Computer Network and its adv. and disadv.

Communication
Communication means sending and receiving information between two or more persons.

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

Data communication

A data communication system is the collection of hardware, software and other devices that allows to exchange data, information and voice between two or more devices through a wire or radio waves.

The components of data communication are data, sender, medium, receiver and protocol.

Any two examples of data communication are e-mail and chat

Data transmission mode

Data transmission mode is the way of transmitting data from one device to another.

The modes of data transmission are simplex mode, half duplex mode, full duplex mode

Simplex mode

The mode of transmission where transmission can take place in only one direction is called simplex mode.

Examples of simplex mode are TV Broadcasting, Radio transmission and Newspaper.

Half-duplex mode

The mode of transmission where data can be transmitted to both directions, but only to one direction at a time is called half-duplex mode.

Examples of half-duplex mode are Wireless handset and Walky-talky

Full-duplex mode

The mode of transmission which allows simultaneous transmission of data to both directions is called full-duplex mode.
Example of full-duplex mode is telephone

Bandwidth
Bandwidth can be defined as the maximum volume of data that can be transmitted through the communication medium.

We can measure bandwidth in digital devices by bits per second and in analogue devices by cycles per second or Hertz (Hz).

Communication or Transmission medium
Transmission medium is a channel through which data or signals can be transmitted from one point to another.

Different types of cables or waves are used to transmit data.

There are two types of transmission medium. They are guided medium and unguided medium

The differences between bounded media and unbounded media

Bounded media	Unbounded media
Bounded media are the physical links through which signals are confined to narrow paths.	Unbounded media are wireless media that do not use any physical connections between the two communicating devices.
It travels in a contained conductor.	It uses a transmission carrier to send data signals through the air instead of cables.
e.g.: coaxial cable, twisted pair cable and fiber optics cable.	e.g.: radio waves, micro waves and infrared waves.

Twisted pair cable

A pair of wires which are made of copper and are twisted with each other is known as twisted pair cable.

A set of four pairs of twisted wires are bundled to form cable.

Wires are twisted with each other so as to reduce the interference.

The types of twisted pair cable are Unshielded Twisted Pair Cable and Twisted Pair Cable

The differences between shielded twisted pair and unshielded twisted pair are:

Shielded twisted pair	Unshielded twisted pair
It is made up of twisted pair wires with additional shielded and drain wires to drain away noioses.	It is made up of twisted pair wires without additional shielded and drain wires.
It covers shorter distance and has better noise rejection capacity.	It covers maximum distance of 100 metres
It is costlier than UTP cables	It is cheaper than STP cables
D-shell connectors are used with shielded twisted pair.	Cat 5 cable with RJ-45 connector is commonly used with unshielded twisted pair.

Co-axial cable

A cable which is used with single ended single reference where the central conductor carries the data signal is called co-axial cable.

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.

Fiber optics 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.          

The advantages of radio wave transmission.

It offers mobility.

It offers ease of communication over different terrain.

It offers freedom from land acquisition rights that are required for laying repairing cables.

It provides cheaper than digging trenches for laying cables and maintaining repeaters and cables if cables get broken by a variety of causes.

The advantages and disadvantages of microwave transmission

Advantages

They have the ability to communicate over oceans.

It offers ease of communication over difficult terrain.

Disadvantages

It is an insecure communication.

It is susceptible to weather effects like rain, thunder storms etc.

The differences between radio wave and microwave are as follows:

Radio wave	Microwave
It is a form of wireless communications in which signals are sent through radio frequency waves.	It is a form of wireless communication in which data signals are sent through pulses of electromagnetic energy.
It provides low bandwidth for data communication.	It provides higher bandwidth for data communication.
It does not require line of sight for data transmission	It requires line of sight for data transmission.

Infrared transmission

Infrared transmissions are just below visible transmission light which allows high speed data transmission.

Computer Network

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

Advantages of  Computer Network

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

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

Computers in a network system share different software packages.

Information can be exchanged rapidly in computer network.

Disadvantages of  Computer Network

The sharing of information may leak the privacy of other clients.
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.
Computers on the network have to depend on the server computer for the recourses.
Data and information may be stolen by computer hackers if the security of network is not reliable.

