COMPUTER NETWORK

COMPUTER NETWORK
• A computer network is a collection of interconnected computers and other
devices to share data and other resources (hardware and software resources).
• Two computers or devices are said to be interconnected if they are capable of
• Two computers or devices are said to be interconnected if they are capable of
sharing and exchanging information with each other by following a protocol (set
of rules).

COMPUTER NETWORK

ADVANTAGE OF COMPUTER NETWORK
Networks have several advantages
•Resource Sharing: The primary use of a network is to share among users
programs/applications, data and peripheral devices connected to the
network, irrespective of their physical location.
network, irrespective of their physical location.
•Improved Communication : A computer network enables fast, reliable and
secure communication between users. It saves time and offers easy
communication methods
•Reduced Cost : Sharing resources also reduces communication cost.

ADVANTAGE OF COMPUTER NETWORK
•Reliability of Data: Reliability means backing up of data, i.e., data can be
copied and stored on multiple computers.
•Central Storage of Data :Files can be stored on a central node (the file
•Central Storage of Data :Files can be stored on a central node (the file
server) that can be shared and made available to each and every user in an
organization. With centralized processing, data is stored and retrieved from a
single central location. Thus, there is no duplication of data and almost no data
redundancy.

EVOLUTION OF NETWORK
•ARPANET (Advanced Research Project Agency Network): ARPANET,
which was jointly designed and named by the Advanced Research Projects Agency
(ARPA) and US Department of Defence (DoD), was the first network and came
into existence in 1969.
into existence in 1969.
•NSFNET (National Science Federation Network): In the mid-80’s,
another federal agency, NSFNET (National Science Federation Network), created
a new network which was more capable than ARPANET. Its main aim was to use
network only for academic research and not for any private business activity.

EVOLUTION OF NETWORK
•Internet : The computers are connected through World Wide Web that
comprises a large network and shares a common communication protocol
(Transmission Control Protocol-Internet Protocol, TCP/IP).
Network of networks makes the internet.
•Interspace : Interspace is a software that allows multiple users in a client-server
environment to communicate with each other by sending and receiving data of
various types such as data files, video, audio and textual data in a 3-D
environment.

EVOLUTION OF NETWORK
ARPANET and NSFNET to make a more capable and broad network—the
Internet. It is the internet that links two or more networks to make a large network
for sharing of information and messages.
ARPANET + NSFNET + PRIVATE NETWORKS = INTERNET
ARPANET + NSFNET + PRIVATE NETWORKS = INTERNET

Elementary Terminology of Networks
•Nodes (Workstations): The term node refers to computers that are attached to a network
and are seeking to share resources.
• Server: A computer that facilitates the sharing of data, software and hardware resources on
the network.
Network Interface Unit (NIU) (MAC Address): A network interface unit is an
•Network Interface Unit (NIU) (MAC Address): A network interface unit is an
interpreter that helps in establishing communication between the server and the client.
• IP Address: Every machine on a TCP bar/IP Network has a unique identifying number
called an IP Address.
• Domain Name: It is a way to identify and locate the computers connected to the internet.
It must be unique.

Types Of Networks
Based on the geographical area covered and data transfer rate, computer networks
are broadly categorised as:
•PAN ( Personal Area Network)
•LAN (Local Area Network)
•MAN (Metropolitan Area Network)
•WAN (Wide Area Network)

PAN ( Personal Area Network)
PANs are small networks used to establish communication between a computer and
other handheld devices in the proximity of up to 10 metres. A personal area network
may be wired or wireless.
The network that belongs to a single
person or user is known as PAN.

