Internet and Email: Protocols, Ports and Terms
Internet and Email notes for competitive exams: ARPANET and the World Wide Web, IP addresses, domains, protocol port numbers and the parts of an email window.
By GK24 Editorial Team· Published · 4 min read
The internet is a network of networks: crores of computers, servers and phones joined by cables, optical fibre, satellites and radio links, all following one common set of rules called TCP/IP. Email is the oldest service still running on it and the one every office uses. Computer Awareness sections in SSC, Railway and Banking papers keep two or three questions from this pair, and they come from a short list: who built what and when, the expansion of an abbreviation, a port number, a domain name, and the fields of a mail window.
How the internet grew
The internet began as ARPANET, a project of the Advanced Research Projects Agency of the United States Department of Defense, which carried its first message in 1969 between four university computers. ARPANET moved to the TCP/IP protocol suite on 1 January 1983, the date usually given for the birth of the internet in its present form. Vinton Cerf and Robert Kahn designed TCP/IP and are called the fathers of the internet. In 1989 Tim Berners-Lee, working at CERN in Switzerland, proposed the World Wide Web, and the first website went online in 1991. India built its first academic network, ERNET, in 1986, and public internet service began on 15 August 1995, when VSNL opened its gateway.
Internet, World Wide Web and intranet
Candidates lose marks by treating these three as one thing. The internet is the network itself. The World Wide Web is only one service running on it, the collection of linked pages read through a browser. Email, file transfer and video calls use the internet without using the web at all. An intranet is a private network inside one office, bank or campus, open only to its own members, while an extranet lets chosen outsiders such as suppliers and dealers in as well.
Addresses: IP, domain and URL
Every machine on the internet carries an IP address. An IPv4 address is 32 bits long and written as four numbers from 0 to 255 separated by dots, such as 192.168.1.1, which allows about 4.3 crore times 100 addresses in all. An IPv6 address is 128 bits long and written in hexadecimal, and it was brought in because IPv4 addresses were running out. Numbers are hard to remember, so the Domain Name System keeps a directory that turns a name such as india.gov.in into the matching IP address. A URL, or Uniform Resource Locator, is the full address of a page and has three parts: the protocol, the domain name and the path of the file.
| Domain | Meant for |
|---|---|
| .com | Commercial organisations |
| .org | Non-profit organisations |
| .net | Network providers |
| .edu | Educational institutions |
| .gov | Government bodies |
| .mil | Military establishments |
| .int | International treaty bodies |
| .in | Country code for India |
Protocols and their port numbers
A protocol is an agreed way for two machines to talk, and a port is the numbered door a protocol knocks on. These pairs are asked directly, so learn the table as it stands.
| Protocol | Work it does | Port |
|---|---|---|
| HTTP | Carries web pages | 80 |
| HTTPS | Carries web pages in encrypted form | 443 |
| FTP | Transfers files to and from a server | 20 and 21 |
| SMTP | Sends outgoing mail | 25 |
| POP3 | Downloads incoming mail | 110 |
| IMAP | Reads mail kept on the server | 143 |
| Telnet | Logs in to a distant computer | 23 |
| DNS | Turns names into IP addresses | 53 |
Email and its parts
Ray Tomlinson sent the first network email in 1971 and chose the @ sign to separate the user's name from the computer's name. Every address therefore has two parts, the user name and the domain, joined by @. A mail window has a To field for the main recipients, a Cc field, standing for carbon copy, whose addresses everyone can see, a Bcc field, standing for blind carbon copy, whose addresses no other recipient can see, a Subject line and an Attachment button for files sent along with the letter.
- Inbox holds mail that has arrived.
- Drafts holds letters written but not yet sent.
- Outbox holds letters waiting to go out.
- Sent keeps copies of letters already despatched.
- Spam or Junk collects unwanted bulk mail.
- Trash or Bin keeps deleted mail until it is emptied.
