Internet and Its Services

The Internet is a worldwide system of interconnected computer networks that exchange data using a common set of rules called TCP/IP (Transmission Control Protocol / Internet Protocol). It is often called a network of networks, because nobody owns it as a whole: a school LAN (Local Area Network), a college campus network and the networks of telecom operators are all joined together, so a computer sitting on any one of them can reach a computer on any other. A definition that earns full marks names three things — that it is global, that it is made of many networks joined together, and that the joining works because every machine follows TCP/IP.

The World Wide Web (WWW, or simply the Web) is not another name for the Internet, and this is the distinction examiners return to most often. The Web is one service that runs on the Internet: a very large collection of linked documents called web pages, stored on web servers, written mainly in HTML (HyperText Markup Language), addressed by URLs and fetched by a browser using the HTTP protocol. The Web was developed by Tim Berners-Lee as an application built on top of the Internet, which already existed before it.

The cleanest way to hold the difference is this: the Internet is the infrastructure — cables, optical fibre, routers, satellites, mobile towers and the addressing system; the Web is the content that travels over that infrastructure. Roads make the same point. The road network is the Internet; the Web is one kind of traffic using it. The proof that the two are different is that a great deal of internet activity never touches the Web at all — sending an email through SMTP, transferring files with FTP, an internet voice call, or an online game exchanging data with its server. Each of those uses the Internet without loading a single web page.

The Web is held together by hypertext — text containing hyperlinks that can jump to another page, possibly on a server in another country, without the reader knowing where the file physically sits. The Web is therefore non-linear: there is no fixed order in which its pages must be read.

To reach any of this you need an ISP, an Internet Service Provider. An ISP is an organisation that provides internet access to homes, schools and businesses, usually against a monthly charge in rupees. Along with the connection, an ISP normally allots an IP address, supplies or configures a modem and a router, and may offer email accounts, web hosting space or a fixed (static) IP address. The common ways of connecting in India are broadband over cable or optical fibre, mobile data on a 4G or 5G network, and a leased line for offices that need a dedicated, guaranteed link.

Two small points are worth fixing now, because they are easy marks. First, Wi-Fi is not the Internet. Wi-Fi is only a wireless way of joining your device to a router; if the router link to the ISP is down, the Wi-Fi still works but no website will open. Second, connection speed is measured in Mbps — megabits per second, not megabytes — so an 8 Mbps link delivers roughly one megabyte of data per second, because 8 bits make 1 byte.

Every device connected to the Internet needs an address, exactly as every house does. That address is the IP address — Internet Protocol address — a unique numeric label that identifies a device on a network so that data can be delivered to it and replies can find their way back. The version most often written in textbooks is IPv4, which is 32 bits long and is written as four numbers separated by full stops, each number between 0 and 255, for example 192.168.1.10. Because 32 bits cannot supply enough addresses for the number of devices now in use, IPv6 was introduced; it is 128 bits long and is written as eight groups of hexadecimal digits separated by colons.

An IP address may be static — fixed, and given to servers that must always be findable at the same address — or dynamic, allotted afresh by the ISP at each connection, which is what an ordinary home broadband link gets.

Numbers are convenient for machines and hopeless for people, so the Internet also has a naming system. A domain name is the readable name of a website, such as irctc.co.in. Read a domain name from right to left. The rightmost part is the top-level domain (TLD): either a generic one such as .com (commercial), .org (organisation), .net (network), .edu (education) or .gov (government), or a country-code TLD such as .in for India. Before it comes the second-level domain, the name the owner registered. In front of that may sit a host name or sub-domain, traditionally www.

DNS, the Domain Name System, is the service that joins the two worlds. It maintains, spread across many servers, the mapping between domain names and IP addresses, and converts a name into the matching number whenever a name is used. The sentence to write in an exam is that DNS acts like a telephone directory of the Internet: you supply the name and it returns the number. The process itself is called name resolution. When a school website name is typed into a browser, the browser first asks a DNS server for that domain IP address, receives the number, and only then contacts the web server. If DNS fails, sites will not open by name even though the connection is perfectly healthy.

A domain name identifies a whole site; a URL identifies one exact resource inside it. URL stands for Uniform Resource Locator and is the complete address of a file on the Web — a page, an image or a PDF. Its parts, in order, are the protocol (also called the scheme), the domain name of the server, an optional port number, the path or folder, and the file name. Some URLs also carry a query string after a question mark, passing extra information such as a search word to the server.

