[#16] – Data Communications and Computer Networks – Questions

Data communication technologies deal with means and methods of data transfer from one location to another. Marriage between computing and data communication technologies is one of the most exciting development that has revolutionized information age. This development gave birth to computer networks.

A computer network is a network of computers that are geographically distributed, but connected in a manner to enable meaningful transmission and exchange of data among them. Sharing of information, resources and processing load is the main objective of a computer network.

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Points To Remember:

  • A computer network is a network of computers that are geographically distributed, but connected in a manner to enable meaningful transmission and exchange of data among them. Sharing of information, resources (both hardware and software), and processing load is the main objective of a computer network.
  • Three basic elements of any communication system are a sender (source) that creates and sends a message, a medium that carries the message, and a receiver (sink) that receives the message.
  • Three modes of data transmission are simplex, half-duplex, and full-duplex. A simplex communication system can transmit data in one direction only. A half-duplex communication system can transmit data in both directions, but in only one direction at a time. A full-duplex communication system allows data to flow in both directions simultaneously.
  • Bandwidth refers to data transfer rate of a communication system (amount of data that it can transfer per unit of time). Higher the bandwidth of a communication system, the more data it can transfer in a given time.
  • Data transfer rate is measured in a unit called baud that is identical to bits per second (bps).
  • There are several types of physical channels (communication media) through which data cna be transmitted from one point to another. Some of the most common data transmission media are twisted-pair wire (UTP cable), coaxial cable, microwave system, communications satellilte, and optical fibers.
  • Modulation is the technique of converting a digital signal to its analog form, and demodulation is the reverse process of converting an analog signal to its digital form.
  • A special device called modem (modulator/demodulator) is used to carry out the process of modulation and demodulation (conversion of digital data to analog form and vice-versa).
  • Data-transmission-service providers are popularly known as common carriers. Types of services typically offered by common carriers are dial-up line, leased line, Integrated Services Digital Network (ISDN), and Value Added Network (VAN).
  • Method of dividing a physical channel into multiple logical channels to enable a number of independent signals to be transmitted simultaneously on it si known as multiplexing. The electronic device that performs this task in known as multiplexer.
  • Two modes of data transmission on a communication line are asynchronous and synchronous. In asynchronous transmission, a sender sends data at any convenient time and receiver accepts it. On the the other hand, in synchronous transmission, a sender and receiver must synchronize with each other to get ready for data transmission before it takes place.
  • Three different methods of establishing communication links between a sender and receiver in a communication network are circuit switching, message switching, and packet switching.
  • Selection of a path to be used to transmit a message/packet in a WAN is determined by the routing technique used.
  • Topology of a network refers to the way in which the network’s nodes are linked together. Although number of possible network topologies is seemingly limitless, four major ones are star network, ring network, completely connected network, and multi-access bus network.
  • Based on characteristics such as geographic distribution of nodes, data rate, error rate, communication link, ownership, and communication cost, networks are classified broadly into two types: LAN and WAN. Networks that share some of the characteristics of both LANs and WANs are sometimes referred to as MANs.
  • A communication or network protocol describes rules for transmission of data over communication networks. These rules provide a method for orderly and efficient exchange of data between sender and receiver, and for proper interpretation of controls and data transmitted as raw bits and bytes.
  • Network interface card, often referred to as NIC or network card, is a hardware device that allows a computer to be connected to a network, both functionally and physically.
  • Computer networks are implemented using a concept of layered protocols.The OSI model provides a standard for layered protocols for WANs. The seven layers of the OSI model are physical, data-link, network, transport, session, presentation, and application. Of the available protocol suites for network systems, the Internet Protocol (IP) suite is the most popular and widely used.
  • Interconnecting two or more networks to form a single network is called internetworking, and resulting network is called an internetwork. The goal of internetworking is to interconnect different physical networks and to hide their details, enabling the internetwork to function as a single coordinated unit. Tools such as bridges, routers, and gateways are used for internetworking. The internet is the best example of an internetwork.
  • A wireless computing system enhances functionality of computing equipment by freeing communication from location constraints of wired computing systems.
  • Wireless computing systems are of two types – fixed wireless systems that support little or no mobility of its computing equipment, and mobile wireless systems that support mobility of computing equipment used to access resources of wireless network.
  • Commonly used wireless technologies include 2G and 3G technologies, wireless LANs, Wireless Local Loops (WLLs), radio-router technology, multihop wireless networks, and Wireless Application Protocol (WAP).
  • A distributed computing system is a configuration in which many independent computer systems (which may be geographically far apart) are interconnected by a communication network, and in which messages, processing tasks, programs, data, and other resources are transmitted between cooperating computer systems, Such an arrangement enables sharing of many hardware and software resources, as well as information, among several users who may be sitting far away from each other.

