CS-602 Computer Networks - May 2023 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
   aWhat is Computer Network? Discuss the importance of Computer network. Give its merits and demerits.
   How to answer

   • Define computer network as interconnection of autonomous computers for resource sharing
   • Explain importance: resource sharing, communication, reliability, cost saving, scalability
   • List merits: sharing hardware/software/data, communication, backup
   • List demerits: security, cost, complexity, dependence
2. 7 Marks
   bExplain the working principle of ISO-OSI reference model with functionality of each layer.
   How to answer

   • Outline 7-layer ISO-OSI model with diagram
   • Explain function of each layer: Physical to Application
   • Explain peer-to-peer communication and encapsulation
   • Summarize working principle as layered services
3. 7 Marks
   aWhat is the data link layer and what are services does it provides?
   How to answer

   • Define data link layer as second layer responsible for node-to-node delivery
   • List services: framing, physical addressing, flow control, error control, access control
   • Briefly explain each service
   • Give position in OSI/TCP-IP
4. 7 Marks
   bWhat is the mechanism of sliding window flow control? Explain with an example.
   How to answer

   • Define sliding window with sender and receiver window
   • Explain Go-Back-N / Selective Repeat concept with sequence numbers
   • Illustrate with example of window size e.g. W=4 and ACK flow
   • State advantages for efficient flow control
5. 7 Marks
   aDiscuss about Guided and unguided transmission media with suitable sketch.
   How to answer

   • Define guided media: twisted pair, coaxial, fiber optic with sketch
   • Define unguided media: radio, microwave, infrared, satellite
   • Compare characteristics: bandwidth, cost, interference
   • Provide suitable sketches for each type
6. 7 Marks
   bWhat is finite state machine model? How finite state machines are used in the study of network protocols? Explain.
   How to answer

   • Define finite state machine: states, events, transitions
   • Explain use for protocol specification and verification
   • Give example of simple protocol (e.g. data link) as FSM
   • State benefits: unambiguous, deadlock/livelock detection
7. 7 Marks
   aExplain the working principle of slotted ALOHA with suitable sketch.
   How to answer

   • Define slotted ALOHA with time divided into discrete slots
   • Explain transmission only at slot boundaries and collision handling
   • Provide timing/sketch showing slots, successful and collided transmissions
   • State efficiency 36.8% vs pure ALOHA
8. 7 Marks
   bA Group of N stations share a 56 Kbps pure aloha channel. Each station outputs a 1000 bits frame on an average of once every 100 sec (stations are buffered). What is the max value of N?
   How to answer

   • Recall pure ALOHA max throughput S_max = 1/(2e) ~ 0.184
   • Compute offered load per station: 1000 bits / 100 sec = 10 bps
   • Compute total capacity for N stations: N*10 <= 0.184*56000
   • Solve N_max ~ 1031 stations
9. 7 Marks
   aDescribe the working principle of Least Cost Routing using suitable example.
   How to answer

   • Define least cost routing with cost metric
   • Explain Dijkstra/shortest path steps
   • Illustrate with example network graph and cost table
   • Show selection of minimum cost path
10. 7 Marks
    bWrite a brief note on ICMP (Internet Control Message Protocol) using its frame formats.
    How to answer

    • Define ICMP purpose for error reporting and control
    • Describe ICMP frame/header format fields: type, code, checksum
    • List message types: echo, destination unreachable, time exceeded
    • Give encapsulation in IP
11. 7 Marks
    aWhat is Limited-Contention Protocols? Explain the working principle of Adaptive Tree Walk Protocol with suitable example.
    How to answer

    • Define limited-contention protocols combining contention and collision-free
    • Explain adaptive tree walk: binary search of ready stations
    • Illustrate with example slots 0,1,collision resolution
    • State performance under low/high load
12. 7 Marks
    bGive the comparative study of IPv4 and IPv6.
    How to answer

    • Compare address size: 32-bit vs 128-bit, header format
    • Compare header fields, checksum, fragmentation, QoS
    • Compare security (IPSec), auto-configuration
    • Tabulate differences with examples
13. 7 Marks
    aWhat is Electronic Mailing. What are different ways of sending electronic mail (E-mail)? Discuss in detail.
    How to answer

    • Define electronic mail and mail system components (UA, MTA)
    • Explain ways: SMTP, POP3, IMAP, Webmail
    • Describe sending/receiving steps with protocols
    • Give architecture diagram
14. 7 Marks
    bDiscuss the concept of TCP flow control and TCP congestion control.
    How to answer

    • Define TCP flow control using sliding window and advertised window
    • Define congestion control: slow start, congestion avoidance, fast retransmit
    • Explain cwnd, ssthresh evolution with diagram
    • Differentiate flow vs congestion control
15. 14 Marks
    Write a short note on any two:

    1. i)Service Primitives
    2. ii)CSMA/CD
    3. iii)IEEE Standards 802 series
    4. iv)Fragmentation and reassembly
    How to answer

    • For each chosen topic give definition and purpose
    • Explain working with diagram/example
    • Mention key features/standards/formats
    • Conclude with applications