CS-602 Computer Networks - May 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
   aGive explanation of different type of topologies in terms of its advantages and disadvantages.
   How to answer

   • Define network topology and list types: bus, star, ring, mesh, tree, hybrid
   • Advantages and disadvantages of each in terms of cost, reliability, scalability, fault tolerance
   • Comparison summary and suitable applications
2. 7 Marks
   bDraw and name all seven layers of ISO-OSI reference model of computer network. Explain the function of each layer and name two protocols of each layer.
   How to answer

   • Draw labelled 7-layer ISO-OSI model diagram
   • Explain function of each layer from Physical to Application
   • Name two protocols per layer
3. 14 Marks
   With the help of suitable diagrams explain the following protocols of data link layer.

   1. a)Stop and wait
   2. b)Go back
   3. c)Selective repeat
   How to answer

   • Explain Stop and Wait ARQ operation with sender-receiver diagram and timeline
   • Explain Go-Back-N sliding window, window size, retransmission on error
   • Explain Selective Repeat, buffering, NAK and efficiency comparison
4. 14 Marks
   Compare the TCP header and the UDP header. List the fields in the TCP header that are not part of the UDP header. Give reason for each missing field.
   How to answer

   • Draw TCP header (20-60 bytes) and UDP header (8 bytes) formats
   • List TCP-only fields: sequence number, acknowledgment number, flags, window, urgent pointer, options
   • Give reason for each missing field: connectionless, no reliability/flow control in UDP
5. 7 Marks
   aExplain various classes of IP addresses in terms of their network-ID bits, host-ID bits, number of possible host, number of possible network and range for each class.
   How to answer

   • Define Class A, B, C, D, E with leading bits and network/host split
   • Give range, number of networks and hosts per class with formulas $2^n-2$
   • Example address per class
6. 7 Marks
   bDefine the term data rate, bandwidth with taking a suitable example.
   How to answer

   • Define data rate (bps) with example
   • Define bandwidth (Hz / bps) with example
   • Relate with Nyquist/Shannon and illustrate difference
7. 14 Marks
   An organization is granted the block 211.17.180.0/24. The administrator wants to create 32 subnets.

   1. a)Find the subnet mask
   2. b)Find the number of addresses in each subnet
   3. c)Find the first and last address in first subnet
   4. d)Find the first and last address in last subnet
   How to answer

   • Calculate new prefix: /24 + 5 bits = /29 for 32 subnets, subnet mask 255.255.255.248
   • Number of addresses per subnet = $2^{3}=8$ (6 usable)
   • Derive first subnet 211.17.180.0/29 and last subnet 211.17.180.248/29 with first/last addresses
8. 14 Marks
   A TCP machine is sending windows of 65535 B over a 1 Gbps channel that has a 10 msec one way delay.

   1. a)What is the maximum throughput achievable?
   2. b)What is the line efficiency?
   How to answer

   • Compute RTT = 2 x 10 ms = 20 ms and bandwidth-delay product
   • Maximum throughput = window size / RTT = $65535 \times 8 / 0.02$
   • Line efficiency = throughput / bandwidth x 100%
9. 7 Marks
   aWhat are the various parameters of quality of service offered by the transport layer? Discuss their significance.
   How to answer

   • List QoS parameters: reliability, delay, jitter, bandwidth, etc.
   • Significance of each for transport service and applications
   • Examples of application requirements
10. 7 Marks
    bWhat is the function of MAC layer? Explain following protocols of MAC layer

    1. i)Pure and slotted ALOHA
    2. ii)CSMA
    How to answer

    • Define MAC layer function: channel access, framing, addressing
    • Explain Pure vs Slotted ALOHA with efficiency $S=G e^{-2G}$ and $S=G e^{-G}$
    • Explain CSMA variants, persistence, collision detection/avoidance
11. 14 Marks
    Write a short notes (any three):

    1. i)Connection Oriented
    2. ii)ARP
    3. iii)CSMA/CA
    4. iv)DNS
    How to answer

    • Select any three topics with definition and purpose
    • Explain working with diagram/example where applicable
    • Give applications, advantages/limitations