Terminology & Miscellaneous

Node

• A node is a component or terminal connected to a network.
• Components like laptops, PDAs(personal digital assistants – a variety of handheld mobile devices), Internet-enabled mobiles, network connecting devices, etc., can be considered as nodes in a computer network.

Client 

Link for Client details

Server

Link for Server details

Proxy Server

• The proxy server is used in a computer network.
• The proxy server is an actual server that acts as an intermediary between the client application and the Web server to save the original server from attack, if any and also reduce the workload of the original server.
• The proxy server is used to improve performance and security and for filtering purposes.
• In an organization, the proxy server can be used to prevent its employees from accessing certain types of websites.
• It provides security and checks to the overall system.
• It can also improve the performance of the network.
• Suppose two users access the web through a proxy server. If user X requests a webpage, say page 1. Sometime later, if user Y requests the same page then this request will not be forwarded to the web server. The proxy server simply returns the same page to which it has access for user X, thus saving a lot of time.

Bandwidth

• Bandwidth is the number of bits transferred by a channel per unit of time.
• Bandwidth is a data transmission rate that tells the maximum amount of information (bits/second) that can be transmitted along a channel.
• It determines how fast data can be transmitted from the source place to the destination place.
• It is measured in kilobits, kbps, 1,000 bits per second, or megabits (Mbps), millions of bits per second.
• Actual data transfer rates are considerably lower than the given bandwidth because of software and protocol overheads.

Virtual Private Network(VPN)

• A VPN may be defined as the secure way of connecting to a private LAN from a remote location using the Internet or any other insecure network.
• In such a case, the data that is to be transmitted over the insecure network is encrypted and has a proper mechanism for authenticating the user.

ISPs(Internet Service Provider)

• The first Internet Service Provider (ISP) is born with the introduction of a commercial version of ARPANET, known as Telenet in 1974.
• The first commercial ISP for the Internet we know and use today is considered to be “The World” which started serving customers in 1989.
• An internet service provider (ISP) is a company or organization that provides internet connection/access to the internet and connects users to the global network, enabling web browsing and email usage.
• Besides facilitating internet connectivity, ISPs offer other related services like web hosting and domain name registration.
• ISPs play a crucial role in ensuring reliable connectivity for various online activities, from streaming movies to video conferencing.
• ISPs can be organized in various forms, such as commercial, community-owned, non-profit, or otherwise privately owned.
• ISPs can provide internet access through multiple means, including dial-up, DSL, cable, wireless, hotspot, and fiber-optic connections.
• The most common types of ISPs are cable, fiber, DSL (Digital Subscriber Line), and satellite internet.
• An ISP is required in order to connect to the internet via a modem in our home or business.
• Without an ISP, we would not be able to access the wealth of information available online.
• ISPs are responsible for making sure to access the Internet, routing Internet traffic, resolving domain names, and maintaining the network infrastructure that makes Internet access possible.
• Jio, Airtel, Excitel, Vi, BSNL, etc. the most popular ISPs in India. 
• ISPs provide a Public IP address to their customers or clients. A public IP address is a one-of-a-kind numeric code that is never repeated by other devices, whereas a private IP address is a non-unique numeric code that can be reused by other private network devices.

Internet

Link for Internet Details

Intranet

• An intranet is a computer network within an organization.
• An intranet is normally  a closed private enterprise network.
• It is usually a local or restricted network with limited access.
• The main purpose of Intranet creation is to support an organization’s employees to store, organize, communicate, share information & other resources, collaborate, and perform their roles very well under a tight security environment.
• An intranet gives a place to store and share company documents in an easy-to-use, easy-to-search location.
• The other purpose of Intranet is to usually the exclusion of access by outsiders.
• Typically an intranet is a LAN network but may be connected with a WAN.
• The intranet may/may not work with the Internet.
• Some world-famous intranets are -Microsoft SharePoint, Huddle, Igloo, Jostle, etc.
• Both Internet and Intranet use IP addresses and protocol suites for proper communications.
• It uses Internet technologies to do its operations.
• It is a highly secure network but the use of web browsers and malicious software makes a loophole for attackers.
• Intranets often run 100–1000 times faster than the internet.
• Unlike the internet, an intranet has an owner or admin to control it.

