networking Grade 10 note Engish

Data Communication

·         Transmitting data and information is called data communication.

·         Data transmission can be carried out between two or more computers or devices such

as printers.

·         Data transmission needs a connection between a sender and a receiver.

·         Creating such a connection is called networking.

Basic components required for data communication

The following are the basic components that are needed for data communication.

•     Sender / Source – the person or the object which sends data

•     Medium – medium used to transmit data (telephone wires / wireless)

•           Receiver/ destination – the person or the object which receives data

Data Transmission Modes

There are several modes of data transmission between sender and receiver.

1    Simplex Mode

·         Data is transmitted from the sender to the receiver only.

·        
Getting print outs,

examples :       watching television

listening to radio

2      Half- duplex Mode

·         Here, data is transmitted to one direction at a time.

·         This means after data is transmitted from sender / source to the receiver, the receiver can transmit data back to the sender / source.

Examples :      Browsing internet to get information

 walkie-talkie used by security forces

3      Full Duplex Mode

·         Data is transmitted to both sides at the same time

examples :Telephone conversation

Data Transmission Media

-          This is another important feature when creating connections among systems.

-          There are two types of data transmission medium.

1        Guided/Wired

2    Unguided/Wireless.  

Guided / Wired

If the physical medium used for data transmission is called guided or wired.

Example 1 - Twisted Pair

ü  Pairs of twisted copper wire are used for data transmission.

ü  There are two types.

1. Unshielded Twisted Pair (UTP)

-     The twisted copper wire pairs used for telephone connections.

-     These are very flexible

-     low-priced.

-     It is difficult to transmit data for a long distance through UTP wires. It is suitable for maximum of 100 meters.

2. Shielded Twisted Pair (STP)

-     STP is a better quality and secure data transmission medium.

-     It is expensive.

Example 2 - Coaxial Cable

ü  This consists of an electronic cable pair.

ü  The outer cable which is like a braided copper net produces electromagnetic field around the central cable.

ü  These two cables are separated by a plastic shield.

ü  These cables are expensive and used for TV antenna and CCTV.

Example 3 - Fiber Optics cable

ü  Fiber Optics cable consists of a pair of an cables.

ü  There is a plastic jacket to separate the two cables.

ü  Core is a glass tube and there is glass cladding around it.

ü  The data transmission is carried out by while reflecting light.

ü  These are used in modern telephone networks.

ü  The cable is relatively more expensive.

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Unguided/Wireless Media

Data is transmitted as signal through the air without using physical medium is

called unguided/wireless media.

Example 1 - Radio waves

ü  Data transmission is performed using radio waves.

ü  Wifi and Bluetooth are examples for radio waves based communication.

Example 2 - Microwaves

ü  Microwaves travel in a linear mode.

ü  Transmission center is positioned facing each other.

ü  The distance between centers are decided based on geographical factor of the area.

ü  Microwaves are used in Satellite communication to transmit data as transponders.

ü  Satellite centers, which are positioned in the sky above 36000 km, capture data transmitted as microwaves through satellite towers positioned in the Earth and then transmit the data back to the required tower.

ü  Using this method, data can be transmitted to any distance.

ü  This is also used in internet communication.

Example 3 - Infrared

ü  Infrared data transmission is used in TV remote controllers, wireless keyboards and mouse etc.

Computer network devices

There should be two or more computers to build a computer network. Connection devices used to connect computers with each other.

(i) Network Interface Card (NIC)

·         NIC has an RJ45 port and is built into the mother board in modern computers.

·         In the port NIC was a separate code to be plugged to the mother board.

(ii) Switch/Hub

·         Switch/Hub acts as the mediator to build a connection between two or more computers.

·         A guided/wired transmission media is used.

·         One end is connected to port in the computer and the other end is connected to the port in the Switch / Hub.

Differences between the switch and hub

v  The main difference is the data transmission speed.

v  Hub sends the transmitted data to all computers but switch sends data to the relevant computer only.

v   Here hub may create an unnecessary network data congestion.

v  In data transmission, hub uses half duplex mode and the switch uses full duplex mode.

(iii) Wireless Fidelity - Wi-Fi

·         Wi-Fi adapter has become the most popular media in computer networking.

·         This allows the users to build a computer network easily and internet connections for mobile phones and laptop computers using radio waves.

