Networking and Telecommunication - SEE Computer Science - Chapter 1

Chapter -1

Networking and Telecommunication

1.      Communication
Communication is sending and receiving information between two or more persons.

2.      Telecommunication
Telecommunication is a system of transmission of sounds, images, texts or data in the form of electronic signals.

3.      Data Communication

Data communication is a process of transferring data electronically from one place to other using different transmission mediums. Eg. E-Mail, Chat and phone calls.

4.      Components of Data Communication.
i) Data         ii) Sender          iii) Medium       iv) Receiver      v) Protocol

5.      Medium
A path through which the sender makes communication to the receiver is known as medium.

6.      Protocol
Protocol is a set of rules by which computers on the network communicate with each other. E.g. TCP/IP, SMTP, HTTP etc.

7.      Data Transmission Mode

Data transmission mode is the way of transmission of data from one location to another. There are three types of transmission mode:
i) Simplex mode       ii) Half duplex mode      iii) Full Duplex Mode

8.      Simplex mode
The transmission mode in which transmission of data can take place in one direction only is called simplex mode.
E.g.: Newspaper, Radio and Television.

9.      Half duplex mode
The transmission mode in which transmission of data can take place in both directions but only in one direction at a time is called half duplex mode. E.g.: Wireless handset and walkie-talkie.

10.   Full duplex mode
The transmission mode in which data can be transmitted in both directions simultaneously is called full duplex mode. E.g.: Telephone, internet etc.

11.   Bandwidth
Bandwidth can be defined as the maximum volume of data that can be transmitted through a communication system. We can measure bandwidth in digital devices by bits per second and in analogue devices by cycles per second or Hertz (Hz).

12.   Transmission medium
Transmission medium is a pathway that can transmit information from a sender to a receiver. The types of communication medium are

i) Guided Medium (Bounded or Wired)
ii) Unguided Medium (Unbounded or Wireless)

13.   Guided medium
The transmission media which comprises of cables or wires through which data is transmitted is called guided medium. They are called guided since they provide a physical channel from the sender device to the receiver device. The signal travelling through these media are bounded by the physical limits of the medium. E.g.: twisted pair cable, co-axial cable, fibre optics cable, etc.

14.   Unguided medium
The transmission media which transfer data in the form of electromagnetic waves that do not require any cables for transmission is called unguided medium. These media are bounded by geographical boundaries. E.g.: radio wave, microwave, infrared etc.

15.   Twisted pair cable

A pair of wires twisted with each other is known as twisted pair cable. A set of four pairs of twisted wires are bundled to form cable. These are the most common medium for LAN. Wires are twisted with each other so as to reduce crosstalk (A disturbance caused by electromagnetic interference, along a circuit or a cable pair). Its types are:        a) Unshielded Twisted Pair Cable       b) Twisted Pair Cable

16.   Unshielded twisted pair (UTP)

Unshielded twisted pair is a popular type of cable that consists of two unshielded wires twisted around each other which are used in telephone wiring and local area networks (LANs). It is called unshielded because it has no additional foil wrap, or shield. RJ-45 connector is commonly used with unshielded twisted pair.

17.   Shielded twisted pair (STP)

Shielded twisted pair is a type of copper telephone wiring in which each of the two copper wires are twisted together and coated with an insulating coating. The extra covering in shielded twisted pair wiring protects the transmission line from electromagnetic interference. D-shell connectors are used with shielded twisted pair.

18.   Co-axial cable

Coaxial (or “coax”) cable is a common type of cable used for transmitting data over long distances. They are most commonly used to transmit cable TV and Internet signals. The connectors used with co-axial cables are BNC, T-connectors and terminators in bus topology. 10 Mbps is the maximum speed of co-axial cable.

19.   Fiber optic cable

Fiber optics cable is one of the costlier cables used in data communication which uses light to carry a data signal through the cable. The connectors used in fiber optics are Screw Mounted Adaptors (SMA), Spring-loaded Twist (ST), SC and FC. It is costlier to maintain, produce and install.

20.   Radio wave transmission

The transmission making use of radio waves through air is called radio wave transmission. It provides low bandwidth for data communication. Radio, TV, cellular phones etc. uses radio transmission in one form or another. The radio waves can travel through walls and through an entire building. Depending upon the frequency, they can travel long distance or short distance. It does not require line of sight for data transmission

21.   Microwave transmission

Microwave is a line-of-sight wireless communication technology that uses high frequency beams of radio waves to provide high speed wireless connections that can send and receive voice, video, and data information. Microwaves do not pass through buildings. So, indoor receivers cannot be used effectively. It provides higher bandwidth for data communication. It requires line of sight for data transmission.

