Introduction to Web Concepts

Introduction to Web

• The lecture was given by Dr. Heba Mamdouh at Minia university.
• The lecture covered basic web concepts.

Internet

• The internet is a global system of interconnected computer networks.
• It uses the Internet Protocol (TCP/IP).
• Each computer on the internet has a unique IP address.
• Internet access is global.

Advantages and Disadvantages

• Advantages: Social networking, education, entertainment, online services.
• Disadvantages: Threat to personal information, spamming, cybercrime, virus attacks.

Intranet

• A private network within an organization
• Used for sharing information and resources among coworkers.

Internet vs. Intranet

• Intranet: Localized network, no internet access, more expensive, more secure, more reliable.
• Internet: Worldwide network, internet access, less expensive, less secure, less reliable.

Extranet

• A private network that securely shares information/operations with external partners.
• Uses the internet to connect to outsiders in a controlled manner.

Extranet vs. Intranet

• Extranet: Internal network accessible externally, extension of company's intranet, for communication between customers, suppliers, and partners.
• Intranet: Internal network not accessible externally, limited to company users, for communication within the company.

Network Overview

• A network connects two or more computers to share resources and communicate.

Networks (LAN & WAN)

• LAN (Local Area Network): Usually within a building or a group of buildings; connects computers and peripherals in a limited area (e.g., schools, labs, homes, offices).
• WAN (Wide Area Network): Connects computers over geographically dispersed areas, often using public or commercial communications networks (e.g., the internet).

The Client/Server Model

• A relationship between two computer programs: client and server.
• Client: Requests a service (e.g., a file or database access) from the server.
• Server: Fulfills the request and transmits the results to the client over a network.

The Internet Client/Server Model

• Client: Web browser
• Server: Web server

World Wide Web (WWW)

• A vast collection of files and documents stored on computers (servers) and written in HTML.
• HTML dictates how browsers display the information.
• A technical definition: all resources and users on the internet that use the HTTP protocol.
• The internet and the web aren't the same thing. The web uses the internet to transfer information.

WWW Operation

• A user enters a URL (e.g., http://www.yahoo.com) into a web browser.
• The browser requests the IP address from a Domain Name Server (DNS).
• The browser sends a request to the web server using the (HTTP) protocol.
• The server finds the requested web page, sends it back to the browser using HTTP.
• The browser displays the web page.

Web Page

• A document available on the world wide web, stored on a web server.
• Viewed using a web browser.
• May include text, graphics, audio, video, hyperlinks which link to other web pages.
• A collection of linked web pages is a website.
• Each web page has a unique Uniform Resource Locator (URL).

Web Browser

• Application software for viewing and exploring information on the web.
• Users request web pages by typing the URL in the address bar.

Most common web browsers

• Internet Explorer (Microsoft)
• Google Chrome (Google)
• Mozilla Firefox (Mozilla)
• Opera (Opera Software)
• Safari (Apple)

How Browsers Display Web Pages

• Reads and interprets HTML files to format the web page.
• Downloads external files (like images) from the server and displays them.
• HTML files are text files with references to external files (not embedded files).

Web Server

• Computer where web content (web pages) is stored.
• Software that responds to requests for web resources.
• For client requests for a webpage search the requested page.
• Sends the page back to the client with an HTTP response. (if not found sends 404 Error)

How Web Servers Work

• When a client sends a request, the web server searches for the requested page.
• If found, the server sends back the page with an HTTP response.
• If not found, the server sends an HTTP response with an error message (e.g., 404 Not Found)
• If the client requests other resources (e.g., images), the web server contacts other servers to get and sends response.

IP Address

• A unique logical address for a device on a network.
• A unique set of numbers identifying a computer's location.
• 32 bits (4 bytes) long.
• Consists of network component and host component.
• Numbers (0 to 255) separated by dots (e.g., 137.170.4.124).

Domain Name

• Locates an organization/entity on the internet.
• A domain name replaces the IP address (easier for users to remember).
• A DNS (Domain Name Server) translates a domain name to its corresponding IP address.

Domain Extension Types

• .com (Commercial)
• .net (Network)
• .org (Organization)
• Country-specific (e.g., .us, .uk)
• Others (e.g., .biz, .info, .tv)

The Domain Name System (DNS)

• Associates domain names with IP addresses.
• Translates domain names into IP addresses automatically.

Uniform Resource Locator (URL)

• Identifies the location of a document on a website.
• Contains the protocol (e.g., HTTP), subdomain/server name, domain name, folder name, and file name (e.g.,http://www.webdevfoundations.net/chapter1/index.html).

Internet Protocols

• Rules describing how clients and servers communicate on a network.
• Multiple protocols are needed for internet and web functionality.

FTP (File Transfer Protocol)

• Set of rules for exchanging files between computers on the internet.
• Commonly used by web developers to transfer web page files to web servers.
• Used to download programs and files.

E-mail Protocols

• Sending: SMTP (Simple Mail Transfer Protocol)
• Receiving: POP (Post Office Protocol), IMAP (Internet Mail Access Protocol)

HTTP (Hypertext Transfer Protocol)

• Set of rules for exchanging files on the web (e.g., text, images, video, etc.).
• Web browsers send HTTP requests for web pages and associated files.
• Web servers send HTTP responses to web browsers.

Basic Web Programming

• HTML (Hypertext Markup Language)
• CSS (Cascading Style Sheets)
• JavaScript
• Other dynamic web programming technologies (e.g., ASP.NET, SQL, AJAX, PHP).

The Web Programming Triangle

• Shows the relationship between HTML, CSS, and JavaScript in web development.

References

• Websites for tutorials on HTML, CSS, and JavaScript.

This quiz explores fundamental concepts related to the web, including the internet, intranet, and extranet. Understand the advantages and disadvantages of using these networks, along with their unique characteristics. Ideal for students of web technology.