Local Area Network (LAN)
LAN is a privately owned computer network covering a small geographical area (small
physical area), like a home, office or a building such as a school. It can cover an area
spread over a few metres to a radius of a few kilometres (5 km to 10 km).
A LAN can be set up using wired media (UTP cables, coaxial cables, etc.) or wireless
A LAN can be set up using wired media (UTP cables, coaxial cables, etc.) or wireless
media (Infrared, Radio waves). If a LAN is set up using unguided media, it is known as
WLAN (wireless LAN). The key purpose of a LAN is to share resources. LAN users can
share data, programs, printer, disk ,modem, etc.
Data transfer rate speed over a Local Area Network can vary from 10 mbps to 1 gbps.

Local Area Network (LAN)

Metropolitan Area Network (MAN)
Metropolitan Area Network (MAN) is an extended form of LAN which covers
a larger geographical area like a city or a town. Data transfer rate in MAN also
ranges in Mbps, but it is considerably less as compared to LAN. Cable TV network
or cable based broadband internet services are examples of MAN. This kind of
or cable based broadband internet services are examples of MAN. This kind of
network can be extended up to 30-40 km. Sometimes, many LANs are connected
together to form MAN.

Metropolitan Area Network (MAN)

Wide Area Network (WAN)
WAN is a telecommunication network. This type of network spreads over a large
geographical area across countries and continents. WANs are generally used to
interconnect several other types of networks such as LANs, MANs, etc. They
facilitate fast and efficient exchange of information at a high speed and low cost. A
facilitate fast and efficient exchange of information at a high speed and low cost. A
WAN uses common carriers like satellite systems, telephone lines, etc.
All types of communication media (guided and unguided) are used to set up a WAN.
The best known example of a WAN is the internet.
A WAN interconnects all the computers across the world.

Wide Area Network (WAN)

Characteristics of PANs, LANs, MANs and WANs

Components of Data Communication
A network comprises several components along with their functionalities that
contribute to its smooth functioning. To form a network, a lot of hardware devices
are required which are described as follows

Components of Data Communication
Sender: A sender is a computer or any such device which is capable of sending
data over a network. It can be a computer, mobile phone, smart watch, walkie-
talkie, video recording device, etc.
Receiver: A receiver is a computer or any such device which is capable of
receiving data from the network. It can be any computer, printer, laptop, mobile
phone, television, etc. In computer communication, the sender and receiver are
known as nodes in a network.

Components of Data Communication
Message: It is the data or information that needs to be exchanged between the
sender and the receiver. Messages can be in the form of text, number, image, audio,
video, multimedia, etc.
Communication media: It is the path through which the message travels
Communication media: It is the path through which the message travels
between source and destination. It is also called medium or link which is either
wired or wireless
Protocols: It is a set of rules that need to be followed by the communicating
parties in order to have successful and reliable data communication. You have
already come across protocols such as Ethernet and HTTP.

Network Switching
The main goal of networking is the reliable exchange of data or information among
several interconnected nodes. For the delivery of data with accuracy, various types
of switching techniques are used, namely:
• Circuit Switching
• Packet Switching
• Message Switching

Circuit Switching
This provides end-to-end connection between two computers. Circuit switching is established
usually in a telephone network where one person is making a call and another is receiving a
call. In telephone system, the communication must be established between the two
participants, i.e., the sender and the receiver. The circuit is established between these two
participants before the transfer of data takes place.
participants before the transfer of data takes place.

Circuit Switching
In this technique, the entire link remains dedicated and no other user can use it even if
the path remains idle. The following actions take place during circuit switching:
1. A request signal is sent by the sender to set up the connection with the receiver. It
establishes a physical connection between the two participants.
establishes a physical connection between the two participants.
2. All intermediate nodes are identified. These nodes are also called switching nodes.
3. If the destination node is available, it sends back the acknowledgement of receiving
a signal. Hence, data transmission begins.
4. When the data transmission is complete, the call can be terminated.