List of Questions:

  1. What is computer network? How it is useful?
  2. Identify basic elements of a communication system and purpose of each.
  3. Differentiate among simplex, half-duplex, and full-duplex modes of data transmission.
  4. Which mode of data transmission is suitable for communication between a terminal and a computer?
  5. “A full-duplex line is faster since it avoids delay that occurs in a half-duplex circuit.” Explain.
  6. Explain the terms “bandwidth” and “baud”.
  7. Differentiate among narrowband, voice band, and broadband communication channels. Write a practical application of each.
  8. What is a wire pair? In what situations they are suitable for use in data transmission?
  9. What is a coaxial cable? Write its practical uses.
  10. Explain how microwave systems are used for communication between two distant stations.
  11. How communications satellites are used? What advantages and limitations are there in using a communication satellite?
  12. What is an optical fiber? How it is used for data communications? What are its advantages?
  13. Differentiate between analog and digital transmission of data. Write their advantages and disadvantages.
  14. What do you understand by modulation and demodulation?
  15. Why is modulation used in signal transmission? Describe three different forms of modulation
  16. What are modems? What purpose do they serve in data communication systems?
  17. Describe some common factors that one should consider while selecting a modem.
  18. What is a repeater? How it is different from an amplifier?
  19. When is public telephone line used to connect two computers? Are modems required for this purpose? Why?
  20. Explain about following types of services offered by common carriers:
    Dial-up line
    Leased line
    Integrated Services Digital Network (ISDN)
    Value Added Network (VAN)
  21. What is ISDN? Differentiate between narrowband and broadband ISDN.
  22. What is a Value Added Network (VAN)?
  23. What is a multiplexer? Explain its function with a diagram.
  24. Describe two basic methods of multiplexing. Write uses of both the methods.
  25. List differences between FDM and TDM. Which method is suitable for communication between computers and why?
  26. Describe asynchronous and synchronous modes of data transmission.
  27. List relative advantages and disadvantages of asynchronous and synchronous modes of data transmission.
  28. Explain how circuit switching is used to link sender and receiver in a communication network. What are its advantages and disadvantages?
  29. Explain store-and-forward method of message switching. What are its advantages and disadvantages?
  30. What is packet switching? Why this method is used for digital data communication between computers?
  31. What is routing? Differentiate between source routing and hop-by-hop routing methods.
  32. What is network topology? Describe three network topologies in common use. Write their relative advantages and disadvantages.
  33. What is a hybrid network? Why they are used?
  34. Write a short note on multi-access bus network.
  35. What is a LAN? What are its main objectives?
  36. What is a WAN? What is a MAN?
  37. Differentiate between a LAN and a WAN. Write one example of each.
  38. What is a communication protocol? What normal functions are performed by these protocols?
  39. Why are communication protocols needed in a computer network?
  40. What is a network interface card? Explain its usage in a computer system.
  41. Why is layering concepts in the OSI model of network architecture with functions of each layer.
  42. What is internetworking? What are the main issues in internetworking? Explain difference among following terms?
  43. What is a wireless computing system? How it is useful?
  44. Differentiate between fixed wireless systems and mobile wireless systems.
  45. What major challenges are in successful use of wireless computing systems?
  46. List some applications that can benefit from wireless computing systems.
  47. Write short notes on:
    2G and 3G technologies
    Wireless LANs
    Wireless Local Loops (WLLs)
    Radio-router technology
    Multihop wireless networks
    Wireless Application Protocol (WAP)
  48. What is a distributed computing system? Why they are gaining popularity?
  49. List advantages and limitations of a distributed computing system.
  50. Write short notes on:
    Data transmission modes
    Data transmission speed
    Data transmission media
    Data transmission services
  51. Write short notes on:
    Microwave system
    Communications satellite
    Optical fibers
  52. Write short notes on:
    Network interface card
    Value Added Network (VAN)
    Dial-up line
    Leased line
  53. Write short notes on:
    Wireless networks
  54. Write short notes on:
    Switching techniques
    Routing techniques
    Network topologies
    Asynchronous and synchronous transmission
  55. Write short notes on:
    LAN versus WAN
    Communication protocols
  56. Write short notes on:
    The OSI model
    Internetworking tools
    Distributed computing systems

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