Note for Web Technologies - WT by shweta singh

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WTCS UNIT 01: INTRODUCTION TO WWW Unit-1: Introduction to the World Wide Web 1.1 Introduction to Internet, Working of Internet, 1.2 Modes of Connecting to Internet, 1.3 Electronic Mail: Introduction to E-mail system, structure of E-mail, Creating E-mail account, 1.4 Web Browsers, How Web works-HTTP and URLs, How browser works, 1.5 MIME types, plug-ins, searching the www: Directories search engines and Meta search engines, 1.6 Working of the search engines 1.1 Introduction to Internet, Working of Internet 1.1.1 What is Internet? The Internet is essentially a global network of computing resources. It is a physical collection of routers and circuits as a set of shared resources. Some common definitions given in the past include − ✓ A network of networks based on the TCP/IP communications protocol. ✓ A community of people who use and develop those networks. ✓ A community of people who use and develop those networks. 1.1.2 Internet-Based Services: Some of the basic services available to Internet users are − i. Email − A fast, easy, and inexpensive way to communicate with other Internet users around the world. ii. Telnet − Allows a user to log into a remote computer as though it were a local system. iii. FTP − Allows a user to transfer virtually every kind of file that can be stored on a computer from one Internet-connected computer to another. iv. UseNet news − A distributed bulletin board that offers a combination news and discussion service on thousands of topics. v. World Wide Web (WWW): A technical definition of the World Wide Web is − All the resources and users on the Internet that are using the Hypertext Transfer Protocol

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(HTTP). In simple terms, The World Wide Web is a way of exchanging information between computers on the Internet, tying them together into a vast collection of interactive multimedia resources. The World Wide Web (WWW), also called the Web, is an information space where documents and other webresources are identified by Uniform Resource Locators (URLs), interlinked by hypertext links, and accessible via the Internet. 1.1.3 WORKING OF INTERNET/ WORKING OF THE WEB On the simplest level, the Web physically consists of the following components ✓ Your personal computer − this is the PC at which you sit to see the web. ✓ A Web browser − A software installed on your PC which helps you to browse the Web. ✓ An internet connection − this is provided by an ISP and connects you to the internet to reach to any Website. ✓ A Web server − this is the computer on which a website is hosted. ✓ Routers & Switches − they are the combination of software and hardware who take your request and pass to appropriate Web server. The Web is known as a client-server system. Your computer is the client and the remote computers that store electronic files are the servers. How the Web/Internet Works? When you enter something like Google.com the request goes to one of many special computers on the Internet known as Domain Name Servers(DNS). All these requests are routed through various routers and switches. The domain name servers keep tables of machine names and their IP addresses, so when you type in Google.com it gets translated into a number, which identifies the computers that serve the Google Website to you. When you want to view any page on the Web, you must initiate the activity by requesting a page using your browser. The browser asks a domain name server to translate the domain name you requested into an IP address. The browser then sends a request to that server for the page you want, using a standard called Hypertext Transfer Protocol or HTTP.

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The server should constantly be connected to the Internet, ready to serve pages to visitors. When it receives a request, it looks for the requested document and returns it to the Web browser. When a request is made, the server usually logs the client's IP address, the document requested, and the date and time it was requested. This information varies server to server. An average Web page actually requires the Web browser to request more than one file from the Web server and not just the HTML / XHTML page, but also any images, style sheets, and other resources used in the web page. Each of these files including the main page needs a URL to identify each item. Then each item is sent by the Web server to the Web browser and Web browser collects all this information and displays them in the form of Web page. In Short We have seen how a Web client - server interaction happens. We can summarize these steps as follows − 1. A user enters a URL into a browser (for example, Google.com. This request is passed to a domain name server. 2. The domain name server returns an IP address for the server that hosts the Website (for example, 68.178.157.132). 3. The browser requests the page from the Web server using the IP address specified by the domain name server. 4. The Web server returns the page to the IP address specified by the browser requesting the page. The page may also contain links to other files on the same server, such as images, which the browser will also request. 5. The browser collects all the information and displays to your computer in the form of Web page. 1.1.4 Difference between the Internet, Extranet and Intranet BASIS FOR COMPARISON INTERNET INTRANET Meaning Connects different network of computers together It is a part of Internet which is privately owned by a particular firm Accessibility Anyone can access the Internet Accessible only by the organization members, having login details.

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Safety Is not as safe as compared to Intranet Safe No of Users Unlimited Limited Visitors Traffic More Less Network Type Public Private Information Provided Unlimited, and can be viewed by everyone Limited, and circulates among the members of an organization Extranet Internet Intranet Definition Extranet is for individuals or group of personnel who want to send private information A global network which is available to anyone who wants to access information An intranet is unique to an organization or group of people who work together at a place Privacy Extremely Private Public Private intermediately Dependency Dependent on internet and intranet Independent Independent yet dependent on internet Firewall Yes No Can have 1.1.5 Introduction to Web Technology: Web technology relates to the interface between web servers and their clients. It includes mark-up languages, programming interfaces and languages and display and standards for document identification. It also refers to the development of the apparatus that allows several computer machines to communicate over a network. This is done by the relevant party who is capable to connect all the computers to a certain LAN. It is a complicated process. Advantages of Web Technology: i. Convenience and a high speed of communication in the computer world.