Packet Switching
In packet switching, each information or message to be transmitted between sender and
receiver is broken down into smaller pieces, called packets. These packets are then
transmitted independently through the network. Different packets of the same message may
take different routes depending on availability.
Each packet has two parts — a header containing the address of the destination and other
Each packet has two parts — a header containing the address of the destination and other
information, and the main message part. When all the packets reach the destination, they are
reassembled and the complete message is received by the receiver.
Each packet is of a fixed size, usually 128 bytes or 512 bytes. Packet switching is similar to
post office operation. Each packet has a source address as well as destination address (IP
address) for being transmitted, in the same way as a postman delivers a letter to a specific
destination address.

Packet Switching
As there is no direct connection established between the sender and the receiver, each packet
follows different routes and, therefore, the packets are delivered in a random order at the
destination address. It is the TCP protocol which then arranges all received packets in a
sequential order.

Message Switching
Message switching is a store and forward switching technique where there is no direct
connection between the sender and the receiver.
In message switching, the sender sends the data to a switching office first, which is then
stored in its buffer. It then checks the available link and if it is free, the data is relayed to
another switching office. This process goes on until the data is sent to the destination
another switching office. This process goes on until the data is sent to the destination
(receiver).

Message Switching

DATA COMMUNICATION TERMINOLOGIES
Channel: A channel is a communication path through which the data is
transmitted from the sender device to the receiver device. The capacity of a
channel is the maximum amount of signals or traffic that a channel can carry. It is
measured in terms of bandwidth and data transfer rate .
measured in terms of bandwidth and data transfer rate .
Bandwidth: The amount of data that can be passed along a communication
channel in a given period of time (1 second) is termed as bandwidth. The
measuring unit is hertz (Hz),
where 103 Hz = 1 Kilo Hertz (KHz),
103 KHz = 1 Mega Hertz (MHz).

DATA COMMUNICATION TERMINOLOGIES
Data and Signals: Information that is stored within computer systems and
transferred over a computer network can be divided into two categories—data
and signals. Data are entities that are stored in the form of 0’s and 1’s, which
convey some special meaning to the computer system. When this data is
convey some special meaning to the computer system. When this data is
transmitted from one place to another, it is converted into signal. Signals are the
electric or electromagnetic encoding of data and are used to transmit data.
Communication/Transmission Media: Communication media is
the way of transmitting the signal from one place to another.

DATA COMMUNICATION TERMINOLOGIES
Data transfer rate : is the number of bits transmitted between source and
destination in one second. It is also known as bit rate. It is measured in terms of
bits per second (bps). The higher units for data transfer rates are:
1 Kbps=210 bps=1024 bps
1 Kbps=210 bps=1024 bps
1 Mbps=220 bps=1024 Kbps
1 Gbps=230 bps=1024 Mbps
1 Tbps=240 bps=1024 Gbps
MBps stands for Megabyte per second whereas Mbps stands for Megabit per second.

Network Devices
To communicate data through different transmission media and to configure
networks with different functionality, we require different devices like Modem,
Hub, Switch, Repeater, Router, Gateway, etc.
Modem: A MODEM (Modulator DEModulator) is an electronic device that enables a
Modem: A MODEM (Modulator DEModulator) is an electronic device that enables a
computer to transmit data over telephone lines. It is a device used to convert digital signals
into analog signals and vice versa. There are two types of modems, namely internal modem
and external modem.

Network Devices
Ethernet Card : Ethernet card, also known as Network Interface Card (NIC
card in short) is a network adapter used to set up a wired network. It acts as an
interface between computer and the network. Ethernet cards can support data
transfer between 10 Mbps and 1 Gbps (1000 Mbps). Each NIC has a MAC
transfer between 10 Mbps and 1 Gbps (1000 Mbps). Each NIC has a MAC
address, which helps in uniquely identifying the computer on the network.

Network Devices
RJ45: or Registered Jack-45 is an eight-pin connector that is used exclusively
with Ethernet cables for networking. It is a standard networking interface that
can be seen at the end of all network cables.
Hub: It is multi-port and unintelligent network device which
Hub: It is multi-port and unintelligent network device which
simply transfers data from one port of the network to another.
A hub is a hardware device used to connect several computers
together with different ports.

