🌐 Computer Networks

MAKAUT B.Tech (ECC602 / PCC-CS602) 2022–23 – Solved Question Paper

✅ Group-A (1 Mark) | Group-B (5 Marks) | Group-C (15 Marks) | Exam-ready answers
📌 Group-A (Very Short Answer – 1 Mark Each)
1(i) Remote login protocol is known as ________

Answer: TELNET

1(ii) What is meant by protocol in computer network?

Answer: A protocol is a set of rules and conventions that govern communication between network devices.

1(iii) Layer-2 Switch is also called ________

Answer: Bridge (Multiport Bridge)

1(iv) Each IP packet must contain ________

Answer: Source IP Address and Destination IP Address

1(v) Token bucket algorithm is an advanced form of ________

Answer: Leaky Bucket Algorithm

1(vi) Mail transfer protocol is known as ________

Answer: SMTP (Simple Mail Transfer Protocol)

1(vii) IP address of loopback address is ________

Answer: 127.0.0.1

1(viii) What are the two categories of QoS attributes?

Answer: 1. Quantitative Attributes, 2. Qualitative Attributes

1(ix) Three main divisions of the domain name space are ________

Answer: Generic Domains, Country Domains, Inverse Domains

1(x) State the function of application layer in brief.

Answer: It provides network services directly to end users such as e-mail, file transfer, web browsing.

1(xi) Receiving window of selective repeat ARQ is ________

Answer: Greater than 1 (More than one frame)

1(xii) Why IP protocol is considered as unreliable?

Answer: Because IP provides best-effort delivery and does not guarantee packet delivery, sequencing, or error recovery.

✍️ Group-B (Short Answer – 5 Marks)
2. Explain the functions of Physical Layer and Data Link Layer.

Physical Layer functions: transmission of raw bits, defines electrical/mech specs, data rate, bit sync, line configuration, transmission mode, topology.

Data Link Layer functions: framing, error detection & correction, flow control, access control, reliable node-to-node delivery, MAC addressing.

3. Compare between CSMA/CD and CSMA/CA
CSMA/CDCSMA/CA
Collision DetectionCollision Avoidance
Used in EthernetUsed in Wireless LAN
Detects collision after occurrenceTries to avoid collision before occurrence
Less overheadMore overhead (RTS/CTS)
Suitable for wired networksSuitable for wireless networks
4. Explain (i) Repeater (ii) Router (iii) Gateway

Repeater (Physical Layer): regenerates weak signals, extends distance. Router (Network Layer): forwards packets via IP addresses, path selection. Gateway: connects heterogeneous networks, protocol conversion.

5. How does firewall protect data?

Firewall monitors & filters traffic: packet filtering, blocks unauthorized access, prevents malware, enforces policies, hides internal network. Acts as barrier between trusted/untrusted networks.

6. What is bit stuffing and why is it used?

Bit stuffing: inserting extra 0 after five consecutive 1s. Example: 11111011111 → 1111100 1111101. Purpose: frame synchronization, avoid flag confusion, error-free delimitation. Used in HDLC.

📘 Group-C (Long Answer – 15 Marks)
7(a). Discuss the working of Twisted Pair Cable. (15 Marks)

Working: Electrical signals via copper wires; twisting reduces EMI. Types: UTP (unshielded, low cost) and STP (shielded, better noise immunity). Advantages: low cost, easy install, flexible. Disadvantages: limited bandwidth, short distance. Applications: Ethernet LAN, telephone systems, DSL.

7(b). What is Optical Fiber? State Advantages of Optical Fiber. (15 Marks)

Optical fiber: uses light signals via total internal reflection (core + cladding). Advantages: very high bandwidth, low attenuation, long distance, immune to EMI, high security, lightweight, corrosion resistant, low error rate. Disadvantages: expensive installation, fragile. Applications: internet backbone, cable TV, medical instruments.

8(a). Write Short Notes: (i) Stop-and-Wait Protocol (ii) Selective Repeat ARQ

Stop-and-Wait: sender sends one frame, waits for ACK; simple but low channel utilization. Selective Repeat ARQ: only erroneous/lost frames retransmitted; requires buffering, higher throughput, complex.

8(b). Discuss VRC with example. (15 Marks)

VRC (Vertical Redundancy Check): parity bit added for error detection. Example: data=1011001 (4 ones) → even parity bit 0 → transmitted 10110010. Detects single-bit errors but fails for even number of errors. Simple, low overhead.

9(a). Explain Token Bucket Algorithm. (15 Marks)

Token Bucket: tokens generated at fixed rate, stored in bucket. Packet transmitted only if enough tokens; allows bursts. Components: bucket, tokens, queue. Advantages over leaky bucket: supports bursts, better QoS, traffic shaping. Used in congestion control.

Token Generator → Bucket → Queue → Transmission
9(b). Draw TCP Header and Explain Its Parts. (15 Marks)
0 15 16 31 +-------------------+--------------------+ | Source Port | Destination Port | +-------------------+--------------------+ | Sequence Number | +----------------------------------------+ | Acknowledgment Number | +----------------------------------------+ | HLEN | Reserved | Flags | Window Size | +----------------------------------------+ | Checksum | Urgent Pointer | +----------------------------------------+ | Options (optional) | +----------------------------------------+

Fields: Source/Destination Port (identify endpoints), Sequence/Acknowledgment Numbers (reliability), Flags (SYN, ACK, FIN, etc), Window Size (flow control), Checksum (error detection), Urgent Pointer, Options.

10(a). Compare Static and Dynamic Routing. (15 Marks)
Static RoutingDynamic Routing
Manually configuredAutomatically updated
No routing protocolUses RIP, OSPF, etc.
Low overhead, more secureHigher overhead, flexible
Slow adaptationFast adaptation, complex
10(b). Explain RIP. (15 Marks)

RIP (Routing Information Protocol): distance-vector protocol, hop count metric (max 15, 16=unreachable). Updates every 30 sec. Advantages: easy config, low complexity. Disadvantages: slow convergence, limited scalability. Versions: RIPv1, RIPv2. Suitable for small networks.

11(a). Explain how FTP can be used to browse websites. (15 Marks)

FTP (File Transfer Protocol): transfers files using TCP ports 21 (control) & 20 (data). For websites: clients upload/download web files, manage directories, publish content. Browsers support FTP URLs. Provides authentication, reliable file transfer, used for website maintenance.

11(b). Discuss Bluetooth Architecture and Protocols Involved. (15 Marks)

Bluetooth (2.4 GHz short-range). Layers: Radio → Baseband → LMP → HCI → L2CAP → RFCOMM → SDP. Piconet: 1 master + 7 slaves; Scatternet: interconnected piconets. Advantages: low power, low cost, cable replacement. Applications: wireless headphones, IoT, file sharing.

📖 Exam-focused Summary

✔ Complete coverage of MAKAUT Computer Networks (ECC602/PCC-CS602) 2022–23 – all groups.
✔ Includes physical layer, data link functions, CSMA/CD vs CA, routers, firewalls, bit stuffing, optical fiber, TCP header, token bucket, RIP, FTP, Bluetooth architecture.
✔ Answers structured for 1, 5, and 15-mark questions with clear headings, tables, and diagrams in exam style.