Splitting a given URL into its parts is a standard question, so practise on one:

https://www.example.edu.in/admissions/form.html

https       -> protocol (scheme) used to fetch the file
www         -> host name or sub-domain
example     -> second-level domain, the registered name
.edu        -> domain type, showing the kind of organisation
.in         -> top-level domain, the country code for India
/admissions -> path, the folder on the web server
form.html   -> file name of the web page requested

Two habits protect marks here. Never call the whole URL a domain name — the domain name is only one component of it. And never confuse a URL with an IP address: the URL is what a person types, the IP address is what the machines use, and DNS turns the first into the second.

A web browser is application software installed on a computer or phone whose job is to request web pages from a web server and display them. Chrome, Firefox, Edge, Safari and Opera are browsers. The browser sends its request using HTTP or HTTPS, interprets the HTML that comes back, and renders the text, images and links on screen. Features such as bookmarks, history, tabs, a download manager and private windows are offered by every mainstream browser, although the names and exact behaviour differ from one browser to another.

A search engine is not software on your machine at all: it is a website, a service, that you reach through a browser. It searches its own index of the Web and returns a list of links matching the keywords you typed. Google, Bing, Yahoo Search and DuckDuckGo are search engines. A search engine works in three stages — programs usually called crawlers or spiders visit pages and follow their links, what they find is stored in a huge index, and when a query arrives the engine ranks the indexed pages and shows the results. The distinction to write down is short: the browser is the software that displays a page; the search engine is a service that helps you find which page to display. The confusion is understandable, because most browsers let the address bar act as a search box — but which engine it uses depends on the browser and its settings.

Next, the vocabulary of the Web itself. A web page is a single document written in HTML that a browser can display; it may hold text, images, audio, video and hyperlinks, and a hyperlink is created with the <a> tag together with its href attribute. A website is a collection of related web pages kept together under one domain name — a school website groups its admission, faculty, results and contact pages. The home page is the first or main page of a website, the one that opens when only the domain name is typed; it normally carries the menu and the links to everything else.

Those pages have to live somewhere. A web server is a computer that is permanently connected to the Internet and runs server software; it stores the pages of a website and sends them to any browser that requests them. Web hosting is the service of renting space on such a server so that a site is reachable by the public. A hosting company charges an amount in rupees per year for that space, and the owner separately registers a domain name and points it at the server. A school that wants a website therefore needs three things — the pages, a domain name, and hosting.

Finally, the difference examiners like at the end of this topic. A static web page has fixed content: the HTML file stored on the server is delivered to every visitor exactly as it is, so everybody sees the same thing until the author edits the file by hand. The About Us page of a school site is static. A dynamic web page is built at the moment it is requested, usually by a program running on the server that reads a database, so its content can change with the user, the time or the data. Seat availability on IRCTC, a bank balance after login, and a board result looked up by roll number are all dynamic. Static pages are faster to serve and cheaper to host; dynamic pages need programming and a database, but can show personalised, up-to-date information that could never be maintained by hand.

A protocol is a set of rules that governs how data is exchanged between devices on a network — how a message is formatted, how it is addressed and how the receiver acknowledges it. Both sides must follow the same rules or nothing can be understood. Each internet service has its own protocol, and the most common question in this chapter describes a situation and asks which protocol is at work.

TCP/IP — Transmission Control Protocol / Internet Protocol — is the suite on which everything else sits. IP handles addressing and routing: it gives every device an IP address and decides the path data takes across the networks. TCP handles reliability: it breaks the message into small numbered pieces called packets, checks at the receiving end that every packet has arrived, asks for a fresh copy of anything missing, and reassembles them in the correct order. In an answer, say that TCP/IP is the foundation and that the protocols below are application-level protocols running over it.

HTTP — HyperText Transfer Protocol — is the set of rules by which a browser requests a web page and a web server sends it back. Its standard port is 80 and it is stateless, meaning each request is handled independently of the last. Plain HTTP sends everything as ordinary readable text, so anyone able to intercept the traffic could read it.

HTTPS — HyperText Transfer Protocol Secure — is HTTP with encryption added by SSL/TLS (Secure Sockets Layer / Transport Layer Security), and its standard port is 443. The data is scrambled before it leaves the browser and unscrambled only at the server, so an interceptor sees nothing useful. Browsers indicate a secure connection with a padlock or similar mark, though the exact symbol and wording differ between browsers. Any page on which you type a password, a card number or a UPI PIN must be HTTPS. Note that the padlock shows the connection is encrypted, not that the site owner is honest.