Network Devices
Switch: A switch (switching hub) is a network device which is used to
interconnect computers or devices on a network. It filters and forwards data
packets across a network.
Router: A router is a networking device that
Router: A router is a networking device that
forwards data packets from the source
machine to the destination machine by using
the shortest path. Routers are used at the
network layer, which is the third layer of the
OSI model.

Network Devices
Repeater : Repeater is a device that amplifies a signal that is transmitted across
the network so that the signal is received in the same way as it is sent.

Network Devices
Gateway: A gateway is a device that
connects dissimilar networks. In
internet, several networks are
communicating with each other and
communicating with each other and
each network has a different
configuration. In order to make reliable
communication, there must be a device
that helps in communicating.

Network Devices
Bridge :A bridge is a device that links two segments together of the original
network.

NETWORK TOPOLOGIES
The pattern of interconnection of nodes in a network is called the Topology. This
layout also determines the manner in which information is exchanged with in the
network.
Types of Topologies
Types of Topologies
Basically, there are five types of topologies and each topology has some advantages
and disadvantages.

NETWORK TOPOLOGIES
Bus topology is a topology for a Local Area Network (LAN) in which all the
nodes are connected to a single cable. The cable to which the nodes connect is
called a “Backbone”. If the backbone is broken , the entire segment fails.

NETWORK TOPOLOGIES
Advantages of Bus Topology
(a) Nodes can be connected or removed easily.
(b) It requires less cable length .
(c) Can be extended up to a certain limit.
(d) It is simple , reliable and easy to use.
Disadvantages of Bus Topology
(a) If there is a fault or break in the main cable, the entire network shuts down.
(b) Terminators are required at both ends of the backbone cable.
(c) Fault isolation is difficult.
(d) Data traffic is high.

NETWORK TOPOLOGIES
Ring topology, each node is connected to
two other nodes on either side of it, forming
a ring network. It shows the line
configuration in which each node is
configuration in which each node is
connected to one predecessor node and one
successor node. Signal is transmitted only in
one direction along the entire ring in a
circular fashion.

NETWORK TOPOLOGIES
Advantages of Ring Topology
(a) The data is transmitted in one direction .
(b) The adding or removing of network nodes is easy .
(c) A central server is not required in ring topology as the data is passed between two nodes
which then pass through the entire network. .
Disadvantages of Ring Topology
(a) If there is a fault in a single node, it can cause the entire network to fail .
(b) Transmission speed becomes slower with an increase in the number of nodes.
(c) If there is a fault or break in a cable to which all other nodes are connected, the entire
network shuts down.

NETWORK TOPOLOGIES
Star topology, each communicating device
is connected to a central controller called
hub. The devices in star topology send and
receive data indirectly; the data passes to and
receive data indirectly; the data passes to and
from the hub. If the data is required to be
sent from one computer and received by
another computer, then this can be
accomplished only by the central controller
as each data is first sent to the hub.

NETWORK TOPOLOGIES
Advantages of Star Topology
(a) It is easy to detect faults in this network .
(b) It is very reliable – If one cable or device fails then all the others will continue to work.
(c) The rate of data transfer is fast as all the data packets or messages are transferred
through central hub.
through central hub.
(d) Easy to extend.
Disadvantages of Star Topology
(a) Extra hardware is required for installation .
(b) All nodes of star topology are dependent on central hub and, therefore, any problem in
the hub makes the entire network shut down.
(c) More cabling is required in star topology

NETWORK TOPOLOGIES
Tree topology, combines characteristics of
Bus and Star topologies. It consists of groups
of star-configured workstations connected to a
linear bus backbone cable.
linear bus backbone cable.