Computer Network reduces expenses of an office. Justify this statement with suitable examples.

Computer network reduces expenses of an office. It is because in offices, there may be more than one computer and they may need to produce hardcopy outputs, scan documents and send faxes. But it is impractical for each individual computer of an office to have expensive computer hardware like laser printer, scanner, fax machine etc. So, to reduce the expenses, computers are kept on the network.

Computer network makes the world a small place. Justify this statement with strong reasons.

Computer network makes the world a small place. Because of computer network, it is easy for the average person using his/her PC to make reservation for airplanes, trains, hotels, check bank balance in account and transfer money from banks and so on anywhere in the world with instant confirmation. The server computer on the network acts as the storehouse and distributor for the data, information and programs.

Mention the reasons of keeping computers on the network.

The reasons of keeping computers on the network are

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

To share data, information and programs.

To communicate with each other.

List the main goals of computer network.

The main goals of computer network are

Resource sharing

Reliability

Communication medium

Access to remote database

Easy data transfer

Hardware Components

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

The hardware components of a network are:

Server

Workstation

Connectors

Cables

NIC

Hub

Repeater

Bridge

Switch

Router

Gateway

MODEM

Server

Server is the main computer that provides services, data and other resources to other computers in the network environment.

Different types of servers are file server, print server, application server etc.

The differences between Dedicated Server and Non-dedicated Server are:

Dedicated Server	Non-dedicated Server
A server computer that controls and provides services hardware and software resources to other computers on the network is called dedicated server.	A computer on a network that allows a user to use it as a workstation and provides facilities of sharing its resources to other computers on the network is called non-dedicated server.
It controls and provides resources to the client computers on the network but does not allow a user to use it as a workstation.	It controls and provides resources to the other computers on the network as well as allows a user to use it as a workstation.

WorkstationWorkstation is a computer, where the client works which requests services, data and other resources available on the server.

The differences between Server and Workstations are:

Server	Workstation
A server is the main computer that provides services, data and other resource to the other computers in the network environment.	A workstation is a computer where the client works that requests services, data and other resources available on the server.
The server computer uses networking operating software like Novell Netware Server, Windows NT Server, Linux, UNIX, etc.	The client computer uses operating system like Windows 98, Windows XP,  Red Hat Linux Workstation,etc.

NodeEach computer or device in a network is called node.

CablesCables are commonly used mediums for physical channel for transmitting data across network.

Examples of cables are coaxial, twisted pair and fiber optic cable.

NIC

A Network Interface Card (NIC) is a hardware device that acts as an interface through which a computer is connected to a network.

The function of NIC is to convert data into electronic signals and transfer them through cables and vice-versa.

ConnectorsConnectors acts as an interface between the NIC of the computer and the cable that passes data from one computer to another.

Examples of connectors are BNC used with coaxial cable, RJ 45 used with UTP cable, ST used with fiber optic cable etc.

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.

Hub is mostly used in physical star topology.

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

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.

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.

The differences between bridge and router are:

Bridge	Router
A bridge is a device that connects two or more similar types of network.	A router is an intelligence device that connects two different networks.
It inspects incoming signals and decides whether to forward the signals or discard them.	It filters and forwards information among different networks.

Switch

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

The differences between hub and switch are:

Hub	Switch
A hub is a device with multiple points or ports which acts as a central point from where different computers and other devices are connected.	A switch is a networking device that has multiple connecting ports which is often used interchangeably with the bridge.
It cannot determine source and destination device of the data. Hub broadcasts the electric signals	It can determine source and destination device of data.

Gateway

Gateway is an interconnecting device that connects two dissimilar networks.

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.

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.

Demodulation

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

How does MODEM help in transmission of data in computer network?

MODEM helps in transmission of data in computer network by transferring the data of one computer to another using a telephone line. It converts the discrete stream of digital ON-OFF electrical pulses used by computers into the continuously variable analog wave patterns over existing telephone lines and vice versa.

Mention the importance of MODEM in computer network.

The importance of MODEM in computer network is that it enables a computer to transmit data and files over a telephone line. It can convert digital signals into analog signals and vice-versa.

The software components of computer network are:

Network operating system

Device drivers

Network protocol

Network Operating System

The group of programs that manages the resources on the network is called the network operating system.

