Internet
- Internet is a global network of billions of computers and other electronic devices. With the internet,
it's possible to access almost any information, communicate with anyone else in the world, and do much
more.
History of internet
- The origins of the internet are rooted in the USA of the 1950s.
- The cold war was at its height and huge tensions existed between North America and the Soviet Union.
- The US realised it needed a communications system that could not be affected by a Soviet nuclear attack
- At this time, computers were large, expensive machines exclusively used by military scientists and university staff.
- These machines were powerful but limited in numbers, and researchers grew increasingly frustrated: they required access to the technology, but had to travel great distances to use it.
- To solve this problem, researchers started ‘time-sharing’. This meant that users could simultaneously access a mainframe computer through a series of terminals, although individually they had only a fraction of the computer’s actual power at their command.
- The difficulty of using such systems led various scientists, engineers and organisations to research the possibility of a large-scale computer network.
- Invention of Internet → When networking technology was first developed, a number of scientists and engineers brought their research together to create the ARPANET. Later, other inventors’ creations paved the way for the web as we know it today.
DNS
- DNS stands for Domain Name System. It is the internet's equivalent of a phone book, and converts
hard-to-remember IP addresses into simple names.
- In the early 1980s, cheaper technology and the apprearance of desktop computers allowed the rapid
development of local area Networks (LANs). An increase in the amount of computers on the network
made it difficult to keep track of all the different IP addresses.
- This problem was solved by the introduction of Domain Name System (DNS) in 1983. DNS was invented by
Paul Mockapetris and Jon Postrel at the university of Southern California. It was one of the
innovations that paved the way for the world Wide Web.
Use of Intenet
Electronic Mail (email)
- People use email for sharing infromation data files, photos, videos, business communications and
more. This has enabled faster communication between people and improved business efficiency. An
email has reduced paper usage and the load of physical mail systems.
FTP File Transfer
- FTP is the file transfer protocol that enables data exchanges between two stakeholders over
internet media in a secure way.
- The data exchange may occur between two business entities or customers with business and vice
versa.
- Usually, email restricts the size of a file that can be shared, and it is not secure to share
sensitive and confidential data accross public Networks. FTP concept is still is use in mobile
apps for file downloading.
Search Engines
- These engines locate the information one seeks, available on whichever server accross the globe
(world wide web).
- One can search for anything on this site, and the search question can be in any format.
E-Commerce
- The internet enables the selling of goods and services in online mode.
- Many e-commerce platform vendors like Amazon and Ola aggregate several products/services
available in market and sell them through their portal to customers.
- Products are procured by platform vendors, stored in their warehouses, packed and distributed by
them in their brand. Customers get a good discount and don't have to visit physical stores.
Online Banking
- Called Net banking, it allows doing banking transactions at ease sitting at home or while on
mobile.
- Any amount of money can be transferred instantaneously through this facility.
- E-Banking supports electricity bills, telephone bills and other services payments.
Education
- The internet offers a wealth of educational material on any subject with structured navigation
and search facilities.
- One can seek any reading material, and the internet will get it for them from any server in any
part of the world, and people need not have to go to libraries to go through books.
Social Networking
- Internet connects people online and enables them to form social groups.
- Information, ideas, views and opinions on social/political issues are exchanged.
- Political and social organization uses this platform to promote their interest among the public.
Advantages of internet
Connectivity, communication and sharing
- One can send a letter or important information to anyone in the e-mail all over the world
through the internet. And, it often will be delivered to the destination in less than a minute.
Information, knowledge and learning
- The internet allows people to learn information about any topic and offers an answer to any type
of question, as it contains endless knowledge and information.
- Using search engine like Google Chrome, Mozilla Firefox, and more they all allow users to ask
any question and find a web page with an answer about that question.
Address, mapping and contact information
- The internet can help users to provide information almost every place in the world on the map
with the help of GPS technology.
- You can find businesses in your area or the quickest route to your location.
Selling and making money
- If you want to sell products and services or run a business, the internet is the best place to
sell goods. Because anyone can find and access your website all over the world with the help of
internet.