NETWORK TOPOLOGIES
Advantages of Tree Topology
(a) The tree topology is useful in cases where a star or bus cannot be implemented
individually.
(b) of one segment does not affect the rest of the network.
(c) Fault identification is easy.
Disadvantages of Tree Topology
(a) As multiple segments are connected to a central bus, the network depends heavily on the
bus. Its failure affects the entire network.
(b) Owing to its size and complexity, maintenance is not easy and costs are high. Also,
configuration is difficult in comparison to other topologies.

Communication/Transmission Media
Transmission Media The media through which data is transferred from one place to
another is called transmission or communication media.
Types of Communication/Transmission Media
All communication/transmission media can be divided into two categories:

Communication/Transmission Media
Guided Media or Wired Technologies: In guided media or wired media, the
computers in a network are connected through wire or cable. The data signal physically gets
transferred from the transmitting computer to the receiving computer through the wired
transmission medium. Some of guided media are given below:
•Ethernet Cable or Twisted Pair Cable
•Co-axial Cable
•Optical Fibre Cable

Communication/Transmission Media
•Ethernet Cable or Twisted Pair Cable : In this cable, wires are
twisted together, which are surrounded by an insulating material and an outer
layer called jacket. One of the wire is used to carry signals to the receiver and
the other is used only as a ground reference. There are two types of twisted pair
cables.
cables.
•Shielded Twisted Pair (STP) Cable : It has shielding of the individual
pair of wires, which protects it from external interference and crosstalk.
•Unshielded Twisted Pair (UTP) Cable: It has two unshielded wires
twisted around each other. UTP cables are found in many LAN networks and
telephone systems.

Communication/Transmission Media
Advantages of Twisted Pair Cable
• Simple structure.
• Physically flexible.
• Easy to install
• Low weight.
• Low weight.
• Very inexpensive.
Disadvantages of Twisted Pair Cable
• Due to high attenuation, signals cannot be transported over a long distance
without using repeaters.
• Due to low bandwidth, it is unsuitable for broadband application.
• Data rates supported are 1 Mbps to 10 Mbps.

Communication/Transmission Media
Co-axial Cable: It consists of a solid wire core surrounded by foil shields or conducting
braid or wire mesh, each separated by some kind of plastic insulator. The inner solid wire
core carries the signal through the network and the shield is used to provide earthing or
ground . Coax cables are widely used for internet connections and cable televisions.

Communication/Transmission Media
Advantages of Co-axial Cable
• Transmission quality of co-axial cable is better than twisted pair cable.
• It can be successfully used for shared cable network.
• It can transmit several channels simultaneously, so that used for broadband
transmission.
transmission.
• It offers high bandwidth.
• It is relatively inexpensive as compared to fibre optic cable.
Disadvantages of Co-axial Cable
• It is expensive compared to twisted pair cable.
• These are difficult to manage and reconfigure as compared to twisted pair cable.

Communication/Transmission Media
Fibre Optic Cable: Optical fibre or fibre optic cable consists of thin threads made
up of glass or glass like material, which are capable of carrying light signals from a
source at one end to another end.

Communication/Transmission Media
Advantages of Fibre Optic Cable
• Fibre optic typically offers better bandwidth and can carry more information at once.
• Fibre optic cables are much thinner and lighter than metal wires.
• Lighter weight makes fibre easier to install.
• A signal can run for 50 km without requiring regeneration.
• A signal can run for 50 km without requiring regeneration.
• Fibre optic cables are also used in research and development.
• Bandwidth is upto 10 Gbps.
Disadvantages of Fibre Optic Cable
• As fibre optic is made of glass, it can be easily broken.
• It is relatively expensive as compared to other guided media.