22.   Infrared transmission

Infrared Transmission is the transmission of data or voice information over infrared (IR) light over short ranges. It requires line-of-sight and is unable to break through walls.

23.   Computer network
A computer network means two or more computers connected with each other to share data, hardware, software and other resources.

24.   Advantages of computer network

a)      Computer in a network can access the network-connected hardware devices like printers, disk drives, etc.

b)     Data in a network environment can be updated from any computer. Updated data can be accessed by all computers on the network.

c)      Computers in a network system share different software packages.

d)     Information can be exchanged rapidly in computer network.

25.   Disadvantages of computer network

a)      The sharing of information may leak the privacy of other clients.

b)     If any computer system in a network gets affected by computer virus, there is a big chance of spreading computer viruses on other computers on the network.

c)      Computers on the network have to depend on the server computer for the recourses.

d)     Data and information may be stolen by computer hackers if the security of network is not reliable.

26.   Services of computer network.

a)      Directory services

b)     File services

c)      Application services

d)     Communication services

27.   Reasons of keeping computers on the network

a)      To share hardware devices like printers, scanners, hard disks etc.

b)     To share data, information and programs.

c)      To communicate with each other.

28.   Goals of computer network

a)      Resource sharing

b)     Reliability

c)      Communication medium

d)     Access to remote database

e)      Easy data transfer

29.   Computer Network reduces expenses of an office. Justify this statement with an example.

Computer Network reduces expenses of an office because computer on a network share different hardware devices like printers, scanners, hard disk etc. And sharing those hardware devices will reduces the expense of an office. For example if there are twenty computers in an office, now for printing the data there is no need to buy twenty printers individually rather than simple network the computer and connect the printer on the network which helps in sharing of the one printer among twenty computers which reduces the cost of buying nineteen printers individually.

30.   Computer network makes the world a small place. Justify.

Computer network makes the world small place. It is true because in computer network we can know about the events and things place outside or inside the country sitting within a room. And we also can communicate with our relatives who are far away from us or has gone to abroad for job or study. Therefore, computer network makes the world a small place.

31.   Hardware components of a computer network (Elements of Network)

Physical parts and devices used to connect computers in the network environment are called hardware components. The hardware components of computer network are

a)      Computer system (Server or Workstation)

b)     Network connectors

c)      Network cables

d)     NIC Card

e)      MODEM

f)      Hub

g)     Bridge

h)     Switch

i)       Router

j)       Gateway

k)     Repeater

32.   Server

A server is the main computer that provides services, data and other resources to the other computers in the network environment. Network operating software used by server is Novell Netware, Linux, Unix etc. Different types of servers are file server, print server, application server etc.

33.   Workstation
Workstation is a computer network that utilizes network resources. Network operating software used by workstation are Windows 98, Windows XP etc.

34.   Node
Each computer or device of network is called node.

35.   Router
Router is an intelligent device that connects two different networks which uses the address for filtering and forwarding the data as well as it has an ability to determine the best route for destination.

36.   NIC
A Network Interface Card (NIC) is the adapter through which the computer is connected to the network. The function of NIC is to convert data into electronic signals and transfer them through cables and vice-versa.

37.   Cable
Cables are commonly used media of physical channel for transmitting data between computers in network. Examples of cables are coaxial, twisted pair and fiber optic cable.

38.   Connector
Connector is an interface between the NIC of the computer and the cable that passes data between computers in network. Examples of connectors are BNC used with coaxial cable, RJ 45 used with UTP cable, ST used with fiber optic cable etc.

39.   Hub

A hub is a network device with multiple points or ports which acts as a central point from where different computers and other devices are connected. It broadcasts all network data across each connection.

Hub is mostly used in physical star topology.

40.   Switch
A switch is a networking device that has multiple connecting ports which is often used interchangeably with the bridge.

41.   Bridge

A bridge is a device that connects two or more similar types of network which filters the data or inspects incoming signals and decides whether to forward the signals or discard them.

42.   Gateway
Gateway is an interconnecting device that connects two dissimilar networks

43.   Repeater
Repeater is a device that amplifies the incoming signals, creates a copy of it and transmits the signal on network.

44.   MODEM

MODEM is a device which is used to transfer the data of one computer to another computer using telephone lines.

The role of MODEM in data transmission is that it transfers data from one computer to another through telephone line. It also converts the digital signal into analog and vice versa.

