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ENCT 304Bachelor in Computer Engineering · Semester 52 Papers Available

Computer Networks

Past examination question papers and complete curriculum syllabus for Computer Networks (ENCT 304), Bachelor in Computer Engineering Semester 5 under Institute of Engineering (IOE), Tribhuvan University.

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Most Frequently Asked Questions

Top recurring IOE board exam questions for Computer Networks with verified mark schemes, formula notation, and recurrence frequency.

Showing 30 of 30 top repeated questions

Introduction

2 Questions
#1Asked in 8 Exam Sessions[8 Marks]Introduction
Compare the OSI 7-layer reference model with the TCP/IP protocol suite. Discuss the functions, protocols, and data units (PDUs) at each layer, and explain the key design issues in layering: encapsulation, addressing, and multiplexing.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Ashwin2074 Ashwin
#2Repeated 4 Times[6 Marks]Introduction
Discuss key issues in Network Layer Design: addressing, error control, flow control, multiplexing, and routing. Explain the Request For Comments (RFC) standardization process within the Internet Engineering Task Force (IETF).
Appeared in:2083 Baishakh2082 Bhadra2079 Bhadra2076 Ashwin

Physical Layer

2 Questions
#1Asked in 7 Exam Sessions[8 Marks]Physical Layer
What factors are considered when selecting transmission media? Explain the construction, propagation characteristics, advantages, and disadvantages of Optical Fiber cables (Single-mode vs Multi-mode). Compare FDM, TDM, and WDM multiplexing techniques.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2078 Bhadra2076 Ashwin2073 Shrawan
#2Repeated 4 Times[8 Marks]Physical Layer
Explain the xDSL family (ADSL, HDSL, VDSL) of broadband access technologies. Describe Discrete Multi-Tone (DMT) modulation, frequency spectrum division, and POTS splitters used in ADSL subscriber lines.
Appeared in:2083 Baishakh2081 Bhadra2078 Kartik2075 Chaitra

Data Link Layer

8 Questions
#1Asked in 8 Exam Sessions[8 Marks]Data Link Layer
Compare byte stuffing and bit stuffing in framing. A received frame is 0101101101 and the generator polynomial is G(x) = x^3 + 1 (or 1001). Check whether the received bit sequence contains transmission errors using Cyclic Redundancy Check (CRC). Show the complete modulo-2 division steps.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2078 Bhadra2076 Chaitra2073 Shrawan2071 Chaitra
#2Repeated 6 Times[6 Marks]Data Link Layer
What is a Virtual LAN (VLAN)? Explain the advantages of VLANs and how frame tagging is implemented according to the IEEE 802.1Q standard. Differentiate between static and dynamic VLANs.
Appeared in:2082 Bhadra2080 Bhadra2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin
#3Repeated 6 Times[8 Marks]Data Link Layer
Compare Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ sliding window protocols. Calculate maximum throughput and line efficiency for a given transmission rate, frame size, and round-trip propagation delay.
Appeared in:2080 Bhadra2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin2071 Chaitra
#4Repeated 6 Times[6 Marks]Data Link Layer
Explain the Medium Access Control (MAC) protocol CSMA/CD used in Ethernet and CSMA/CA used in IEEE 802.11 wireless networks. Why is collision detection not feasible in wireless transmissions?
Appeared in:2081 Baishakh2080 Baishakh2079 Bhadra2078 Bhadra2076 Ashwin2072 Kartik
#5Repeated 4 Times[8 Marks]Data Link Layer
Derive the throughput expressions for Pure ALOHA ($S = G e^{-2G}$) and Slotted ALOHA ($S = G e^{-G}$). Explain why maximum throughput of Slotted ALOHA is $1/e \approx 36.8\%$ while Pure ALOHA is only $1/(2e) \approx 18.4\%$.
Appeared in:2082 Bhadra2080 Bhadra2078 Kartik2076 Chaitra
#6Repeated 4 Times[8 Marks]Data Link Layer
Explain Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Compare 1-persistent, p-persistent, and non-persistent CSMA. Why must frame transmission time be at least twice the round-trip propagation delay ($T_{fr} \ge 2\tau$)? Explain Binary Exponential Backoff.
Appeared in:2083 Baishakh2081 Bhadra2080 Bhadra2077 Magh
#7Repeated 4 Times[8 Marks]Data Link Layer
Compare Sliding Window Flow Control Protocols: Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ in terms of sender window size ($W_s$), receiver window size ($W_r$), sequence numbering, link utilization, and buffer overhead.
Appeared in:2082 Bhadra2080 Bhadra2079 Bhadra2075 Chaitra
#8Repeated 4 Times[8 Marks]Data Link Layer
Describe the IEEE 802.11 Wireless LAN (Wi-Fi) architecture and MAC sublayer. Explain CSMA/CA protocol, DIFS/SIFS/PIFS inter-frame spaces, the Hidden Terminal and Exposed Terminal problems, and the RTS/CTS handshake mechanism.
Appeared in:2083 Baishakh2081 Bhadra2079 Bhadra2076 Ashwin

