: U = W × Td / (Td + 2 × Tp) for W ≤ 1 + 2Tp/Td
Go-Back-N ARQ
- Mechanism: Sender can send up to W frames; if frame N is lost, retransmit N and all subsequent frames
- Window Size: W ≤ 2^k - 1 (where k = sequence number bits)
- Receiver Window: Always 1 (only accepts in-order frames)
Selective Repeat ARQ
- Mechanism: Only retransmits the specific lost/damaged frame
- Window Size: W ≤ 2^(k-1) (where k = sequence number bits)
- Receiver Window: Can be > 1 (buffers out-of-order frames)
- More efficient than Go-Back-N but more complex
Congestion Control
Congestion occurs when too many packets are in the network, causing delays and loss.
TCP Congestion Control Algorithms
Slow Start
- Mechanism: Congestion window (cwnd) starts at 1 MSS, doubles every RTT (exponential growth)
- Threshold (ssthresh): When cwnd reaches ssthresh, switch to Congestion Avoidance
Congestion Avoidance
- Mechanism: cwnd increases by 1 MSS per RTT (linear growth / additive increase)
- AIMD: Additive Increase, Multiplicative Decrease
Fast Retransmit
- Trigger: 3 duplicate ACKs received
- Action: Retransmit lost segment immediately (don't wait for timeout)
- Assumption: 3 dup ACKs means a segment was lost but later segments arrived → network still has capacity
Fast Recovery
- After Fast Retransmit: Set ssthresh = cwnd/2, set cwnd = ssthresh (not 1)
- Result: Skip slow start, go directly to congestion avoidance
TCP Variants
- Tahoe: Slow Start → Congestion Avoidance; on timeout: cwnd=1, ssthresh=cwnd/2
- Reno: Same as Tahoe but uses Fast Recovery on 3 dup ACKs
- NewReno: Improved Reno — handles multiple losses in one window
Routing Algorithms
Non-Adaptive (Static) Routing
- Flooding: Send packet on all outgoing links except incoming — generates duplicates
- Fixed Routing: Pre-computed routes stored in routing table
- Shortest Path Routing: Uses Dijkstra's algorithm
Adaptive (Dynamic) Routing
Distance Vector Routing (e.g., RIP)
- Concept: Each router maintains a table of distances to all destinations
- Bellman-Ford Algorithm: D(x,y) = min {c(x,v) + D(v,y)} for all neighbors v
- RIP (Routing Information Protocol):
- Max hop count: 15 (16 = unreachable)
- Updates every 30 seconds
- Uses hop count as metric
- Problem: Count to infinity → solved by split horizon, poison reverse
Link State Routing (e.g., OSPF)
- Concept: Each router discovers neighbors, measures cost, builds link-state packets, floods to all routers
- Dijkstra's Algorithm: Computes shortest path from source to all destinations
- OSPF (Open Shortest Path First):
- Uses cost (based on bandwidth) as metric
- Supports hierarchical routing (areas)
- Converges faster than RIP
- Supports authentication
Path Vector Routing (e.g., BGP)
- BGP (Border Gateway Protocol): Used between autonomous systems (inter-domain routing)
- Maintains full path information to avoid loops
- Policy-based routing — most important internet routing protocol
Routing Protocol Comparison
| Protocol | Type | Algorithm | Metric | Domain |
|---|---|---|---|---|
| RIP | Distance Vector | Bellman-Ford | Hop Count | Intra-domain |
| OSPF | Link State | Dijkstra | Cost (bandwidth) | Intra-domain |
| BGP | Path Vector | Policy-based | Path attributes | Inter-domain |
IP Addressing (IPv4/IPv6)
IPv4
- Address Length: 32 bits (4 bytes)
- Notation: Dotted decimal (e.g., 192.168.1.1)
- Total Addresses: ~4.3 billion (2³²)
IPv4 Classes (Classful Addressing)
| Class | First Octet Range | Network Bits | Host Bits | Default Subnet Mask | # Networks | Hosts/Network |
|---|---|---|---|---|---|---|
| A | 1-126 | 8 | 24 | 255.0.0.0 (/8) | 126 | 16,777,214 |
| B | 128-191 | 16 | 16 | 255.255.0.0 (/16) | 16,384 | 65,534 |
| C | 192-223 | 24 | 8 | 255.255.255.0 (/24) | 2,097,152 | 254 |
| D | 224-239 | Multicast | — | — | — | — |
| E | 240-255 | Reserved | — | — | — | — |
Private IP Ranges
- Class A: 10.0.0.0 – 10.255.255.255
- Class B: 172.16.0.0 – 172.31.255.255
- Class C: 192.168.0.0 – 192.168.255.255
Subnetting
- Purpose: Divide a large network into smaller sub-networks
- Subnet Mask: Distinguishes network portion from host portion
- CIDR Notation: e.g., /26 means 26 network bits, 6 host bits
- Formula:
- Number of subnets = 2^n (n = borrowed host bits)
- Hosts per subnet = 2^h - 2 (h = remaining host bits; subtract 2 for network and broadcast)
Example: 192.168.1.0/26
- Subnet mask: 255.255.255.192
- Subnets: 2² = 4 subnets
- Hosts per subnet: 2⁶ - 2 = 62