FTP — File Transfer Protocol, standard port 21 — is used to upload and download files, including whole folders, between a client computer and a server. It is the traditional way a site owner puts website files on to a hosting server. Plain FTP sends the password unencrypted, so secured versions such as FTPS and SFTP are preferred today.

Mail is split across three protocols, and telling them apart is asked very often. SMTP — Simple Mail Transfer Protocol, standard port 25 — is used to send outgoing mail, from your mail program to your provider mail server and onward to the recipient server. POP3 — Post Office Protocol version 3, standard port 110 — is used to receive: it downloads messages from the server to one device and, in its traditional setting, removes the server copy, so a message read on a laptop is then not visible on the phone. IMAP — Internet Message Access Protocol, standard port 143 — also receives mail, but keeps the messages on the server and synchronises a view of them, so folders, read marks and deletions match on every device. IMAP suits an account opened on several devices; POP3 suits a single device with intermittent connectivity. Whether an account uses POP3 or IMAP is a setting, and providers differ in what they enable by default.

The port numbers quoted here are standard defaults; an administrator can run a service on another port. Remember the purpose rather than the number: HTTP and HTTPS for web pages, FTP for files, SMTP to send mail, POP3 and IMAP to read it, TCP/IP underneath all of them.

Electronic mail, or email, is the internet service that lets a user send a message — with files attached if needed — from one mailbox to another. It is asynchronous: the recipient need not be online at the moment you send, because the message waits on the mail server until it is read. That single property is why email, rather than chat, is still the accepted medium for formal communication such as leave applications, admission queries and job correspondence.

An email address has two parts joined by the at sign: the user name, which identifies the mailbox, and the domain name of the mail server, as in principal@school.edu.in. The user name must be unique within that domain, spaces are not allowed, and in ordinary practice addresses are treated as not case sensitive.

Composing a message uses a small, fixed set of fields, and knowing exactly what each one does is examinable. To holds the address of the main recipient, the person expected to act on the message. Cc stands for carbon copy: these people receive a copy for information, and every recipient can see the whole Cc list. Bcc stands for blind carbon copy: these people also receive a copy, but their addresses are hidden from everyone else, so no other recipient knows they were copied. Bcc is the correct field when one notice goes to a hundred parents, because it keeps each family address private from the other ninety-nine. Subject is a one-line description of what the message is about, and an attachment is any file — a PDF, an image, a spreadsheet — clipped to the message and delivered with it.

To      : classteacher@school.edu.in
Cc      : coordinator@school.edu.in
Bcc     : parent@example.com
Subject : Leave application for 12 and 13 August
Attach  : medical-certificate.pdf

Attachments come with limits. Every provider caps the total size of a message including its attachments, and the exact limit differs from provider to provider, so a large file is normally placed in cloud storage and shared as a link instead. Providers also block file types commonly used to carry malware. Never open an attachment from an unknown sender — an infected file is a standard way a computer catches a virus.

A mailbox is organised into folders whose names vary between services: Inbox for received mail, Sent for copies of what you have sent, Drafts for unfinished messages, Spam or Junk for unwanted bulk mail set aside by the filter, and Trash or Bin for deleted messages. Three buttons are worth distinguishing: Reply answers the sender alone, Reply All answers the sender together with everybody in the To and Cc lists, and Forward passes the message on to somebody new.

The advantages make a tidy list: delivery in seconds anywhere in the world, no charge per message beyond the internet connection, files can be attached, a dated written record is kept, one message can reach many recipients, and it can be sent or read at any hour. The limitations: it needs an internet connection, the recipient may not check the mailbox promptly, mailboxes fill with spam, attachments can carry viruses, and a message sent to a wrong address cannot reliably be taken back. Basic netiquette — a meaningful subject line, polite language, no typing entirely in capitals, and a check of the address before sending — is often asked as a short answer.

Email and the Web are only two of the services the Internet carries. The rest usually appear as a question asking you to explain any five services, so each needs a one-line definition, an example and, where possible, an advantage.

Chat, also called instant messaging, is real-time exchange of typed messages between two or more people who are online at the same time. It is synchronous, which is exactly what email is not, so it suits short, quick exchanges rather than formal ones. A chat room is a shared space where many users can talk together on one topic.

