Networking and Telecommunication:
Introduction:
Communication:
Communication is simply the act of transferring
information from
one place to another.
Types of Communication:
i) Telecommunication:
Telecommunication is the transmission of messages, over significant distance,
for the purpose of communication.
ii) Data communication: The process
of transferring data or information between computers is called data
communication.
Data Transmission Modes
There are three modes for transmitting data from one device to another. They are:
i)
Simplex ii) Half Duplex iii) Full Duplex
i) Simplex: A simplex communication
system can transmit data in one direction only. Devices connected to such a
circuit are either send-only or receive-only data. Example : Television, Radio
etc.
ii) Half Duplex: A half duplex
communication system can transmit data in both directions, but in only one
direction at a time. Example: Walkie-Talkie.
iii) Full-Duplex: A full duplex communication
system can transmit data in both directions simultaneously. It is a faster mode
for transmitting data because no time wastes in switching directions. Example:
Telephone, mobile etc.
Computer Network
A
computer network is a logical or physical interconnection between two or more
computers such that they could communicate with each other. It is used to provide users with the access
to share resources such as data files, application software and hardware.
OR
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.
OR
Computer
network is a group of interconnected computers through transmission media in
order to communicate and share resources like hardware, data and software.
Advantages of computer network:
i) It allows the sharing of resources such
as disk storage, printers, image scanners, modem and central servers.
ii) It allows sharing of information held on
disk accessible by all users.
iii)We can easily send and receive messages by
networking .
iv) It allows the connection of different
types of computer which can communicate with each other.
Disadvantages of computer network:
i) Possible loss of privacy through hacking.
ii)
Computer virus spreading each mostly through the network.
iii)
Computers on the network have to depend on the server computer for resources.
iv) Data
and information may be stolen by computer hacker if the security of network is
not reliable.
Band Width:
Band
width is the amount of data that can be transmitted through communication
channels in a fixed time period.
The
Bandwidth of digital signal is measured in bits per second (bps) whereas the
bandwidth of analog signal is measured in cycle per second or Hertz.
Communication Media/Transmission Media:
A
communication medium or transmission channel is the electronic path through
which data information and files transfer from one computer to other computers
in the form of electromagnetic wave.
Types of Communication Channel:
There
are two main types of communication channels. They are:
i) Guided Transmission media / Wired Media
ii)
Unguided Transmission media / Wireless Media
Guided Transmission Media:
It is the transmission media in which signals are confined to a specific
path using wire or cable
Basically
three types of guided are used in computer networking they are:
(i)
Twisted Pair Cable
Twisted pair cable consists of two
insulated strands of copper wire twisted around each other. The reason for
twisting is to reduce electrical interference. It is the cheapest and easily
available wire, which can carry data/information to a large distance without
data loss. Twisted pair can be categorized into two types – Shielded Twisted
Pair (STP) and Unshielded Twisted Pair (UTP).
a) Unshielded Twisted Pair :- UTP cable consists of a number of twisted pairs of wires with a simple plastic casing. UTP is commonly used in telephone systems.
(iii) Fiber optic Cable
Fiber-optic
cable is made of a light-conducting glass or plastic core surrounded by more
glass, called cladding, and a tough outer sheath. A fire-optic cable consists
of a bundle of glass threads, each of which is capable of transmitting messages
modulated onto light waves.
Unguided Transmission Media:
Unguided transmission media relates to data transmission through the air and is commonly referred to as wireless.
Unguided transmission media relates to data transmission through the air and is commonly referred to as wireless.
(i) Microwave:
In the
microwave system, a high frequency radio signals are used to transfer data
through the space. These signals can travel only on the straightway and they
cannot bend. The hills and mountains can block the signals. The transmitter and
receiver of a microwave system should be in a line of sight so, they are
mounted on very high towers.
