Internet
Network is a group of devices
linked to one another. It helps to share the information and resources. It is
generally seen in computer application. Hence it is also termed as computer
network (CN).
Components of Computer Network
Computer Network
is the interlinked computers. It can be linked with cables. In this case there
are three components namely
1. Sender Component
2. Communication Channel
3. Receiver Component
4. Modem
If the computer network is linked
with telephone cable, another component namely modem is required. Modem
converts digital signals into analog and also analog to digital signals.
Communication Channel (Transmission Media)
Cables are
mainly used to connect two or more work stations and are working as
communication channel. The media may be either Guided or Unguided media.
1. Guided Media (Wired media)
Guided media
is otherwise called Bound media/Wired media. It uses a cabling system that
guides data signals. It can further be classified into
a. Twisted Pair Cable: It is a commonly used one. In a twisted pair
cable, wires are twisted together in pairs.
b. Co axial cable: It is
mainly used for TV Cable network. In this case there is a conductor in the
inner side of the cable and is covered by an insulator which is covered by a
wired mesh and finally an outer shield covered the entire cable.
c. Optical Fiber: It
consists of thin glass fibers that can carry information. This consists of a
very narrow thread of glass called cladding. It is protected with a plastic
coating called Jacket/Shealth.
2. Unguided Media/Wireless Media/Unbound Media
In this case,
the data communicated are not bound to a cable media and hence it is called
unbound media.
1. Long Distance Media:
a. Microwave: Without cables. It travels in a straight line
and free from material obstacles.
b. Radio wave: It was Short wave
(long distance), Medium Wave (Medium Distance), Frequency Modulation (Short
Distance)
c. Satellite: Received and
transmitted by earth stations through distant satellites. Satellites act as a
relay station for communication. Satellite receives signals from earth stations
and they are amplified and transmit the signals to other Earth Stations.
2. Short Distance Wireless Media
This is for transmitting information up to a few kilometers.
a. Infrared: It is a secure way
of transmission of data. It is commonly used in our daily life. Example: T.V remote, Auto door locks etc…
b. Laser: It is used in
point- to- point transmission typically between buildings. It may be adversely
affected by the changes in weather condition.
c. Bluetooth: It is a short-range wireless connection
device. It is commonly used in mobile phones, laptops, personal digital
assistants, notebooks etc.
d. Wi-Fi (Wireless
Fidelity): It is used to access internet without wired connection in a shorter
area. It requires: a. Broadband internet connection, b. Wireless router, and c.
A Desktop/Laptop with internet receiver.
e. Wi Max: It provides
broadband wireless access up to 50 kms. Wimax base station (same as mobile
towers) provides signals to the clients. It is a wireless Internet Service Provider
(ISP).
Types of network
LAN-Local Area Network
MAN-Metropolitan Area Network
WAN-Wider Area Network
Internet
Internet is the network of networks.
It helps to communicate all over the
world with less cost. It helps a variety of activities to individuals,
business, institutions, government etc... It has contributed much in various sectors
during the last decade. It grew tremendously during the latter half of 1990s.
History
At first it was introduced by the US military to establish a
communication system which cannot be destroyed by Russian attack.
In 1968, US defense department funded an agency called ARPA
(Advanced Research Project Agency) to connect university computer scientists
and engineers together through their computer lines.
This property named ARPANET allowed researchers to share
each other over a long distance. Later the National Science Foundation (NSF)
was increased the number of super computers and expanded the range of sites for
business, universities, government and military installations.
Features
Text 2.1 to 7
Uses
1. Business - E Business activities. Access lot of financial data.
2. E Governance – Video conferencing, issue certificates,
issue licenses etc..
3. E Mail – speed, less cost,
4. Education- online education, Study materials etc..
5. Research-
6. Published works-
7. Establish Research Groups-
8. Entertainments etc..
Open System Interconnections
In the
initial stages of development of internet there was no ‘network architecture’.
Companies were implemented crude and socially unacceptable software and
hardware communication solutions. There was no standard format at that time,
later the idea of layering really came into existence with the introduction of
International Standard called the Open Systems Interconnection (OSI) model by
the International Standards Organization (ISO) in 1982.
In 1978,
the ISO technical committee-97 (committee handle standardization in IT) started
to develop an architecture, which stood as a foundation stone for all the
developments which can now be seen in this field. They have worked hard a long
period of time, for this purpose.