Network Layer

8 Questions
#1Asked in 8 Exam Sessions[10 Marks]Network Layer
Suppose a company has an assigned network IP address 150.10.0.0/16 (or 202.35.91.32/25) with 6 departments containing 1010, 505, 225, 107, 60, and 45 hosts. As a network engineer, design an IP addressing plan using Variable Length Subnet Masking (VLSM). List out the CIDR prefix, subnet mask, network ID, broadcast ID, usable host IP address range, and number of wasted IP addresses for each department.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin
#2Asked in 7 Exam Sessions[8 Marks]Network Layer
What are the features of the IPv6 base header compared to the IPv4 header? Explain IPv4 to IPv6 transition mechanisms: Dual Stack, Tunneling (6to4, 4to6, configured tunnels), and Network Address Translation - Protocol Translation (NAT-PT).
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Baisakh
#3Asked in 7 Exam Sessions[8 Marks]Network Layer
Differentiate between Distance Vector Routing and Link State Routing algorithms. Explain the working principle of Routing Information Protocol (RIP) with its timers. What is the Count-to-Infinity problem in distance vector routing and how is it resolved using Split Horizon with Poison Reverse?
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin
#4Repeated 5 Times[6 Marks]Network Layer
Explain how the Address Resolution Protocol (ARP) resolves an IP address to a physical MAC address with request and reply frame structures. What is the role of ICMP and how is it used in ping and traceroute diagnostics?
Appeared in:2082 Bhadra2080 Bhadra2079 Bhadra2076 Chaitra2074 Ashwin
#5Repeated 4 Times[8 Marks]Network Layer
Compare Distance Vector Routing with Link State Routing protocols. Explain Bellman-Ford and Dijkstra algorithms. Describe the Count-to-Infinity problem and explain mitigation methods (Split Horizon and Poison Reverse).
Appeared in:2083 Baishakh2081 Bhadra2079 Bhadra2076 Ashwin
#6Repeated 4 Times[8 Marks]Network Layer
Describe the architecture of Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP). Explain OSPF Area hierarchy (Backbone Area 0, ABR, ASBR) and contrast intra-domain link-state routing with inter-domain path-vector routing.
Appeared in:2082 Bhadra2080 Bhadra2078 Kartik2075 Chaitra
#7Repeated 4 Times[6 Marks]Network Layer
Explain Network Address Translation (NAT) and Port Address Translation (PAT/NAPT). Discuss RFC 1918 private IPv4 address allocations, NAT translation tables, and NAT traversal challenges for peer-to-peer protocols.
Appeared in:2082 Bhadra2080 Bhadra2077 Magh2075 Chaitra
#8Repeated 4 Times[6 Marks]Network Layer
Explain the working of Address Resolution Protocol (ARP) and Reverse ARP (RARP). Describe ARP cache table operations, ARP request broadcasting, unicast ARP reply, and Proxy ARP in subnets.
Appeared in:2082 Bhadra2079 Bhadra2077 Magh2074 Chaitra

Transport Layer

2 Questions
#1Asked in 8 Exam Sessions[8 Marks]Transport Layer
Compare TCP and UDP header formats and functionalities. How is a connection established and terminated in TCP using the three-way handshake? How is congestion handled using the Token Bucket and Leaky Bucket algorithms? Explain with block diagrams.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 4 Times[8 Marks]Transport Layer
Explain TCP Congestion Control mechanisms: Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery. Sketch and annotate the Congestion Window ($cwnd$) versus Transmission Round plot showing Tahoe and Reno behaviors.
Appeared in:2083 Baishakh2081 Bhadra2080 Bhadra2076 Chaitra

