world wide web


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world wide web

  1. 1. Disclaimer:This presentation is prepared by trainees ofbaabtra as a part of mentoring program. This is not officialdocument of baabtra –Mentoring PartnerBaabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt .Ltd
  2. 2. WORLD WIDE WEB Ashwin Anand V Facebook
  3. 3. WWW History• 1989-1990 – Tim Berners-Lee invents the World Wide Web at CERN – Means for transferring text and graphics simultaneously – Client/Server data transfer protocol • Communication via application level protocol • System ran on top of standard networking infrastructure
  4. 4. – Text mark up language • Not invented by Bernes-Lee • Simple and easy to use • Requires a client application to render text/graphics
  5. 5. What Is the World Wide Web? The world wide web (web) is a network of information resources. The web relies on three mechanisms to make these resources readily available to the widest possible audience:1. A uniform naming scheme for locating resources on the web (e.g., URIs).2. Protocols, for access to named resources over the web (e.g., HTTP).3. Hypertext, for easy navigation among resources (e.g., HTML).
  6. 6. TYPES OF WEB• Public web• Invisible web/deep web
  7. 7. WWW Structure• Clients use browser application to send URIs via HTTP to servers requesting a Web page• Web pages constructed using HTML and consist of text, graphics, sounds plus embedded files• Servers respond with requested Web page• Client’s browser renders Web page returned by server – Page is written using HTML – Displaying text, graphics and sound in browser – Writing data as well• The entire system runs over standard networking protocols (TCP/IP, DNS,…)
  8. 8. Standard Generalized Markup Language (SGML)• Based on GML (generalized markup language), developed by IBM in the 1960s• An international standard (ISO 8879:1986) defines how descriptive markup should be embedded in a document• Gave birth to the extensible markup language (XML), W3C recommendation in 1998
  9. 9. SGML ComponentsSGML documents have three parts:• Declaration: specifies which characters and delimiters may appear in the application• DTD/ style sheet: defines the syntax of markup constructs• Document instance: actual text (with the tag) of the documentsMore info could be found: http://www.W3.Org/markup/SGML
  10. 10. HTML Background• HTML was originally developed by Tim Berners-Lee while at CERN, and popularized by the Mosaic browser developed at NCSA.• The Web depends on Web page authors and vendors sharing the same conventions for HTML. This has motivated joint work on specifications for HTML.• HTML standards are organized by W3C :
  11. 11. HTML FunctionalitiesHTML gives authors the means to:• Publish online documents with headings, text, tables, lists, photos, etc – Include spread-sheets, video clips, sound clips, and other applications directly in their documents• Link information via hypertext links, at the click of a button• Design forms for conducting transactions with remote services, for use in searching for information, making reservations, ordering products, etc
  12. 12. Sample Webpage
  13. 13. Sample Webpage HTML Structure<HTML> <HEAD> <TITLE>The title of the webpage</TITLE> </HEAD> <BODY> <P>Body of the webpage </BODY></HTML>
  14. 14. HTML Structure• An HTML document is divided into a head section (here, between <HEAD> and </HEAD>) and a body (here, between <BODY> and </BODY>)• The title of the document appears in the head (along with other information about the document)• The content of the document appears in the body. The body in this example contains just one paragraph, marked up with <P>
  15. 15. HTML Hyperlink<a href="relations/alumni">alumni</a>• A link is a connection from one Web resource to another• It has two ends, called anchors, and a direction• Starts at the "source" anchor and points to the "destination" anchor, which may be any Web resource (e.g., an image, a video clip, a sound bite, a program, an HTML document)
  16. 16. Resource IdentifiersURI: Uniform Resource Identifiers• URL: Uniform Resource Locators• URN: Uniform Resource Names
  17. 17. Introduction to URIsEvery resource available on the Web has an address that may be encoded by a URIURIs typically consist of three pieces:• The naming scheme of the mechanism used to access the resource. (HTTP, FTP)• The name of the machine hosting the resource• The name of the resource itself, given as a path
  18. 18. URI Example• There is a document available via the HTTP protocol• Residing on the machines hosting• Accessible via the path "/TR"
  19. 19. ProtocolsDescribe how messages are encoded and exchangedDifferent Layering Architectures• ISO OSI 7-Layer Architecture• TCP/IP 4-Layer Architecture
  20. 20. ISO OSI Layering Architecture
  21. 21. ISO’s Design Principles• A layer should be created where a different level of abstraction is needed• Each layer should perform a well-defined function• The layer boundaries should be chosen to minimize information flow across the interfaces• The number of layers should be large enough that distinct functions need not be thrown together in the same layer, and small enough that the architecture does not become unwieldy
  22. 22. TCP/IP Layering Architecture
  23. 23. TCP/IP Layering Architecture• A simplified model, provides the end-to-end reliable connection• The network layer – Hosts drop packages into this layer, layer routes towards destination – Only promise “Try my best”• The transport layer – Reliable byte-oriented stream
  24. 24. HTTP Basics• Protocol for client/server communication – The heart of the Web – Very simple request/response protocol – Relies on URI naming mechanism• Three versions have been used – 09/1.0 – very close to Berners-Lee’s original – 1.1 – developed to enhance performance, caching, compression – 1.0 dominates today but 1.1 is catching up
  25. 25. GET Method in HTTP
  26. 26. HTTP Response Codes• 1xx – Informational – request received, processing• 2xx – Success – action received, understood, accepted• 3xx – Redirection – further action necessary• 4xx – Client Error – bad syntax or cannot be fulfilled• 5xx – Server Error – server failed
  27. 27. Domain Name SystemDNS (domain name service): mapping from domain names to IP addressIPv4:• IPv4 was initially deployed January 1st. 1983 and is still the most commonly used version.• 32 bit address, a string of 4 decimal numbers separated by dot, range from to• Revision of IPv4 with 128 bit address
  28. 28. Top Level Domains (TLD)Top level domain names, .com, .edu, .gov and ISO 3166 country codesThere are three types of top-level domains:• Generic Domains were created for use by the Internet public• Country code domains were created to be used by individual country• . arpa domain Address and Routing Parameter Area domain is designated to be used exclusively for Internet-infrastructure purposes
  29. 29. Registrars• Domain names ending with .aero, .biz, .com, .coop, .info, .museum, .name, .net, .org, or .pro can be registered through many different companies (known as "registrars") that compete with one another• InterNIC at• Registrars Directory:
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