Under this
OSI concept, the process of communication between two points in a telecom
network can be divided into seven layers. Each layer has its own special
functions. While sending a message from one end to another end, it will be
travelled through each layer one by one and finally it reaches in the hands of
the receiver (end user).
OSI Model
The OSI
Model uses ‘7 layers’ to organize the network architecture. Each module
provides specific functions for the next layer. A layer is a set of related
functions to be performed as a group. Two nearby layers communicate by some set
of programs called interface. For each layer there will be different set of
protocols. Each layer only cares about its interface to the next layer in the
network.
ISO Model
1. Physical Layer: The
physical layer transmits data through the networks communication channel. It
includes the physical elements (hardware) which are required to perform this
function. The layer includes the transmission lines which connects the computers
on the network. Data transmission methods, like central signals, and timing are
also parts of the physical layer. The Physical layer determines the mechanical
and electrical properties of the network.
2. Data Link Layer: The data
link layer transfers raw data between the physical layer and network layer. The
primary function of this layer is to detect and prevent data corruption (Errors)
within the physical layer. This layer minimizes the flow of information across
the boundaries between the physical layer and network layers.
The physical layer manages raw data as bits (0’s and 1’s).
This layer formats and transforms raw binary data into something meaningful to
the network layer. The data link layer also accepts information from the
network layer and translates the data into the current binary format for the
below physical layer.
3. Network Layer: The
network layer determines the route that the data follows to reach its destination
on the network. The network layer handles network traffic congestion and speed
of transmission. It is a delivery system within the network. It also helps to
send the data in right direction and receiving incoming transmissions at the
packet level. (routing of data)
4. The Transport layer:
After the network layer delivers data to the correct host address, the transport
layer delivers data to the correct application within the destination host. It
ensures the complete transfer of data or manages the end to end control of
traffic.
5. The Session Layer: This
layer handles details such as account name, passwords, user I Ds etc. For
example on all networks, one can login into it after entering the user I Ds,
password etc. This layer examines the given details are correct and then
permits to login if all are correct. A network professional says each such
login as sessions (Any number of times that an user can login. Each login will
be each session). This is the user’s interface to a network.
6. The Presentation layer (Syntax Layer): The presentation Layer
consolidates common functions that networks must repeatedly uses during network
communication. It defines how the network presents itself to the hardware and
software. It is a part of the operating system. It converts the incoming and
outgoing data from one presentation format to another format.
7. The Application Layer: The
application layer contains details about network-wide application. All programs
for network computer users are part of networks application layer. The
communication partners are identified in this layer. Quality of service is
identified and consider privacy and user authentication.
Internet Protocols
An internet protocol is a set of rules for exchanging
information in a network. It allows different kind of computers using different
operating system (Widows, Linux etc..) in the network. The commonly used protocols
are
1. Transmission Control
Protocol/Internet Protocol (TCP/IP)
2. File Transfer Protocol (FTP)
3. Hyper Text Transfer Protocol
(HTTP)
4. Telnet
5. Gopher
6. Wide Area Information
Service
1. Transmission Control Protocol/Internet Protocol (TCP/IP) –
Vinton Cerf of ‘Standard University was developed a
communication protocol called TCP and the addressing protocol IP. The major
internet application such as ‘World Wide Web’, Email, remote administration and
file transfer are based on TCP.TCP/IP is a collection of protocols that govern
the way of travel from one computer to another across networks. It provides a
communication service at an intermediate level between application program and
IP.
When an application program wants
to send a large mass of data across the internet using IP, can issue a single
requirement to TCP and it will handle the IP details. It will never divide the
data into small packets. IP usually divides the data into small pieces which
are called ‘packets’. A packet is a sequence of ‘octets’ which consists a
‘header’ and ‘body’.
The header - describes the
destination of the packet.
The routers - are generally used
to forward the data until it arrives its destination.
The body - contains the data
which is transmitted.
TCP guarantees the delivery of data
from one computer to another through internets without duplication or loss of
data. Under this protocol, the receiver sends an acknowledgement message as and
when he received the data. The next packet will be sent only after receiving
the acknowledgement from the receiver. If the sender is not getting the
acknowledgement within a stipulated time, it will re-transmit this packet.