VoIP — Voice over Internet Protocol — is the technology that carries voice calls as data packets over the Internet instead of over the traditional telephone network. Because the call travels on your data connection, a long-distance or international call costs no more than the data it uses; its main limitation is that quality depends on the speed and steadiness of that connection.

Video conferencing is a live meeting in which participants at different places see and hear one another through cameras, microphones and internet connections. Schools use it for online classes and parent meetings; companies use it to avoid travel. Answers should mention what it saves — travel time and cost — and what it needs — a camera, a microphone and adequate bandwidth.

E-commerce is buying and selling of goods and services over the Internet. A customer browses an online store, adds items to a cart, places the order and pays by UPI, net banking, a debit or credit card, or chooses cash on delivery; the seller then ships the item. Its advantages: the shop is open at all hours, prices can be compared quickly and a wide choice is available even in a small town. Its limitations: the product cannot be examined before purchase, delivery takes time, and payment fraud is a risk on untrustworthy sites.

E-learning is learning delivered through the Internet — recorded lessons, live classes, notes, quizzes and assignments — which lets a student learn at a convenient time and repeat a lesson as often as needed. It cannot fully replace laboratory work or a teacher watching a student struggle, so it is normally described as a supplement.

E-banking, or internet banking, is the use of a bank website or app to operate an account: checking the balance, viewing statements, transferring money through NEFT, RTGS, IMPS or UPI, paying bills, and requesting a cheque book. It saves a trip to the branch and works outside banking hours. Safety rules belong in the answer: use only HTTPS pages, never share the PIN, one-time password or card details, avoid banking over an untrusted public network, and log out when finished.

An e-group (mailing list or discussion group) is an online group whose members share a common interest and where a message sent to the group address reaches every member. A class group used to circulate notes and notices is the familiar example. Social networking is the use of websites and apps on which users create a profile and connect with others to share text, photographs, videos and links; the same platforms are used by schools and businesses to reach an audience. The standard caution belongs with it — whatever is posted may be copied and stored by others, so personal details and address should not be shared publicly, and privacy settings should be reviewed.

E-governance — government services delivered online, such as applying for a document or paying a fee — is a useful extra example when a question asks how the Internet has changed daily life in India.

Downloading means copying a file from a remote computer or server on to your own device, so the direction of travel is server to you. Saving an admit card from a board website, saving a chapter PDF from a school site, or installing an app from a store are all downloads. Uploading is the opposite: copying a file from your own device to a remote server, so the direction is you to server. Attaching a photograph to an online application form, submitting an assignment to a school portal, or a site owner sending web pages to a hosting server by FTP are all uploads. In one line for the exam: downloading receives data from a server, uploading sends data to a server.

Two practical notes are worth adding to that answer. Most home connections are asymmetric, which means the download speed is higher than the upload speed, so sending a large video usually takes longer than receiving one of the same size. And a download can carry malware, so files should be taken only from official or trusted websites and checked by antivirus software.

Cloud storage is a service that keeps your files on servers maintained by a provider and reached over the Internet, instead of only on the hard disk of your own computer. Google Drive, Microsoft OneDrive, Apple iCloud and Dropbox are examples; the free space given, the paid plans and the sharing options differ from provider to provider. The word cloud means the user need not know which machine holds the file — the provider manages the hardware and the backups.

Working with cloud storage involves a few standard actions. You upload a file to the account, and it can then be downloaded again on any device where you sign in. Many services offer synchronisation, in which a folder on the computer and the copy in the cloud are kept identical automatically, so an edit made on one device appears on the others. Files can be shared by link rather than as an email attachment, with permission usually set either to view-only or to allow editing.

The advantages fall into a neat list. Files can be reached from any device with an internet connection. The cloud copy survives if a laptop is lost, stolen or damaged, so it acts as a backup. Large files can be shared as links, avoiding attachment size limits. Several people can work on the same document, and space can be increased by paying for a larger plan instead of buying a new disk.

The limitations must appear in the same answer for full marks. Cloud storage needs an internet connection — without one, files that have not been made available offline cannot be opened. Your data sits on a company server, so privacy and security depend on that company and on the strength of your own password, which is why two-step verification is recommended. Free space is limited and continued use of a large amount costs money in rupees every month or year. If the service suffers an outage or the account is locked, access is lost until it is restored. The safest habit is to keep one copy on the device and one in the cloud.

In short: local storage is fast and entirely under your control, but is limited to one machine and is lost with it; cloud storage is reachable everywhere and survives hardware failure, but depends on a connection, a provider and your password discipline.