Examples of network operating system are Novell Netware, Microsoft Windows NT, Linux, Unix etc.

ProtocolsProtocols are set of rules that the computers on the network must follow to communicate and to exchange data with each other.

Some examples of protocols are TCP/IP, ARP, HTTP, FTP etc.

Device driver

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

Example NIC driver controls the functionality of NIC

The different types of computer networks on the basis of range are LAN, MAN and WAN

Local Area Network (LAN)

A LAN is a network of computers that are relatively near with each other and are connected in a way that enables them to communicate by using cables and a small wireless devices.

Metropolitan Area Network (MAN)

A MAN is a network of computer is computers which are spread over a metropolitan area such as within a city.

Wide Area Network (WAN)

A WAN is a network system of connecting two or more computers generally across a wide geographical area such as cities, districts, and countries.

The differences between LAN and MAN are:

LAN	MAN
It is a network which covers small area i.e. within a room, building, or short distance.	It is a network which covers an entire city or a big area.
It is controlled by a single organization.	It is controlled by single or group of organization.
It uses private connection media.	It uses private or public connection media.
E.g.: network in a school, college or cyber café.	E.g.: interconnection between different branches of banks of same branch

The differences between MAN and WAN are:

MAN	WAN
It is a network which covers an entire city.	It is a network that covers large area or whole world.
It is controlled by single or group of organization.	It is controlled by group of organization.
It uses private or public connection media.	It uses public connection media.
E.g.: interconnection between different branches on same branch	Eg. Internet

The differences between LAN and WAN are:

LAN	WAN
The network of computers that exists within a single room or within a building is called LAN.	The network system of connecting two or more computers generally across the wide geographical area is called WAN.
It is controlled by a single organization. So, it uses private connection medium.	It is controlled by multiple organizations. So, it uses public connection medium.

Features of Local Area NetworkThe diameter is not more than a few kilometres.
LAN offers bandwidth of 10-100 Mbps.
It is controlled by single organization.

Features of Metropolitan Area NetworkIt covers a larger geographical area than LAN and connects larger number of computer.
It is owned by single or multiple organizations.
It uses cable or wireless communication media to connect computers.
It uses private or public connection mediums.

Features of Wide Area NetworkIt is not restricted to a geographical location. It covers whole world.
It uses public connection mediums such as telephone lines and wireless technology.
It is owned by multiple organizations.

A WAN is composed of LANs and MANs. Justify this statement.

A WAN is composed of LANs and MANs. A WAN can have many groups of LANs and MANs. There may be large number of LANs in a MAN. And the branches of WAN may have many LANs and the computers on one branch may be connected with computers of other branches through telephone lines and unbounded media.

WANs are different from  LANs. Explain.

WANs are different from LANs because WAN covers a larger geographical area whereas LAN covers very small area. WAN is owned by multiple organizations whereas LAN is owned by single organization. WAN uses public connections mediums such as telephone lines, wireless technology etc.

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

Centralized computing network

Client / Server Network

Peer to Peer Network

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.

Client/Server networkClient/ 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.

Peer-to-Peer networkPeer-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.

The differences between Client Server and Peer-to-Peer model are:

Client Server Network	Peer-to-Peer Network
The client server network consists at least one server and one or more clients or workstations, where users do their work.	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 provides central security administration and the network administrator is responsible for data security and other resources management 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.

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

Star Topology

Bus topologyThe 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.

The advantages of bus topology are:

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

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

It is easy to add new node to the network.

The disadvantages of disadvantages are:

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

The network slows down if additional computers are connected.

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

Ring topology (Loop topology)

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

Advantages of ring topology are:

It is easy to set up and reconfigure.

Each computer gets equal opportunity to access the network resources.

Disadvantages of ring topology are:

Failure of any cable or single computer may affect the entire network.

It is difficult to detect the errors in this type of network.

Adding or removing the devices affects the entire network.

Star topology

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

The advantages of star topology are :It is easy to detect errors in star topology.

It is set up and configure.

Failure of a single computer or cable does not affect the entire network.

The disadvantages of star topology are: It requires more cable in comparison of bus topology so it is costlier.
Failure of central devices (hub or switch) break down the whole system.