SMTP pushes a letter out of your computer. POP3 brings it down to one device and normally removes it from the server, while IMAP leaves it on the server so that the same mailbox looks identical on a phone, a laptop and an office machine.
Words the paper repeats
- An ISP, or Internet Service Provider, is the company that sells the connection.
- A browser such as Chrome, Firefox or Edge displays pages; a search engine such as Google or Bing finds them. The two are not the same.
- A cookie is a small file a site leaves on your machine to recognise you later; the cache stores page matter to open it faster next time.
- Bandwidth is measured in bits per second, and a modem is a modulator-demodulator.
- Phishing is a fake mail or page that fishes for passwords and card numbers; spam is unwanted bulk advertising.
- Download brings a file to your machine; upload sends one out of it.
Exam Point of View
Examiners ask five things from this topic. First, the dates and names: 1969 for ARPANET, 1983 for TCP/IP, 1989 and 1991 for the Web, 1995 for public access in India. Second, expansions of abbreviations, where HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, DHCP, ISP, URL and Wi-Fi all appear. Third, port numbers, usually as a single direct question. Fourth, the fields and folders of a mail window, where Cc against Bcc and Drafts against Outbox are the standard traps. Fifth, the difference between look-alike pairs: internet and World Wide Web, browser and search engine, download and upload, POP3 and IMAP, intranet and extranet. A question naming 1989 as the birth of the internet is testing whether you can separate the Web from the network.
Important Facts
| First message on ARPANET | 1969, between four American university computers |
|---|---|
| Fathers of the internet | Vinton Cerf and Robert Kahn, for TCP/IP |
| Inventor of the World Wide Web | Tim Berners-Lee, at CERN, 1989 |
| First website | Went online in 1991 |
| Internet in India | Public service from 15 August 1995 through VSNL |
| First academic network in India | ERNET, started in 1986 |
| IPv4 and IPv6 length | 32 bits and 128 bits |
| First email | Sent by Ray Tomlinson in 1971; he chose the @ sign |
| HTTP and HTTPS ports | 80 and 443 |
| Mail protocol ports | SMTP 25, POP3 110, IMAP 143 |
| FTP ports | 21 for commands and 20 for data |
| DNS port | 53 |
| Modem | Modulator-demodulator, converts digital and analogue signals |
| Bandwidth unit | Bits per second, bps |
Practice MCQs on this topic
Deleted emails are stored in
- A.Drafts
- B.Trash
- C.Inbox
- D.Sent mail
Show answer
When a letter is deleted from a mailbox it is not wiped out at once. It is moved to a folder called Trash, or Bin in some services, and kept there for a fixed number of days so that a letter deleted by mistake can be restored.
Read the full explanation →In Gmail, the email address of the recipients can be entered in __________ field.
- A.Subject
- B.To
- C.Message
- D.From
Show answer
The To field of a mail window is meant for the addresses of the people the letter is written to.
Read the full explanation →ARPANET, the forerunner of the internet, carried its first message in which year?
- A.1959
- B.1969
- C.1979
- D.1989
Show answer
ARPANET was funded by the Advanced Research Projects Agency of the United States Department of Defense, and in 1969 it linked computers at four American universities and passed its first message between them.
Read the full explanation →Who is credited with inventing the World Wide Web?
- A.Vinton Cerf
- B.Charles Babbage
- C.Tim Berners-Lee
- D.Ray Tomlinson
Show answer
Working at CERN in Switzerland, he proposed a system of linked documents in 1989, wrote the first browser and server, and put the first website online in 1991.
Read the full explanation →Which symbol was chosen by Ray Tomlinson to separate the user name from the host name in an email address?
- A.#
- B.&
- C.@
- D.*
Show answer
Ray Tomlinson sent the first message between two computers on ARPANET in 1971 and needed a character that would never appear in a person's name.
Read the full explanation →What is the default port number of HTTPS?