Communication/Transmission Media
Unguided Media or Wireless Technologies:
When the computers in a network are interconnected and data is transmitted
through waves, then they are said to be connected through unguided media. Some
of the unguided media are given below:
of the unguided media are given below:
1. Microwave
2. Radio Waves
3. Satellite Link
4. Infrared
5. Bluetooth

Communication/Transmission Media
Microwave: Microwave signals are used to transmit data without the use of cable. It is a
line-of-sight transmission as signal travels in a straight line. In microwave communication,
two directional parabolic antennas are mounted on towers, buildings or hills to send and
receive signals through air. However, they must be properly aligned with each other,
otherwise the signal will not be focused well at the receiving antenna.
otherwise the signal will not be focused well at the receiving antenna.

Communication/Transmission Media
Advantages of Microwave
• Microwave transmission does not require the expense of laying cables.
• It can carry 25000 voice channels at the same time.
• It is a cheaper source of communication as it avoids using cables and maintaining repeaters.
• Microwave system permits data transmission rate of about 16 gigabits per second.
• Microwave system permits data transmission rate of about 16 gigabits per second.
Disadvantages of Microwave
• It is an insecure mode of communication.
• Installation and maintenance of microwave links is very expensive.
• The transmission is affected by weather conditions like rain, thunderstorms etc.

Communication/Transmission Media
Radio Waves: When two terminals communicate by
using radio frequencies, then such type of communication is
known as radio wave transmission. Radio wave transmission
set-up has two parts; Transmitter and Receiver.
Devices which transmits signals are termed as
•Devices which transmits signals are termed as
transmitter.
•Devices which receives signals are termed as
receiver.
Both the transmitter and receiver use antennas to radiate
and capture the radio signal.

Communication/Transmission Media
Advantages of Radio Waves
• They can be used indoors or outdoors.
• They are omnidirectional and can travel in any direction.
• Transmitter and receiver antenna do not need to be physically aligned.
• Radio wave transmission offers mobility.
• It is cheaper than laying cables and fibres.
Disadvantages of Radio Waves
• Radio wave communication is an insecure mode of communication.
• It is affected by the weather conditions such as rain, storms, thunder, etc.

Communication/Transmission Media
Satellites are an essential part of
telecommunications systems worldwide. They can
carry a large amount of data in addition to TV signals.
When the data is transmitted using satellite then it is
said to be satellite communication.
said to be satellite communication.
Satellites are especially used for remote locations,
which are difficult to reach with wired infrastructure.
Also communication and data transfer on Internet, is
only possible through satellites.

Communication/Transmission Media
Advantages of Satellite Link
• The area covered is quite large.
• The wired communication is almost impossible and too costly to use across the
continents, where the satellite communication proves to be the best alternative.
• It is very useful in long distance television distribution.
• Earth station, which receives the signals can be fixed position or relatively mobile.
Disadvantages of Satellite Link
• It is very expensive as compared to other transmission mediums.
• Installation is extremely complex.
• Due to low antenna signals, bandwidth are over crowded.

Communication/Transmission Media
Infrared communication requires a transceiver (a combination of transmitter and
receiver) in both devices that communicate. Infrared communication is playing an
important role in wireless data communication due to the popularity of laptop
computers, personal digital assistants (PDAs), digital cameras, mobile phones, pagers
and other devices but being a line-of-sight transmission, it is sensitive to fog and other
atmospheric conditions.
Advantages of Infrared
•Power consumption is less.
•Circuitry cost is less.
•Secure mode of transmission.
Disadvantages of Infrared
•Line of sight, need to be in a straight line for communication.
•Limited in a short range.
•Can be blocked by common materials like walls, people, plants, etc.