2. File Transfer Protocol (FTP)
It is a set of rules while transferring files
from one computer to another in a network. It was originally developed to allow
the researchers to access the programs and data files one another. FTP allows
two types of access:
1. Protected access: In
this form the users are protected these files with user ID and passwords.
2. General Access: In this
case there is no restriction of access of files.
3. Hyper Text Transfer Protocol (HTTP)
HTTP is an internet standard or set
of rules that allows the exchange of information on the www. Hypertext is a
method of preparing and publishing text ideally suit to the computer and the
users can select and read/download text they want. For preparing Hypertext the
whole material is divided into small segments such as single pages of text. These
small segments are called ‘nodes’. Then Hyperlinks are embedded in the text.
When the user clicks on the hyperlink, the software will display the relevant
pages (node) . The process of navigating among the nodes linked in this manner
is called ‘browsing’. A collection of nodes that are interconnected by
hyperlinks is called a web. HTTP allows the user to go from one node to another
according to his requirements.
Steps
1. User opens a connection
2. Then the user sends a request to the server with the
help of a browser.
3. The server sends the resource as per the request of
the user.
4. User closes the connection.
4. Telnet
It is a protocol that enables the
user to connect to another computer linked to this network. It is otherwise
called remote login. Then user’s computer is the local computer and the
computer being connected is termed as the remote computer/host computer. The host
is executed the commands of the user’s computer.
Eg: Library catalogues are available through telnet without
giving any password.
5. Gopher
Gopher is a protocol linked to the
internet to search, retrieve and display documents from remote sites on the
internet. It is a mean based program that helps the user to find a file,
program, definition and other topics that the user specifies. Gopher allows the
user to browse without specify the details of hosts, directory and file name. The
browsing becomes easy with the help of menus.
6. Wide Area Information Service (WAIS)
WAIS is a internet search tool and
describes as a protocol for computer to retrieve information from computer. It
is a program that permits the users to search information worldwide based on
‘keywords’. WAIS has the capabilities of searching in more than one database
simultaneously.
Multimedia Information Tools
1. World Wide Web: WWW is one of the newest and most popular hyper
text based internet tools. It allows the users to access and display documents
and graphics stored on any server on the internet. Its capability is to provide
an enormous resource of information in a colorful and graphical manner.
Components of WWW: The main components
of WWW are:
a. Uniform Resource Locator (URL):
URL, is the location at which the file
is on the internet. It contains the name of protocol, a domain name (that
identifies the specific computer on the internet), pathname and file name that it
is saved in the server.
b. Hyper Text Markup Language (HTML):
HTML is the language at which documents are written for WWW. It allows the
users to produce web pages that includes text, graphics etc.
c. Hyper Text Transfer Protocol
(HTTP) :
Web System Architecture
The architecture of a web system consists of the following:
1. Web Server and Application
Server
2. Web Browser
3. Web Servers
4. Web Pages
5. Web sites
1. Web Server and Application
Server-It is a client server on the internet. It communicates on the
basis of HTTP.
2. Web Browser- Web Browser
is software that is used to request resources from the internet. It is an
application program, which helps the user to manipulate from one another on the
internet. It is a client program that adopts HTTP to make requests for
information from the server. The browser locates the resource by using the URL
from the Internet. An ideal browser should be able to present different types
of information in different form viz text, audio, video, images, graphics etc.
Most web browsers support Email and FTP.
The first web browser was come in
force during 1990 named ‘world wide web’, and then it changed to ‘Nexus’. The
first web browser with geographical user interface was came in force is known as
‘Mosaic’, in 1993. It then went into ‘Netscape navigator’. Another browser
developed by Microsoft is ’Internet explorer.’
Others: Google chrome, Mozilla Firefox, Safari, Linux, Opera
etc..
3. Web servers: Tim
Berners – Lee was developed a code for hyper text server programme and
made it available on the internet. A hypertext server is a computer that stores
files written in the HTTP and it supplies these files to users on request.
4. Web Pages: Web pages are
text file stored on the web server. The files contain instructions and
information. The instructions are in HTML and it tells the browser how to
format and present the information to the end user.
5. Web sites: A
website is a group of related web pages stored in one or more directories on a
web server. Web sites contain lot of information which is to be useful for the
clients/end users.
a. Institution-news, photo gallery
b. Government-different departments, police, online
application etc
c. Business- Online trading
d. Entertainment – Games etc..
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