Upper Layers and Network Design

4 Questions
#1Asked in 8 Exam Sessions[8 Marks]Upper Layers and Network Design
Explain why Domain Name System (DNS) is hierarchical and distributed in nature. Differentiate between Iterative DNS query and Recursive DNS query with a step-by-step resolution diagram for www.facebook.com. What is the role of a proxy server and web caching?
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Ashwin2073 Chaitra
#2Repeated 6 Times[6 Marks]Upper Layers and Network Design
Draw the architecture of an Electronic Mail system showing User Agents (UA), Message Transfer Agents (MTA), and Message Access Agents (MAA). Compare Post Office Protocol (POP3) and Internet Message Access Protocol (IMAP).
Appeared in:2082 Bhadra2081 Baishakh2080 Baishakh2078 Bhadra2076 Ashwin2073 Chaitra
#3Repeated 5 Times[6 Marks]Upper Layers and Network Design
Explain HTTP request methods (GET, POST, PUT, DELETE) and HTTP status code categories (2xx, 3xx, 4xx, 5xx). Compare persistent HTTP with pipelining versus non-persistent HTTP connections.
Appeared in:2081 Baishakh2080 Bhadra2079 Bhadra2078 Bhadra2075 Bhadra
#4Repeated 4 Times[6 Marks]Upper Layers and Network Design
Explain the Dynamic Host Configuration Protocol (DHCP). Detail the 4-step DORA message exchange (Discover, Offer, Request, Acknowledge) with transport port numbers (UDP 67/68), broadcast flags, and IP lease renewals.
Appeared in:2083 Baishakh2081 Bhadra2080 Bhadra2078 Bhadra

Advanced Topics

4 Questions
#1Asked in 8 Exam Sessions[8 Marks]Advanced Topics
Describe the CIA (Confidentiality, Integrity, Availability) security principle. Explain the RSA public-key cryptographic algorithm step-by-step. Encrypt the plaintext word 'virus' (or 'hacker', 'MACHINE') using RSA given prime numbers p, q, and encryption key e.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2080 Baishakh2079 Bhadra2078 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 6 Times[6 Marks]Advanced Topics
Explain IP Security (IPSec) architecture: Authentication Header (AH) vs Encapsulating Security Payload (ESP), and Transport Mode vs Tunnel Mode. Differentiate between Packet-Filtering Firewalls and Application-Level Gateways.
Appeared in:2082 Bhadra2081 Baishakh2080 Bhadra2078 Bhadra2076 Baisakh2073 Shrawan
#3Repeated 4 Times[8 Marks]Advanced Topics
Compare Symmetric Key and Asymmetric Key Cryptography. Explain the RSA public-key algorithm (key generation, encryption, and decryption steps). Describe how Digital Signatures provide message authentication, non-repudiation, and data integrity.
Appeared in:2082 Bhadra2080 Bhadra2078 Kartik2075 Chaitra
#4Repeated 4 Times[6 Marks]Advanced Topics
Explain IP Security (IPsec) architecture. Compare Authentication Header (AH) and Encapsulating Security Payload (ESP). Differentiate between Transport Mode and Tunnel Mode in IPsec VPN implementations.
Appeared in:2083 Baishakh2081 Bhadra2080 Bhadra2077 Magh

Curriculum Syllabus & Course Topics

Sourced from TU curriculum portal
Full Syllabus (PDF)Micro Syllabus (PDF)
Chapter-wise Units & Micro-Syllabus Topics (7 Units)

  1. 1. Introduction

    • 1.1Computer network, importance and applications
    • 1.2Types of computer networks
    • 1.3Network topologies
    • 1.4Client/server and P2P networks
    • 1.5Protocols and standards, need of standardization
    • 1.6Layered network architecture, OSI and TCP/IP reference models
    • 1.7Addressing at different layers
    • 1.8Networking devices: Repeater, hub, bridge, switch, router, gateway

  2. 2. Physical Layer

    • 2.1Network monitoring: Bandwidth, throughput, delay, round-trip-time
    • 2.2Multiplexing - FDM, TDM, WDM
    • 2.3Switching - circuit switching, packet switching, datagram and virtual circuit switching
    • 2.4Transmission media - Guided (twisted pair, coaxial, optical fiber) and unguided media (radio waves, microwaves, infrared)
    • 2.5Ethernet cable standards (twisted pair and optical fiber)
    • 2.6Data encoding: Manchester, NRZ-I, MLT3, 4B/5B