Communication/Transmission Media
Bluetooth
It is used for exchanging data over a short distance from fixed and mobile devices.
The name bluetooth is derived from Harald Bluetooth, a king in Denmark.
Advantages of Bluetooth
• We are able to share data without any cord.
• We are able to share data without disclosing our private data.
• We are able to share data without disclosing our private data.
• We can use Bluetooth on many different devices, as it is available in all devices
such as laptops, cell phones, music players, hand sets, printers and a lot more
other products.
Disadvantages of Bluetooth
• Battery consumption
• Data transfer is very slow

Network Protocol
Protocol refers to the set of rules applicable for a network. The protocol defines
standardized format for the data packet to be transmitted through the network.
Protocols define:
• how computers identify one another on a network.
• how computers identify one another on a network.
• the form to which the data should be converted for transit.
• how to decide whether the data received is for that node or to be forwarded to
another node.
• ensuring that all the data have reached the destination without any loss.
• how to rearrange the packets and process them at the destination.

Network Protocol
HTTP (HyperText Transfer Protocol) : HTTP stands for HyperText Transfer Protocol. It is
widely used protocol. This protocol is used by the world wide web. HTTP defines how messages are
formatted and transmitted and what actions web servers and browsers should take in response to
various commands. It is a request/response standard between a client (end-user) and a server
(website).
(website).
TCP/IP (Transmission Control Protocol/Internet Protocol) : It is a set of standardised
rules that uses a client-server model of communication in which a user or machine (a client) requests
a service by a server in the network. The IP protocol ensures that each computer or node connected
to the Internet is assigned an IP address . TCP ensures that the message or data is broken into
smaller chunks, called IP packets. Each of these packets are transmitted through the Internet.
It is also responsible for ordering the packets so that they are delivered in sequence.

Network Protocol
FTP (File Transfer Protocol) : is the protocol used for transferring files from one machine to
another. Like HTTP, FTP also works on a client-server model. When a user requests for a file transfer
with another system, FTP sets up a connection between the two nodes for accessing the file.
SMTP (Simple Mail Transfer Protocol) : SMTP is used for sending email messages to other
networks or computers. It handles only outgoing messages and not incoming messages. SMTP does
networks or computers. It handles only outgoing messages and not incoming messages. SMTP does
not create messages; rather, it helps in forwarding messages between client servers.
PPP (Point-to-Point Protocol) : is a communication protocol which establishes a dedicated and
direct connection between two communicating devices. This protocol defines how two devices will
authenticate each other and establish a direct link between them to exchange data. For example, two
routers with direct connection communicate using PPP. The Internet users who connect their home
computers to the server of an Internet Service Provider (ISP) through a modem also use PPP.

Network Protocol
POP3 (Post Office Protocol 3) :The POP (Post Office Protocol 3) is a simple and standard
method to access mailbox and download messages to the local computers. The user can receive
messages with the help of POP protocol. The advantage is that once the messages are downloaded, an
internet connection is no longer needed to read the mail. A user can read all emails offline as these
are saved on the computer’s hard disk.
are saved on the computer’s hard disk.
TELNET (Remote Login) :Telnet is a remote login that helps a user to log on to another user’s
terminal without being its original user. A user who is logging in to their own system can also get
access to log on to another user system and perform various functions such as accessing files or
sharing files to/from the remote system.
Voice over Internet Protocol (VoIP): VoIP is a protocol that is used for transmitting voice data
and multimedia data over internet protocol. It uses high speed broadband internet connection.

INTRODUCTION TO WEB SERVICES
Internet offers several important and extensively used features or services which are described
as follows:
WWW (World Wide Web) : WWW is an information service that can be used for sending
and receiving information over the internet through interlinked hypertext documents. Web
pages may contain text, images, videos and other multimedia components as well as web
pages may contain text, images, videos and other multimedia components as well as web
navigation features consisting of hyperlinks.
Hyper Text Markup Language (HTML) : HTML is a language that is used to create web pages
which are then displayed by web browsers. This language tells the browser how to display text,
pictures and links on the screen. HTML is a language that supports multimedia documents and
consists of audio, video, graphics, pictures, etc. It also helps in creating hyperlinks so that various
documents can be linked together.