- Subnets: 192.168.1.0, 192.168.1.64, 192.168.1.128, 192.168.1.192
IPv6
- Address Length: 128 bits
- Notation: Hexadecimal, colon-separated (e.g., 2001:0db8:85a3::8a2e:0370:7334)
- Total Addresses: 2¹²⁸ ≈ 3.4 × 10³⁸
- Key Features:
- No need for NAT (vast address space)
- Simplified header (fixed 40 bytes)
- Built-in IPsec support
- No broadcast (uses multicast and anycast)
- Stateless address autoconfiguration (SLAAC)
- Extension headers for optional features
IPv4 vs IPv6 Comparison
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address Size | 32 bits | 128 bits |
| Header Size | 20-60 bytes | Fixed 40 bytes |
| NAT | Required | Not needed |
| IPsec | Optional | Built-in |
| Broadcast | Yes | No (replaced by multicast) |
| Checksum | In header | Removed (handled by upper layers) |
NAT, DHCP, DNS
NAT (Network Address Translation)
- Purpose: Maps private IP addresses to public IP addresses
- Types:
- Static NAT: One-to-one mapping (private ↔ public)
- Dynamic NAT: Pool of public addresses assigned dynamically
- PAT (Port Address Translation/NAT Overloading): Many-to-one mapping using port numbers — most common in home routers
- Advantage: Conserves public IP addresses, adds security layer
- Disadvantage: Breaks end-to-end connectivity, complicates some protocols
DHCP (Dynamic Host Configuration Protocol)
- Purpose: Automatically assigns IP addresses and network configuration
- DORA Process:
- Discover: Client broadcasts DHCP Discover
- Offer: Server responds with IP offer
- Request: Client requests the offered IP
- Acknowledge: Server confirms assignment
- Also provides: Subnet mask, default gateway, DNS server, lease time
DNS (Domain Name System)
- Purpose: Resolves domain names to IP addresses
- Hierarchy: Root → TLD (.com, .in, .org) → Authoritative
- Record Types:
- A: Domain → IPv4 address
- AAAA: Domain → IPv6 address
- MX: Mail server for domain
- CNAME: Canonical name (alias)
- NS: Authoritative name server
- PTR: Reverse lookup (IP → domain)
- Resolution Types:
- Recursive: DNS server does all the work
- Iterative: Server refers to next server in chain
Application Layer Protocols
HTTP/HTTPS
- HTTP (HyperText Transfer Protocol): Port 80, request-response model
- HTTPS: HTTP + TLS/SSL encryption, Port 443
- HTTP Methods: GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS
- Status Codes:
- 1xx: Informational
- 2xx: Success (200 OK, 201 Created)
- 3xx: Redirection (301 Moved, 302 Found)
- 4xx: Client Error (400 Bad Request, 403 Forbidden, 404 Not Found)
- 5xx: Server Error (500 Internal Error, 503 Service Unavailable)
FTP (File Transfer Protocol)
- Port: 20 (data), 21 (control)
- Modes: Active (server initiates data connection), Passive (client initiates)
- Types: FTP (plain), SFTP (SSH-based), FTPS (FTP + TLS)
SMTP / POP3 / IMAP
- SMTP (Simple Mail Transfer Protocol): Port 25/587 — sends email
- POP3 (Post Office Protocol v3): Port 110 — downloads email to local device, deletes from server
- IMAP (Internet Message Access Protocol): Port 143 — syncs email across devices, keeps on server
Other Important Protocols
- Telnet: Port 23 — remote login (unencrypted)
- SSH: Port 22 — secure remote login (encrypted)
- SNMP: Port 161 — network management
- TFTP: Port 69 — trivial file transfer (UDP-based, no authentication)
Network Devices
| Device | Layer | Function | Key Feature |
|---|---|---|---|
| Hub | Physical (L1) | Repeats signal to all ports | No intelligence; single collision domain |
| Repeater | Physical (L1) | Amplifies/regenerates signal | Extends network distance |
| Bridge | Data Link (L2) | Connects two LAN segments | Filters frames using MAC address table |
| Switch | Data Link (L2) | Forwards frames to specific port | Each port = separate collision domain; uses MAC table |
| Router | Network (L3) | Routes packets between networks | Uses IP address; separate broadcast domains |
| Gateway | All layers | Protocol translation between different networks | Most complex; connects dissimilar systems |
| Modem | Physical (L1) | Modulates/demodulates signals | Converts digital ↔ analog |
Switch vs Router vs Hub
| Feature | Hub | Switch | Router |
|---|---|---|---|
| Layer | 1 | 2 | 3 |
| Address Used | None | MAC | IP |
| Collision Domain | Single | Per port | Per port |
| Broadcast Domain | Single | Single | Per port |
| Intelligence | None | Moderate | High |
SDN Basics
Software-Defined Networking (SDN) separates the control plane from the data plane.
