AL-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 (CN)? Give its architecture and briefly explain each components of CN.
   How to answer

   • Definition of computer network as interconnection of devices for resource sharing and communication
   • Network architecture types - client-server, peer-to-peer, layered architecture
   • Brief explanation of components - hosts, transmission media, NIC, hub/switch/router, protocols, NOS
2. 7 Marks
   bDraw the ISO-OSI reference model and explain the functionalities of each layer in detail.
   How to answer

   • Draw 7-layer ISO-OSI reference model diagram
   • List layers from Physical to Application
   • Explain functionality of each layer in detail
   • Role of headers, interfaces and peer protocols
3. 7 Marks
   aWhat is the need of Flow control? Explain the common approaches for flow control at data link layer.
   How to answer

   • Need of flow control - prevent fast sender overwhelming slow receiver, avoid buffer overflow
   • Stop-and-Wait flow control mechanism
   • Sliding window flow control mechanism
   • Comparison of approaches at data link layer
4. 7 Marks
   bDiscuss the following:

   1. i)Go-Back-N
   2. ii)Hybrid ARQ
   How to answer

   • Go-Back-N: sliding window, sender retransmits all frames from lost frame, receiver window size 1
   • Working with example and window sizes
   • Hybrid ARQ: combination of ARQ and FEC, types and retransmission with error correction
   • Applications and comparison
5. 7 Marks
   aGive the difference between Connection oriented and connection less services.
   How to answer

   • Definition of connection-oriented service with connection setup, transfer, teardown
   • Definition of connectionless service with independent datagrams
   • Difference on reliability, ordering, overhead, applications
   • Examples - TCP vs UDP/IP
6. 7 Marks
   bExplain the working of ARP and RARP.
   How to answer

   • ARP purpose - mapping IP address to MAC address
   • ARP request/reply broadcast working steps
   • RARP purpose - mapping MAC to IP for diskless stations
   • Message formats and limitations
7. 7 Marks
   aExplain Binary Exponential Back-off (BES) with suitable example.
   How to answer

   • Concept of contention and collision in CSMA/CD
   • Binary exponential back-off algorithm steps with random wait $0$ to $2^k-1$ slots
   • Suitable example with two or more stations colliding
   • Stability and capture effect
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

   • Pure ALOHA maximum efficiency $S_{max}=1/(2e) \approx 18.4\%$
   • Usable bandwidth $= 56 \times 0.184$ Kbps and per-station requirement $1000/100=10$ bps
   • Compute $N =$ usable bandwidth / per-station rate
   • Result $N \approx 1032$ stations
9. 7 Marks
   aWhat is the need of Network layer? What are services provided by this layer? Explain.
   How to answer

   • Need of network layer - routing, logical addressing, internetworking
   • Services: packet forwarding, routing, congestion control, QoS
   • Connection-oriented vs connectionless network service
   • Relation with data link and transport layers
10. 7 Marks
    bDescribe the working of Bellman Ford algorithm using suitable example.
    How to answer

    • Bellman-Ford principle of distance vector relaxation for $n-1$ iterations
    • Steps with initialization, relaxation, negative cycle detection
    • Worked example on small graph showing distance updates
    • Complexity and comparison with Dijkstra
11. 7 Marks
    aWhat is MAC Addressing? What are the three types of MAC address discuss with examples.
    How to answer

    • Definition of MAC address - 48-bit physical address
    • Three types: unicast, multicast, broadcast with address ranges
    • Examples of each type
    • Role in data link layer delivery
12. 7 Marks
    bWhat is Fragmentation and Reassembly? Why do we need fragmentation and reassembly at network? Explain.
    How to answer

    • Definition of fragmentation and reassembly
    • Need due to differing MTU across networks
    • Fragmentation fields - identification, offset, MF flag
    • Example of transparent vs non-transparent fragmentation
13. 7 Marks
    aDiscuss the following:

    1. i)WWW
    2. ii)HTTP
    How to answer

    • WWW: hypertext system of linked documents, URL, browser, web server
    • HTTP: application layer request-response protocol, methods, stateless nature
    • Working with example of fetching web page
    • HTTP versions and HTTPS
14. 7 Marks
    bDraw and explain the header format of a User Datagram Protocol (UDP).
    How to answer

    • Draw 8-byte UDP header with source/destination port, length, checksum
    • Explain function of each field
    • Characteristics - connectionless, unreliable, low overhead
    • Use cases
15. 14 Marks
    Write a short note on any two:

    1. i)SNMP
    2. ii)Broadcast and Multicast Routing
    3. iii)MLMA
    4. iv)Service Primitives
    How to answer

    • For each chosen topic: definition/purpose and key components
    • Working/steps with example or diagram
    • Advantages, limitations and applications
    • Concise structured short note