- With online business, you are able to sell goods every day at all times as the internet is
always on and always available.
- Also, the internet provides the advantage to promote your business online in the world through
advertising. Additionally, there are several ways to make money online by performing other
online services.
Banking, bills and shopping
- If you want to view your bank balance without leaving your home, the internet offers you the
benefit to access your bank account to view the balance. Also you can send money, pay bills
through internet.
- Other advantage of internet is online shopping, which allows people to find products of interest
and buy them without having to visit a store.
- You can compare prices between companies for any product through the internet. Also, you can get
help to make better purchasing decisions by online reviews, which describes what others thing
about a product.
Donations and funding
- with the help of an internet connection, anyone can help fund projects and ideas that interest
them or quickly donate to their favorite charity.
- Also, if you want to donate and looking for charity services, you can find many online services
on the Internet that help make it easier to support their causes or help donate.
Entertainment
- The internet provides people to access endless entertainment. With the internet, you can watch
movies, videos, play games online, listen to music, etc.
- There are many sites available on the internet, which contain different entertainment material
like music, videos and more.
- Also, you can watch onine videos on a platform like Youtube.
- Futhermore, you can download any movies, videos or other entertainment material via the internet
on devices like computers or mobile phones that can be played anytime without an internet
connection.
Work from home
- The internet offers people benefit to connect with others around the world.
- There are various online services that help you to communicate and work with other people all
over the world.
- Also, it can make services and producing new products faster.
Cloud storage
- One of the biggest advantages of the internet offers connectivity to your computer and internet
enabled devices to connect with cloud services in which we store our data.
Types of Network based on size
- This is based on the area it covers and its physical architecture.
LAN (Local Area Network)
- Group of interconnected computers within a small area. (room, building, campus).
- Two or more pc's can form a LAN to share files, folders, printers, applications and other
devices.
- Coaxial or CAT 5 cables are normally used for connections.
- Due to short distances, errors and noise are minimum.
- Data transfer rate is 10 to 100 mbps.
- Example → A computer lab in a school.
MAN (Metropolitan Area Network)
- Design to extend over a large area.
- Connecting number of LAN's to form larger network, so that resources can be shared.
- Networks can be up to 5 to 50 Km.
- Owned by organization or individual.
- Data transfer rate is low compare to LAN.
- Example → Organization with different branches located in the city.
WAN (Wide Area Network)
- These are country and worldwide networks.
- Contains multiple LAN's and MAN's.
- Distinguished in terms of geographical range.
- Uses satellites and microwave relays.
- Data transfer rate depends upon the ISP provider and varies over the location.
- Example → internet.
Other Types
- WLAN (Wireless LAN)
- A LAN that uses high frequency radio waves for communication.
- Provides short range connectivity with high speed data transmission.
- PAN (Personal Area Network)
- Network organized by the individual user for its personal use.
- SAN (Storage Area Network)
- Connects servers to data storage devices via fiber-optic cables.
- E.g.: Used for daily backup of organization or a mirror copy
Types of Internet service
Dial-up
- It is a broadband connection that uses a modem to establish data connections over the public
switched telephone network (PSTN).
- Dial-up modems are slower than high-speed modems and are often limited in the connection speeds
they support.
Leased Line
- A leased line is a high-speed internet connection between two locations.
- The service involves renting a deciated cable to connect two offices or branches together,
enabling users to transfer large volumes of data and giving an consistent connection to the
internet.
- A single channel leased line offers speeds of up to 10Mb/s, while a double channel leased line
can provide up to 40Mb/s.
Cable
- A cable is a collection of wires twisted together to provide a path for electrical signals.
- The twists reduce signal interference that might otherwise occur due to electromagnetic or other
source.
- The twists also accomodate the higher frequencies used in fast data-transfer applications.
Fibre-Optics
- Fibre-Optics cables use light waves to carry data from one place to another.
- Fiber-optics cables work by transmitting light waves through glass threads that are thinner than
human hair. Because of this, fiber cables have better efficiency than copper wires.
Wireless or Wi-Fi
- It is a way of connecting different devices to a network. In other words, Wi-Fi allows devices to
connect to the internet wirelessly.
