CY-403 Computer Networks - Jun 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aDescribe each of the seven layers of the ISO/OSI model. For each layer explain its function and provide examples of protocols and devices associated with it.
   How to answer

   • List seven layers: Physical, Data Link, Network, Transport, Session, Presentation, Application
   • Function of each layer in data communication
   • Example protocols per layer e.g. RS-232, HDLC, IP, TCP/UDP, SIP, JPEG, HTTP
   • Example devices per layer e.g. hub/repeater, switch/bridge, router, gateway
2. 7 Marks
   bWhat is Shannon's Theorem and what does it state about the maximum data rate of a communication channel? Establish a relationship between channel capacity, bandwidth and signal-to-noise ratio (SNR) according to Shannon's Theorem.
   How to answer

   • Definition of Shannon's Theorem for noisy channel
   • Formula $C = B \log_2(1+SNR)$ with terms defined
   • Relation between capacity, bandwidth and SNR
   • Implication for maximum data rate with example
3. 7 Marks
   aWhat do you understand by transmission media. Give the difference between Guided and Unguided media.
   How to answer

   • Definition of transmission media
   • Types and examples of guided media
   • Types and examples of unguided media
   • Comparison table: propagation, cost, maintenance, bandwidth, applications
4. 7 Marks
   bWhy is error control necessary in data communication? Describe the methods used for error detection and correction in the Data Link Layer.
   How to answer

   • Need for error control due to noise and distortion
   • Error detection methods: parity, CRC, checksum
   • Error correction: Hamming code, ARQ, FEC
   • Role of Data Link Layer in framing and control
5. 7 Marks
   aCalculate the CRC checksum for a data word represented by the polynomial $D(x) = x^5 + x^4 + x^2 + 1$ and a CRC polynomial $C(x) = x^3 + x + 1$.
   How to answer

   • Convert $D(x)$ to data bits 110101 and $C(x)$ to 1011
   • Append degree 3 zeros and perform modulo-2 division
   • Obtain 3-bit remainder as CRC checksum
   • Write transmitted codeword
6. 7 Marks
   bHow does ALOHA handle contention among multiple devices trying to access the shared channel? Give the advantages and limitations of the pure ALOHA protocol.
   How to answer

   • Working of pure ALOHA: transmit anytime, ACK and random backoff
   • Contention handling and collision detection
   • Advantages: simplicity, no synchronization
   • Limitations: low efficiency 18.4%, high collisions
7. 7 Marks
   aDescribe the key features and characteristics of the IEEE 802.3 Ethernet standard.
   How to answer

   • IEEE 802.3 as CSMA/CD Ethernet standard
   • Frame format, addressing and access method
   • Speeds, media and topology characteristics
   • Key features like collision handling and interoperability
8. 7 Marks
   bWhat is a network switch and what role does it play in computer networking? How does a switch build and maintain its MAC address table?
   How to answer

   • Definition of network switch as Layer 2 device
   • Role in forwarding using MAC addresses, collision domain separation
   • Learning by source address and flooding unknown
   • Aging and maintenance of MAC table
9. 7 Marks
   aWhat are the primary design issues in the Network Layer and also discuss the main functions performed by the Network Layer?
   How to answer

   • Design issues: store-and-forward, addressing, routing, congestion
   • Functions: routing, forwarding, fragmentation, addressing
   • Connectionless vs connection-oriented service
   • Examples of protocols e.g. IP
10. 7 Marks
    bExplain the concept of Shortest Path Routing with suitable example. Also discuss the advantages and limitations of Shortest Path Routing.
    How to answer

    • Principle of shortest path routing using graph distance
    • Example with Dijkstra's algorithm steps
    • Advantages: optimal, simple, widely used
    • Limitations: static, no load balancing, count issues
11. 7 Marks
    aExplain the role of each layer in the TCP/IP protocol stack with suitable layered architecture.
    How to answer

    • Four layers: Link, Internet, Transport, Application
    • Layered diagram showing encapsulation
    • Role of each layer with protocols e.g. IP, TCP, HTTP
    • Comparison with OSI in brief
12. 7 Marks
    bWhat is ICMP? Describe the role of ICMP messages in network communication. What types of information do ICMP messages convey? Explain.
    How to answer

    • Definition of ICMP as network layer support protocol
    • Role in error reporting, ping and traceroute
    • Types: echo, destination unreachable, time exceeded
    • Information conveyed for diagnostics
13. 7 Marks
    aWhat is the Domain Name System (DNS) and what role does it play in computer networking? Explain how DNS translates domain names to IP addresses and vice versa.
    How to answer

    • Definition of DNS as hierarchical naming system
    • Role in mapping names to IP and reverse lookup
    • Resolution process: resolver, root, TLD, authoritative
    • Record types and caching
14. 7 Marks
    bWhat is load shedding and how does it relate to congestion control? Discuss some techniques used for load shedding in the Transport Layer.
    How to answer

    • Definition of load shedding for congestion control
    • Relation to dropping packets under overload
    • Techniques: RED, choke packets, priority dropping
    • Transport layer role in throttling source
15. 14 Marks
    Write a short note on any two :

    1. a)Circuit, Packet and Message Switching
    2. b)HDLC
    3. c)Router and Gateways
    4. d)Connection establishment and release
    How to answer

    • Select any two topics from a-d
    • Definition, working and diagram for each chosen topic
    • Advantages, applications and limitations
    • Comparison where relevant e.g. switching types