Extranet

• An extranet is an extended form of intranet.
• An extranet is a controlled private network that allows access to external third parties, partners, vendors or suppliers, or authorized key customers, outside the organization – normally to share a subset of the controlled information/operations/data/applications accessible from an organization’s intranet.
• It is very much like an intranet.
• Usually, it’s a web platform where the customers/third party of a company can log onto, to make or track orders.

Web Browser/Browser

• A web browser is popularly called a browser.
• Initially, the browsers were designed to show plain text, without any formatting but now the situation is reversed.
• A web browser is application software for accessing and displaying the contents of the World Wide Web(web pages) through the internet by searching a requested web page from a website located on a web server.
• Examples of web browsers are – Mosaic(World’s first stable browser, developed by National Centre
  for Supercomputing Application (NCSA),1993), Netscape Navigator(first to introduce graphical interface,1994), Konqueror, Lynx, Google Chrome(Most popular and Fastest,2008), Safari(from Apple’s Company,2003), Internet Explorer(1995), Microsoft Edge, Mozilla Firefox(2002), Opera, Brave(Most secure and private), Tor, Chromium, Bromite(Android), Vivaldi, Kingpin, Iridium etc.
• Web Pages are viewed with a program called a web browser. The browser fetches the page requested, interprets the text and formatting commands on it, and displays the page, properly formatted, on the client screen.
• Most browsers are downloaded from their websites and finally installed.
• The first web browser, called WorldWideWeb, was created in 1990 by Sir Tim Berners-Lee and this is completely different from the World Wide Web we use today. It was later named “Nexus” to avoid any confusion with the World Wide Web. Tim Berners-Lee, then recruited Nicola Pellow to write the Line Mode Browser(a type of browser), which displayed web pages on dumb terminals. But, Mosaic was credited as the world’s first stable & popular browser in 1993.
• When strictly say, a browser is vital for browsing the web but, browsers aren’t completely necessary. After all, the Internet existed before the World Wide Web. Many other tools and protocols are available to let us get online without a browser but not as easy and with several facilities like a web browser.
• Multiple web pages can be opened at the same time using a web browser.
• There are several options like Home, Back, Forward, Reload/Refresh, Bookmark, History, etc. available on the web browser, which makes using them easy and convenient.
• Web browsers are used mostly on a range of devices that use the internet such as Desktops PC, Laptops, Tablets, Smartphones/Mobiles, etc.
• The main function/purpose of a web browser is to fetch given contents from the Web via Internet and display/make available it on a user‘s device.
• Most browsers use/create an internal cache of web page resources to improve loading times for next/subsequent visits to the same page.
• Page display performance may be poor in the browser, this is due to DNS not responding, the server not responding, or simply network congestion during page transmission.
• Structure: 
  • Although a browser is basically an HTML interpreter and most browsers have numerous buttons and features to make searching easier to navigate the Web.
  • Most have a button for going back to the previous page, a button for going forward to the next page (only operative after the user has gone back from it), and a button for going straight to the user’s own start page.
  • Most browsers have a button or menu item to set a bookmark on a given page and another one to display the list of bookmarks, making it possible to revisit any of them with only a few mouse clicks.
  • Searched Web Pages can also be saved to disk or printed.
  • Several other numerous options are generally also available for controlling the screen layout and setting various user preferences. 
• The working mechanism of a web browser is – 

• • First, enter a URL in the web browser’s address bar and press Enter button.
  • The browser finds the IP address of that URL for the domain using DNS.
  • The browser initiates a connection with the server.
  • Next, it sends an HTTP request to the web server.
  • The server handles the request and sends out an HTTP response to the client.
  • Now, contents appear on the client’s screen browser.