- Wi-Fi is short for Wireless Fidelity. It is a technology that uses radio waves instead of wires
to have an internet connection.
Broadband
- Broadband is a brand name for high-speed internet access, and internet services provided by
telecom companies.
- The term broadband is used to differentiate these services from traditional dial-up connections.
- The suffix "broad" refers to the wide bandwidth of the medium being used to transmit the data.
Satellite
- A satellite network is a communication network that uses the satellite system rather than
cables.
- the satellite network is used in a situation where the cable network is not possible and can
handle the high traffic volume.
- The satellite network is more expensive than the cable network because it uses the satellites in
orbit to send data and the satellite is not owned by the company.
- The satellite consists of a satellite dish, a receiver and a transmitter to communicate with the
satellite.
Types of network devices
Router
- Router is a particular type of device used to connect two or more subnets that cannot be
similar.
- It serves two primary functions: managing traffic between these networks by forwarding data
packets to their intended IP addresses, and allowing multiple devices to use the same internet
connection.
- There are several types of routers, but most routers pass data between LANs (local area
networks) and WANs (wide area networks). A LAN is a group of connected devices restricted to a
specific geographic area. A LAN usually requires a single router.
Hub
- A hub is a networking device that is used to connect multiple devices or segment on a local
network.
- It is physical layer (layer-1) device that simply broadcasts all incoming data to all other
output ports, means if a hub has eight ports, then any input data that irrives on port 1 will be
transmitted on all ports 2 to 8.
- Hub works like an electric wire, it receives data signals from one device and forwards them to
all other ports, except the source port.
- It does not have any capability to identify any frames to know where it should forward because
it does not maintain any kind of table like switch. So there is a lot of traffic on the network
and network performance is also very poor, only one device transmits information at a particular
time.
Bridge
- A bridge is a device used to connect multiple LANs together with a larger Local Area Network
(LAN). The network aggregation is known as bridging.
- The bridge is a physical or hardware device but operates at the OSI model's data link layer and
is also known as a layer of two switches.
- It is used to divide a network connections into sections, now each section has separate
bandwidth. and it is used to improve network performance.
Gateway
- A gateway is a network node that forms a passage between two networks operating with different
transmission protocols.
- Depending upon the functionality, a gateway can operate at any of the seven layers of OSI model
however it operates on network layer most commonly.
Switches
- Switches are networking devices operating at layer 2 or a data link layer of the OSI model.
- They connect devices in a network and use packet switching to send, receive or forward data
packets or data frames over the network.
- A switch has many ports, to which computers are plugged in. When a data frame arrives at any
port of a network switch, it examines the destination address, performs necessary checks and
sends the frame to the corresponding devices.
Repeaters
- Repeaters are network devices operating at physical layer of the OSI model that amplify or
regenerate and incoming signal before retransmitting it.
- They are used in networks to expand its coverage area. They are also known as signal boosters.
Modem
- Modem stands for Modulator and Demodulator.
- It is a device that modulates signals to encode digital information for transmission and
demodulates signals to decodes the transmitted information.
- A modem transmits data in bits per second (bps).
- Is is necessary because it acts as translator between the devices and rapidly transmits the
information.
- It converts the digital signal to Analog and vice versa to communicate between devices.
OSI
- OSI stands for Open Systems Interconnection
- It was created as a framework and reference model to explain how different networking technologies
work together and interact.
- Created by International Standards Organization (ISO)
- Each layer has specific functions it is responsible for.
- All layers work together in the correct order to move data around a network.
Physical Layer
- Deals with all aspects of physically moving data from one computer to the next
- Converts data from the upper layers into 1s and 0s for transmission over media
- Defines how data is encoded onto the media to transmit the data
- Device example: Hub
- Used to transmit data
Data link Layer
- Is responsible for moving frames from node to node or computer to computer
- Can move frames from one adjacent computer to another, cannot move frames across routers
- Encapsulation = frame
- Requires MAC address or physical address
- Protocols defined include Ethernet Protocol and Point-to-Point Protocol (PPP)
- Device example: Switch
Network Layer
- Responsible for moving packets (data) from one end of the network to the other, called
end-to-end communications.