(iv) Router

·         Router is the device used to build a connection between two or more computer networks.

·         It is also called a Gateway.

·         This finds out the most suitable ports for data transmission in network communication.

(v) Modem

·         The modem is used to connect the computers of a computer network or a personal

computer at home to the internet.

·         The modem acts as a data translator.

·          Digital signals sent from the computer is translated to analog signals (MOdulation) and the analog signals send to the computer from the internet is translated to digital signals (DEModulation

·          There are different types of MODEMs. Those are

internal,

external

wireless modems.

·         Today’s routers have a modem inbuilt in the device.

(vi) Firewall

·         Firewall is a network security.

·         Instructions to control the data and instruction transmission between internet and computer network are built into the system.

·          A firewall operates as a secured barrier between internet and network.

·         Firewalls exist in both forms as software and hardware.

Client/Server network

Ø  A server computer responds to the client computer connected to the server.

Ø  A network operating system is installed to the server.

Ø  The one who requests data or information via internet or from an area network is called a client and the one who provides data and information is called the server.

Types of Computer Network

• Computer Networks

Computer networks can be classified according to the geographical distribution and user requirement

(i) Local Area Network (LAN)

ü  A LAN connects computers inside a room or several rooms in a building.

Examples : A computer network built in a school

             University

 A small scale business or an office

(ii) Metropolitan Area Network - (MAN)

ü  MAN is a combination of several Local Area Networks

ü   Which covers less than 16miles.

 Examples :  Banking networks

              Institutes and universities with branches.

(iii) Wide Area Network - WAN

ü  These networks cover a wide area.

ü  This can be within or outside a country.

Example : Internet

Network Topology

·         Network topology is the pattern of connection in designing computer network.

·         There are different types of network topologies.

i) Star Topology

-   This is a commonly used design and built by centralizing a switch/hub and computers.

Advantages

§  It is very easy to install a star network

§  It is relatively easy to identify and correct errors there.

     Disadvantages

§  Necessity to use a large number of wires to connect computers to one another

§  If the computer, hub or switch in the middle breaks down, the whole system will be broken.

ii) Bus Topology

-       All the connections are established through a main cable.

-      

 This cable is called the backbone

Advantages

§  This design is easy in networking

§  Few cables are required.

Disadvantages

§  A limited number of computers can be connected.

§   Any issue with the network affects all the computers in the network.

§   Closing the main wire at both ends using terminators is a difficult task.

ii) Ring Topology

-          Here, computers are positioned in a ring/bangle and connected through cables.

-           Data or information moves in a circular manner.

Advantages

§  Few cables are required.

Disadvantages

§  The breakdown of one computer or cable can lead to the breakdown of the entire network.

iv) Tree Topology

-          This has characteristics of both bus and star topologies.

-          In this design several star topologies are connected to a bus backbone cable.

Advantages

§  Ability to control each network individually.

Disadvantages

§    building and controlling this network can be  a bit complicating task

§  The function of the network depends on main wire.

v) Mesh Topology

-     All the computers in the network are connected  with each other.

-          Mesh networking can be found on internet.

Advantages

§  A breakdown of one computer does not affect the connections in the network.

Disadvantages

§  This is a complex connection pattern

§  It is costly

§   Difficult to control.

Benefits of Networking’s

1        Data and information can be shared between computers.

 Data and information in a server, can be accessed by clients connected to the server.

2        Less storage space

The same data is not stored in several computers

3        Ability to share resources

The devices like printer, scanner and modem can be connected to network and shared by multiple users.

4        Ability to control central software

Software can be installed on a server computer and shared by many users through client computers.

5    Ability to connect at anywhere and at any time

By connecting to internet, a user can access his / her documents and data at anywhere and anytime (24×365).

6        Security

Only the authorized clients can access the server computer.

7    Electronic mail

E-mail is a convenient method of sharing information between computers.

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Disadvantages of Networking

1    Possible security issues

Server can be accessed through any computer connected to the network. Hence it is difficult to secure it from the hackers (people who try to gain access to data without permission).

2    Breakdown of network

In some topologies, breakdown of a computer or a cable can affect the function of the other computers of the network.

3    Virus

If one of the computes in the network gets a virus attack, this can spread to other computers as well.

4    Computer break downs

Due to defects or breakdown of the server, the other the clients can be affected.

5    Training requirements

Well trained person need in network administration.

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