(ii)Communication Satellite:
A
communication satellite is an artificial satellite stationed in space for the
purpose of telecommunications. It is placed in outer space and moves its own
orbit. The satellite is visible from any point of the earth so the sender and
receiver can easily communicate with each other by using antenna aiming the
satellite. Placing the satellite along the earth’s orbit takes very high cost.
Network Connecting Devices
(a)
Network Adapter:
(b) Hub:
Hubs are centrally connectivity devices that connect
computers in a star topology. Hub contains multiple ports for connecting to
network components. It amplifies (/increase) the signals and sends them to all
connected devices. Use of hub has become very common in most of the computer
networking as it cost lower and easier to install.
(c)
Switch:
Switches are similar to bridge but offer a more
direct network connection between the source and destination computers. The
main difference between bridge and switch is the way that filtering happens.
With a switc0h, filtering and performance better than bridge.
(d)
Bridge:
A bridge is a device that passes data packets
between multiple network segments that use the same communication protocol. A
bridge passes one signal at a time. It filters the data or inspects incoming
signals and decides whether to forward the signals or discard them.
(e)
Router:
Router is a device that acts like a bridge or
switch but provides more functionality. It uses addresses for filtering and
forwarding the data. Router enable all user in a network to share a single
connection to the Internet or a WAN.
(f)
Gateway:
A gateway is a device that enables communication
between different network architecture. A gateway takes the data from one
network and repackages it, so that each network can understand the other
network’s data.
(g)
Repeater:
A repeater is a physical layer device used to
interconnect the media segments of an extended network. It amplifies the
incoming signals, creates a new copy of it and transmits the signals on the network.
A repeater essentially enables a series of cable segment to be treated as a
single cable.
(h)
Modem:
A modem
is a communication device that enables a computer to transmit information over
a standard telephone line. A modem is required when connecting to the Internet
using telephone line. It is an essential link between the computer running
browser and dial up service providers. A modem is needed to convert digital
signal to analog signal and vice versa. During the modulation phase, it is used
to translate digital signals of a computer to analog signals, which are then
transmit across the standard telephone line. The reverse takes place during its
demodulation phase, as the MODEM receives analog signals from a phone line and
converts them into digital signals for the computer.
Network Architecture:
The
Network Architecture can be broadly classified into two types:
(i)
Peer to Peer Network
In a
peer to peer network, there are no central authority server, no network
administration who handles security, user accounts, passwords, management and
so on. It can take both a client and server role. Each workstation has equal
responsibilities. There is no centralized control over shared resources.
Advantages of Peer to Peer Network
(a) It is
easy to set up.
(b) In this
network, users at each computer can determine the resources to be shared among
other computers.
(c) Any
required software can be installed on individual computers, so they don’t have
to depend on the server.
Disadvantages of Peer to Peer Network
(a) It tends
to slowdown with heavy use.
(b) It is
suitable for only small geographical area.
(c) The
network expansion is limited and cannot be expanded as we wish.
(ii)
Client Server Network
The
client server network consist at least one server and one or more clients or
workstations, where user does their work. The server is the main computer which
gives services to the workstation. It stores and protects the user files and
security of entire network.
Advantages of Client-server Network
(a) The
network can be expanded to any size as we wish.
(b) It is
administrated centrally so unauthorized user cannot access network.
(c) Any
required software can be installed in the server so it reduces the cost and
time for installation on individual computer.
(d) It
provides high level of security.
Disadvantages of Client-server Network
(a) It is
difficult to setup and trained network administrators are required to handle
the system.
(b) It is
expansive as compared to peer to peer network.
Differences between client-server network
and Peer-To-Peer network:
Client-Server Network
|
Peer-To-Peer Network
|
It is a
network model where there is at least one server and one or more client
computers.
|
It is a
network architecture where there is no server computer. All the computers on
this network are workstations.
|
Cabling
Scheme is difficult and network administrator is required
|
Cabling
scheme is simple.
|
In this
network architecture, all the rights are with the server computer.
|
In this
network architecture, each computer has equal responsibilities.
|
In this
network, the server computer controls and provides resources to client
computers.
|
In this
network, there is no computer that controls other workstations. All computers
can provide resources to other workstations.
|
It
provides high level of security.
|
It has
low level of security.
|
Types of Computer Network:
The
Different types of computer network are:
(i)
Local Area Network (LAN)
Local
Area Network is a network of computers located relatively near to each other
connected in such a way to enable communication by means of high-speed cable or
wireless link. The main purpose of LAN is to share resources like high-speed
laser printer and to facilitate communication among computers.
