CY-403 Computer Networks - Jun 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
   aDraw the ISO-OSI architecture and outline the function performed by each layer.
   How to answer

   • Draw 7-layer ISO-OSI stack in order
   • Outline function of each layer: Physical to Application
   • Show peer-to-peer communication / encapsulation
   • Mention OSI vs TCP/IP relevance
2. 7 Marks
   bCompare and contrast guided and unguided media for transmission.
   How to answer

   • Define guided media with types: twisted pair, coaxial, fiber
   • Define unguided media with types: radio, microwave, infrared, satellite
   • Compare on basis of medium, cost, bandwidth, interference, mobility
   • Contrast applications
3. 7 Marks
   aList out the functions of the Data Link Layer. One channel with a bit rate of 190 kbps and another with a bit rate of 180 kbps are to be multiplexed using TDM with no synchronization bits.

   1. i)What is the size of a frame in bits?
   2. ii)What is the data rate?
   How to answer

   • List Data Link Layer functions: framing, flow, error, access control
   • Use TDM slot proportional to bit rates 190:180 = 19:18
   • Frame size = 19+18 = 37 bits with no sync bits
   • Data rate calculation for TDM multiplexed line
4. 7 Marks
   bDefine the relationship between transmission delay and propagation delay, if the efficiency is at least 50% in STOP N WAIT protocol.
   How to answer

   • Define transmission delay $L/B$ and propagation delay $d/v$
   • Write Stop-and-Wait efficiency formula
   • Set efficiency $\ge 0.5$ condition
   • Derive relation $T_t \ge T_p$ or equivalent
5. 7 Marks
   aDifferentiate between Virtual Circuit versus Datagram Subnets.
   How to answer

   • Define Virtual Circuit and Datagram approaches
   • Compare connection setup, routing, reliability, ordering
   • Tabulate differences
   • Give example networks
6. 7 Marks
   bThe IP network 200.198.160.0 is using subnet mask 255.255.255.224. Design the subnets.
   How to answer

   • Identify /27 mask 255.255.255.224, block size 32
   • Calculate number of subnets, hosts per subnet
   • List subnet addresses, broadcast and usable ranges from 200.198.160.0
   • Show subnet design table
7. 7 Marks
   aExplain Distance Vector Routing (DVR) with working example in detail.
   How to answer

   • Define distance vector concept and Bellman-Ford basis
   • Explain routing table exchange with neighbours
   • Work out example with table updates and count-to-infinity
   • Mention advantages and limitations
8. 7 Marks
   bDiscuss in detail about ICMP role in network layer.
   How to answer

   • Define ICMP and its position in network layer
   • List message types: echo, destination unreachable, time exceeded
   • Explain error reporting and diagnostics like ping/traceroute
   • Explain ICMP encapsulation
9. 7 Marks
   aWhat is the format of an Email? Explain the architecture of a mailing system.
   How to answer

   • Define Email format: envelope, header, body/MIME
   • Explain header fields: To, From, Subject, etc.
   • Describe mailing system architecture: UA, MTA, MAA, protocols
   • Mention SMTP, POP3, IMAP roles
10. 7 Marks
    bProvide few reasons for congestion in a network. What is the purpose of the Domain Name System?
    How to answer

    • List congestion causes: high traffic, limited buffers, slow links
    • Explain effects: packet loss, delay
    • Define DNS purpose: hierarchical name to IP resolution
    • Mention DNS hierarchy and lookup
11. 7 Marks
    aExplain network topological design with necessary diagram and brief the advantages and disadvantages of various topologies.
    How to answer

    • Draw bus, star, ring, mesh, tree, hybrid topologies
    • Explain each topology structure
    • List advantages and disadvantages of each
    • Conclude suitable applications
12. 7 Marks
    bDiscuss the issues in the data link layer and about its protocol on the basis of layering principle.
    How to answer

    • List data link layer issues: framing, error, flow control
    • Discuss medium access, physical addressing
    • Explain protocols based on layering principle
    • Give examples: HDLC, PPP, ALOHA, CSMA
13. 7 Marks
    aAssume we want to send a data from S to R and there are 2 routers in between. What will be the total time taken if total number of packets is 5? Data is like: $Tp=0$ ms, Data size$=1000$ bytes, $BW=1$ mbps, Header of the packet$=100$ bytes.
    How to answer

    • Compute packet size = data + header = 1100 bytes
    • Compute transmission time per hop $L/BW$
    • Apply pipeline formula: $(N+H-1)\times T_t + H\times T_p$ with H=3 hops, N=5
    • Calculate total time in ms
14. 7 Marks
    bExplain CSMA/CD in detail.
    How to answer

    • Define CSMA/CD principle: carrier sense, collision detection
    • Explain algorithm steps: listen, transmit, detect, jam, backoff
    • Explain binary exponential backoff
    • Mention Ethernet application and efficiency
15. 14 Marks
    Write Technical short note on any two:

    1. i)Introduction to ISDN
    2. ii)HDLC
    3. iii)HUB
    4. iv)Jitter control
    How to answer

    • For any two chosen topics give definition and purpose
    • Explain key features / frame format / operation
    • Add neat diagram or example where applicable
    • Mention applications / advantages