  3. 3. Data Link Layer

    • 3.1Data link layer functions - Framing, error control, flow control, access control
    • 3.2Error control codes: Parity, checksum, CRC
    • 3.3Data link protocols: PPP, HDLC
    • 3.4Logical link control (LLC) and media access control (MAC) sublayers
    • 3.5Random access protocols: ALOHA, CSMA, CSMA/CD, CSMA/CA
    • 3.6Token based protocols: Token bus, token ring, FDDI
    • 3.7Ethernet (IEEE 802.3) and its evolution, bridged and switched Ethernet
    • 3.8WLAN (Wi-Fi) and IEEE 802.11
    • 3.9VLAN and its importance
    • 3.10Virtual circuit switching: ATM, MPLS

  4. 4. Network Layer

    • 4.1Network layer functions and services
    • 4.2Connection oriented and connectionless network services
    • 4.3Logical addressing and its importance
    • 4.4IPv4 addressing and classes, private and public IP address, sub-netting and super-netting, VLSM, CIDR
    • 4.5Unicast, multicast and broadcast addresses
    • 4.6Routing and types of routing: Static and dynamic, unicast and multicast, interior and exterior, distance vector and link state
    • 4.7Routing protocols: RIP, OSPF, EIGRP, BGP
    • 4.8Network address translation (NAT)
    • 4.9IPv6 addressing, need and features of IPv6
    • 4.10Protocols: IPv4, ARP, ICMP, IPv6, ICMPv6
    • 4.11Transition from IPv4 to IPv6 and strategies
    • 4.12Traffic shaping and congestion control mechanisms

  5. 5. Transport Layer

    • 5.1Transport layer functions and services
    • 5.2Elements of transport layer protocols: process-to- process communication, addressing, multiplexing and de-multiplexing, segmentation and reassembly, error control, flow control
    • 5.3Transport protocols: TCP and UDP
    • 5.4TCP services: connection setup and release, reliable, stream oriented, flow-control, error-control
    • 5.5Introduction to socket and socket programming

  6. 6. Upper Layers and Network Design

    • 6.1Functions and services of session, presentation and application layers
    • 6.2Introduction to upper layer protocols: DHCP, HTTP, HTTPS, FTP, SMTP, POP, IMAP
    • 6.3DNS, its function and DNS queries
    • 6.4Network management tools and protocols (SNMP)
    • 6.5Basics of web, e-mail, DNS and proxy server configurations
    • 6.6VoIP, FoIP and IP interconnection
    • 6.7Network design and configuration guidelines

  7. 7. Advanced Topics

    • 7.1Introduction to software- defined networking (SDN), basic architecture, importance and applications
    • 7.2Network security and its importance
    • 7.3Overview of content delivery networks (CDNs), named data networking (NDN), intent based networking (IBN)
    • 7.4Quantum network, network virtualization and recent trends in networking

Examination Scheme & Marks Distribution

Evaluation Structure

  • Final Board Theory Exam: 60 Marks (Pass mark: 24)
  • Internal Assessment: 40 Marks (Pass mark: 16)
  • Practical / Lab Exam: 25 or 50 Marks (Continuous lab evaluation + viva, where applicable)

* This is the general current IOE 60/40 scheme; verify course-specific details in the syllabus above.

Exam Preparation Guidelines

  • Review the 2 available past examination papers to identify recurring patterns, core problem types, and chapter weightage.
  • Cross-reference key answers with official syllabus units, standard textbooks, and lecture notes.
  • Structure answers with labeled diagrams, concise bullet points, and highlight final answers in numerical solutions.

Frequently Asked Questions (Computer Networks)

Q: How can I download Computer Networks past question papers?

You can preview or download the Computer Networks question papers (PDF) directly using the built-in viewer on this page with zero redirects or paywalls.

Q: What is the pass mark for Computer Networks?

The general current scheme is a 60-mark final theory exam and a 40-mark internal assessment, with pass marks of 24 and 16. Verify the course-specific syllabus above.

Q: Where can I find the complete syllabus for this subject?

The available chapter-wise syllabus and topic breakdown is indexed in the Syllabus section above, with links to the curriculum PDF source.

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