Architecture
- Application Layer: Network applications (load balancer, firewall)
- Control Layer: SDN Controller (centralized brain) — e.g., OpenDaylight, ONOS
- Infrastructure Layer: Physical/virtual switches and routers (forwarding devices)
Key Concepts
- Southbound Interface: Controller → Switches (e.g., OpenFlow protocol)
- Northbound Interface: Applications → Controller (REST APIs)
- East-West Interface: Controller ↔ Controller (for distributed controllers)
Advantages
- Centralized network management
- Programmable network behavior
- Faster innovation and deployment
- Better traffic management and QoS
- Vendor independence
Quality of Service (QoS)
QoS ensures reliable and predictable network performance for critical applications.
Key QoS Parameters
- Bandwidth: Available data rate
- Latency (Delay): Time for packet to travel source → destination
- Jitter: Variation in latency (critical for VoIP, video)
- Packet Loss: Percentage of packets that don't reach destination
QoS Mechanisms
Traffic Classification and Marking
- DSCP (Differentiated Services Code Point): 6-bit field in IP header for priority marking
- CoS (Class of Service): 3-bit field in 802.1Q VLAN tag
Queuing Mechanisms
- FIFO (First In First Out): No priority; simple but unfair
- Priority Queuing (PQ): High-priority queue served first — can starve low priority
- Weighted Fair Queuing (WFQ): Bandwidth allocated proportionally by weight
- Class-Based WFQ (CBWFQ): Traffic classes with guaranteed bandwidth
- Low Latency Queuing (LLQ): Strict priority queue + CBWFQ — ideal for VoIP
Traffic Shaping and Policing
- Traffic Shaping: Buffers excess traffic and sends at regulated rate (smooths bursts)
- Traffic Policing: Drops or re-marks excess traffic immediately (no buffering)
- Token Bucket Algorithm: Controls rate and allows controlled bursts
Integrated Services (IntServ)
- Resource Reservation Protocol (RSVP): Reserves resources end-to-end
- Guaranteed service for real-time applications
- Drawback: Not scalable (per-flow state)
Differentiated Services (DiffServ)
- Per-hop behavior (PHB): Each router treats packets based on DSCP marking
- Scalable: No per-flow state required
- Classes: Expedited Forwarding (EF), Assured Forwarding (AF), Best Effort (BE)
Key Formulas Summary
| Formula | Description |
|---|---|
| C = B × log₂(1 + SNR) | Shannon's Channel Capacity |
| C = 2B × log₂(L) | Nyquist Bit Rate |
| U = Td / (Td + 2Tp) | Stop-and-Wait Efficiency |
| 2^r ≥ m + r + 1 | Hamming Code (r parity bits for m data bits) |
| Subnets = 2^n | Subnetting (n = borrowed bits) |
| Hosts = 2^h - 2 | Hosts per subnet (h = host bits) |
| W ≤ 2^k - 1 | Go-Back-N window size |
| W ≤ 2^(k-1) | Selective Repeat window size |
Exam Tips
- OSI vs TCP/IP: Know which protocols belong to which layer — most asked topic
- Subnetting: Practice CIDR calculations — guaranteed question
- TCP vs UDP: Comparison table is frequently tested
- Hamming Code: Practice calculating parity bits and error detection
- Routing Protocols: RIP vs OSPF vs BGP differences are commonly asked
- TCP Congestion Control: Understand AIMD, slow start, fast retransmit
- Network Devices: Know which device operates at which layer
- CRC: Understand the division process for error detection
Practice Questions
10 MCQs for Data Communication and Computer Networks with detailed explanations.
Q1. Consider the following about defined by ISO (ISO 7498) that standardizes network communic...
- A. It is not applicable in distributed systems
- B. It requires a minimum of O(n²) time complexity
- C. defined by ISO (ISO 7498) that standardizes network communication.