The importance of MODEM are: to access internet, perform modulation and demodulation process and transfer data from one computer to another through telephone line

45.   Modulation

The process of translating digital signals of a computer to analog signals, which are then transmitted across the standard telephone lines, is known as modulation.

46.   Demodulation

The process of translating analog signals from a phone line and converts then into digital signals for the computer is known as demodulation.

47.   Software components of a computer network

a)      Network protocol

b)     Network operating system

c)      Device driver

48.   Network operating system
Network operating system is a set of computer program that manages the resources on network. E.g. Novell network, Microsoft Windows NT, Linux, Unix etc.

49.   Device driver

Device driver is a program that controls the functionality of the hardware device.

50.   Types of Network

a)      LAN (Local Area Network)

b)     MAN (Metropolitan Area Network)

c)      WAN (Wide Area Network)

51.   LAN (Local Area Network)

A LAN is a type of network which covers small area i.e. within a room, building, or short distance by using cables or small wireless devices. It is controlled by a single organization. It uses private connection media. E.g.: network in a school, college or cyber cafe. The diameter is not more than a few kilometres. LAN offers bandwidth of 10-100 Mbps.

52.   MAN (Metropolitan Area Network)

A MAN is a type of network which covers an entire city. It is controlled by single or group of organization. It uses private or public connection media. E.g.: interconnection between different branches on same branch and ISP providing internet services. It offers a number of network services compatible with bandwidth from 128 kbps to 1 Gbps.

53.   WAN (Wide Area Network)

A WAN is a type of network which  connects two or more computers generally across a wide geographical area such as cities, districts, and countries. It is controlled by group of organization. It uses public connections media like telephone lines, satellite links or microwave system to connect several LANs and MANs.  E.g. internet. Data transmission in WAN is slower than LANs and WANs.

54.   Network topology (LAN topology)
The arrangement or connection pattern of computers or nodes and other devices of the network is called network topology. The three basic topologies are bus topology, ring topology and star topology

55.   Bus topology
The network topology in which computers and other devices are arranged in linear format which uses a common backbone or wire to connect all the computers and devices is called bus topology.

57.   Advantages of bus topology

a)      It is easy to set up computers and other devices in bus topology, because all the devices are connected through a single wire.

b)     It requires fewer cable media, so it is cheaper than other topologies.

c)      It is easy to add new node to the network.

d)     Failure of one workstation does not affect other computers on the network.

58.   Disadvantages of bus topology

a)     The whole network system collapses if the cable or backbone is damaged.

b)     The network slows down if additional computers are connected.

c)     The limited length of the cable in a network may restrict to connect the workstation or devices.

d)     It is difficult to find fault in this network topology.

59.   Ring topology

The network topology in which computers are connected in the shape of a circle without any end points is called ring topology. Each workstation contains two neighbours for communication or an input and output connections.

61.   Advantages of ring topology

i) It is easy it set up and configure.
ii) Each computer gets equal opportunity to access the network resources.
iii) It supports high data transmission rate.

iv) Performs better than a star topology under heavy network load.

62.   Disadvantages of ring topology

i)Failure of any cable or single computers may affect the entire network.
ii) It is difficult to detect the errors.
iii) Adding/removing the devices affect the entire network.

iv) Much slower than an Ethernet network under normal load.

63.   Star topology

The network topology in which all computers or other devices are connected through a central device through a central device called hub or switch is called star topology.

65.   Advantages of star topology

i) Easy to set up and configure.
ii) Failure of single computer or cable doesn’t affect the entire network.
iii) It is easy to find the fault.
iv) It is easy to extend to network by attaching new devices to the central devices.

66.   Disadvantages of star topology

i) It requires more cable in comparison of bus topology so it is more costly.
ii) Failure of central devices (hub or switch) break down the whole system.

67.   Network architecture (Models of Computer Network)

The arrangement of the computers on the network which is based on the computing model is called network architecture. Its types are

a)      Centralized computing network

b)     Client / Server Network

c)      Peer to Peer Network

68.   Centralized computing network

A centralized computing network is a network in which a central host computer performs data processing and storage on behalf of clients.

69.   Client/server network

Client/ server network is a type of network architecture that consists of at least one server and one or more clients or workstations, where users do their work. It provides central security administration and the network administrator is responsible for data security and other resources management of the network.

70.   Peer-to-peer network
Peer-to-Peer network is a group of computers, which function both as servers and workstations to share data, information and other resources of the network. It lacks centralized network administration, where the network administrator needs to manage security on each computer. It provides no reliable security and might put data in higher risks.