Internet Basics, IP, DNS and URL Structure
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Key points
- The internet is the network; the web is a service on it, invented by Tim Berners-Lee in 1989
- IPv4 is 32 bits, IPv6 is 128 bits, a MAC address is 48 bits
- DNS converts domain names to IP addresses; DHCP assigns addresses automatically
- .ac.in is academic, .res.in research, .gov.in and .nic.in government
- Intranet is internal only; extranet opens part of it to outsiders
- Incognito mode hides nothing from the network administrator or ISP
- Download time in seconds = file size in MB x 8 divided by speed in Mbps
On this page
Internet and the World Wide Web
The internet is the global network of computer networks connected using TCP/IP. It grew out of ARPANET, started in 1969 by the US defence department, and TCP/IP was designed by Vint Cerf and Bob Kahn.
The World Wide Web is a service running on the internet: a system of web pages joined by hyperlinks, proposed by Tim Berners-Lee at CERN in 1989.
Key point
The internet is the network; the web is one service on it. Tim Berners-Lee invented the web, not the internet.
Addresses
- IPv4: 32 bits, written as four numbers such as 192.168.1.10.
- IPv6: 128 bits, written in hexadecimal.
- MAC address: a 48-bit hardware address, not an IP address.
DNS, the Domain Name System, translates a domain name into an IP address and is often called the telephone book of the internet. DHCP assigns IP addresses to devices automatically.
Structure of a URL
Take an illustrative address of the form https://www.example.ac.in/recruitment/notice.pdf
| Part | Meaning |
|---|---|
| https | Protocol, showing an encrypted connection |
| www.example.ac.in | Host or domain name |
| .in | Country-code top-level domain |
| /recruitment/notice.pdf | Path to the file on the server |
Indian domains
- .ac.in: academic institutions such as IITs and universities
- .res.in: research institutions
- .gov.in and .nic.in: government bodies
The .ac.in, .edu.in and .res.in domains are administered by ERNET India.
Network types
| Type | Coverage |
|---|---|
| PAN | Personal, such as Bluetooth |
| LAN | One building or campus |
| MAN | One city |
| WAN | Wide area; the internet is the largest WAN |
An intranet is a private network for staff only. An extranet opens part of it to authorised outsiders such as vendors.
Browser concepts
A browser is the software that opens web pages, such as Chrome, Edge or Firefox. A search engine is a website or service, not a browser. Cookies are small files a site stores in the browser to remember logins and preferences, and the cache stores copies of pages so they open faster.
Incognito or private mode stops the browser from saving history, cookies and form data on that device. It does not hide activity from the network administrator or the internet service provider.
Bandwidth and download time
Formula
Download time in seconds = (File size in MB x 8) divided by speed in Mbps
File size is measured in bytes and bandwidth in bits, so multiply by 8 to convert.
Example
A 600 MB file on a 40 Mbps line: 600 x 8 = 4800 Mb, and 4800 divided by 40 = 120 seconds, that is 2 minutes. Shortcut: 40 Mbps is 5 MB per second, so 600 divided by 5 = 120 seconds.
Exam tip
Forgetting to multiply by 8 is the standard error in download questions, and the wrong figure always appears as one of the options.
Practice questions
Answer all, then check. Explanations appear after checking.
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