Layer 7 — Application Layer
-
- D. It applies only to sequential processing models
✅ Correct Answer: Option C
Explanation:
The correct answer is Option C — defined by ISO (ISO 7498) that standardizes network communication.
Layer 7 — Application Layer
-.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option B (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q2. Consider the following about Reduces data size for transmission
-...
- A. It requires a minimum of O(n²) time complexity
-
B. Reduces data size for transmission
- C. It is not applicable in distributed systems
- D. It applies only to sequential processing models
✅ Correct Answer: Option B
Explanation:
The correct answer is Option B — Reduces data size for transmission
-.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option C (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q3. Consider the following about Establishes, manages, and terminates sessions (connections) ...
- A. It applies only to sequential processing models
- B. It requires a minimum of O(n²) time complexity
-
C. Establishes, manages, and terminates sessions (connections) between applications
- D. It is not applicable in distributed systems
✅ Correct Answer: Option C
Explanation:
The correct answer is Option C — Establishes, manages, and terminates sessions (connections) between applications
-.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option B (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q4. Consider the following about Transmission of raw bit stream over physical medium
-...
- A. It requires a minimum of O(n²) time complexity
- B. It applies only to sequential processing models
-
C. Transmission of raw bit stream over physical medium
- D. It is not applicable in distributed systems
✅ Correct Answer: Option C
Explanation:
The correct answer is Option C — Transmission of raw bit stream over physical medium
-.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option B (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q5. Consider the following about Bit rate, physical topology (star, bus, ring, mesh), transmi...
- A. It is not applicable in distributed systems
- B. It requires a minimum of O(n²) time complexity
- C. It applies only to sequential processing models
- D. Bit rate, physical topology (star, bus, ring, mesh), transmission mode (simplex, half-duplex, full-duplex), signal encod
✅ Correct Answer: Option D
Explanation:
The correct answer is Option D — Bit rate, physical topology (star, bus, ring, mesh), transmission mode (simplex, half-duplex, full-duplex), signal encod.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option B (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option C (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q6. Consider the following about Quality of Service (QoS)](#qos)
OSI Model (All 7 La...
- A. It applies only to sequential processing models
- B. It is not applicable in distributed systems
- C. It requires a minimum of O(n²) time complexity
- D. Quality of Service (QoS)](#qos)
OSI Model (All 7 Layers)
The OSI (Open Systems Interc
✅ Correct Answer: Option D
Explanation:
The correct answer is Option D — Quality of Service (QoS)](#qos)
OSI Model (All 7 Layers)
The OSI (Open Systems Interc.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option B (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option C (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q7. Consider the following about Purpose:** Interface between user applications and network s...
- A. It is not applicable in distributed systems
- B. Purpose:** Interface between user applications and network services.
- C. It requires a minimum of O(n²) time complexity
- D. It applies only to sequential processing models
✅ Correct Answer: Option B
Explanation:
The correct answer is Option B — Purpose:** Interface between user applications and network services..
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option C (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q8. Consider the following about Key Protocols:** HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, SN...
- A. It applies only to sequential processing models
- B. Key Protocols:** HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, SNMP, Telnet, SSH
- C. It is not applicable in distributed systems
- D. It requires a minimum of O(n²) time complexity
✅ Correct Answer: Option B
Explanation:
The correct answer is Option B — Key Protocols:** HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, SNMP, Telnet, SSH.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option C (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q9. Consider the following about Functions:** File transfer, email, web browsing, virtual ter...
- A. It requires a minimum of O(n²) time complexity
- B. It applies only to sequential processing models
- C. Functions:** File transfer, email, web browsing, virtual terminal access
- D. It is not applicable in distributed systems
✅ Correct Answer: Option C
Explanation:
The correct answer is Option C — Functions:** File transfer, email, web browsing, virtual terminal access.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option B (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
Q10. Consider the following about Key Concept:** Does NOT refer to the application itself, but...
- A. It requires a minimum of O(n²) time complexity
- B. Key Concept:** Does NOT refer to the application itself, but the services the application uses
- C. It is not applicable in distributed systems
- D. It applies only to sequential processing models
✅ Correct Answer: Option B
Explanation:
The correct answer is Option B — Key Concept:** Does NOT refer to the application itself, but the services the application uses.
This is a standard concept in Data Communication and Computer Networks. The answer follows from the fundamental definitions and properties covered in this topic.
Why other options are incorrect:
- Option A (It requires a minimum of O(n²) time complexity...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option C (It is not applicable in distributed systems...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.
- Option D (It applies only to sequential processing models...) — This does not correctly answer the question as it either misstates the concept or refers to a different context.