- Requires logical addresses such as IP addresses
- Device example: Router
- Routing is the ability of various network devices and their related software to
move data packets from source to destination
Transport Layer
- Takes data from higher levels of OSI Model and breaks it into segments that can
be sent to lower-level layers for data transmission
- Conversely, reassembles data segments into data that higher-level protocols
and applications can use
- Also puts segments in correct order (called sequencing ) so they can be
reassembled in correct order at destination
- Concerned with the reliability of the transport of sent data
- May use a connection-oriented protocol such as TCP to ensure destination
received segments
- May use a connectionless protocol such as UDP to send segments without
assurance of delivery
- Uses port addressing
Session Layer
- Responsible for managing the dialog between networked devices
- Establishes, manages, and terminates connections
- Provides procedures for establishing checkpoints, adjournment, termination,
and restart or recovery procedures
Presentation Layer
- Concerned with how data is presented to the network
- Handles three primary tasks: -Translation, -Compression, -Encryption
- Translation → Changes data so another type of computer can understand it
- Compression → Makes data smaller to send more data in same amount of time.
- Encryption → Encodes data to protect from interception
Application Layer
- Contains all services or protocols needed by application software or operating system to communicate on the network.
- Examples → Firefox web browser uses HTTP
- There is another model called TCP/IP Model
- It is protocol suite having large number of related protocols that work together to allow networked computers to communicate.
Types of Networking Protocols
- A network protocol is a group of rules accompanied by the network.
- Network protocols will be formalized requirements and plans composed of rules, procedures and types
that describe communication among a couple of devices over the network.
- The protocol can be described as an approach to practices that enable a couple of entities of a
communication program to transfer information through various physical mediums.
HTTP or HTTPS
- This stands for Hypertext Transfer Protocol or Hypertext Transfer Protocol (secure).
- The secure version is encrypted, meaning that we will encrypt all the data as we send it from
the client to the server.
- Now client and server here become very important with application layer protocol. Nearly all application layer protocols use this model, using one device on the client's network and the other on the server.
- Now when we are using HTTP or HTTPS or tranferring a file. Transferring a file in the format of the hypertext. Hypertext is readable by a web browser.
FTP (File Transfer Protocol)
- The FTP allows us to transfer files from a client to a server or from a server to a client.
- We can do it in both directions here.
- FTP typically require a username and password to transfer these files.
TCP/IP
- TCP/IP stands for Transmission Control Protocol/Internet Protocol. The term is used to describe a
set of protocols that govern how data moves through a network.
- After the creation of ARPANET, more networks of computers began to join the network, and the need
arose for an agreed set of rules for handling data.
Internet Services
Web
- The world wide web - usually called the web for short - is a collection of different websites you
can access through the internet. A website is made up of related text, images, and other resources.
WWW v/s Internet
- The terms 'World Wide Web' and 'internet' are often confused. The internet is the networking
infrastructure that connects devices together, while the World Wide Web is a way of accessing
information through the medium of the internet.
- Tim Berners-Lee first proposed the idea of a 'web of information' in 1989. It relied on 'hyperlinks'
to connect documents together. Written in Hypertext Markup Language (HTML), a hyperlink can point to
any other HTML page or file that sits on top of internet.
- Berners-Lee also created a piece of software that could present HTML documents in an easy-to-read
format. He called this ‘browser’ the ‘WorldWideWeb’.
Email
- An electronic communication invented in the 1970s to do communication faster during the era of letters and telegrams that changed the way people communicate with each other is called an Email.
- Ray Tomlinson is called as the father of the email system, and he sent a communication between two computer systems for ARPANET.
- Email is called so since it is an electronic mail sent to a person or to a system, and unlike the normal mail, the physical letter or paper is not needed for the same. Instead of a postal service and an address, an email address and an internet connection are needed.
Usenet
- Usenet or "Unix users' network" is an extensive collection of discussion groups consists of articles and message submitted by its worldwide users.
- This collections of articles contains different interest of users. They are commonly known as 'newsgroups'.