Features of LAN:
§ It is
normally owned by single organization.
§ It
offers the higher bandwidth for transferring data. The data can transmit at the
rate of 10 to 100 mbps.
§ It is
unaffected by environment factors.
(ii) Metropolitan Area Network (MAN)
The
interconnection of computers through phone line, co-axial cable or wireless
communication system to share data and information within a large geographical
area is called MAN.
Features of MAN:
§ It may
be owned by single or multiple organizations.
§ It uses
cable or wireless connection.
§ It uses
private or public connection mediums.
(iii)
Wide Area Network (WAN)
The
network that connects two or more LANs together generally across a wide
geographical area is called WAN. It is the largest network in the world. The
connection mediums used in WAN are telephone lines, microwaves and satellite
links. The Internet is an example of a WAN.
Features of WAN:
§ It is
not restricted to a geographical location. It covers whole world.
§ It uses
satellite links or microwave system to connect several LANs and WANs.
§ It is
owned by multiple organizations.
Network Topology (LAN Topology)
The
cabling structure or geographical arrangement of computers in Local Area is
known as Network Topology or LAN Topology. There are several types of topology
used in networking some of them are :
Bus Topology
In bus
topology all workstations are connected to a single communication cable called
bus or common back bone. Computer and other devices are arranged in linear
format. Data are transmitted on the network through the back bone using the
computer destination address.
Advantages of Bus Topology:
(a) It is
simple, reliable and easy to use.
(b) It is
easy to add more stations without disrupting the network.
Disadvantages of Bus Topology:
(a) The
whole network goes down if the main cable fails at any point.
(b) Cable
faults is difficult to identify and isolate.
(ii)
Ring Topology
In a
ring topology all the nodes are connected to each-other in such a way that they
make a closed loop. Each workstation is connected to two other components on
either side and it communicates with these two adjacent neighbours. Data travel
around the network, in one direction that is clockwise or anti-clockwise.
Advantages of Ring Topology
(a) Very
high transmission rates of data are possible.
(b) It has
short cable connection, which increases in network reliability.
Disadvantages of Ring Topology
(a) If a
single computer fails, at least a portion of the network will not work.
(b) It is
difficult to change network structure.
(iii)
Star Topology
In star
topology all computer or network devices are connected through a central
device. The common devices used for the central connection are hub and switch.
Advantages of Star Topology
(a) It is
easy to add or remove computers from this topology.
(b) If one
cable fails, the other workstations are not affected.
Disadvantages of Star Topology
(a) If the
central hub fails, the whole network goes down.
(b) It may
be costly to install since long cable length is required.
Communication Protocol
The term
communication protocol refers to the set of rules and procedures that govern
the transmission of message over a physical networking medium.
Some
common protocols are
Protocol
|
Full Form
|
Use
|
TCP / IP
|
Transmission
Control Protocol / Internet Protocol
|
Deal with
slicing the data into small sized packets and routing them along the
communication channel
|
SMTP
|
Simple
Mail Transfer Protocol
|
Sending
e-mail messages between servers
|
FTP
|
File
Transfer Protocol
|
File
Transfer
|
HTTP
|
HyperText
Transfer Protocol
|
Fetching
pages on the WWW
|
POP
|
Post
Office Protocol
|
Collect
incoming mails and store to mailbox.
|
IPX/SPX
|
Internet
Packet Exchange / Sequential Packet Exchange
|
|
NetBEUI
|
NetBIOS
Extended User Interface
|
|
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