INTRODUCTION TO WEB SERVICES
Extensible Markup Language (XML) : Extensible Markup Language is a text-based Markup
Language that allows the user to create their own tags to store data in a structured format.
Domain Names : A domain name is a unique name that identifies a particular website and represents
the name of the server, where the web pages store. Domain names are formed by the rules and
procedures of the Domain Name System (DNS). Domain names are used in URLs to identify particular
web servers, for example, in the URL https://www.cbse.nic.in/welcome.htm, the domain name is
cbse.nic.in.
A domain name consists of the following parts.
1. Top-level domain name or primary domain name, and
2. Sub-domain name(s).
For example, In the domain name cbse.nic.in: .in is the primary domain name , .nic is the sub-
domain of in , cbse is the sub-domain of nic.

INTRODUCTION TO WEB SERVICES
The top-level domains are categorized into following domain names:
Generic Domain Names
·com - commercial business
·edu - Educational institutions
·gov - Government agencies
Country Specific Domain Names
.in - India
·au - Australia
·ca - Canada
·gov - Government agencies
·mil - Military
·net - Network organizations
·org - Organizations (non-profit)
·ca - Canada
.ch - China
.nz - New Zealand
.pk - Pakistan
.jp - Japan
.us - United States of America

INTRODUCTION TO WEB SERVICES
URL stands for uniform resource locator that stores the address of a web page.
URL consists of three parts:
• Network protocol
• Host name or address
• File or resource location.
• File or resource location.
These parts are separated by special characters as follows
Protocol://host/location
An example of a typical URL would be "http://en.example.org/wiki/Main_Page".
Website : A website is a collection of various web pages, images, videos, audios or other kinds of
digital assets that are hosted on one or several web servers. The first page of a website is known as
home page where all the links related to other documents are displayed.

INTRODUCTION TO WEB SERVICES
Web Page : A web page is an electronic document/page designed using HTML. It displays
information in textual or graphical form. Traversal from one web page to another web page is
possible through hyperlinks. A web page can be classified into two types:
• Static web page: A web page which displays same kind of information whenever a user visits it is
known as a static web page. A static web page generally has .htm or .html as extension.
known as a static web page. A static web page generally has .htm or .html as extension.
• Dynamic web page: An interactive web page is a dynamic web page. A dynamic web page uses
scripting languages to display changing content on the web page. Such a page generally has .php,
.asp, or .jsp as extension.
Web Browser : It is a software that helps in accessing web pages and, thus, is also called web client.
It helps the user to navigate through the World Wide Web and display web pages. Some popular web
browsers are: Mozilla Firefox, Opera, AOL, Webkit, Iceweasel, etc.

INTRODUCTION TO WEB SERVICES
Web Server : A web server is a server that stores web pages and when a web client sends any
request to a server, the server responds to the request and displays the requested web pages. A
web server is a program that runs on a computer connected to the internet.
Some popular web servers are: Apache web server, Netscape enterprise web server, Microsoft
internet information server, etc.
internet information server, etc.
Web Hosting : Web hosting is a service which is provided by companies to its clients to
allow them to construct their own websites which are accessible to the internet users via World
Wide Web. Such companies are known as web hosts.
Web 2.0 refers to added features and applications that make the web more interactive and
easy to provide information using newsgroups, social networking sites, RSS, etc.

INTRODUCTION TO WEB SERVICES
Web Scripting : Website Scripting is used for creating web pages to publish them on the web
interactively. The communication between web browser and web server happens through small
programs called web scripts.
Client-Side Web Scripting Languages : Client-side scripting enables the user to interact with
web pages. The client-side scripts are downloaded at the client end and then interpreted and
web pages. The client-side scripts are downloaded at the client end and then interpreted and
executed by the web browser. Some Popular Client-Side Scripting Languages are:
(a) JavaScript (b) VBScript (c) PHP
Server-Side Script : Server-side scripting gets executed on the server before displaying the
information requested.
(a) ASP (Active Server Pages)
(b) (b)JSP (Java Server Pages)