AL-602 Computer Networks - Jun 2025 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
   aDifferentiate between connection-oriented and connectionless services with use-case scenarios. How are service primitives used in both?
   How to answer

   • Define connection-oriented vs connectionless service
   • Differentiate on reliability, ordering, overhead with use-case scenarios
   • Explain service primitives used in each (LISTEN, CONNECT, SEND, RECEIVE, DISCONNECT etc.)
2. 7 Marks
   bCompare and contrast the OSI and TCP/IP models with detailed layer-wise functionality. Which model better suits modern networks and why?
   How to answer

   • List layers of OSI and TCP/IP models
   • Explain layer-wise functionality of each
   • Compare architectures and argue which suits modern networks and why
3. 7 Marks
   aWhat are the different types of transmission media (guided and unguided)? How do bandwidth, data rate and media influence network performance?
   How to answer

   • Classify guided media (twisted pair, coaxial, fiber) and unguided (radio, microwave, infrared)
   • Define bandwidth and data rate concepts
   • Explain how bandwidth, data rate and media choice influence performance
4. 7 Marks
   bCompare Go-Back-N and Selective Repeat sliding window protocols. Discuss advantages and disadvantages with diagrams and example sequences.
   How to answer

   • Describe Go-Back-N and Selective Repeat sliding window operation
   • Compare with diagrams and example sequences
   • Discuss advantages and disadvantages of each
5. 7 Marks
   aWhat are Petri Net Models? Represent and explain the working of a data link layer protocol using a Petri Net diagram.
   How to answer

   • Define Petri Net Models (places, transitions, tokens)
   • Represent data link layer protocol using Petri Net diagram
   • Explain working / state transitions of the protocol
6. 7 Marks
   bGiven a data bit sequence $1101011011$ and generator polynomial $10011$, compute the CRC code and show how error detection works using it.
   How to answer

   • Perform binary division of data bits $1101011011$ by generator $10011$
   • Obtain CRC remainder / code and form codeword
   • Show error detection by re-dividing received codeword
7. 7 Marks
   aExplain the Binary Exponential Back-off (BEB) algorithm. How does it manage collisions in Ethernet networks?
   How to answer

   • Define Binary Exponential Back-off (BEB) algorithm steps
   • Explain random back-off time calculation after collisions
   • Explain how it manages collisions in Ethernet networks
8. 7 Marks
   bDescribe the collision-free protocols such as Basic Bit Map, BRAP and Binary Countdown. How do they eliminate data collisions?
   How to answer

   • Describe Basic Bit Map, BRAP and Binary Countdown operation
   • Explain reservation / contention mechanism in each
   • Show how data collisions are eliminated
9. 7 Marks
   aCompare and analyze Pure ALOHA and Slotted ALOHA protocols. Derive expressions for throughput and efficiency.
   How to answer

   • Describe Pure ALOHA and Slotted ALOHA operation
   • Derive throughput expressions $S = G e^{-2G}$ and $S = G e^{-G}$
   • Compare efficiency and maximum throughput
10. 7 Marks
    bDefine hierarchical routing. Compare it with flat and source routing. Under what network conditions is it preferable?
    How to answer

    • Define hierarchical routing concept
    • Compare with flat and source routing
    • State network conditions where hierarchical routing is preferable
11. 7 Marks
    aDescribe the differences in IPv4 and IPv6 packet formats. What improvements does IPv6 bring over IPv4?
    How to answer

    • Describe IPv4 and IPv6 packet header formats
    • Differentiate field by field
    • List improvements of IPv6 over IPv4
12. 7 Marks
    bAn IP packet of size 3000 bytes must be transmitted over a link with MTU of 1000 bytes. Show how IPv4 fragmentation is performed.
    How to answer

    • Note IP header size and MTU of $1000$ bytes
    • Compute number of fragments, offsets and MF flags
    • Show fragmentation of $3000$ byte packet over IPv4
13. 7 Marks
    aDiscuss the impact of TCP congestion control mechanisms such as Slow Start, Congestion Avoidance, and Fast Retransmit on network performance.
    How to answer

    • Explain Slow Start, Congestion Avoidance, Fast Retransmit mechanisms
    • Show cwnd evolution and thresholds
    • Discuss impact on throughput and network performance
14. 7 Marks
    bExplain the TCP connection management process (three-way and four-way handshakes). Why is graceful termination necessary?
    How to answer

    • Describe three-way handshake for connection establishment
    • Describe four-way handshake for termination
    • Explain need for graceful termination
15. 14 Marks
    Write short notes on (any two):

    1. i)CSMA/CD and CSMA/CA protocols
    2. ii)IEEE Standards 802 series
    3. iii)HTTP and DNS Protocol
    4. iv)SMTP, MIME and IMAP email protocols
    How to answer

    • Select any two topics from i-iv
    • Define key concepts and operation for each
    • Give examples / diagrams and applications