Computer Awareness Notes: Networking (Part 1)

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Computer Awareness Notes: Networking (Part 1)
Dear Aspirants,
Welcome to Mentor for Bank Exams. Here we are sharing the study material on Computer Networking, that will help you succeed in Bank, Insurance and oter competitive Exams.
Computer Networks means interconnected set of autonomous system that permit distributed processing to information.
Basic Elements of a Communication System
The following are the basic requirements for working of a communication system.
  • sender (source) which creates the message to be transmitted.
  • medium that carries the message.
  • receiver (sink) which receives the message.
In data communication four basic terms are frequently used.
  • Data: A collection of facts in raw forms that become information after processing.
  • Signals: Electric or electromagnetic encoding of data.
  • Signaling: Propagation of signals across a communication medium.
  • Transmission: Communication of data achieved by the processing of signals.
Characteristics of Networking:
  • Topology: The geometrical arrangement of the computers or nodes.
  • Protocols: How they communicate.
  • Medium: Through which medium.
Basic Types of Networks:
Mainly three types of network based on their coverage areas: LAN, MAN, and WAN.
  • LAN (Local Area Network): LAN is privately owned network within a single building or campus.A local area network is relatively smaller and privately owned network with the maximum span of 10 km.
  • MAN (Metropolitan Area Network): MAN is defined for less than 50 Km and provides regional connectivity within a campus or small geographical area. An example of MAN is cable television network in city. A MAN can be owned by a private company or it may be a service provided by a public company such as local telephone company. Telephone companies provide a popular MAN service called (SMDS) Switched Multi-megabit Data Services.
  • WAN (Wide Area Network): A wide Area Network (WAN) is a group Communication Technology ,provides no limit of distance. A wide area network or WAN spans a large geographical area often a country. The Internet is a system of linked networks that are world wide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, World Wide Web and newsgroups etc.
Network Topology
Network topology is the arrangement of the various elements of a computer or biological network. Essentially it is the topological structure of a network, and may be depicted physically or logically.
The common network topologies include the following sections
  • Bus Topology: Each node is directly connected to a common cable.
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  • Star Topology: Each node has a dedicated set of wires connecting it to a central network hub. Since, all traffic passes through' the hub, it becomes a central point for isolating network problems and gathering network statistics.
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  • Ring Topology: It is  logically closed loop. Data packets travel in a single direction around the ring from one network device to the next. Each network device acts as a repeater to keep the signal strong enough as it travels.
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  • Mesh Topology: Each system is connected to all other systems in the network.  
o   In bus topology at the first, the message will go through the bus then one user can communicate with other.
o   In star topology, first the message will go to the hub then that message will go to other user.
o   In ring topology, user can communicate as randomly.
o   In mesh topology, any user can directly communicate with other users.
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  • Tree Topology: In this type of network topology, in which a central root is connected to two or more nodes that are one level lower in hierarchy.
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Data Transmission Modes
There are three ways for transmitting data from one point to another:
  • Simplex: In simplex mode the communication can take place in one direction. The receiver receives the signal from the transmitting device. In this mode the flow of information is Uni.-directional.
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  • Half-duplex: In half-duplex mode the communication channel is used in both directions, but only in one direction at a time. Thus a half-duplex line can alternately send and receive data.
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  • Full-duplex: In full duplex the communication channel is used in both directions at the same time. Use of full-duplex line improves the efficiency as the line turn-around time required in half-duplex arrangement is eliminated. Example of this mode of transmission is the telephone line.
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Digital and Analog Transmission: 
Data is transmitted from one point to another point by means of electrical signals that may be in digital and analog form.
  • In analog signal the transmission power varies over a continuous range with respect to sound, light and radio waves. Analog signal is measured in Volts and its frequency in Hertz (Hz).
  • digital signal may assume only discrete set of values within a given range.
  • When digital data are to be sent over an analog form the digital signal must be converted to analog form. So the technique by which a digital signal is converted to analog form is known as modulation and the reverse process, that is the conversion of analog signal to its digital form, is known as demodulation. The device, which converts digital signal into analog, and the reverse, is known as modem.