• Type of Web Browsers
  • Text-based Web Browser :
    • A web browser that renders only the text contents of web pages, and ignores most graphic content is called a text-based web browser.
    • This browser uses comparatively small bandwidth connections; searches pages faster than graphical web browsers due to no CSS, or JavaScript in the contents hence also uses low CPU resources.
    • Text-based browsers are often very useful for users with visual impairment or partial blindness.
    • They are also useful with speech synthesis or text-to-speech software, which reads content to users.
    • Examples are – Lynx, Browsh, Line Mode Browser, etc.
  • GUI-based Web Browser :
    • A GUI-based web browser is a web browser that renders multimedia contents of web pages and ignores nothing.
    • This browser uses comparatively large bandwidth connections; search pages are slower than text web browsers due to CSS, and JavaScript being present with the contents hence using heavy CPU resources too.
    • Most of today’s browsers are GUI-based browsers.
    • Examples are – Chrome, Safari, Opera, Internet Explorer, Microsoft Edge, Mozilla Firefox, Brave, etc.

Search Engine

• A search engine is a number of programs (hence complex) that search documents for information on any topic from the web using a specified set of keywords.
• Some famous search engines are provided by: www.google.com, wikipedia.com, webopedia.com, MSN.com, Yahoo.com, etc
• A search engine basically works in three phases:-
  • The search engine sends a program (called the spider) that searches the web pages on the Internet for the keyword.
  • After the spider fetches the result, another software called the indexer reads these results. The indexer then creates an index based on the words contained in each of the documents returned by the spider.
  • After indexing, the search engine presents only the documents matching the search criteria to the user.

URL/Uniform Resource Locator

• Any website located on the Internet has a unique address associated with it indicating the location of the website. Every page has an address associated with it. This address is known as the URL. 
• A URL tells us the location of the web page being displayed and other related information.
• A unique location (address) of a web element which may be a website or a web page is required in the World Wide Web to view it in the browser.
• Uniform Resource Identifier (URI), which is a universal system for referencing resources on the Internet, such as hypertext documents & images.
• URIs, often called URLs, are defined by the IETF’s RFC 3986 / STD 66. 
• A URL is the complete address of a web page located on a web server.
• In other words, a web page is identified using its URL i.e. the unique address of a website is called URL.  It is often simply called a Web address and is, literally, the address of a file on the Internet.
• The URL consists of four basic parts, namely, server type, host/DNS name, folder/directory name, and filename. Each one of these has a specific function. The “server type” indicates the type of Internet server (Protocol) being accessed. The server type is always followed by “://” and the hostname. The hostname is the Internet address of a remote/server computer on which the files reside. The folder name indicates the name of the directory in which the files are located. The filename specifies the name of the specific document to be displayed in the browser. The filename itself consists of two pieces of information, the name of the file to be displayed and the file extension, which specifies the file type (.htm for an HTML file, .txt for a text file, .bmp for a bitmap image, etc.)
  The structure/syntax of a URL can be represented as follows:
  Syntax: Server type://Hostname/directory/sub-directory/…/filename.

Web/WWW/W3

Link for WWW Details

Web Page

• The electronic pages available on the Internet are known as web pages.
• Many web pages are linked with each other through the hyperlinking process and combining to form a website.
• A web page can be written in HTML.
• Every single web page consists of some information with a number of links, which connect other related web pages. To visit the linked web pages, just click over the linked text and the next web page opens up.
• To view a web page we need special software called a web browser.

Portals

• The term “portal” can vary widely based on the context in which it is used.
• It generally refers to a gateway or entry point, either in a physical or digital sense, that provides access to something else, whether it’s information, services, or new experiences.
• There may be several types of Portals such as Web portals, Enterprise portals, Gaming portals, Science Fiction portals, Government portals, Computing portals, etc. but the most common are Web portals, Government portals, etc.
• Web Portal:
  • In the context of the Internet, a web portal is a website or web application that serves as a gateway or starting/entry point for accessing a variety of information, services, resources, or functionalities on the web.
  • Web portals often provide a single point of entry to access email, news, weather, search engines, social media, and other online services.
  • Examples of web portals include AOL, Yahoo, MSN, and iGoogle (now defunct).
• Government Portal:
  • Many government organizations, at various levels, have developed online portals to provide citizens with access to government services, information, and resources.
  • These portals can include services such as paying taxes, renewing licenses, accessing public records, and more.

CAT5

• CAT5 is a type of Twisted Pair Cable used widely in network communication.
• The bandwidth of the CAT5 cable is 100 Mbps.
• The recommended CAT5 cable length between the switch and the PC is 100 meters.
• The pin no. 1,2,3,6 are used in CAT5 cables.