- A.21
- B.80
- C.110
- D.443
Show answer
HTTPS is HTTP wrapped in encryption, and web servers listen for it on port 443. When an address begins with https, the browser opens a secure channel on that port, and the padlock shown beside the address means the traffic on it is coded.
Read the full explanation →In an email, which field is used to send a copy to a person whose address the other recipients cannot see?
- A.To
- B.Cc
- C.Bcc
- D.Subject
Show answer
Bcc stands for blind carbon copy. An address typed there receives the letter, but it is hidden from everyone else on the list, and the people in Bcc cannot see one another either.
Read the full explanation →An IPv6 address is of how many bits?
- A.32 bits
- B.64 bits
- C.128 bits
- D.256 bits
Show answer
IPv6 was framed because the older scheme was running out of addresses, and its 128-bit length yields a pool so large that shortage is no longer a worry.
Read the full explanation →Which protocol is used to send an outgoing email from a client to a mail server?
- A.SMTP
- B.POP3
- C.IMAP
- D.FTP
Show answer
SMTP stands for Simple Mail Transfer Protocol and is the rule set that pushes a letter out of your mail program to the server and onward from one server to the next until it reaches the receiver's mailbox.
Read the full explanation →The system that converts a domain name such as india.gov.in into its numeric address is called
- A.DNS
- B.DHCP
- C.HTTP
- D.URL
Show answer
The Domain Name System is the directory of the internet. People remember names, while machines route traffic by numbers, so a DNS server looks up the name typed in the browser and returns the matching IP address before the page is fetched.
Read the full explanation →The domain name .gov in a web address shows that the site belongs to
- A.a commercial company
- B.a government body
- C.an educational institution
- D.a network provider
Show answer
The last part of a domain name is the top-level domain and tells you the kind of owner. Government offices use.gov, often with the country code added, as in india.gov.in for the National Portal of India.
Read the full explanation →Which protocol is used to upload files to and download files from a remote server on the internet?
- A.SMTP
- B.Telnet
- C.FTP
- D.IMAP
Show answer
FTP stands for File Transfer Protocol. It opens two channels with a server, one on port 21 for commands and one on port 20 for the matter itself, and moves whole files in either direction, which is how web pages are put on a hosting server.
Read the full explanation →Frequently Asked Questions
Is the internet the same thing as the World Wide Web?
No. The internet is the network of connected machines, while the World Wide Web is one service running on it, namely linked pages read through a browser. Email and file transfer use the internet without touching the web, so the two words are not interchangeable in an exam answer.
What is the difference between Cc and Bcc in an email?
Both send a copy of the letter. Addresses written in Cc, or carbon copy, are visible to every recipient. Addresses written in Bcc, or blind carbon copy, are hidden from everyone else, and people in Bcc cannot see one another either.
Which protocol sends mail and which one receives it?
SMTP, on port 25, sends mail out. POP3, on port 110, downloads mail to one device and usually deletes it from the server, while IMAP, on port 143, keeps mail on the server so the same mailbox looks alike on every device.
Why was IPv6 introduced when IPv4 was already working?
An IPv4 address has only 32 bits, so the pool of addresses ran short as the number of connected devices grew. IPv6 uses 128 bits, which gives an enormous pool, and it is written as eight groups of hexadecimal digits separated by colons.
When did internet service start for the public in India?
On 15 August 1995, when Videsh Sanchar Nigam Limited opened its gateway for public use. Before that, from 1986, the academic and research network ERNET carried traffic for institutions.
Is Google a browser or a search engine?
Google is a search engine, which finds pages. Google Chrome is a browser, which displays them. Firefox, Edge and Safari are browsers, while Bing, Yahoo and DuckDuckGo are search engines, and papers often mix the two lists in one question.
Sources
- A Short History of the Web — CERN
- Service Name and Transport Protocol Port Number Registry — Internet Assigned Numbers Authority
- About the .IN Registry — National Internet Exchange of India
