IT-502 Computer Networks - Nov 2022 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
   aDescribe the OSI model along with functions of each layer? Also give similarities and differences of OSI with TCP/IP protocol suite.
   How to answer

   • List 7 layers of OSI in order with one-line function each
   • Explain encapsulation, peer-to-peer communication and services at each layer
   • Describe TCP/IP 4-layer suite and its protocols
   • Compare similarities and differences in table form
2. 7 Marks
   bExplain LAN Communication standards? Describe all the techniques what should a station will do when the channel is busy or idle.
   How to answer

   • Define LAN and IEEE 802 standards for LAN communication
   • Explain channel sense states: idle vs busy
   • Describe persistence techniques: 1-persistent, non-persistent, p-persistent, CSMA/CD, CSMA/CA
   • Explain backoff, collision handling and station action flow
3. 7 Marks
   aThe following is a dump of a TCP header in hexadecimal format. $05320017\ 00000001\ 00000000\ 500207FF\ 00000000$

   1. i)What is the source port number?
   2. ii)What is the destination port number?
   3. iii)What is the sequence number?
   4. iv)What is the acknowledgment number?
   5. v)What is the length of header?
   6. vi)What is the type of segment?
   7. vii)What is the window size?
   How to answer

   • Parse TCP header fields: ports 16-bit, sequence 32-bit, ack 32-bit, data offset, flags, window
   • Convert hex 0532, 0017, 5002, 07FF to decimal/binary
   • Identify header length from data offset and segment type from flags
   • Report window size value
4. 7 Marks
   bExplain the basics of Line coding in physical layer. Code the binary stream $010011100$ in:

   1. i)Manchester scheme
   2. ii)Differential Manchester scheme
   How to answer

   • Define line coding need, DC component, synchronization, bandwidth
   • Explain Manchester: transition in middle, 0 as high-to-low, 1 as low-to-high
   • Explain Differential Manchester: transition always at middle, 0 with transition at start, 1 without
   • Draw waveforms for 010011100 in both schemes
5. 7 Marks
   aCreate 16 subnet for IP address $200.133.175.0$, each with 16 host (including all the reserved addresses), also provide the addresses range of each subnet's hosts.
   How to answer

   • Determine class C default mask and bits needed for 16 subnets and 16 hosts
   • Calculate new subnet mask /28 and increment size
   • List 16 subnet network addresses from 200.133.175.0
   • Give usable host range, broadcast for each subnet
6. 7 Marks
   bJustify the need of ARP and RARP in data transfer. When it is known that each machine has its own unique IP address? Given class C IP address $200.133.175.0$. What will be the default subnet mask for this address?
   How to answer

   • Explain need for IP-to-MAC and MAC-to-IP mapping in data transfer
   • Describe ARP request/reply and RARP operation with packet flow
   • Explain use in LAN delivery despite unique IP addresses
   • Give default Class C mask 255.255.255.0 for 200.133.175.0
7. 14 Marks
   Give the comparisons among the following:

   1. a)Leaky Bucket and Token Bucket
   2. b)Pure and Slated metal
   How to answer

   • Define traffic shaping vs policing purpose for congestion control
   • Compare leaky bucket vs token bucket on burst handling, packet loss, algorithm
   • Compare pure vs slotted system on vulnerability, throughput, synchronization
   • Summarize differences in table
8. 7 Marks
   aWhat are the functionalities of Transport Layer? Give a brief description on TCP and UDP header.
   How to answer

   • List transport layer services: addressing, multiplexing, flow and error control
   • Explain connection-oriented vs connectionless service
   • Describe TCP header fields and UDP header fields with sizes
   • Compare TCP vs UDP reliability and use cases
9. 7 Marks
   bExplain Routing Information Protocol (RIP). How RIP table get updated?
   How to answer

   • Define RIP as distance-vector interior gateway protocol
   • Explain hop count metric, max 15, routing table contents
   • Describe periodic updates, triggered updates and split horizon
   • Explain table update with Bellman-Ford and timers
10. 7 Marks
    aExplain the metrics used in determining the best path for a routing protocol.
    How to answer

    • Define routing metrics: hop count, bandwidth, delay, load, reliability, cost
    • Explain how metrics combine to compute best path
    • Give examples from RIP, OSPF, EIGRP metric use
11. 7 Marks
    bDiscuss various Network topologies. Differentiate among star and mesh topologies.
    How to answer

    • Define topology and list bus, ring, star, mesh, tree, hybrid
    • Explain star and mesh structure with diagrams
    • Differentiate on cost, reliability, fault tolerance, cabling
    • Give applications of each
12. 7 Marks
    aA broadcast LAN that is two kilometers long and uses CSMA/CD has a bandwidth of $107$ bps. The speed of the signal along the wire is $2 \times 10^8$ metres per second. What is the smallest size of the packets that are allowed to be sent over this network?
    How to answer

    • Recall CSMA/CD minimum frame condition: transmission time >= 2*propagation time
    • Compute propagation delay = distance / speed = 2000 / 2x10^8
    • Compute minimum bits = bandwidth x round-trip time
    • Convert to bytes and state smallest packet size
13. 7 Marks
    bExplain any two sliding window strategies. Also discuss the usage of piggy backing in networking.
    How to answer

    • Explain sliding window concept with sender/receiver windows
    • Describe Go-Back-N vs Selective Repeat operation with example
    • Define piggybacking and its frame format advantage
    • Discuss efficiency gain by combining ACK with data
14. 14 Marks
    Explain the following:

    1. i)Working of DNS system
    2. ii)HTTP
    How to answer

    • Explain DNS hierarchy, resolvers, name servers and lookup steps
    • Explain HTTP request/response model, methods, statelessness
    • Mention port numbers and use over TCP
    • Give examples of resolution and web transaction